# Can Altruism Evolve Between Species? (52138)

Christopher Quickfall

*University of Sheffield.*

Multi-species associations, involving co-adapted species, are widespread in nature; examples include multi-species biofilms, plant-pollinator associations, and associations between algae and fungi to form lichens. Hamilton showed how altruism can evolve between members of the same species, due to genetic relatedness. However, the literature is much less clear on whether altruistic acts can evolve between species, whereby a member of one species reduces their reproductive success to benefit other species, without a direct or indirect fitness return. One potential problem is that genetic relatedness between species appears to be ill-defined and thus might normally be assumed to be zero. These arguments bear on the fundamentals of social evolution theory.

We clarify these issues, using simple models to define the evolutionary conditions favouring costly donation between species without immediate return benefits. In particular, we examine inter-species models that are intended to represent, as much as possible, Hamilton’s scenario for altruism within species. Results are found both analytically, and through deterministic and stochastic simulation. We find that costly donation between species can evolve with a specific type of whole-genome assortment between species, but argue that it is explained by indirect fitness benefits within the donating species, using partner species as vectors for altruism.

Poster session A - GEN 2000

# Diversity of moral strategies in human reputation-based cooperation (52206)

Martijn Egas, Violet Swakman, Lucas Molleman, Aljaz Ule.

*Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam (UvA);*
*The Centre for Decision Research and Experimental Economics (CeDEx), University of*
*Nottingham; Center for Research on Experimental Economics and political Decision-making*
*(CREED), UvA.*

The question why humans often help others without selfish material interest intrigues many scientists. In theory such human reciprocal cooperation can be explained when helping is directed to individuals with a good reputation of helping others. Evolutionary models predict stable cooperation when reputations are based on moral assessment rules incorporating whether helping someone is justified, which requires information on the behavior of the person to be judged but also of the persons (s)he interacted with. Here, we provide first empirical evidence that such information indeed affects cooperative decision making: more help is provided to people who helped cooperative players and refused to help uncooperative players. A detailed analysis of individual strategies reveals that many subjects base their decisions solely on their recipients’ past behavior. Some classify as unconditional cooperators or defectors, and a few as maintaining a fixed level of helpfulness. Importantly, however, a substantial proportion of individuals consistently consider the motivations behind behaviors. Our results provide strong empirical support for the use of moral strategies that theoretically
underpin reputation-based cooperation, but also challenges theory by highlighting the
existence of pronounced individual variation in human cooperative strategies.

# Pattern and process in the evolutionary history of the mycorrhizal symbiosis
(52299)

Hafiz Maherali.

*University of Guelph.*

The vast majority of plants form symbioses with mycorrhizal fungi, which provide them with soil nutrients in return for sugars from photosynthesis. The high frequency of the mycorrhizal symbiosis in plants could be explained by two non-mutually exclusive hypotheses. First, the symbiosis may be adaptive in many different plant lineages, leading to convergent evolution. Second, possessing the symbiosis may cause higher speciation and lower extinction rates, leading to higher net diversification in mycorrhizal relative to non-mycorrizal lineages over evolutionary time. To test these hypotheses, we reconstructed the evolution of the symbiosis using maximum likelihood based multiple state speciation and extinction models (MuSSE) applied to a ~3000 taxon mycorrhizal state database matched with a fossil calibrated molecular phylogeny. Results supported the first hypothesis but not the second hypothesis. Transition rates to the mycorrhizal symbiosis from the non-mycorrizal state were an order of magnitude more frequent than losses, and the mycorrhizal state was much more stable over time than the non-mycorrizal state. By contrast, net diversification rates were lower in mycorrhizal than non-mycorrizal plant lineages. The high frequency with which the mycorrhizal symbiosis evolves from non-mycorrizal ancestors suggests that there is strong selection to form the symbiosis in one or both partners.

# Birds of almost the same feather flock together: phenotypic clumping characterises the composition of mixed-species bird flocks, worldwide (52410)

Hari Sridhar, Umesh Srinivasan, Robert Askins, Julio Cesar Canales-Delgadillo, Chao-Chieh Chen, David Ewert, George Gale, Eben Goodale, Wendy Gram.

Centre for Ecological Sciences, Indian Institute of Science, Bangalore, India; National Centre for Biological Sciences, Bangalore, India; Department of Biology, Connecticut College, New London, Connecticut, USA; Department of Behavioral Biology, University of Osnabur"ck, Osnabur"ck, Germany; Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung; The Nature Conservancy, Lansing, Michigan, USA; School of Bioresources and Technology, King Mongkut's University of Technology, Bangkok, Thailand; Division of Biological Sciences, University of California, San Diego, California, USA; National Ecological Observatory Network, Boulder, Colorado, USA.
Our current understanding of animal sociality comes, mainly, from an intraspecific context. Heterospecific sociality, although widely prevalent, finds little mention in theories and discussion on group-living. This could be because heterospecific sociality is thought to be qualitatively different, i.e., while single-species groups are based on cooperation among ecologically-similar individuals, heterospecific association is believed to be for obtaining benefits from ecologically-dissimilar individuals. While this is certainly true for some of the most striking heterospecific associations known (e.g., grouper-moray eel; babbler-drongo), whether it is also true for larger multi-species groups is unclear.

Using a multi-continent dataset on mixed-species bird flock composition (55 presence-absence matrices, 2421 flocks), we find that flocks are, largely, groupings of ecologically-similar species. Null model-randomization approach, followed by meta-analysis, revealed that body-size similarity, foraging behaviour similarity and taxonomic relatedness in flocks is higher than expected at random, in most locations. These results suggest that benefits in multi-species groups might, in fact, be qualitatively similar to single-species groups, and highlight the need to think of sociality along a continuum from conspecifics to heterospecifics. We discuss conditions that might promote grouping with heterospecifics over conspecifics, especially in relation to competition and conspecific availability.

# The implications of Termitomyces domestication for gut microbiome function in fungus-growing termites (52663)

Michael Poulsen, Haofu Hu, Cai Li, Duur K. Aanen, Jacobus J. Boomsma, Guojie Zhang.

University of Copenhagen; BGI Shenzen; University of Copenhagen, BGI Shenzen; Wageningen University; University of Copenhagen; University of Copenhagen, BGI Shenzen.

Thirty MYA, the ancestors of the higher termite sub-family Macrotermitinae and the basidiomycete fungus Termitomyces joined forces in what was to become one of the most sophisticated plant biomass decomposition symbioses on Earth. The degree to which the innovation of fungiculture induced a functional shift in the gut microbiota has remained unclear. We used 16S rRNA 454 pyro-sequencing to portray the community composition of the core gut microbiota associated with the Macrotermitinae and Illumina sequencing to obtain metagenome insight into the functional gut community roles. Focusing on carbohydrate-active enzymes encoded by Termitomyces and gut microbes from the termite Macrotermes natalensis, we found that gut bacteria primarily contribute enzymes for final digestion after Termitomyces has degraded the most complex carbohydrates. We also pursued comparative analyses of fungal-cell-wall-degrading enzymes in gut bacteria associated with M. natalensis and Odontotermes yunnanensis. These gut communities share remarkably similar enzyme profiles and the bacteria producing these enzymes are generally over-represented in fungus-growing termites relative to termites that rely on cellulolytic gut microbes. The shift in gut metagenome function after Termitomyces domestication thus appears to have involved both complementary division of labour and targeted digestion of the novel food offered by Termitomyces.
# The bacterial network: Cooperative nutrient exchange via nanotubes (52763)

Samay Pande, **Shraddha Shitut**, Lisa Freund, Martin Westermann, Felix Bertels, Claudia Colesie, Ilka Bischofs, Christian Kost.

*Experimental Ecology and Evolution group, MPI for Chemical Ecology, Jena; The Evolutionary biology group, ETH Zurich; Centre for Electron Microscopy, Jena University Hospital, Friedrich Schiller University of Jena; Department of Plant Ecology and Systematics, University of Kaiserslautern; Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH); Center for Quantitative Analysis of Molecular and Cellular Biosystems (BioQuant), Heidelberg.*

Bacterial interactions frequently involve an exchange of essential metabolites. However, it remains unclear whether such cross-feeding relies exclusively on diffusion of metabolites through the cell-external environment, or if bacteria also utilize contact-dependent mechanisms to directly transfer metabolites between cells. To test this, we have synthetically generated interactions within and between Escherichia coli and Acinetobacter baylyi, in which both species reciprocally exchanged essential amino acids. Our results show that the two distantly related bacterial species can exchange cytoplasmic amino acids and protein by connecting to each other through membrane-derived nanotubes. The inter-cellular connections seem to be induced by the amino acid auxotrophy mutations introduced into the organism. The nutrient exchange was dependent on the nutritional status of the cell, thus indicating that the exchange may primarily serve to satisfy the metabolic requirements of nanotube-forming cells. Altogether, our findings show for the first time that bacteria can use direct cell-to-cell connections to exchange essential metabolites. The possibility that by connecting via nanotubes two or more bacterial cells can extend their biochemical repertoire without the need for genetic change, suggests that bacteria may function as multicellular, interconnected entities rather than as individual, physiologically autonomous units

# Negotiation and appeasement are more effective drivers of sociality than kin selection (52769)

**Andres Quiñones**, Ido Pen, Sander van Doorn, Franjo Weissing, Michael Taborsky.

*University of Groningen; University of Bern.*

Conflicts of interest are common in group-living organisms, since behaviour that maximizes an individual's reproductive success often compromises that of other group members. One way to prevent such conflicts from undermining sociality is to restrict group membership to genetically related individuals. Alternatively, unrelated individuals can prevent being exploited by utilizing a conditional strategy, enabling two pro-social partners to negotiate a mutually beneficial outcome by responding to each other's previous actions. How these two processes – kin selection and negotiation – interact in the evolution of sociality remains an open question. Here we show, using a mathematical model inspired by cooperatively breeding
fish with dominant breeders and subordinate helpers, that negotiation can be more effective
than kin selection at resolving social conflict and promoting high levels of help. When the two
processes act in concert, evolving populations can reach two alternative equilibria. In the first,
negotiation drives subordinates to appease dominants, resulting in high levels of help and low
levels of aggression. In the alternative equilibrium, which evolves by kin selection,
subordinates help their kin unconditionally. Our model demonstrates that negotiation and kin
selection do not necessarily interact synergistically and that kin structure can hamper rather
than facilitate the evolution of efficient cooperation.

Insights into the asymmetrical nature of nursery pollination mutualisms: the
Trollius-Chiastocheta interaction as a case study (52962)

Tomasz Suchan, Nadir Alvarez.

University of Lausanne, Dept. of Ecology and Evolution; University of Lausanne, Dept. of
Ecology and Evolution.

The nursery pollination interaction between the European globeflower Trollius europaeus and Chiastocheta flies is often cited as an example of a specific and obligate mutualism — the flies pollinate the plant and their larvae eat a fraction of developing seeds. We tested this hypothesis by examining seed set and traits related to offspring fitness in isolated Trollius populations, some in which Chiastocheta communities went extinct. We found that despite a significant drop in the seed set, the seeds produced in the absence of flies were larger and showed higher germination rate, a result compatible with the resource allocation hypothesis. Therefore, relative fitness in the populations without flies was similar to those with flies, a result of the tradeoff between the number of seeds produced and their germination rate. This outcome highlights the role of Chiastocheta flies as seed parasites, and the asymmetry of their interaction with Trollius — while the flies need the plant to reproduce, the opposite is not true.

Genital form and the evolution of reinforcement in Littorininae (51576)

Johan Hollander.

Lund University.

Speciation requires reproductive isolation and biologists have examined multiple different
processes of lineage splitting by which it could evolve. Within this range, reinforcement is
recognised as having a special position as the only process in which natural selection directly
favours an increase in reproductive isolation. Similarly, a role for genital form influencing
copulatory and post-copulatory components of reproductive isolation has long been suspected
because, among animals with internal fertilization, male genitalia demonstrate rapid divergent
evolution and species-specific forms. However, reinforcement and genital form have virtually
always been studied separately. In order to increase our understanding of how genital form
may influence the evolution of reinforcement, I will present a comparative analysis (on an
unusually large and complete phylogeny of the marine gastropod subfamily Littorininae 147
species, 97% complete) which show a strong signal of greater genital divergence in sister-
species pairs with overlapping ranges than in those with allopatric ranges, providing a prima
facie case for widespread reinforcement, suggesting that diversification and genital evolution
are intimately linked. These results are combined with a detailed experiment, between a
specific Littorininae sister-species pair from Australia, confirming reinforcement in mating
behaviour.

Poster session A - MAX 412

Edaphic adaptation in Arabidopsis: a genomic perspective on the calcicole-calcifuge problem (51582)

Alessia Guggisberg, Xuanyu Liu, Léonie Suter, Alex Widmer.

Institute of Integrative Biology, ETH Zürich, Universitätstrasse 16, CH-8092 Zürich.

It remains unclear what type of factors drives edaphic adaptation in plant communities
occupying either calcareous or siliceous bedrocks, advocating for comparative genomic
studies on calcicole-calcifuge vicariants, i.e. sister taxa that grow on either calcareous or
siliceous substrates. We study the genetic basis of edaphic adaptation in two diploid species of
Arabidopsis (A. lyrata and A. arenosa, Brassicaceae) that grow on both soil types, using
whole-genome re-sequencing data obtained from both individual and pooled DNA libraries.
We have identified hundreds of loci that carry a clear signature of divergent selection. These
loci are enriched for genes involved in ion transport, and do sometimes overlap with soil-
specific tandem duplications. Yet, balancing selection may also contribute to the maintenance
of adaptive genetic variation in mixed habitats. Overall, our results suggest that chemical soil
composition constitutes the main cause of ecological differentiation in these species, and that
A. lyrata and A. arenosa underwent parallel edaphic evolution at the biochemical, genic and
sometimes even SNP level.

Poster session A - MAX 412

Genetics of Jaw Divergence in a Trophically Polymorphic Cichlid Fish (51587)

C. Darrin Hulsey, Francisco J. García De León, Kate Bell, Chris NIce.

University of Konstanz ; Centro de Investigaciones Biológicas del Noroeste (CIBNOR); Texas State; Texas State.

Trophically polymorphic species could represent lineages that are rapidly diverging along an
ecological axis or could phenotypically mark the collapse of species through introgressive
hybridization. We investigated patterns of introgression between the trophically polymorphic
cichlid fish Herichthys minckleyi and its relative H. cyanoguttatus using a combination of population genomics and species tree analyses. Using rad-tag sequencing, we also investigated whether hybridization could explain the variation in the jaws of this phenotypically variable cichlid.

## Meiotic drive and inter-population incompatibilites (51680)

**Rudi Verspoor**, Tom Price, Gregory Hurst.

*University of Liverpool.*

Intragenomic conflict is a major contender for driving speciation. X chromosomes that enhance their transmission by killing Y-bearing sperm are particularly likely to drive differentiation. As males carrying X chromosome drive produce few or no sons, the costs are very high for the rest of the genome, potentially causing the evolution of genes that suppress the sperm killing mechanism. This counter-adaptation could create cycles of rapid co-evolution between the driving X and the suppressors. This population specific evolution could create interpopulation differences in reproduction genes, and generate hybrid incompatibilities. However, meiotic drivers themselves could also reduce differences between populations, because a driver that enters a naive population might spread rapidly through it (if the naive population carries no suppressors), potentially homogenising the two populations, at least for the driving chromosome. So does meiotic drive homogenise populations, or create barriers to hybridisation?

We investigate this using an X-chromosome meiotic driver in Drosophila subobscura. We show that suppression has evolved in the native population, but not in a nearby naive population. However, meiotic drive carrying males suffer severe fertility costs in crosses with the naive population, suggesting that in this system meiotic drive is causing hybrid incompatibilities and population differentiation.

## Adaptation and selection processes at the invasion front of a globally expanding vertebrate (51682)

**Irene Kalchhauser**, Jost Borcherding, Patricia Holm.

*University of Basel; University of Cologne.*

Ponto-Caspian gobies are invasive fish that have spread through much of Europe and North America during the last decades. Translocation over large distances is attributed to ship traffic.

Ponto-Caspian gobies present a wonderful case of an evolutionary field experiment. These fish are continually exposed to novel environments at the invasion front. Populations in
harbors, which are invasion hotspots, continually receive genetic input from various source populations. Importantly, Ponto-Caspian gobies perform remarkably well in diverse environments and display plasticity in morphology and life history traits.

As a starting point towards using Ponto-Caspian gobies as a model of evolution and adaptation, we analyzed the connectivity of the invasion edge of bighead goby populations in the Rhine.

We genotyped over 500 bighead goby from North-Rhine Westphalia (NRW) and two populations in Basel, Switzerland for 16 microsatellite loci. We find that the Basel harbor populations is genetically closer to the NRW population than to the Basel river population. Mitochondrial D-loop haplotypes, in contrast, reflect the geographic distribution. Ship movement patterns may explain the highly differentiated genetic structure of the Basel population. Tank ships from the Northern Rhine anchor close to the river population, while cargo ships from the Rhine-Main-Danube channel anchor close to the harbor population.

Poster session A - MAX 412

# Variability in the incidence of hybrid seed failure within and among wild tomato species (52074)

Morgane Roth, Thomas Städler.

Institute of Integrative Biology, ETH Zurich, Universitätstrasse 16, CH-8092 Zurich, Switzerland.

The tomato clade (Solanum section Lycopersicon) is emerging as a model system in evolutionary biology and speciation research. Wild tomato species diverged recently and are notable for their dissimilar levels of postzygotic isolation. After performing reciprocal cross-pollinations, we characterized postzygotic barriers within and between three self-incompatible taxa, namely S. peruvianum, S. chilense and S. arcanum var. marañón. Based on the proportions of viable and inviable (aborted) seeds and subsequent germination tests, we explored the overall strength and variability of postzygotic isolation. Reciprocal interspecific crosses involving S. peruvianum yielded almost no viable seeds whereas crosses between S. chilense and S. arcanum var. marañón produced an intermediate proportion of viable seeds. Moreover, and unlike the “strong” postzygotic barrier between S. peruvianum and the two other taxa, the proportion of viable seeds was frequently asymmetric in reciprocal hybrid crosses involving S. chilense and S. arcanum var. marañón. Intraspecific crossings have revealed a considerable proportion of inviable seeds in S. chilense, highlighting the possibility of rapid build-up of postzygotic isolation in this group. Our phenotypic data will be augmented by surveys of endosperm transcriptomes from developing seeds, as endosperm is the seed component that is most likely causally involved in hybrid seed failure.

Poster session A - MAX 412

# Genomics of speciation and species cohesion in the adaptive radiation of tillandsioids in Neotropical mountains (51754)
**de La Harpe Marylaure**, Paris Margot, Loiseau Oriane, Olivares Ingrid, Weigand Anna, Till Walter, Kessler Michael, Salamin Nicolas,��, ,--@

University of Fribourg; University of Lausanne; University of Zurich; University of Vienna.

The adaptive radiation of bromeliads is one of the most diverse and enigmatic of the
Neotropics. The Tillandsioideae subfamily represents a pertinent system for studying the
genomic and molecular footprints of divergent ecological selection during adaptive radiation.
Our main research aim is to unravel drivers and limits of diversification at different time
scales. Tillandsioid taxa were sampled along elevation gradients of various Central and South
American mountain regions. Common species (geographic replicates) and local endemics
were defined based on their natural distribution ranges and ecological preferences.
Geographic replicates were chosen preferentially to disentangle evolutionary mechanisms
responsible for speciation and species cohesion. A genomic approach, including RNA-
sequencing and restriction site Associated DNA sequencing (RAD-seq), will generate data for
both neutral and non-neutral genomic regions. It will be employed to characterize gene flow
and allelic diversity within and among populations and species occurring along elevation
gradients and across a range of geographic scales. Great emphasis will be given on analyses
of population divergence to circumscribe genetic mechanisms responsible for species
cohesion and persistence, including genomic scans for allelic diversity, differentiation, gene
flow within and between species. Current results and key points from this research will be
presented, including proof-of-concept data from RAD-seq, and available sampling designs.

Identifying the genetic basis of ecologically important traits in Nicotiana attenuata using advanced-inter crossing recombinant inbred lines (AI-RIL) (51775)

Xu Shuqing, Wenwu Zhou, Pia Backmann, Anke Kügler, Celia Diezel, Ian Baldwin.

Max Planck Institute for Chemical Ecology.

Identifying the genetic basis of ecologically important traits and estimating their fitness effects are essential for understanding how adaptation proceeds. We established the first advanced intercross-recombinant inbred lines (AI-RIL) in Nicotiana attenuata, a diploid annual tobacco plant, to investigate the genetic basis of leave and floral traits that are relevant to plant fitness. The two parental lines used to establish the AI-RILs varied in many different traits, such as concentration of phenolics, green leaf volatiles, floral display and volatiles, which are important for plant-herbivore and plant-pollinator interactions, thus allowing us to investigate how insect herbivore and pollinator-imposed selections drive phenotypic divergence in plants. The high density genetic markers for the established AI-RIL population were obtained using genotyping by sequencing. With the combined approaches of genetic mapping and reverse genetics, such as virus induced gene silencing, we aim to identify the causal genetic variations that are involved in plant-herbivore and plant-pollinator interactions. Furthermore, the quantitative fitness effects contributed by each trait and its underlying genetic architecture will be measured in the native environment of N. attenuata in the spring
of 2015. Our results will shed light on how plant-herbivore and plant-pollinator interactions
drive the evolution of phenotypic traits in plants.

From whole-genome scans for divergence to the discovery of speciation genes
in oaks (51801)

Thibault Leroy, Jean-Marc Aury, Catherine Bodénès, Laure Villate, Grégoire Le Provost, Jérôme Salse, Joëlle Amselem, Antoine Kremer, Christophe Plomion.

BioGeCo, INRA/Université de Bordeaux, FR; CEA, Genoscope, FR; GDEC, INRA Clermont-
Ferrand, FR; URGI, INRA Versailles, FR.

Understanding the nature, the number and the strength of barriers to gene flow is a major goal in speciation genomics. Yet, few speciation genes have been reported to date in plants. Considering the costs of NGS are still coming down, it becomes possible to identify such speciation genes at the pan-genomic level even for non-model species. This presentation will review our latest advances regarding this research topic within the European white oak complex.

We first established a reference genome for oak (1.5Gb/2C) organized into pseudo-
chromosomes and used a deep pool sequencing approach to characterize 4 sympatric and
interfertile species (Quercus petraea, Q. robur, Q. pyrenaica, Q. pubescens). Even if these
species exhibit different ecological requirements (e.g. soil pH or moisture), they are still
connected by substantial levels of 'interspecific' gene flow (FST < 0.2). As a consequence,
loci related to intrinsic selection against hybrids are expected to be revealed together with the
gene driving ecological divergence. A whole-genome scan for divergence was performed
using up to 250x genome coverage per species. Here, we report evidences for genomic islands
of differentiation and identified some candidate speciation genes for both endogenous and
exogenous barriers including some genes involved in flowering or drought tolerance.

Coupling genomics with experiments to study divergence-with-gene-flow in
trees (51820)

Luisa Bresadola, Kai N. Stoelting, Céline Caseys, Dorothea Lindtke, Christian lexer.

University of Fribourg; University of British Columbia; University of Sheffield.

Rapid recent progress in ecological and evolutionary genomics is imparting fresh perspectives to the study of speciation. A particularly active field of research at the current time is the study of “divergence-with-gene-flow”, that is, divergence that involves episodes of sym- or parapatry and thus genetic contact during some stage of the process, before reproductive isolation is complete. In this project, we address key questions regarding the ecological and evolutionary genomics of “divergence-with-gene-flow” in Populus alba and P. tremula, two
widespread Eurasian tree species related to Populus trichocarpa, the first completely
sequenced forest tree. In particular, defined key questions and hypotheses concerning the
following topics are addressed: (1) roles of early vs. late-acting reproductive barriers in the
maintenance of species boundaries, (2) genomic architecture and selective value of species
differences maintained in the face of gene flow, (3) role of genetic incompatibilities as early
postmating barriers in species isolation. We address these topics with the help of high-
throughput "genotyping-by-sequencing" approaches in natural and experimental populations,
and by coupling genomics with evolutionary ecology experiments. The results are expected to
advance our understanding of the origin and maintenance of reproductive barriers in
hybridizing tree species representing keystone or foundation species in terrestrial habitats.

Differential gene expression according to race and host plant in the pea aphid
(51835)

**Isobel Eyres**, Julie Jaquiy, Akiko Sugio, Ludovic Duvaux, Karim Gharbi, Jean-Christophe Simon, Carole Smadja, Roger Butlin, Julia Ferrari.

University of Sheffield; INRA Rennes; University of Edinburgh; University of Montpellier; University of York.

The pea aphid, Acyrthosiphon pisum, provides a powerful system for examining the genetics of host-plant adaptation and speciation, as it comprises multiple host-associated races which form a continuum of genetic divergence. Because pea aphids live and reproduce year-round on their chosen host plant, host acceptance differences between races are responsible for multiple components of reproductive isolation, and understanding the genetics of the aphid-host interaction is likely to go a long way towards understanding speciation in this system.

By conducting comparative gene expression studies, it is possible to identify biological
functions involved in the adaptation of organisms to their surrounding environments. An
ecological understanding of the plant-aphid interaction gives us hypotheses to test by
molecular genetic methods. Using aphid clones collected from six host races in England, we
examine gene expression both on their collection host and on a 'universal' host using an
RNA-seq approach. This enables the identification of genes involved in direct host-plant
response as well as genes that differ between aphid races. Recent studies have indicated a role
for chemosensory genes in the process of host-race formation, so in addition to analysing
overall patterns of expression, we specifically examine the involvement of salivary protein
and chemosensory genes.

Comparative and evolutionary studies of lysosomal glycosidases in the
liver/hepatopancreas of different aquatic organisms. (51916)

Elizaveta Vdovichenko, Rimma Vysotskaya.
Lysosomal glycosidases are enzymes involved in the metabolism of carbohydrates and glycoconjugates performing a variety of functions in organisms: energy, structural, biological recognition et al. Their role in adaptive responses of aquatic organisms are still under study. So, the aim of the present study was to investigate and compare the activity of 3 lysosomal glycosidases in the liver/hepatopancreas of blue mussels and fish species - pike, white-fish, roach, perch. The activity of β-glucosidase and β-galactosidase was several times higher in the hepatopancreas of mussels in comparison with fish liver. The activity of β-glucuronidase was significantly lower. The main strategy of adaptation for bivalves to get isolated from the environment is to close shell valves and minimize the metabolism. The transition to anaerobic energy supply and regulation of metabolic reconstructions require a high glucosidase and galactosidase activity. Fishes use other mechanisms of biochemical adaptation and β-glucuronidase plays a more important role in their metabolism.

The research was carried out using the facilities of the Equipment Sharing Centre of the Institute of Biology, KarRC of RAS and supported by Grant of the Russian Federation President "Leading scientific school of Russia" 1410.2014.4;COOPENOR: "Combined effects of Petroleum and the Environment in bivalves from the Norwegian-Russian Arctic".

# The Effects of Pollination and Range Shifts on the Diversification of the Tribe Antirrhineae (51933)

Ezgi Ogutcen, Jolan Theriault, Daniel B. King, Jana C. Vamosi.

Range shifts are considered an important precursor to evolutionary divergence because they place populations in different environments that favour different characters. Long-distance dispersal promotes an expansion in niche breadth in terms of pollination syndromes in angiosperms, potentially explaining a wide variety of pollination syndromes. Antirrhineae, a tribe under Plantaginaceae, is a useful group for studying the interplay between dispersal and pollination in macroevolution because it has members in the Old World and the New World, and exhibits numerous transitions in major pollinating groups.

By integrating predictive modeling and range reconstructions with phylogenetic analysis, We aim to: i) reconstruct where major range shifts have occurred within Antirrhineae; ii) determine whether range overlap increases or decreases with time since divergence within the tribe; and iii) examine whether shifts in geographic distribution and pollination syndromes are associated with differences in speciation rates in Antirrhineae.

We find that distribution or pollination alone does not affect speciation rates, but the interaction of these two characters have a significant effect on speciation rates in Antirrhineae. Our age-range correlation analysis also suggest that sympatric speciation is predominant in the tribe, with a trend towards young nodes having more range overlap than older nodes in the phylogeny.
# A colourful genomic landscape: patterns of gene flow in an Australian colour polymorphic finch (51935)

Peri Bolton, Adam Cadelini, Lee Rollins, James Brazill-Boast, Sarah Pryke, Sarah Legge, Kimberley Maute, Simon Griffith.

Macquarie University; Deakin University; Deakin University; Macquarie University; Australian National University; Australian Wildlife Conservancy; University of Wollongong.

Colour polymorphic species are good models for investigating genetic mechanisms of sympatric speciation. Colour can facilitate pre-zygotic isolation through habitat specialisation and sexual signalling, and colour is often correlated with behavioural and physiological traits. The Australian endemic Gouldian finch (Erythrura gouldiae) has a simple sex-linked head-colour polymorphism. Previous work has identified the region responsible for head-colour on the avian Z-chromosome. Head-colour is associated with different strategies, and captive birds have been demonstrated to exhibit strong pre- and post-zygotic isolation between morphs. However, microsatellite markers indicate that there is extensive gene-flow between head-colour morphs in the wild, so how are these different morph strategies maintained? Using Genotyping-by-Sequencing, we use a genome-wide approach to clarify population structure across the range and between morphs. We discuss our results in the context of the biogeographic origin of the head-colour polymorphism, and models of speciation with gene flow.

# Selection on floral volatiles in sister species of Alpine orchids (Gymnadenia) (52009)

Kelsey JRP Byers, Roman T Kellenberger, Philipp M Schlüter.

Institute of Systematic Botany, University of Zürich.

Pollinator-mediated reproductive isolation is a major factor in driving the diversification of flowering plants. Studies of floral traits involved in reproductive isolation have focused nearly exclusively on visual signals, such as flower color. The role of less obvious signals, such as floral scent, has been studied in detail only recently. The genetics of floral volatiles involved in mediating reproductive isolation remains largely unknown, particularly in systems with more generalist pollinators. The sister species Gymnadenia densiflora and G. rhellicani (Orchidaceae) demonstrate minimal post-zygotic reproductive isolation, and their stable coexistence in sympatry appears to be largely due to floral isolation. Multiple floral traits are divergent in this system, including color, inflorescence size and shape, nectar spur length, and floral scent. Both species emit a complex blend of volatiles, with limited overlap. Previous work has shown multiple floral volatiles found in these species to be important in pollinator neural response and behavior. Genes responsible for three of these volatiles are known, but their evolutionary history remains unclear. I will discuss these volatiles, covering three main areas: species differences in coding and expression in their biosynthetic genes, molecular
signatures of selection on volatiles, and the interplay between selection on these volatiles and population structure.

# Evolutionary consequences of the hybridization on the genetic architecture in two close species of Silene (Caryophyllaceae) (52093)

**Fernanda Baena-Diaz**, Niklaus Zemp, Alex Widmer.

ETH Zürich; ETH Zürich; ETH Zürich.

Understanding the consequences of hybridization and introgression in plants is very important because these processes can alter the evolutionary trajectories of the involved species, by increasing extinction rates, but also by promoting the origin of new linages and adaptive evolution through introgression. When two species hybridize, new combinations of traits from the parental species are formed, however, this new combination of traits will depend on the genetic architecture of the parental species, thus affecting the evolutionary outcome of the hybrids. The goal of this project is to determine the genetic architecture of the species differences between Silene latifolia and S. dioica by mapping morphological traits on F2 hybrids between these species, with special interest in the role of sex chromosomes. We build a male and female genetic linkage map on F2 hybrids between these two species based on SNP's obtained by rad sequencing and measure 13 traits to obtain QTL's. The markers mapped to 12 linkage groups corresponding to the haploid chromosome number of these species. The QTL analysis reveals that traits related to reproductive isolation are clustered in sex chromosomes, thus reducing recombination of these traits and probably maintaining species differences even when introgression occur in natural populations.

# Metabolic adaptations to decomposition of plant biomass in fungus-growing termite symbionts (52129)

**Rafael da Costa**, Michael Poulsen.

University of Copenhagen.

Fungus-growing termites along with Termitomyces fungi and gut bacteria play significant roles in the turnover of organic matter through plant biomass decomposition in the Old-World. The termites predigest plant material before inoculation into the fungus comb, where Termitomyces decomposes the main plant components. After the fungus comb has passed a second gut passage, the plant substrate is almost perfectly degraded, supporting that Termitomyces and gut microbes play complementary roles in plant decomposition. However, because different fungus-growing termites species collect different plant substrates, it is conceivable that co-evolutionary adaptations have occurred over the course of the 30 MYA tripartite association. To investigate this, we are undertaking comparison of the metabolic
capacities of fungal and bacterial symbionts using growth assays, enzyme assays, polysaccharide content analysis of fungus combs, and fungal and bacterial transcriptomics. The use of combinatorial approaches will allow identification of whether different Termitomyces lineages and associated gut bacteria are adapted to decompose specific plant substrates. This will allow for a more thorough understanding of evolutionary adaptations and specificity of symbionts associated with fungus-growing termite species, and more broadly shed light on the understanding of complementary roles played by diverse symbionts in complex mutualisms.

## Alternative splicing in candidate genes involved in diapause and cold acclimation in northern Drosophila montana (53718)

**Maaria Kankare**, Ville Hoikkala, Kalevi Trontti.

*University of Jyvaskyla.*

Alternative splicing (AS) structural variation in the messenger RNA and is known to entail adaptive potential of the organisms. However, splice variation is widely unexplored in many important phenomenon connected to adaptation. Several insect species inhabiting high latitudes have evolved different ways to survive the harsh winter conditions with long lasting subzero temperatures. Here we investigate AS under diapause and cold acclimation in a northern malt fly species, Drosophila montana. This species is adapted to seasonally varying environments at high latitudes, is relatively cold tolerant and shows robust photoperiodic reproductive diapause. First, we compiled RNA-sequence data to a denovo assembly using Trinity and analyzed differential expression of the contigs from diapausing and cold acclimated females. The 29 M reads used in the assembly were curated for high quality and confirmed to be species specific in order to avoid producing false variation and any non-species contigs. Finally, to identify candidate genes the list of differentially expressed (DE) genes was parsed for contigs having AS variation. Our current results indicate several genes with AS isoforms that are DE under investigated processes. The genes were annotated e.g. to metabolic and structural genes as well as to genes with a putative immune function.

## The evolution and development of petal spots in the Angiosperms (52211)

**Gregory Mellers**, Allan Ellis, Beverley Glover.

*University of Cambridge; University of Stellenbosch.*

Angiosperms are the most diverse division of extant land plants, occurring in almost every environment on Earth. A key element in the formation of such a speciose group is their intimate co-evolution with pollinator species. Typically such pollination syndromes are gross features such as corolla colouration or floral scent. However, it is becoming increasingly
apparent that finer scale features may also attract pollinator species. One such characteristic is the appearance of petal spots on the corolla which have previously been shown to increase reproductive success.

Our work investigates how petal spots develop in the species Gorteria diffusa. Previous work has found there to be multiple “morphotypes” of the species which represent natural mutations fixed within discrete populations. These allow for comparative analyses to be undertaken with the intention of elucidating the molecular regulation of spot generation. Some evidence suggests a role for MYB genes in the formation process hence comparative expression analyses and heterologous expression studies are being undertaken. Furthermore, restriction-site associated DNA (RAD) sequencing is being used to acquire high SNP coverage in an attempt to understand the relationship between these morphotypes. It is hoped that through these techniques a hypothetical model for spot formation may be found and subsequently perturbed for validation.

Poster session A - MAX 412

# Genetics of Cold Aclimation in Drosophila montana (52250)

**Felipe Vigoder**, Darren Parker, Nicola Cook, Maaria Kankare, Michael Ritchie.

UFRJ; University of St-Andrews; University of Jyväskylä.

The ability to cold acclimate has important implication to organisms fitness because it allows individuals to remain active for longer when the temperature starts to drop over winter and also allows them recover faster from a cold shock. In insect, despite many physiological studies on the subject little is known about the genetic basis of this phenotype. Recently, transcriptome analyses in Drosophila virilis and Drosophila montana suggested the involvement of 3 candidate genes involved in cold acclimation; santa-maria (stm), period (per) and Inos. We aim to test the actual role of these 3 genes candidates genes on cold acclimation in D. montana using a RNAi approach. D. montana has a circumpolar distribution being adapted to live within a large seasonal temperature variation. Our preliminary results confirm the involvement of both STM and Inos but not per on cold acclimation in D. montana. To our knowledge this is the first time any candidate gene from a transcriptome analysis is confirmed as being involved in a phenotype. Further details will be discussed at the presentation.

Poster session A - MAX 412

# Whole transcriptome analysis on three Cuban Anolis lizard species adapting to different thermal microhabitats (52254)

**Hiroshi D Akashi**, Antonio Cádiz Díaz, Shuji Shigenobu, Takashi Makino, Masakado Kawata.

Tohoku University; Havana University; National Institute for Basic Biology.
Environmental temperature is a primary factor limiting performance and survival of ectotherms. The physiological mechanisms and its underlying molecular basis with which ectotherms respond to environmental temperature have received considerable recent interest in light of man made climate warming. In Cuba, three Anolis lizards, A. sagrei, A. homolechis and A. allogus, coexist in the same forest but occupy different thermal niches. Here, we performed RNA-seq to examine the transcriptional responses among these three species to different thermal environments. We exposed the animals for 5 days to 26 °C and 33 °C prior to transcriptional analysis. The experimental temperatures were chosen as they reflect the selected body temperatures of A. allogus and A. sagrei in the field, respectively. We found that out of approximately 15,000 transcripts obtained for each species, 75 % were expressed under both temperatures in all species. Most interestingly, transcripts with temperature-dependent differential expressions within species were not shared across species, except for a single gene (CYP2J2). Our study indicates that the molecular basis underlying thermal physiology may be strikingly diverse among closely related species with different thermal preferences. We discuss more about other differentially expressed genes detected to show the evolution of thermal physiology.

Poster session A - MAX 412

**Specialization to the host plant in Lepidoptera pests: pattern and process**
**(52259)**

**Marion Orsucci**, Réjane Streiff, Emmanuelle d'Alençon, Philippe Audiot, Syvie Gimenez, Nicolas Nègre.

UM2,INRA-DGIMI,INRA-CBGP; INRA-CBGP; UM2,INRA-DGIMI; INRA-CBGP; UM2,INRA-DGIMI; UM2.

Specialization to host plant can be a driver of the high diversification of phytophagous insects. Indeed, in this process, host shifts can lead to the evolution of new specialist races or species. In this context, we study variants of moth species that are genetically differentiated and specialized to different hosts, as shown by their larval performances and preference for oviposition sites. These differently specialized moth variants live in sympatry, which makes them pertinent candidates to study ecological speciation by host plant specialization. We first determined the pattern of specialization of the different variants with a reciprocal transplant experiment on larvae. In this experiment, we measured various life history traits (survival, weight, developmental time) in response to native and alternative host plants. Then, we conducted an RNA-seq analysis to study the molecular processes involved in the larval performance. We collected RNA pools of larval tissues sampled from different experimental modalities (moth strains/host plants). Differential gene expression between modalities is then interpreted in light of the phenotypic variations we measured. This combined approach aims to identify the gene families and biological functions putatively involved in host specialization of moth larvae.

Poster session A - MAX 412
## Post-mating pre-zygotic barriers and Haldane's rule (52298)

Joanna Bundus, Asher Cutter.

*University of Toronto.*

Haldane's rule is one of the most general observations in speciation research, but the influence of post-mating pre-zygotic barriers on Haldane's rule has been relatively underappreciated. For gametic barriers to affect Haldane's rule, gametes bearing different sex chromosomes must differ in fertilization success in interspecific crosses. Outbreeding Caenorhabditis briggsae initially produce hermaphrodite offspring (XX), with more male offspring (X0) produced later, due to a competitive advantage of X-bearing sperm over nullo-X sperm. Crosses between C. briggsae and its sister species C. nigoni exhibit Haldane's rule, producing more females than males. These crosses also stop producing offspring soon after mating, because sperm are rapidly lost from the reproductive tract. We hypothesized that the combination of an X-bearing sperm competitive advantage and rapid sperm loss contributes to Haldane's rule, because many nullo-X sperm are lost before fertilizing any eggs. We compared the sex ratio of hybrids laid on the first day after mating to those laid on the second day after mating. Consistent with our hypothesis, the proportion of hybrid males was lower among early progeny than late progeny, indicating that X-bearing sperm have a fertilization advantage in the interspecific cross, contributing to Haldane's rule.

Poster session A - MAX 412

## Feeling the pressure: extremophilic adaptation of hsp90 and hsp70 heat-shock proteins in deep-sea amphipod species (52300)

Heather Ritchie, Alan Jamieson, Stuart Piertney.

*Zoology, University of Aberdeen; Oceanlab, University of Aberdeen.*

The enormous hydrostatic pressure ranges (60-110 MPa) of the oceanic hadal zone (>6000 m depth) pose great challenges to hadal organisms, affecting growth, viability and distribution. Nevertheless, the hadal zone hosts extremely taxonomically diverse floral and faunal communities, highlighting a capacity for local evolutionary adaptation.

One key mechanism facilitating extremophilic adaptation may be the evolution of heat-shock proteins (HSPs). These are molecular chaperones that assist protein folding, regulation and degradation in response to various environmental stressors such as fluctuations in hydrostatic pressure. Examining the patterns of inter- and intra-specific variation of HSPs can elucidate a species' ability to inhabit extreme environments, such as the hadal zone.

Here we examine the role of HSP evolution in ubiquitous Lysianassoidea amphipod species, whose distributions exceed a kilometre in depth equating to pressure changes exceeding 10 MPa. A total of 28 species across seven Pacific trenches and four Atlantic sites, representing pelagic, abyssal and hadal depths, were characterised at hsp70 and hsp90 genes. Genetic patterns among and within species are combined with environmental data (i.e. hydrostatic
pressure, temperature etc) using phylogenetic and seascape genomics approaches to infer the extent to which HSP evolution is driven by adaptation to the extreme deep sea environment.

# Bacterial microbiota associated with Cottus (Pisces) across a secondary contact zone (52363)

**Sunna Ellendt**, Arne W. Nolte.

*Max Planck Institute for Evolutionary Biology.*

Natural hybrid zones often emerge at habitat clines where distinct populations meet, mate and hybridize. The possible factors that govern the dynamics of a hybrid zone are insufficiently explored. For example symbiotic bacteria can induce selection pressure by influencing the host's immune system, nutrition, development and behavior. These interactions are in turn influenced by environmental factors. We use a contact zone where Cottus rhenanus and invasive Cottus hybridize at a habitat ecotone to study the association of symbiotic microbiota, habitat and host genotype to infer whether host-bacterial interaction may act as evolutionary force. We extracted genomic DNA from fin samples of wild caught fish and assessed bacteria through pyrosequencing of 16S rRNA markers. The host genetic makeup was inferred based on 80 nuclear SNP markers that permit to classify all fish into parental forms and recent hybrids. Phylogenetic and statistical analyses revealed significant differences in bacterial diversity and abundance in the distinct habitats whereas we did not detect any differences between distinct host genotypes. However, the analysis of hybrids suggests, that the microbial community is altered from both parents which possibly decreases the fitness of hybrids.

# Developmental plasticity of a key evolutionary trait in East African cichlids – insights in evolutionary mechanisms that shaped these cichlids’ adaptive radiations (52480)

**Ralf F. Schneider**, Helen M. Gunter, Immanuel Karner, Christian Sturmbauer, Axel Meyer.

*University of Konstanz; University of Edinburgh; University of Graz.*

The ‘modern haplochromine’ cichlid fishes are a famous example of repeated rapid adaptive radiations - one in each of the three East African Great Lakes. Astatoreochromis alluaudi is a riverine species that is basal to these adaptive radiations, putatively resembling the common ancestor of this group. A mechanically-stimulating diet induces pronounced plasticity in A. alluaudi’s pharyngeal jaw apparatus, a structure considered to be a key evolutionary trait in cichlids. We compared the morphological and transcriptional effects of experimentally induced plasticity in this trait in A. alluaudi, to three representatives of the adaptive radiations and one out-group. Our results indicate that the adaptive plasticity is most pronounced in non-
radiating species, followed by the recently radiating species and is lowest in the oldest
adaptive radiation. Next, we investigated the expression of plasticity-related genes for species
that showed a plastic response. Through comparing co-expression between species, we
observed that similar sets of functionally related genes were co-expressed in both basal and
more derived species, suggesting conserved transcriptional ‘modules’. We conclude that the
ancestral cichlid lineage was probably phenotypically plastic and that module-like
transcriptional alterations in developmental trajectories putatively shaped the parallel
evolution of highly diverse trophic phenotypes among these adaptively radiating cichlid
lineages.

Poster session A - MAX 412

Genomic analyses of two differentially migrating bird subspecies (52553)

Max Lundberg, Susanne Åkesson, Staffan Bensch.

*Department of Biology, Lund University.*

Migration requires adaptations in behavioural, morphological and physiological traits. These
traits have been shown to have a strong genetic basis, but very little is known about the
underlying genes. Here we use whole-genome resequencing and a customized snp array to
detect genetic differences between two differentially migrating subspecies of the willow
warbler Phylloscopus trochilus. We find that the genomes are extremely similar, with
differences clustered in three divergent chromosome regions that potentially represent
inversion polymorphisms. One of the regions does not contain alleles that are strictly
associated with each of the subspecies, but instead appears to be associated with adaptation to
high altitude and latitude. The other two chromosome regions contain alleles specific to either
subspecies and may contain differences related to the different migratory phenotypes of the
subspecies.

Poster session A - MAX 412

Comparative population genomics in three species of Chorthippus
grasshoppers (52560)

Emma Berdan, Camila Mazzoni, **Frieder Mayer**.

*Museum für Naturkunde Berlin; Berlin Center for Genomics in Biodiversity Research.*

Emerging genomic tools can reveal the genetics of speciation in non-model groups with no
previous genetic resources. Grasshoppers of the Chorthippus biguttulus species group differ
strongly in calling song (and corresponding female preferences) but are almost identical
morphologically, suggesting that sexual selection has been the main force driving premating
hybridization barriers in this group. Here we performed a population genomic scan by
sequencing individuals' transcriptomes to search for outlier loci. We sequenced 20 individuals
of each of the three Chorthippus biguttulus, C. mollis, and C. brunneus. We called SNPs for
all three possible species pairings and used FST based approaches to identify outliers. We
found approximately 1% of SNPs in each comparison to be outliers. Between 37 and 40
percent of these outliers were non-synonymous SNPs (as opposed to a global level of 17%)
indicating that we recovered loci under selection. Among the outliers were several genes
involved in song production and hearing as well as a plethora of genes involved in other traits
such as metabolism. This indicates that ecological processes besides sexual selection on
acoustic signals contributed to the divergence of these three species.

The role of visual adaptation in cichlid fish speciation (52571)

D. Shane Wright, Ole Seehausen, Ton G.G. Groothuis, Martine E. Maan.

University of Groningen; University of Bern, EAWAG.

In less than 15,000 years, Lake Victoria cichlid fishes have radiated into as many as 500 different species. Ecological and sexual selection are thought to contribute to this ongoing speciation process, but genetic differentiation remains low. However, recent work in visual pigment genes, opsins, has shown more diversity.

Unlike neighboring Lakes Malawi and Tanganyika, Lake Victoria is highly turbid, resulting in a long wavelength shift in the light spectrum with increasing depth, providing an environmental gradient for exploring divergent coevolution in sensory systems and colour signals via sensory drive.

Pundamilia pundamila and Pundamilia nyererei are two sympatric species found at rocky islands across southern portions of Lake Victoria, differing in male colouration and the depth they reside. Previous work has shown species differentiation in colour discrimination, corresponding to divergent female preferences for conspecific male colouration. A mechanistic link between colour vision and preference would provide a rapid route to reproductive isolation between divergently adapting populations. This link is tested by experimental manipulation of colour vision - raising both species and their hybrids under light conditions mimicking shallow and deep habitats. We quantify the expression of retinal opsins and test behaviours important for speciation: mate choice, habitat preference, and foraging performance.

Genomic heterogeneity of species diversification in an avian superspecies
complex (52731)

Jelmer Poelstra, Christen Bossu, Nagarjun Vijay, Matthias Weissensteiner, Jochen Wolf.

Uppsala University.

As species diverge, accumulating genetic changes tend to be clustered in few regions of the
genome. Yet, our understanding of the underlying evolutionary forces generating
heterogeneous landscapes of genome diversification remains limited. There is a need to disentangle the relative importance of processes such as local differences in recombination rates, gene flow, and positive selection. One way forward is to compare patterns of genome differentiation along the speciation continuum, that is across several levels of overall genomic divergence and gene flow. Here, we re-sequenced 128 genomes of crows from a superspecies complex with striking parallel divergence in plumage colouration, sampling across two independent hybrid zones between all black carrion and black-and-grey hooded crows, as well as from the black-and-white collared crow. While several differentiation peaks were strongly correlated with overall divergence levels, others were unique to specific population comparisons or in accordance with plumage features. We conclude that while most genomic differentiation was best explained as a result of processes independent of speciation, several genomic regions harbour evidence for divergent selection partly in relation to phenotypic divergence.

**Association between genotype and plumage pigmentation in the Tytonidae: candidate gene approach (52744)**

Vera Uva, Luca Fumagalli, Alexandre Roulin.

University of Lausanne.

The evolution and maintenance of phenotypic variation is a central question in evolutionary biology, and the diversity of plumage colouration in birds has long attracted the interest of scientists. Colour patterns play a relevant role in speciation and adaptation, and the Melanocortin System is known to be involved in the control of melanin pigment synthesis, and to pleiotropically regulate a number of physiological and behavioural traits in vertebrates. It comprises the POMC gene, encoding the MSH and ACTH peptides, the melanocortin receptors (MC1-5Rs and antagonists, agouti proteins (ASIP and AGRP)). Barn owls (Tyto alba) vary continuously across continental gradients in ventral plumage colouration from white to dark-reddish, and number and size of black spots located on feather tips. A key MC1R non-synonymous substitution was found in Europe, where the I allele individuals are redder, and homozygous VV individuals are whiter. In the POMC gene, serine repeats were found, which can potentially be associated with pigmentation patterns. Due to their cosmopolitan distribution and striking variation in colouration across continental gradients, the Tytonidae family provides a unique opportunity for a worldwide study on the evolution and maintenance of melanin-based pigmentation, using a candidate gene approach focusing for now on the MC1R and POMC genes.

**Gain and loss of GDF6 expression and the evolution of skeletal traits (52798)**

Vahan Indjeian, Felicity Jones, David Kingsley.
Dramatic skeletal changes have evolved within most vertebrate groups. High-resolution mapping experiments with natural populations of sticklebacks identify two distinct, but very closely linked loci that regulate different aspects of armour plate size. The Growth/differentiation factor 6 (GDF6), a secreted bone morphogenetic protein, is the only gene in both intervals. Freshwater fish with reduced armour plates show elevated levels of GDF6 expression and transgenic overexpression of GDF6 in large-plated marine fish results in smaller or missing plates. Gdf6 null mice have skeletal phenotypes, and in humans there is a unique loss of conserved non-coding element in the GDF6 gene. The chimpanzee allele of the enhancer missing in humans drives expression in the hindlimbs but not forelimbs, in anatomic domains that have been specifically modified during the human transition to bipedalism. These results suggest that both upregulation and downregulation of GDF6 contribute to natural variation in skeletal morphology in fish and primates.

## Ecological adaptation of a desert-specialist, on the edge of life (52824)

Nina Serén, José C. Brito, Phillip C. Watts, Rui Faria, Tapio Mappes, Zbyszek Boratyński.

CIBIO/InBIO, Research Center in Biodiversity and Genetic Resources, University of Porto;
Institute of Integrative Biology, Biosciences Building, Crown Street, University of Liverpool;
Department of Biology, University of Oulu; IBE, Institute of Evolutionary Biology (UPF-CSIC), Universitat Pompeu Fabra; Dep. Biological and Environmental Science, University of Jyväskylä.

How climate change impacts biodiversity is one of the hottest topics in evolutionary biology. Among different mechanisms that species hold to resist severe environmental changes, the microevolutionary response is particularly challenging, as adaptation can occur at a slower pace than current climate changes.

One way to circumvent this limitation is to learn from past events where species currently experiencing extremely arid conditions had to cope with environmental changes. We have chosen the Lesser Egyptian Jerboa (Jaculus jaculus) to study the genetic mechanisms of adaptation to divergent habitats in the Sahara desert, region exposed to extreme environmental conditions which experienced profound climatic oscillations. Two previously described jerboas ecotypes that differ in fur colour are being analysed for genomic regions involved in adaptation to different habitats. Preliminary results from digital photo RGB code and spectrophotometer light reflectance measurements (phenotypic characterization), and from sequencing mitochondrial and candidate nuclear genes of a mix of museum and contemporary samples, will be presented. Ongoing genomic analyses will permit to identify the genomic regions and genetic mechanisms underlying adaptation.
# Effects of genetic divergence between two *Arabidopsis lyrata* populations on germination traits (52833)

Tuomas Hämälä, Päivi H. Leinonen, Outi Savolainen.

*University of Oulu, Finland; Duke University, Durham, NC, USA.*

Timing of seed germination, one of the most important life-history traits in plants, is known to be significantly differentiated between plant populations. However, the genetic basis of germination differences and their potential roles in postzygotic isolation has not been well studied. We investigated the consequences of genetic divergence on germination traits between two highly diverged Arabidopsis lyrata populations from Karelia, Russia and North-Carolina, USA. Comparisons of germination percentages between reciprocal F1 and F2 hybrids and their parents showed evidence of Bateson-Dobzhansky-Muller type incompatibilities, as hybrids germinated worse than both parental populations and F2 seeds worse than F1 seeds. Additionally, reproductive isolation showed asymmetry in the first hybrid generation but not in the second, suggesting a more complex background than simple cytonuclear interactions. By using genetic mapping based on a RAD sequencing modification we hope to clarify the genetic architecture of seed dormancy differences. Are they dominated by few large effect QTLs or by several small ones? And do we find a signal of DOG1 – a locus found to be major effector of seed dormancy in Arabidopsis thaliana.

Poster session A - MAX 412

# Evolution of antifreeze glycoprotein (AFGP) in Antarctic icefish (notothenioids) (52849)

Marisa Zubler.

*Zoological Institute, University of Basel.*

Notothenioidei, Antarctic icefish, are a marine species flock that underwent adaptive radiation thanks to the evolution of antifreeze glycoprotein in an ancestral lineage. This protein enables icefish to survive in the ice-cold, thermally isolated and therefore island-like environment of the Antarctic Ocean. Existing phylogenies based on various nuclear and mitochondrial genes show that notothenioids have evolved from a common ancestor. It would be of importance to sequence notothenioid AFGP since this gene is thought to be a evolutionary key innovation. AFGP gene has so far only fully been sequenced in one species (Dissostichus mawsoni) since obtaining sequence data is being complicated by highly repetitive sequences and multiple copy variants. Regardless, it would be interesting to shed light on whether or not a phylogeny based on AFGP mirrors existing phylogenies. Furthermore, we will include sequences from a notothenioid species in which AFGP gene seems to have lost its function due to relaxed selection pressure in warmer regions.

To approach this we have amplified AFGP gene of 20 notothenioid species using a High-Fidelity DNA Polymerase and will subsequently use next-generation sequencing to obtain results.

We expect that the phylogeny based on AFGP will be in accordance with existing phylogenies.
# Intraspecific diversity and incipient speciation in a planktonic unicellular eukaryote (52857)

**Mickael Le Gac**, Christophe Destombe, Laure Guillou, Raffaele Siano, Myriam Valero, Annie Chapelle.

*Ifremer; UPMC Sorbonne Universités; CNRS; Ifremer; CNRS; Ifremer.*

Adaptation, ecological divergence and ultimately speciation are processes that are especially hard to understand when considering phytoplanktonic species. Such organisms are non sessile, their dispersion and distribution almost entirely depend on hydrodynamism, and very often, they live in a highly dispersive and unstable environment. In such system, at what point adaptation may drive evolution and the kind of selective pressure involved remain virtually unknown. Empirically speaking, studying adaptation and speciation in the pelagic environment is complicated by the dynamic nature of the environment, by the microscopic nature of the organims, and by the absence of closely related model organisms. In the present study, we investigated intraspecific diversity as well as incipient speciation in the toxic bloom forming dinoflagellate Alexandrium minutum using two approaches: 1. performing growth assays under various in vitro conditions using 18 strains isolated from several blooms and 2. analyzing the mRNA sequences (RNAseq) of the same strains. We focused on both the phenotypic and genetic patterns of divergence as well as on the functional implications of this divergence.

# Speciation, introgression and molecular evolution in the carnivorous pitcher plant Nepenthes (52876)

**Mathias Scharmann**, Alex Widmer.

*ETH Zürich.*

The spatial coexistence of species with realised gene flow implies strong selection against certain admixed genotypes, since parental lineages would otherwise have merged. These scenarios hold the promise of being able to distinguish those genetic and phenotypic traits that were and are relevant in (selection-based) speciation processes from mere neutral divergence. On the other hand, novel genotypes created by gene flow might be adaptive, and thus promote divergence. We study these questions in the carnivorous pitcher plant Nepenthes. The dioecious genus has radiated across the Malay Archipelago (150+ species); their modified leaves catch and digest insects, canopy litter, or even mammal faeces with a variety of mechanisms and mutualistic interactions. In sympatric communities of up to seven species in Borneo and Singapore, we detect recent hybrids and older signatures of introgression using RAD-seq. Introgression is increased in habitats with human disturbance, indicating that species barriers have an ecological component in Nepenthes. Consequently, we compare the
molecular evolution of genes with a function in plant carnivory (shotgun proteomics and RNA-seq) across species pairings with contrasting trapping mechanisms and ages. We hypothesise that carnivory genes should be outliers against the transcriptome background, if this trait is disproportionally contributing to speciation and divergence.

# Anthropogenic pressure and introgression in malaria vectors (52880)

**Chris Clarkson.**

*Liverpool School of Tropical Medicine.*

Though common in plants, introgression between animal species is rarely reported. However, in malaria vector mosquitoes it may actually be a common occurrence. The intense selective pressure that vector control insecticide regimes impose upon the insects, in concert with high levels of sympatry and the fact that even quite distantly related species naturally hybridise (e.g. Anopheles gambiae x An. Coluzzii separated by ~1.85 Ma), allows regions of the genome with advantageous insecticide resistance properties to introgress. Using whole genome sequence data from An. gambiae, coluzzii and arabiensis we investigate regions of the genome that have been transferred through introgression and show that this is an important mechanism in the evolution of these insects.

# Function and evolutionary consequences of Diplostigmaty (52897)

**Jonathan Kissling.**

*University of Neuchâtel.*

Differentiation of female sexual organs in flowering plants is rare, and contrasts with the wide range of male reproductive strategies. An unusual example involves diplostigmaty, the possession of spatially and temporally distinct stigmas in insect-pollinated species of the Cape of South Africa. Here, the single pistil within a flower has an apical stigma, as in most flowering plants, but also a secondary stigma that occurs mid-way down the style. Floral manipulations and measurements of fertility and mating patterns of Sebaea aurea provide evidence that this system serves as a mechanism of reproductive assurance in population with low plant density. Furthermore, diplostigmaty is evolutionarily stable and associated with higher diversification rates than related monostigmatic lineages, suggesting long-term ecological advantages to this flexible mixed mating strategy resulting from the possession of dimorphic stigma function.
# Divergent selection and reduced dispersal drive phenotypic diversification at a very small spatial scale in an island bird (52954)

**Borja Milá**, Yann Bourgeois, Joris Bertrand, Josselin Cornuault, Boris Delahaie, Christophe Thébaud.

*National Museum of Natural Sciences, Madrid, Spain; University of Basel, Switzerland;*
*National Taiwan University, Taiwan; University of Toulouse, France.*

The Reunion grey white-eye, Zosterops borbonicus, a passerine bird endemic to Reunion Island in the Mascarene archipelago, represents an extreme case of microgeographical plumage colour variation in birds, with four distinct colour forms occupying different parts of this small island (2512km2). To understand whether natural selection could explain such variability, we compared patterns of variation in morphological and plumage colour traits within and among populations, and found that variation among the different forms was greater than would be expected if genetic drift alone was responsible for phenotypic divergence. Analyses of structure and gene flow using microsatellite and RADseq data also revealed very low levels of historical and contemporary gene flow among populations. Genome-wide divergence and the existence of narrow contact zones across narrow geographic barriers suggest the evolution of incipient reproductive isolation among parapatric forms. We conclude that divergent natural selection and reduced dispersal appears to be the dominant mechanisms explaining phenotypic divergence in morphological and plumage colour traits at an exceptionnally small spatial scale in Z. borbonicus.

Poster session A - MAX 413

# Differentiation in the tomato red spider mite: a novel method to study the genetics of hybrid lethality by genotyping viable and inviable hybrids (52281)

**Bram Knegt**, Tomos Potter, Martijn Egas.

*University of Amsterdam.*

When hybrids have reduced fitness, they typically suffer from sterility or lethality. Studying hybrid lethality is notoriously hard, because individuals with lethal genotypes do not develop and thus cannot be sampled. Therefore, most studies in hybridization genetics have traditionally focused on sterility rather than lethality, and when lethality was considered, lethal genotypes could only indirectly be inferred from their absence in viable individuals. However, using molecular tools it is in principle possible to genotype inviable individuals. Here, we present a model system demonstrating this novel method of studying the genetics of hybrid lethality.

The spider mite Tetranychus evansi (Acari: Tetranychidae) is a haplodiploid herbivore for which two genetically distinct types have been described. Gene flow between these types occurs, but in the F2 generation only ~5% of the eggs hatch, demonstrating strong hybrid incompatibility. We collected genetic material from both hatched individuals and unhatched eggs, and could thus genotype viable and inviable hybrids using 8 microsatellite markers fixed for different alleles in the two types. We found that recombination between these
markers frequently leads to inviability, providing direct evidence for Bateson-Dobzhansky-Muller incompatibilities. Our methodology opens up new possibilities for studying the genomics of speciation.

# Cryptic species, ecomorphs and GFP/GFP-like profiles in the cnidarian Anemonia viridis (52290)

**Cédric Mallien**, Caroline Olivier, Thamilla Zamoum, Didier Forcioli, Paola Furla.

UMR 7138 EPS UPMC CNRS.

Cryptic species have recently been identified in many cnidarians despite a lack of morphological variation. Only the use of molecular markers allowed the detection of these taxonomic entities.

Contrastingly, 5 clearly different morphs have been described in the sea anemone Anemonia viridis, based on the expression profiles of GFP-like proteins. However, no clear genetic differences had been

found so far among these morphs, even if they were thought to display different reproductive strategies (clonal vs. sexual reproduction).

In this study, we tested if these morphs belong to the same species or to independent gene pools, using a set of 10 genes whose expression patterns are modified by environmental factors. For each of these genes, an EPIC marker has been developed (by comparison with published cnidarian genomes)

and will be sequenced on individuals of the three most common morphs from population of the Mediterranean Sea and English Channel.

Our sampling scheme will allow us to test whether the geographic origin or the GFP morph is the structuring factor for the genetic diversity in *A. viridis*. Moreover, putative adaptive genes, a priori more

divergent than neutral markers, should be more efficient to detect independent gene pools within a species.

# Genome-wide divergence among population pairs of parasitic and non-parasitic lampreys (52413)
**Quentin Rougemont**, Sophie Launey, Arnaud Gaigher, Gilles Lassalle, Jerome Goudet, Guillaume Evanno.

INRA; INRA; UNIL; INRA; UNIL; INRA.

The mechanisms underlying speciation with gene flow remain largely unknown and encompass those related to models of sympatric speciation and secondary contact. Lampreys are ancient vertebrates that often exist as pairs of closely related species with distinct life histories representing putative cases of speciation with gene flow. In Europe, such a pair is represented by Lampetra fluviatilis that is parasitic and anadromous and Lampetra planeri that is non-parasitic and resident in freshwater. Using microsatellite markers we previously showed various levels of gene flow between ten population pairs suggesting different levels of reproductive isolation along the speciation continuum. Here we used a RAD sequencing approach of sympatric, parapatric and allopatric population pairs together with diffusion-approximation analyses incorporating heterogeneous effective migration among loci to i) understand the patterns of genome-wide divergence at different stages along the speciation continuum ii) identify loci putatively involved in the adaptive divergence of the two forms and iii) reconstruct the most probable demographic scenario of divergence between these lampreys. Results will allow investigating the respective effects of neutral processes and divergent selection on the genomic basis of speciation with gene flow.

Poster session A - MAX 413

# Mosaic hybridization in two species of the Jaera albifrons complex (52535)

**Ambre Ribardière**, Thomas Broquet.

*Station Biologique de Roscoff, France.*

Mosaic hybrid zones allow us to compare the action of isolating mechanisms in mixed populations with and without hybridization. Here we test whether such a mosaic hybridization scenario happens with two marine isopods from the Jaera albifrons complex. Morphological descriptions suggested that hybridization exceptionally happens in some populations (Solignac, 1978).

To test this hypothesis, we described the distribution of genetic variance between species Jaera albifrons and Jaera praehirsuta using nuclear and mitochondrial markers in several sites where hybridization is or isn't suspected (in Normandy and Brittany, respectively). In Normandy, the nuclear genome appeared much more homogeneous, pointing to a reduction of isolating barriers (environmental, behavioral, and genetic) in this region. Yet the two parental species morphs are largely conserved, suggesting that the permeability to interspecific gene flow might be variable across the genome. This hypothesis is further supported by our observation of an outlier microsatellite marker showing a stronger level of differentiation in this population where hybridization occurs compared to other populations where the two species do not hybridize. These populations thus provide an interesting situation for a comparative analysis of the genomic architecture of reproductive isolation, currently under way using genomic analyzes.
# Speciation genomics in European columbines (Aquilegia) (52562)

**Gokce Akoz**, Magnus Nordborg.

*Vienna Graduate School of Population Genetics & Gregor Mendel Institute of Molecular Plant Biology; Gregor Mendel Institute of Molecular Plant Biology.*

The formation of new species has been a major challenge in evolutionary biology. This is partly because of the fact that by the time "species" are recognized, many isolating barriers have accumulated and it has become impossible to identify the initial barrier(s) leading to divergence between populations. The columbine genus Aquilegia (Ranunculaceae) could be an important model to reveal genomic scale changes that result from speciation since several findings imply a recent and rapid radiation event in this group. To get a glimpse of the patterns of genetic variation in the poorly studied European taxa, we initially whole-genome sequenced seven individuals of A. vulgaris, which as the most widespread species of the genus is found from southern Scandinavia throughout Europe, and one individual of A. pyrenaica native to the Pyrenees. Principal Component Analysis on genotypes indicate that A. pyrenaica is separated from all A. vulgaris individuals, and also that A. vulgaris individuals are separated by geography, following a pattern of Isolation by Distance. We aim to sequence a few other Aquilegia species to extend our understanding of genetic variation, which will, in turn, be decisive for further sampling required to delve more deeply into within population dynamics.

# The fragmented distribution of the Apollo butterflies in Sierra Nevada (Spain): How isolated are they? (52606)

**Oscar Mira**, Juan G. Martínez, Alberto Tinaut, Cristina Sánchez-Prieto, Deborah A. Dawson, Terry Burke.

*Universidad de Granada; University of Sheffield.*

Small and isolated populations have high inbreeding levels that may endanger their long-term survival. The Apollo butterfly (Parnassius apollo) is represented by small and local populations. In Spain, the mountain ranges isolate different subspecies: P. apollo nevadensis inhabits the Sierra Nevada mountain range between 1,950 and 2,700 metres.
18 microsatellite markers specifically developed were used to genotype 400 individuals to estimate inbreeding coefficients, other population statistics and gene flow among populations. The results show limited but significant genetic structure (Fst = 0.01; p = 0.0001) and that the genetic distances among locations are partially explained by geographical distance (R2 = 0.216; p < 0.0001). Although the discontinuous nature of the habitat, Bayesian clustering methods (Structure, BAPS, TESS) group all locations into one panmictic population; however, Geneland was able to identify four different populations. Estimated gene flow (BayesAss) was low in most cases, but sufficient to maintain the observed connectivity among locations.
This indicates that no locations are genetically isolated, but the fact that there is genetic structure suggests the operation of metapopulation dynamics. Gene flow appears to be weaker between the more distant locations, but also between locations separated by natural obstacles (mountain peaks and valleys) and human-induced barriers, such as roads or the skiing station.

## The Footprint of Adaptive Introgression After Secondary Contact (52621)

**Derek Setter**, Joachim Hermisson, Jeffrey Jensen.

*University of Vienna; Ecole Polytechnique Federale de Lausanne.*

The sources of genetic variation and their relative contributions to adaptation is a central topic in the study of evolution, and mounting evidence points to an important role for genetic variation introduced through interspecific gene flow. Introgressive adaptive alleles must overcome the barriers to gene flow generated by locally maladapted alleles and genetic incompatibilities. Using a multi-locus Moran model, we study the influence of such deleterious variants on the process of adaptive introgression. Strongly deleterious alleles may greatly reduce the probability of adaptation from introgressive variation, and this effect increases with tighter linkage. Weakly deleterious alleles reduce the introgression probability only when tightly linked. In this case, they may alter the fixation process of the adaptive allele to generate a genomic signature of selection that is unique to introgressive adaptive variation. We calculate the expected change in the frequency of neutral alleles linked to an introgressive adaptive allele and compare this to adaptive alleles that either appear as new mutations or exist as standing genetic variation. Under a range of biologically-relevant scenarios, adaptive introgression generates patterns in polymorphism data that are distinguishable from those of de-novo mutations and standing genetic variation.

## Genomic evolution at the tip of the cichlid phylogenetic bush (52666)

**Hugo Gante**, Martin Malmstrøm, Michael Matschiner, Emiliano Trucchi, Sissel Jentoft, Walter Salzburger.

*University of Basel; University of Oslo; University of Vienna.*

Recent efforts in genome sequencing revealed major patterns of genome evolution in a phylogenetic backbone of African cichlids from different lakes and rivers. We use de novo genome sequencing of additional Neolamprologus species with divergent phenotypes to gain insight into processes acting as new species diverge. In these analyses, focused on the tip of the phylogenetic bush, we look at the landscape of genome divergence and patterns of incomplete lineage sorting to gain an understanding of genomic features and mechanisms underlying phenotypic divergence. We complement this search of divergence islands with
genome scans using RADtags. Overall we find relatively few regions involved in adaptive
divergence between species.

# Population Genomics of Two Teleogryllus Cricket Species that Provide a Rare Exception to Haldane's Rule (52820)

Peter Moran, Mike Ritchie, Nathan Bailey.

*University of St Andrews.*

Determining the mechanisms and processes underlying the development and maintenance of reproductive barriers is important for understanding speciation and species coexistence. In this talk I report on a broad scale transect of phenotypic and population genomic data, combined with results from lab hybridization experiments on Teleogryllus commodus and T.oceanicus. These two closely related field cricket species are a classic study system for sexual selection and speciation. Both species overlap across an extensive area and hybrids are easily produced in the laboratory. However, chemical and acoustic signals appear to act as strong premating barriers to gene flow. Here I describe RAD-seq results that test patterns of genomic divergence within and between species and how this relates to variation in acoustic and chemical signals. Additionally lab hybridization experiments reveal that these species provide a remarkably rare exception to Haldane's rule, as both reciprocal F1 hybrid females are sterile, while males are fertile. X linked incompatibilities may contribute disproportionally to reproductive isolation. Integration of these findings with population genomic analysis of sex linked markers raises new insights into the role of sex chromosomes in maintaining species boundaries.

# Is selection on habitat gradients correlated with phenotypic and genomic differentiation in cichlid fish populations? (52827)

Jacco C. van Rijssel, Florian N. Moser, Catherine E. Wagner, Ole Seehausen.

*Fish Ecology and Evolution, EAWAG, Kastanienbaum, Switzerland; Institute of Ecology and Evolution, University of Bern, Bern, Switzerland.*

Textbook examples of adaptive radiation in lakes provide insight into how the origin of species is facilitated. Disruptive selection between habitats and differential resource utilization are thought to play important roles in speciation. However in the majority of cases, speciation does not occur despite the existence of suitable selective environments. The absence of speciation might be due to populations 1) not encountering rugged adaptive landscapes 2) failing to respond to disruptive selection or 3) adapting through mechanisms that do not require speciation. To test these alternatives, we compared individual fitness proxies and genome-wide signatures of selection between sympatric cichlid populations
coexisting along environmental gradients. We chose paired populations, in each case contrasting species which show clear morphological divergence or incipient speciation along environmental gradients to species lacking morphological divergence. Using growth rate as a fitness proxy, we inferred fitness landscapes for phenotypic traits and multivariate phenotypes in these populations. We then used genome-wide SNP data to examine patterns of genomic divergence along environmental gradients. By using morphological, genomic and fitness proxy data, we seek to link selection to morphology and to genomic patterns of divergence, and thus provide a unique window onto the basis of genomic divergence during cichlid speciation.

## An insight into Lacertid speciation through the comparative genomics of *L. viridis* and *L. bilineata* (52879)

**Rohit Kolora**, Anne Weigert, Christoph Bleidorn, Peter Stadler, Klaus Henle, Rui Faria, Katja Nowick, Martin Schlegel.

German Center for Integrative Biodiversity Research - iDiv; Molecular Evolution and Animal Systematics, Institute of Biology, University of Leipzig; Institut für Informatik, Universität Leipzig; IZBI/Bioinformatik, Universität Leipzig; Department of Conservation Biology, Helmholtz Centre for Environmental Research - UFZ; CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBio, Universidade do Porto; IBE, Institute of Evolutionary Biology (UPF-CSIC), Universitat Pompeu Fabra, PRBB.

Suppressed recombination models (SRM) suggest that chromosomal rearrangements (CRs), which act as barriers to gene flow, can play an important role in speciation by potentially leading to the accumulation of genetic incompatibilities between parental species that will often manifest in their hybrids in terms of misexpression, inviability and/or loss of the reproductive function. Another important feature of CRs, is that they can directly contribute to gene expression differences between species by disrupting genes or by altering the gene regulatory regions. To test the role of CRs in speciation, we are studying the genomes and transcriptomes of two closely-related species – Lacerta viridis and *L. bilineata* that are widely distributed in Europe and are able to form hybrids. We sequenced the genomes of both species using Illumina with libraries of different insert sizes, which allowed us to produce a high-quality contig assembly. We compared the genome assemblies against each other and identified CRs through changes in synteny. We also investigated the relationship between genomic and gene expression changes in our species based on gene annotations and regulatory regions. Finally, we are characterizing genome-wide divergence between these Lacertid species to identify signatures of selection.

## The genomic landscape of speciation in a classic “Great Speciator”: the *Myzomela* honeyeaters (52896)
**Jason M. Sardell**, J. Albert C. Uy.

*University of Miami.*

Islands systems have played prominent roles in our understanding of the origins of biodiversity, but few studies of speciation genomics have examined divergence within island radiations. In this study, we examine genomic divergence within one of Mayr & Diamond's classic examples of “great speciators”, the Myzomela honeyeaters of the Indo-Pacific. Specifically, populations of M. tristrami and M. cardinalis on Makira in the Solomon Islands represent a rare example of recent secondary contact between island species, with sympatry dating to the turn of the 20th-century. These species fill similar ecological niches, but differ significantly in plumage, a presumed sexual signal. Previously, we determined that hybridization is ongoing between these taxa, but asymmetric, with all successful hybridization events involving the matriline of the colonizing species, M. cardinalis. Furthermore, sequencing of 6 nuclear introns suggests that alleles associated with melanism in M. tristrami are introgressing into the genomic background of M. cardinalis, which possesses red carotenoid-based plumage. We used RAD-seq to generate genome-wide data sets for 72 individuals from this complex, representing allopatric and sympatric populations of each species as well as phenotypic intermediates. The resulting insights into the genomic landscape of speciation in this system will be discussed in this presentation.

Poster session A - MAX 413

**Is massive introgression limited to the mitogenome? Lessons from whole-genome sequencing in hares. (52907)**

**Fernando Seixas**, Liliana Farelo, Paulo Célio Alves, Pierre Boursot, José Melo-Ferreira.

CIBIO-INBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto; Université Montpellier 2, CNRS UMR 5554, Institut des Sciences de l'Evolution, Montpellier, France; Wildlife Biology Program, College of Forestry and Conservation, University of Montana, Missoula, USA; Departamento Biologia, Faculdade de Ciências da Universidade do Porto, Porto, Portugal.

Introgressive gene flow after speciation is commonly observed and sometimes massive. The evolutionary causes and consequences of this spectacular phenomenon are yet poorly understood but can be valuably addressed by exploring its genome-wide patterns, in relation to variations of structural, functional and transmission characteristics across the genome. The mitogenome of a boreal species, Lepus timidus, thrives massively in northern populations of three hare species occurring in Iberia. Massive introgression also occurred species-wide in one case at an X-linked locus, in contrast with the general pattern of limited nuclear gene flow inferred using 20 random other nuclear loci. Such patterns of introgression may result from demographic processes (allele surfing) during species replacements accompanying deglaciation but may have also been driven by selective processes. By analyzing whole-genome sequencing data we will detect genomic regions massively introgressed from L. timidus into two species in Iberia, L. europaeus and L. granatensis. Particular attention will be given to co-introgression of nuclear-encoded mitochondrial genes which may uncover adaptive mito-nuclear co-introgression and/or co-evolution. Comparisons across genomic
regions with various characteristics and functions should allow us to balance the relative roles
of historical contingencies and selective processes (adaptive or not) in determining patterns of
reticulation and massive introgression.

# Iberian Pied flycatchers: differentiation history and local adaptation (52937)

Vera Warmuth, **Hans Ellegren**.

*Evolutionary Biology Center.*

The pied flycatcher (Ficedula hypoleuca) is part of a relatively young (1.5-2 my) species complex that also includes the collared flycatcher (F. albicollis), the Atlas flycatcher (F. speculigera) and the semicollared flycatcher (F. semitorquata). Ficedula flycatchers have emerged as an important study system for speciation research; however, most studies to date have focused on comparisons between pied and collared flycatchers, a taxonomic pair that has evolved strong reproductive barriers and may therefore be considered at one extreme of the speciation continuum. The processes driving or maintaining differences between populations in the latter stages of speciation are not necessarily the same as those in the early stages. Here we present the results of model-based studies of demography and selection in pied flycatchers. Previous work has shown that pied flycatchers from the Iberian Peninsula are significantly differentiated from all other pied flycatcher populations at both neutral and adaptive loci. This makes them an ideal system to study the evolutionary processes driving differentiation at this early stage of divergence. Knowledge of the processes shaping the genetic variation within pied flycatchers will further our understanding of its divergence from other flycatcher species.

# Identification of hybrid male-sterility genes in sibling species of Drosophila
(52971)

**Marjorie Liénard**, Luciana Araripe, Dan Hartl.

*Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA; Institute of Biology, Department of Genetics, University of Rio de Janeiro, Brazil.*

Hybrid male sterility (HMS) is a common postzygotic reproductive barrier caused by intrinsic incompatibilities between genes that have undergone functional divergence in isolated subpopulations. To understand how genomic incompatibilities relate to postzygotic isolation as well as the molecular nature and epistatic effects of genes driving HMS, we have studied two recently diverged fruitfly species, the cosmopolitan Drosophila simulans and the island-endemic D. mauritiana, for which interspecific matings conform to the Haldane's rule in producing sterile F1 hybrid males. To complement introgression genetic mapping, we
analyzed fertility in transgenic organisms to identify the genetic factors responsible for male sterility in a small 20-kb autosomal region in chromosome 3R denoted region HMS1.
Whereas hybrid SimB fruitfly males homozygous for D. mauritiana at HMS1 are typically sterile, we find that, on average, 58% males in all agt-sim-transformed and 45% males in all TAF1-sim-transformed hybrid lines have fertility in the normal range. Our results emphasize the highly polygenic nature of postzygotic reproductive isolation. The findings also indicate that the evolutionary basis of HMS1 likely results from the passive accumulation of functional divergence in the agtmau and TAF1mau alleles leading to negative epistatic incompatibilities affecting male sterility in the hybrid background.

## Past episodes of local gene flow in F1 dominated hybrid zones (51827)

Camille Christe, Kai Stölting, Daniel Wegmann, Luisa Bresadola, Christian Lerer.

University of Fribourg, Unit of Ecology & Evolution, CH-1700 Fribourg; University of Fribourg, Unit of Biochemistry, CH-1700 Fribourg.

Hybrid zones are frequently used as tools for understanding the genomics of adaptation, reproductive isolation, and speciation, but very little information is available about patterns of local ancestry along hybrid chromosomes. Our study focuses on two ecologically divergent species of poplar and aspen (Populus alba and P. tremula) known to hybridize in Eurasia. We use Restriction site Associated DNA (RAD) sequencing and a Hidden Markov approach to study the history of recombination in three large natural 'mosaic' hybrid zones at the genome level.

Patterns of local ancestry along hybrid chromosomes indicate that the studied hybrid zones are composed primarily of first generation hybrids (F1) and few backcrosses. The paucity of recombinant hybrids among adult trees from P. alba x P. tremula hybrid zones and their increased juvenile mortality in a common garden trial point to strong post-zygotic barriers acting during early life stages. Despite strong selection against recombinants, genome scans between the parental species indicate candidate regions for introgression pointing to more ancient episodes of gene flow. Our study raises questions regarding the mechanisms that allow the occasional breakdown of very strong reproductive barriers, resulting in the genetic exchange of defined genome regions between genomically cohesive species.

## Secondary contact, reproductive barriers, and introgression: habitat alterations influencing the evolutionary history of two subterranean rodent species (Rodentia: Ctenomyidae) (51841)

Carla Martins Lopes, Simone Souza Freitas Ximenes, Thales Renato Ochotorena de Freitas.

Universidade Estadual Paulista "Júlio de Mesquita Filho"; Universidade Federal do Rio Grande do Sul.
Hybridization events provide insights into central questions in evolutionary biology regarding mechanisms of reproductive isolation and speciation. We investigated in the present study how extrinsic (e.g., geographical barriers, human impacts) and intrinsic (e.g., chromosomal polymorphisms, reproductive barriers, dispersal ability) factors can influence the evolutionary history of two highly karyotype-polymorphic sister species of burrowing rodents (Ctenomys minutus and Ctenomys lami) from the southern Brazilian coastal plain, which have a narrow contact zone resulted from habitat alterations. We analyzed mitochondrial DNA sequences and 14 microsatellite loci, together with cytogenetic data, for both species and hybrids sampled over their entire distributional ranges. Results suggest that C. minutus and C. lami were not sufficiently isolated in time and space, resulting in a pattern of incomplete lineage sorting. A pattern of cyto-nuclear genome discordance was observed in the hybrid zone as consequence of pre- and/or post-zygotic isolation mechanisms, combined with sex-biased dispersal, and differential inheritance of cytoplasmic and nuclear genomes. A substantial clinal introgression of microsatellite alleles of C. lami into C. minutus was observed near to the region of contact. Although C. minutus and C. lami are incipient species, conservation efforts should focus mainly on preserving the integrity of pure populations of each species.

# New insights into European white oaks evolution of reproductive isolation from heterogeneous divergence levels across genomic regions. (51844)

Pauline GARNIER-GERE, Pierre ABADIE, Tiange Lang.

INRA, UMR 1202 Biodiversity Genes & Communities, France; INRA, UMR 1202 Biodiversity Genes & Communities, France; CAS, Xishuangbanna Tropical Botanical Garden, China.

In the European white oaks Quercus robur and Q. petraea, research spanning more than 20 years has focused on estimating hybridization rates and their significance in terms of introgression dynamics, despite acknowledged ecological divergence among species. These studies have led to a paradigm of “weak” reproductive barriers compatible with low molecular divergence at anonymous and low coverage markers, recent publications emphasizing “high rates of interspecific gene flow” or “recurrent” or “ongoing gene flow” between those two species. However, older results and very recent quantitative estimates of the strength and genotypic variation of post-mating reproductive barriers suggest a different story and the existence of significant intrinsic incompatibilities. Using a population genomics approach based on more than 500 gene regions, a few thousands haplotype blocks and ~10000 SNPs, we argue that previous observations are compatible with strong reproductive barriers, and that these barriers probably involve various mechanisms determined by a large number of genes. We then test and compare possible scenarios of divergence among species using coalescent-based and Approximate Bayesian Computation methods and show how they bring new insights into the European white oak species evolutionary history and maintenance of reproductive barriers across their range, despite hybridization events.
# Anthropogenic secondary-contact of cryptic penguin species (51926)

**Stefanie Grosser**, Christopher P. Burridge, Amanda J. Peucker, Nicolas J. Rawlence, R. Paul Scofield, Ian Smith, Jonathan M. Waters.

*Department of Zoology, University of Otago; School of Biological Sciences, University of Tasmania; School of Life and Environmental Sciences, Deakin University; Canterbury Museum; Department of Anthropology and Archaeology, University of Otago.*

The use of genetic and genomic tools has facilitated the discovery of new species that were previously indistinguishable using traditional approaches due to morphological similarities. These cryptic species complexes have even been found within some conspicuous and well-studied vertebrate taxa and it has been suggested that many well-known and widespread species could harbour substantial unrecognised species diversity. Here we present genetic evidence for two cryptic, reproductively isolated species within the world's smallest penguin. We used mitochondrial, microsatellite and intron markers to reveal two highly divergent Eudyptula lineages, one Australian and one New Zealand lineage, which co-occur in southern New Zealand, with minimal hybridisation. This finding exemplifies that even within an iconic group such as penguins the full level of species diversity remains to be uncovered. Coalescent modelling indicates that the Australian lineage likely expanded into southern New Zealand within recent centuries, supporting the hypothesis of an anthropogenic extinction-replacement event. We use ancient DNA analysis and carbon dating of fossil and archaeological Eudyptula remains to further assess this hypothesis.

# Mitochondrial and nuclear discordance in a widespread passerine: genomic signatures of natural selection and local adaptation (51927)

**Hernán Morales**, Alexandra Pavlova, Leo Joseph, Richard Major, Paul Sunnucks.

*Monash University; Australian National Wildlife Collection, CSIRO; Australian Museum.*

Directional selection imposed by environmental variation can reduce intraspecific gene flow and promote population divergence. This is especially true if selection acts on traits with large fitness effect, for example metabolic pathways. The Eastern Yellow Robin (Eopsaltria australis) has eastern and western mitochondrial haplogroups (6.6% on ND2) distributed across most of the species' extensive range in eastern Australia; nuclear genetic structure is minimal and perpendicular relative to mtDNA. Interestingly, mitochondrial groups are strongly correlated with maximum temperatures of the warmest month, even after accounting for spatial location. This mitonuclear discordance cannot be explained by selectively neutral mechanisms (e.g. incomplete lineage sorting, sex-biased asymmetries, secondary contact). Instead, it is inferred to be the result of natural selection mainly in females affecting either mitochondrial genes, W-chromosome genes, autosomal genes, or interactions among these. As a first step to test whether the observed mitonuclear discordance is the result of local adaptation, we comprehensively assessed the species' genetic variation using complete mitochondrial genomes and genome-wide reduced-representation scans. We identified outlier
# Genome Wide Association Studies on a sexually selected trait in two closely related passerines (52090)

**Eryn McFarlane**, Anna Qvarnström.

*Uppsala University.*

Sexually selected traits are expected to be polygenic and to evolve quickly, possibly because of high additive genetic variance. Here, we compare the genetics of two Ficedula flycatcher species that have been diverged for approximately one million years and that express the same sexually selected display trait, a white forehead patch. Pied flycatchers (PF) have a wider distribution but a smaller effective population size than collared flycatchers (CF), which may lead to local adaption and/or released selection on this trait due to bottlenecking. Using a 50K SNPchip and a wild, sympatric population, we find similar genomic heritabilities between both species, and 6 suggestive SNPs for pied patch size, while collared patch size appears more polygenic. While the effect sizes we have estimated are certainly inflated, I discuss simulations used to address these concerns. Genetic variation in condition may be more strongly coupled to patch expression in collared flycatchers, making it harder to find suggestive SNPs in CF. Future research will investigate whether there is evidence for local adaption of these SNPs associated with patch size in different European populations of PF and whether selection has acted on these SNPs since the recent secondary contact of CF and PF in Sweden.

# Using genome-wide data to study the demographic history of two parapatric field cricket species: Approximate Bayesian Computation and analysis of the allele frequency spectrum (52100)

**Thomas Blankers**, Emma Berdan, Frieder Mayer.

*Humboldt University Berlin; Museum für Naturkunde Berlin, Leibniz Institute for Evolution and Biodiversity Science.*

Development in sequencing technologies and bioinformatics has enabled demographic inferences in non-model organisms using genome-wide data. Field crickets are an interesting system for these inferences, because many species diverged in close geographic proximity and little intrinsic isolation has developed between the species. The Texas field cricket (G. texensis) and its daughter species, the southeastern field cricket (Gryllus rubens), co-occur in most of their ranges. The species are mainly separated by behavioral isolation via the calling song (males) and song preference (females). Here, we tested for interspecific genomic
differentiation and investigated the demographic history. Twenty individuals of each species
were collected from two populations and we used RNA-Seq to identify polymorphisms in the
transcriptome. We uncovered high genetic divergence between species with over 10% of
40,254 polymorphic SNPs fixed and found no intraspecific population substructure. Using
approximate Bayesian computation and analysis of the allele frequency spectrum, we tested
different demographic models against the data. Population expansion for G. rubens and gene
flow between G. rubens and G. texensis were included in the best supported model in both
approaches. Despite evidence for recent divergence with gene flow and sparse phenotypic
diversification, the species are strongly genetically differentiated with many fixed SNPs.

Poster session A - MAX 413

Genomic atolls of differentiation in coral reef fishes (Hypoplectrus spp,
Serranidae) (52145)

Oscar Puebla, Eldredge Bermingham, Owen McMillan.

GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany; Patricia and Phillip Frost Museum of Science, Miami; Smithsonian Tropical Research Institute, Panama.

Since the vast majority of species are well-diverged, relatively little is known about the
genomic architecture of speciation during the early stages of divergence. Here, we leverage
the shallow radiation in the hamlets (Hypoplectrus spp, brightly coloured reef fishes from the
tropical western Atlantic) to characterize genomic divergence during the early stages of
speciation. A survey of approximately 100,000 restriction-site associated SNPs in 126
samples from three sympatric species across three replicate populations reveals extremely
slight genome-wide divergence among species (Fst=0.0038), indicating that
ecomorphological differences and reproductive isolation are maintained in sympatry in a
backdrop of extraordinary genomic similarity. A very small proportion of SNPs (0.05% on
average) are identified as Fst outliers among sympatric species, and remarkably a single SNP
is identified as an outlier in repeated populations for the same species pair. A mini-contig
assembled de novo around this SNP falls into the genomic region containing the HoxCa10
and HoxCa11 genes in 10 teleost species, suggesting an important role for Hox gene evolution
in this radiation. Behavioural observations made in the same species and populations sampled
for genetic analysis and complemented with individual-based simulations suggest a key role
for natural and sexual selection in driving the genomic patterns.

Poster session A - MAX 413

Speciation reversal in ravens: genomic evidence of the collapse of cryptic
lineages in North America (52170)

**Anna Kearns**, Arild Johnsen, Silje Hogner, Marco Restani, Ildiko Szabo, Hayley Richardson, Jin Ah Kim, Robert Fleischer, Kevin Omland.
Natural History Museum, University of Oslo; St. Cloud State University; Beaty Biodiversity
Museum; University of Maryland Baltimore County; National Zoological Park & National
Museum of Natural History, Smithsonian Institution.

There is increasing evidence that gene flow between phenotypically distinct species is a
common and important evolutionary process. Introgressive hybridization can result in at least
three different outcomes: simple introgression, hybrid speciation or speciation reversal (i.e.,
collapse of distinct lineages). However, only speciation reversal results in a decrease in
species diversity, and only speciation reversal requires the complete breakdown of
reproductive isolation. More and more cases have been documented in several animal
lineages, especially in fishes. However, most of these cases involve recent divergences (e.g.,
~12,000 ybp) and are human caused. In contrast, several cases in birds seem to be much older
and show no role for human disturbance. Common Ravens have two deeply diverged
mitochondrial clades that are widely sympatric over the western US. We found no evidence of
phenotypic differences between the clades and no evidence of assortative mating or
reproductive isolation. Data from nuclear introns and RAD SNPs provides strong support for
two formerly distinct lineages that now hybridize across most of western North America. We
are now using a range of next generation and multilocus coalescent approaches to test the
hypothesis that speciation reversal is occurring in ravens against alternative hypotheses.

Fuzzy species limits in the Eunicella gorgonians : interaction with adaptation and symbiosis (52238)

Didier Aurelle, Isabelle Dabat-Pivotto, Marine Malfant, Nur Eda Topçu, Anne Haguenauer, Camille Roux, Didier Forcioli.

Aix Marseille Université IMBE; Istanbul University; Université de Lausanne; Université de Nice.

The genetic study of speciation allows a deeper understanding of processes generating or
eroding species limits. Thanks to a higher number of molecular markers and to the use of
appropriate statistical tools, we can now test and understand a wider range of evolutionary
scenarios leading to the observed inter-specific differentiation. The Eunicella spp. octocorals
provide a good model to study speciation in interaction with adaptation. Three closely related
species can be observed in sympatry in the Mediterranean sea : E. cavolini, E. singularis, and
E. verrucosa. They present different ecological patterns and E. singularis is the only
Mediterranean octocoral harbouring photosynthetic symbionts (Symbiodinium). We
sequenced two introns on a wide range of Eunicella individuals to study the phylogeography
and species limits of this group : our result demonstrate a lack of clear genetic limits between
them with putative hybridization events. The study of transcriptome polymorphism of eight E.
cavolini and two E. singularis allowed to estimate the heterogeneity in differentiation levels.
Different scenarios are proposed and tested with approximate bayesian computation to explain
these results.
# Reproductive isolation and sexual dimorphism driven by natural and sexual selection on a polygenic communication system (51648)

**Rüdiger Riesch**, Bernard J Crespi, Gerhard Gries, Regine Gries, Rebecca Safran, Patrik Nosil.

Royal Holloway, University of London, UK; Simon Fraser University, BC, Canada; University of Colorado, CO, USA; University of Sheffield, UK.

How exactly natural and sexual selection interact in evolution and species formation remains debated. Cuticular hydrocarbons (CHCs) are waxy chemicals expressed on the skin of all insects that could be subject to natural selection because they control desiccation resistance and sexual selection because they affect mate choice. Here we show how selection on CHCs, genomic variation, and the environment combine to drive ecological speciation in Timema stick insects. Perfuming experiments demonstrate a causal role for CHCs in mate choice and sexual isolation. Thus, males choose females as mates based on CHC profiles, which are especially divergent between the sexes. As predicted by natural selection, CHCs vary among populations according to climatic conditions, but this effect is stronger in males. Consistent with sexual selection on female CHCs, induced environmental influences on CHCs are strongest in females. Nonetheless, genome wide association mapping shows that CHC variation in both sexes is affected by a modest to large number of widely distributed genomic regions that often have pleiotropic effects on multiple CHC compounds; however, the genomic basis for CHC variation is sex-specific. The results demonstrate how selection on communication systems can drive biological diversification via combined effects of phenotypic plasticity and polygenic divergence.

# Joint effects of history and genetics in maintaining genetic variation under sexual selection (51768)

**Aditya Ponkshe**, John Endler.

Centre for Integrative Ecology, Deakin University.

The maintenance of genetic variation for sexually selected traits is something of a puzzle (Pomiankowski & Moller 1995). Lande (1981) and Kirkpatrick (1982) were the first to model the dynamics of sexual selection, but these and subsequent models were more concerned with equilibrium than what conditions maintain genetic variation for sexually selected traits. We use an extension of Kirkpatrick's (1982) model and calculate the equilibrium amount of genetic variation in sexual traits for different initial conditions under various scenarios. Initial conditions that favour the maintenance of sexual trait genetic variation form a band or polymorphic zone with distinct boundaries in genotype frequency space. Populations starting with genotype frequencies of males and females anywhere inside the polymorphic zone maintain genetic variation in sexual traits while populations initially outside the zone lose genetic variation. Populations starting on different sides of the zone boundaries have very different evolutionary outcomes even if all other conditions are identical; both history and
genetically determined mating parameters determine the genetic variation in sexual traits and evolutionary outcomes. Populations can differ radically with respect to genetic variation and genotype frequencies even if environmental conditions are identical and populations are too large to diverge due to genetic drift.

## A genetic correlate of red ketocarotenoid coloration in ploceids (52216)

**Hanlu Twyman**, Staffan Andersson, M. Prager, N.I. Mundy.

*University of Cambridge; University of Gothenburg.*

Red carotenoid-based colours are classic sexual or social signals in animals, particularly in birds where signal selection and evolution are extensively studied. However, the crucial mechanism behind most brilliant red colours in birds, namely metabolic conversion (oxygenation) of dietary yellow carotenoids to red ketocarotenoids, is unknown at the genetic level. Here we explore a candidate ketolase, encoded by a cytochrome P450 gene cluster (CYP2J2), in the African weaverbirds (Ploceidae), where ketocarotenoids are documented or indicated in many genera, especially the iconic widowbirds and bishops (Euplectes spp). We find a strong association between red ketocarotenoid pigmentation and expression of a CYP2J2 locus in the liver, the suspected site of conversion, whereas no CYP2J2 expression was detected in the livers of taxa lacking ketocarotenoids. This suggests that the CYP2J2 gene cluster holds one of the key genetic mechanisms underlying the evolution of red carotenoid coloration in birds, with important implications for both adaptive and non-adaptive hypotheses of sexual selection and colour diversification.

## Opsin expression reveals sexual dimorphism in the visual system of New World warblers (Birds, Parulidae) (52255)

**Natasha Bloch**, Trevor Price.

*University of Chicago; University College London.*

Asymmetries in reproductive investment between the sexes lead to the expectation that males should be under stronger sexual selection, and that females should be the choosier sex. Accordingly, spectacular examples of sexual dimorphism in plumage have evolved in passerine birds. How these colors are perceived, and thus female visual perception, is predicted to play a critical role in the evolution of such dimorphic plumage colors. We studied the evolution of Sws2 opsins, one of the visual pigments that mediate vision, in 16 species of New World warblers (Parulidae). We found Sws2 expression varies extensively across species and between sexes. Most notably, female, but not male Sws2 expression is associated with the degree of plumage dichromatism across warblers. This fits predictions of classic sexual selection models in which the sensory system changes in females, presumably
impacting female preference, and co-evolves with male plumage. Exactly how opsin expression impacts color perception is unclear, but we suggest possible mechanisms. Spectral tuning for this opsin however, is completely conserved across warblers. We argue that regulation of Sws2 opsin expression allows for fast adaptive evolution of the visual system and could be the target of sex-specific selection pressures leading to divergence in mating preferences.

# Costs of reproduction explain a gradual change from a male-biased to a female-biased sex difference in human lifespan (52272)

**Elisabeth Bolund**, Virpi Lummaa, Ken R. Smith, Alexei A. Maklakov.

*Uppsala University; University of Sheffield; University of Utah.*

Sex differences in lifespan are common across taxa. In humans, women commonly outlive men. However, this sex difference is generally less pronounced in pre-industrial societies. Using the Utah population database, we show that the population changed from a significant male biased lifespan before (1800-1880) the demographic transition to low mortality and fertility rates to a significant female biased lifespan during (1880-1920) the transition. A rapid and pronounced reduction in female fertility may have precipitated this change in longevity patterns, because we found a cost of reproduction in terms of shortened lifespan at high parities in women but not in men. Because female adult lifespan increased as fertility decreased, while male adult lifespan remained stable over the demographic transition, the differential cost of reproduction in the two sexes may partly explain shifting patterns of sex differences in lifespan across human populations. Further, such rapid phenotypic changes in fertility and lifespan may be reflected in changes in the genetic basis of these traits. We will show how the genetic variances and covariances between family size and lifespan in the two sexes have been affected by the demographic transition and discuss how this might influence the population response to future environmental changes.

# Is the expression of specific mitochondrial ORFs involved in sex determination and mitochondrial inheritance in Mytilus? (52391)

**Artur Burzynski**, Sophie Breton, Beata Śmietanka, Tomasz Sańko, Marek Lubośny, Aleksandra Przyłucka.

*Institute of Oceanology PAN; University of Montreal.*

Unlike the system of strict maternal inheritance described in other animal species, Mytilus species instead possess a system of doubly uniparental inheritance (DUI) of mitochondrial DNA (mtDNA). Specifically, DUI is a "mother-to-daughter" and "father-to-son" mtDNA inheritance system where females transmit their mt genomes (F mtDNA) to both sons and
daughters, and males transmit their mt genomes (M mtDNA) to their sons. Recently, the presence of a novel F genome-specific ORF of significant length that most likely has functional significance in Mytilus bivalves was demonstrated. The "formerly reported as missing" atp8 gene has been identified in Mytilus mtDNA but it hasn't been shown to actually produce a protein in vivo. There are also controversies regarding the length of some other mitochondrial ORFs associated with the supposedly "non-coding" fragments which differ in length between the Mytilus lineages, a situation similar to the one described and positively verified in freshwater Unionoid bivalves. Here we report the results of our investigations into the functional properties of these ORFs. Their existence suggests that animal mitochondrial genomes have a considerably larger functional repertoire than previously believed. In our opinion, novel mitochondrial ORFs with key biological functions await discovery in other animal species, including humans.

## The evolution of sex-biased gene expression in Mercurialis (52458)

**Melissa Toups**, Guillaume Cossard, John Pannell.

*University of Lausanne.*

Several animal species with sex chromosomes present a nonrandom distribution of sex-biased genes. The pattern appears to evolve quickly with the suppression of recombination. For example, sex-biased genes have become enriched in the neo-X chromosome of the Japan Sea stickleback, which formed ~1 MYA. We are still far from knowing how general this phenomenon is, and very little is known about patterns of sex-biased gene expression particularly in dioecious plants. Here, we present analyses of transcriptome sequence data from a large experiment to reveal the patterns of gene expression based on RNAseq for multiple species within the annual clade of the plant genus Mercurialia. By including data from both dioecious and related hermaphroditic species of Mercurialis, as from populations with different ploidy levels grown under identical conditions, we are able to tease apart the effects of changes in sexual system on sex-biased gene expression from those of polyploidization, which is also currently attracting much interest. Because separate sexes have evolved independently more than once in Mercurialis we could test the hypothesis that the same genes, in the same genomic regions, have evolved similar patterns of sex-biased expression after a transition from hermaphroditism.

## Purging of mutations via sexual selection is dependent upon which sex chooses a mate (52538)

**Brian Mautz**, Alexei Maklakov.

*Uppsala University.*
Spontaneous mutations introduce new alleles in natural populations. The large majority are deleterious and result in relative fitness differences between individuals. Sexual selection is predicted to eliminate these mutations as those with lower mutation loads are chosen as mates. It has been assumed that sexual selection acts most strongly on males, but can also act on females via male mate choice. Thus, male mate choice might also act to increase population fitness. However, sexual selection via mate choice can differentially affect fitness of sons and daughters and potentially eliminate deleterious mutations in a sex-specific manner. We divided replicate homozygous (f≈0.99) lines of an outcrossing nematode (Caenorhabditis remanei) into three mutation accumulation (MA) regimes: MA (control), MA + female mate choice, MA + male mate choice for 20 generations. Female fitness showed the strongest response to sexual selection, but in opposite directions depending on which sex was allowed to choose mates. Male fitness responded in a similar direction within lines, but effects were weak. These results show that sexual selection can have counter intuitive effects on fitness via sex-specific expression of mating preferences resulting in both the purging and accumulation of deleterious mutations.

# Mutation, Condition, and the Evolution of Longevity (52551)

**Christopher M Kimber**, Adam K Chippindale.

Linköping University; Queen's University.

The evolutionary theory of aging predicts that longevity will decline via drift or age-specific tradeoffs when selection favors early life fitness. Many Drosophila melanogaster populations continually terminated at young adult ages retain surprisingly long postselection lifespans. We compiled three decades of longevity data from the Ives population, demonstrating that postselective longevity was both substantial (30 days) and temporally stable over this period. Recently, alleles with positive pleiotropic effects between adjacent ages, particularly those affecting overall condition, have been integrated into the theory and may explain the extended longevity observed. We experimentally tested this hypothesis by isolating hemiclones from Ives and allowing spontaneous mutations to accumulate (MA). Fitness and longevity were positively genetically correlated in control females, and both traits declined due to MA. Crucially, MA induced a strong positive genetic correlation between the traits in both sexes, implying that mutations with early-life impacts also reduce late-life survival. Our results suggest that extended postreproductive longevity is actively maintained by selection for early-life fitness, possibly mediated by the positive pleiotropy of alleles affecting overall organismal condition. Thus mutation-selection balance for early fitness may govern variance in longevity in this system: a balance struck remarkably long after selection for continued survival ceases.

# Sex differentiation in the ant Cardiocondyla obscurior (52701)
Antonia Klein, **Eva Schultner**, Jan Oettler.

*University of Regensburg; University of Helsinki.*

Primary signals for sex determination vary among insects. However, common to all systems is the transduction of primary signals into differential transcription of terminal sex differentiation genes. New genomic resources allow the study of sex differentiation in non-model organisms. We use the ant Cardiocondyla obscurior to elucidate the transcription of the terminal regulator gene doublesex (dsx). In addition to two female castes (queens, workers), C. obscurior exhibits two male forms (wingless, winged). With RACE-PCR we identified male- and female-specific splice forms of dsx. Contrary to the male full-length transcript, the female transcript contains an early stop codon that produces a shortened transcript. Subsequently we measured expression levels of sex-specific splice forms in young female and male larvae (prior to caste determination) and in adult females and males of all castes. To investigate how expression varies across development stages we additionally analysed dsx expression using RNAseq data generated from individual late-stage larvae of known sex and caste. In a final step, we will analyse dsx expression in gynandromorph individuals who share characteristics of both sexes. The results of this study will shed first light on sex differentiation in ants, and help elucidate the mechanisms that regulate sex-specific phenotypic variation in insects.

**Molecular evolution of mammalian testes under polyandry and monandry**
**(52730)**

Mehmet Somel, **Ekin Saglican**, Rori Rohlfs, Ezgi Ozkurt, Haiyang Hu, Babur Erdem, Philipp Khaitovich.

*Middle East Technical University; University of California, Berkeley; CAS-MPG Partner Institute for Computational Biology.*

Female promiscuity, or polyandry, can strongly shape male behavior and anatomy. In polyandrous mammalian species, males have larger testicles and produce faster sperm, compared to monandrous species where females mate with a single male - an example of convergent evolution. Here we asked whether testis transcriptomes also evolve convergently under polyandry or monandry. Combining multiple datasets and performing a phylogenetic test for convergent evolution by mating type, we found an excess of genes with convergent testis expression in polyandrous species, such as chimpanzees and mice, as opposed to monandrous species, such as humans and marmosets. Likewise, polyandrous species' testes were found to contain more spermatocytes/spermatids than non-meiotic or pre-meiotic cell types. We next compared adult testis transcriptomes with testis developmental series. Testis profiles of monandrous species appeared paedomorphic compared to those of polyandrous species, suggesting that heterochrony in testis development could underlie convergent evolution. Finally, we compared nucleotide diversity patterns in testis-specific and testis development-related genes in humans and in chimpanzees, to find evidence for significant shifts in selection pressure since the last common ancestor of the two species. Our results
underscore how evolving mating systems can rapidly change genes, developmental processes, transcriptomes, and anatomy.

# Nature via nurture of carotenoid colour evolution: the metabolic conversion of yellow to red pigments is controlled by a cytochrome P450 in widowbirds and bishops (Euplectes) (52947)

Staffan Andersson, Maria Prager, Hanlu Twyman, Nicholas I. Mundy.

*Dept of Biological & Environmental Sciences; Dept of Zoology, Cambridge University.*

The colourful breeding plumages of male widowbirds and bishops (Euplectes spp.), with slightly to extremely elongated tails and striking red or yellow carotenoid displays, are iconic and spectacular examples of sexual selection and sexual dimorphism, but the diversity in signal design and expression resist adaptive explanations given the similarities in ecology and behaviour. Also non-adaptive radiation due to drift or Fisherian runaway processes seems unlikely since both the epigamic tails and the agonistic colour signals have evolved in a directional and convergent manner. The increasingly supported scenario is instead one of generalized female and male receiver biases, and diversification due to historical contingencies such as genetic constraints. Here we report on a long predicted but now revealed key innovation behind the evolution of red carotenoid coloration in birds; the ability to convert (oxygenate) dietary yellow carotenoids to red ketocarotenoids. In Euplectes and other weaverbirds (Ploceidae), the central (liver) expression of this gene (CYP2J2B) is associated with ketocarotenoid pigmentation, but not found in the equally red species among 'true' widowbirds, a mechanism as yet unknown. We reconstruct the evolutionary history of CYP2J2B in weaverbirds and discuss the implications for sexual selection, costs and honesty, and colour diversification.

# Comparison of genetic background of flowering time variation among *Lotus japonicus* in Japan based on whole-genome sequence (52064)

Tomomi Wakabayashi, Stig Andersen, Shusei Sato, Yoshihiro Handa, Masayoshi Kawaguchi, Hiroaki Setoguchi.

*Kyoto University; Aarhus University; Tohoku University; National Institute for Basic Biology.*

The purpose of this study is to reveal the genetic factors for variant flowering time in Lotus japonicus in Japan. Flowering time is critical for plants as the different timing can cause reproductive isolation hence intraspecific differentiation. L. japonicas, a legume model plant, distributes throughout the Japanese archipelago and has variant flowering time according to their geographical regions.
131 wild accessions from Japan, which are maintained by National Bio Resource Project, were grown in a same condition to measure the flowering time. They flowered in a different timing correlated with the latitude of their origin. Subsequently whole-genome sequencing of additional five lines to the already sequenced 131 lines by Kazusa DNA Research Institute and Aarhus University and whole-genome comparison between extremely early and late lines among them were conducted. Three SNPs were identified which possibly affected the flowering time. One of the SNPs was on the orthologous to Embryonic flower, one of the famous flowering genes. Prediction of the protein structures suggested that the two of three SNPs could affect the structures of the functional domain of the protein. In addition, there were significant differences of the days between germination and first flowering in 122 wild lines between the genotypes.

**(Epi)genetics and ecology of floral colour polymorphisms in the alpine orchid
Gymnadenia (=Nigritella) rhellicani (52094)**

Roman T Kellenberger, Kelsey JRP Byers, Florian P Schiestl, Philipp M Schlüter.

*University of Zurich.*

Selection of novel, adaptive (epi)mutations is the main process behind the incredible diversity of organisms on this planet. In entomophilous plants, adaptation to specific pollinating insect taxa led to the evolution of flowers of an enormous variety of shape and colour. Understanding the evolution of floral traits therefore requires both knowledge about molecular mechanisms behind (epi)mutations and adaptive values of the induced phenotypic alterations. We are investigating the evolution of floral colour polymorphisms in the alpine orchid species Gymnadenia (=Nigritella) rhellicani. While flowers of G. rhellicani are usually dark red, some populations are highly polymorphic with 1-40% light red to entirely white inflorescences. Our work focuses on molecular and ecological experiments to highlight mechanisms and consequences of this phenomenon. Preliminary data suggest an (epi)genetic cause of colour variation and a potential linkage to differences in the floral scent bouquet. We aim to characterize the underlying molecular mechanisms in a forward genetics approach. Phenotypic traits such as levels of different anthocyanins are quantified for the different morphs. A comparison with RNA-seq data should later identify candidate genes for targeted (bisulphite) sequencing. Selection pressure on different morphs will be assessed with pollinator behavioural studies and manipulation experiments under artificial and natural conditions.

**Integrating phylogenetics, ecology and evo-devo to understand a key
innovation: floral nectar spurs in Linaria and related genera (52327)**

Mario Fernández-Mazuecos, Beverley Glover.
Floral nectar spurs are considered a key innovation promoting diversification in angiosperms. Spurs are tubular outgrowths of floral organs containing a nectar reward for pollinators. It is hypothesized that they mediate reproductive isolation by promoting pollinator specialization. Here we apply a multidisciplinary (phylogenetics, pollination ecology, evolutionary developmental biology) and multi-scale (genera, species, populations) approach to understand the evolution of nectar spurs and their role in speciation in the tribe Antirrhineae (Plantaginaceae; c. 330 species). Phylogenetic comparative methods are used to estimate the correlation between nectar spur evolution and speciation rates of Antirrhineae. Ancestral state reconstructions indicate three to four acquisitions of nectar spurs in the course of Antirrhineae evolution, including that in the most successful genus Linaria (c. 160 species). In particular, we are investigating mechanisms of speciation and spur evolution in a recently-diversified clade formed by eight species of Linaria that display wide variation in spur length. Phylogenetic relationships are resolved using next-generation sequencing techniques (RAD-Seq). The relative roles of pollinators and other isolating factors (including ecological and post-pollination barriers) are quantified, and the ontogenetic and genetic basis of spur length variation and evolution is investigated using an evo-devo approach.

Experimental tests of the effect of flower architecture, fragrance and visual stimuli on the pollination of a dimorphic plant (52845)

Juan Arroyo, César A. Abarca, Rocío Santos-Gally, Rocío Pérez-Barrales, Florian Schiestl.

University of Seville, Spain; Universidad Autónoma Metropolitana, México; Instituto de Ecología, UNAM, México; School of Biological Sciences, University of Portsmouth, UK; Institute of Systematic Botany, University of Zürich, Switzerland.

Style length polymorphisms are flower traits thought to be related to the specialized activity of pollinators, which promote disassortative mating by transferring pollen between morphs. We investigated whether other flowers traits putatively related to olfactory and visual signals play a role in the attraction of them in the daffodil Narcissus papyraceus. By means of experimental manipulation of the flower corona, the reputed scent producing organ, and setting on experimental populations, we tested if legitimate long-tongued pollinators (mainly moths) involved in the maintenance of style polymorphism are attracted by corona fragrance. We also tested the effect of the distance between plants on their reproductive success through a possible limitation by compatible pollen. We repeated the experiments in a region where the short-styled morph is absent and pollination is performed mainly by short-tongued insects (hoverflies), to explore if they are differently attracted by the corona. Additionally, we considered the possibility that the flower corona represents a visual stimulus for flower visiting insects, by means of an analysis of reflectance patterns of flower parts. These results show that the maintenance of style polymorphism is more related with flower handling by insects and morphological filters than with different attraction systems of flower parts.
# The effect of sex on the repeatability of evolution (51580)

**Josianne Lachapelle**, Nick Colegrave.

*The University of Edinburgh.*

If evolution is repeatable, the evolutionary trajectories taken by different lineages and the final outcomes of evolution in given conditions will be the same. The mode of reproduction, either asexual or sexual, can affect repeatability by altering the relative contribution of selection, chance and history to evolutionary change. We tested this idea by propagating experimental populations of the unicellular alga Chlamydomonas reinhardtii in a novel environment. The populations differed by their mode of reproduction, and their initial genetic composition. We carried the experiment in four different novel environments. Preliminary results suggest that the amount of divergence among sexual populations can be higher or lower than that among asexual populations, depending on the novel environment. Fitness assays to be carried in the next months will reveal how the contribution of selection, chance, and history varies over time in sexual and asexual populations. By examining how sex contributes to the rise and fall of diversity during evolution, we can better understand the factors that maintain sex in populations. The generality of our findings across all four environments tested will inform us about the role of ecology on the repeatability of evolution in sexual populations.

# Genomic evidence for ameiotic evolution and adaptation without sex in an animal lineage, the bdelloid rotifer Adineta vaga (51714)

**Karine Van Doninck**, Olivier Jaillon, Nicolas Debortoli, Boris Hespeels, Jean-François Flot.

*University of Namur; Genoscope; University of Namur; University of Namur; University College London.*

Loss of sex is an evolutionary dead end for metazoans, but bdelloid rotifers challenge this view having persisted asexually for millions of years. We found that the genome structure of the bdelloid Adineta vaga is indeed incompatible with conventional meiosis. At gene scale, the genome is tetraploid and comprises anciently duplicated segments and less divergent allelic regions. In contrast to sexuals, the allelic regions are rearranged and sometimes found on the same chromosome. Such genome structure does not allow meiotic pairing. Instead, we find abundant evidence of gene conversion, limiting the accumulation of mutations in the absence of meiosis. Gene conversion may occur during mitotic recombination repair of broken DNA following cycles of desiccation and rehydration experienced by bdelloids in their temporary habitats. Indeed during desiccation the genome of A. vaga is broken in hundreds of DNA fragments that get repaired once rehydrated.

In the genome of A. vaga 8% of the genes are likely of non-metazoan origin and probably acquired horizontally. These genes appear to be functional and many of those involved in resistance to desiccation have been acquired through HGT. Whether genetic exchange via
HGT is a key innovative mechanism in those eukaryotes allowing adaptation in the absence of sex is an important question we are investigating.

# Inventory of meiotic genes in New Zealand stick insect Clitarchus hookeri (Phasmatodea) and their expression in sexual and asexual females (51767)

CHEN WU, RICHARD NEWCOMB, HOWARD ROSS, THOMAS BUCKLEY.

*Landcare research; The University of Auckland; Allan Wilson Centre; The New Zealand Institute for Plant & Food Research Ltd.*

Meiosis is the process specific to all sexual eukaryotes and genes with well-characterised roles in meiosis promote and regulate this process. Studying meiotic genes in organisms reproducing both sexually and asexually might shed light on the molecular requirements for sexual reproduction and transition between the two reproductive modes. Clitarchus hookeri is geographical parthenogen, widely-distributed in New Zealand. They reproduce bisexually in northern New Zealand, generating offspring with relatively equal number of sexes; in comparison, they form parthenogenetic populations in southern New Zealand. The Clitarchus hookeri asexual lineage was separated from the sexual lineages approximately 0.43 mya and appears to be isolated from those sexual populations. This primary reproductive isolation was supported by results from a crossover experiment where females from most of the parthenogenetic populations still produce only females after they were mated with sexual males. To investigate whether molecular change within meiosis might be involved in this isolation, we firstly sequenced and annotated the genome of C. hookeri, then conducted comparative transcriptomic analysis on the reproductive organs from both bisexual and parthenogenetic females, in which, we specifically focus on meiotic genes. Identification of the C. hookeri meiotic genes might also provide insights into stick insect reproductive flexibility.

# Fitness consequences of sexual and parthenogenetic reproduction in the Australian spiny leaf insect, Extatosoma tiaratum (51878)

Yasaman Alavi, Therésa Melanie Jones, Mark Adrian Elgar.

*University of Melbourne.*

Empirical studies investigating the costs and benefits of sexual reproduction have typically been unable to remove confounding effects present in comparisons between sexual and asexual species or populations. Species in which individuals are capable of switching between reproductive modes provide promising model systems to resolve this issue, but many alter their reproductive mode according to their condition or environmental factors and thus comparisons remain confounded. Females of the facultatively parthenogenetic Australian
spiny leaf insect, Extatosoma tiaratum, can reproduce sexually or asexually, depending only upon the availability of males/sperm. Virgin females produce parthenogenetic daughters, while mated females produce both sons and daughters through sexual reproduction. In this study, we examine the fitness outcomes of sexual and asexual reproduction of females derived from known modes of reproduction. We compare survival and reproduction in the daughters of virgin, once mated and twice mated mothers. Our results will provide unambiguous and novel insights into the costs and benefits of sexual reproduction.

## Genetic diversity and population structure in thrips with different reproductive modes (52086)

Amaranta Fontcuberta, Zoé Dumas, Tanja Schwander.

*Department of Ecology and Evolution, Uni Lausanne.*

Understanding how genetic diversity is generated and maintained in asexual lineages can provide insights into the maintenance of sexual reproduction in natural populations. Here we quantified genetic diversity and population structure in different sexual and asexual populations of the grassthrips Aptinothrips rufus. This species is native to Europe, but has been introduced throughout the Holarctic region, whereby all known introduced populations consist of asexual females only. We found extremely high levels of clonal diversity in both native and introduced asexual populations and much greater genetic diversity than in sexual populations. Individual asexual lineages were found on different continents with little or no isolation by distance, indicating extensive mixing and continuous exchange of asexual individuals between geographically distant populations. In contrast to the asexuals, sexual A. rufus population were strongly isolated genetically, with little or no gene flow even at short geographic distances. Asexuality in A. rufus, induced by an endosymbiont, appears to have entailed population dynamic changes that strongly affect the distribution of genetic variation within and between populations in an unexpected way. Current sexual populations may be transient and disappear upon colonization by genetically diverse clonal assemblages.

## Changes in sexual reproduction in response to human-induced eutrophication in a cladoceran community (52120)

Anu Vehmaa, Miia Mannerla, Laura Sartamo, Ulrika Candolin.

*Tvärminne Zoological Station, University of Helsinki; University of Helsinki, Department of Biosciences; University of Helsinki, Department of Environmental Sciences.*

Continuous records that aquatic organisms leave in the sediments offer an intriguing possibility for time travel. Most cladocerans (zooplankton) are cyclic parthenogens, i.e. the
yearly cycle includes parthenogenic and sexual reproduction. Generations of parthenogenic females are followed by sexual females and males, which produce fertilized resting eggs when environmental conditions deteriorate. Resting eggs hatch after a latent period, however some may be buried in the sediment, where they can survive for decades or even longer. Besides resting eggs, some cladocerans leave also traces of their exoskeleton in the sediments. By comparing the proportion of resting eggs vs. other subfossils of the same species, it is possible to estimate the contribution of sexual reproduction. We took sediment core samples from two coastal sites of the Baltic Sea, which has suffered from severe human-induced eutrophication during the past decades. We dated the cores, and identified and counted the cladoceran resting eggs as well as other subfossils in sliced 1-cm subsamples. The presented results will reveal potential long-term changes in the cladoceran reproductive strategies, and show if periods of high sexual reproduction coincide with rapid changes in the environment, such as the introduction of a new cladoceran predator or intensive algal blooms.

# A breakdown of doubly uniparental inheritance (DUI) system in hybridisation area of European Mytilus edulis and Mytilus trossulus (52204)

**Beata Śmietanka**, Artur Burzyński, Aleksandra Przyłucka, Marek Lubośny.

*Institute of Oceanology of Polish Academy of Sciences.*

The doubly uniparental mode of mitochondrial inheritance (DUI) is best known in blue mussel Mytilus. Under this system two types of mitochondrial DNA (mtDNA) exist. The female (F) transmitted from females to offspring of both genders and the male (M) transmitted exclusively from males to sons. The genomes are highly divergent but a replacement of typical M genome by the F genome resulting in reduction of sequence divergence has occasionally been observed. Here we present a case of DUI breakdown in Mytilus population from the North Sea (Norway). Our comparative analysis is based on the part of coding region sequence (ND2-COIII) of mtDNA of 55 Mytilus specimens classified as M. trossulus or M. trossulus/M. edulis hybrids by diagnostic nuclear markers. We have found typical M haplotypes in 6 individuals only, two of them were females. All these M haplotypes were derived from M. edulis. We have also found two classes of F haplotypes: one derived from M. edulis and the second from M. trossulus. The F haplotypes did not show any sex bias either, but heteroplasmy seemed to be positively biased towards males. This apparent breakdown of DUI system seems to be related to the hybridisation between two Mytilus species

# The tastier sex? Herbivore preference varies among the habitats of Mercurialis perennis (52212)

**Luka Rubinjoni**, Vukica Vujić, Sara Selaković, Dragana Cvetković.
The role of herbivorous insects in plant mating system evolution is a topic of growing interest. This interaction has been studied in the context of plant resistance/tolerance, constitutive versus induced defenses, resistance/reproduction trade-offs, and herbivore affinity to a specific sex. One potential benefit of dioecy is herbivore-related risk distribution between male and female plants. A premise to this is the presence of sex-specific herbivory in natural conditions. The object of our study is Mercurialis perennis, a widely distributed dioecious perennial. We collected plants from a range of habitats in Serbia, and estimated the herbivore load by scoring leaf damage on an ordinal scale. The initial analysis, based on transformed herbivory indices representing average leaf damage per plant, did not confirm a significant bias in the observed loads. We further investigated the data using R package ordinal. In a comparison of generalized linear mixed models, plant sex did not emerge as the key factor for describing variation in leaf damage scores in the complete dataset. However, the most informative model showed a significant effect of sex within the sites. We conclude that sex-specific herbivory is present, but the preference varies among the habitats.

# MALE REPRODUCTIVE SUCCESS AND INDIRECT GENETIC BENEFITS IN THE ITALIAN TREEFROG (Hyla intermedia) (52296)

**VALENTINA BOTTO**, SERGIO CASTELLANO.

The present work aims at testing the ‘good genes’ hypothesis in a small population of Italian treefrogs (Hyla intermedia). For two years, we recorded the calls and behavior of all males attending the lek, and, in both years, we found that male reproductive success was positively affected by male mating effort (i.e. number of nights spent at the lek and number of recording sessions).

A subset of males was used in a North Carolina II Breeding Design to estimate maternal and paternal effects on two traits known to affect froglets’ fitness, Snout-Vent Length (SVL) and age at metamorphosis. For each half-sib and full-sib family, 30 tadpoles were reared to metamorphosis in two replicates.

We found a statistically significant maternal effect on SVL and age at metamorphosis and a significant paternal effect only on age at metamorphosis. Although we found no evidence for a positive association between male mating success and offspring SVL, we did observe a positive association between offspring age at metamorphosis and paternal mating effort.

Our results confirm the ‘good-genes’ assumption that males’ genes can affect offspring fitness and provide some evidence for a positive association between paternal mating effort and offspring fitness.
# Is there an opportunity for sexual selection to aid adaptation and does it increase in novel environments? (52415)

**Ivain Martinossi-Allibert**, Göran Arnqvist, David Berger.

*Evolutionary Biology Center, Dept of Animal Ecology.*

Sexual reproduction imposes a cost on population productivity, but can also create genetic variation and remove deleterious mutations. Males are generally expected to experience stronger sexual selection than females. This selection on males can purge the mutation load on population health and benefit both sexes, at a low demographic cost as population productivity mostly relies on female fecundity. Fisher's geometric model predicts that the strength of selection will increase whenever a population is pushed off its fitness peak. Due to sexual selection, males experience stronger stabilizing selection than females and may fall off their fitness peak faster. Males would consequently exhibit a stronger increase in the intensity of selection, improving the potential for sexual selection to purge the mutation load.
We tested this prediction by measuring the sex-specific variance in fitness of seed beetles (Callosobruchus maculatus) from fourteen genetic lines across five environments of varying quality. Total phenotypic variance in fitness increases with stress for both sexes, and increases faster in males. However the genetic component was hard to estimate, and seemed to decrease with increasing environmental stress. Thus, while the strength of selection increases faster in males under stress, the response to selection may be counteracted by declining heritabilities.

# Genomic consequences of long-term parthenogenesis in oribatid mites (52455)

**Alexander Brandt.**

*Georg-August-University Göttingen, Dept. of animal ecology.*

Oribatid mites are important model organisms for studying the evolutionary consequences of parthenogenetic reproduction. Sex was lost in several lineages of oribatid mites independently – in some of them tens of millions of years ago. We analysed the genome and transcriptome of two sexual and two parthenogenetic oribatid mite lineages for consequences of the absence of sex. In order to check for an accumulation of mildly deleterious mutations, we compared dN/dS ratios between sexual and parthenogenetic lineages. Further, we compared GC-content and codon usage bias of mitochondrial genomes. We found no accumulation of mildly deleterious mutations in protein-coding genes of parthenogenetic oribatid mites. However, we found a marked difference in mitochondrial GC-content, possibly due to selection as revealed by comparisons of the GC-content at third codon positions and the effective number of codons. We argue that the differences in GC-content might be suited to serve as a marker for long-term parthenogenesis in oribatid mites. Accordingly, the absence of the accumulation of mildly deleterious mutations in protein-coding genes of parthenogenetic oribatid mites might be explained by the evolution of mechanisms to counteract the accumulation of deleterious mutations, rather than by cryptic sex.
# Hybridisation patterns between sexual and asexual species (52601)

**Susana Freitas**, Marine Arakelyan, James Harris, Miguel Carretero, Roger Butlin.

Cibio - University of Porto; University of Sheffield; Yerevan State University.

Unisexual species have been found to keep assexuality for millions of years, which disrupts the notion that without sex species would get extinct. However, it is not clear whether asexuals can maintain gene flow with their closest sexual relatives.

The model used is a genus of rock lizards (Darevskia) that show both sexual and asexual species. Of its 29 species, seven are parthenogenetic lineages originated from hybridisation between two sexual species.

In the rare cases where parthenogenetic lineages are found in sympatry with their paternal species, hybrids are found.

We studied one sympatric locality with the sexual *D.valentini* and the parthenogens *D.unisexualis* and *D.armeniaca*. Here, the parthenogens are known to backcross with *D.valentini* males originating polyploid hybrids.

PCoA based studies show a clear structure, three groups each corresponding to one of the species present. Even though the hybrid origin, hybrid individuals match the original parthenogenetic parent species, and not the sexual. Polyploid levels are biased for *D.valentini* × *D.unisexualis*.

Here we aim to understand if these parthenogenetic species maintain their genetic identity, or if new parthenogenetic lineages may arise through time. Given the young age of these lineages is it possible that they are being replaced by new parthenogenetic individuals arising from this population?

# Female genitalia evolves slower than male genitalia in a coevolutionary scenario in a clade of Neotropical stink bugs (52714)

**Bruno Genevcius**, Daniel Caetano, Cristiano Schwertner.

University of São Paulo; University of Idaho; Federal University of São Paulo.

Two hypotheses may explain how female genitalia evolve: i) female traits may respond to modifications on its male counterparts in a coevolutionary dynamics; ii) female traits may evolve independently from male modifications under neutral process or stabilizing selection. Although theory predicts that sexually selected genital traits evolve fast, rates of evolution of male and female genitalia have only been assessed separately. We tested between the two hypotheses using a clade of Neotropical stink bugs, a good model for genital evolution because males and females have externally well-developed genitalia. We employed a partial least square approach to test for a coevolutionary scenario, and geometric morphometrics to capture genital variation. We also tested for differences in rates of evolution of the genitalia
using a Brownian motion rate parameter for multidimensional data, and compared them with
two non-genital traits. The shape of the genitalia showed positive significant correlation
(r=0.8; p=0.02). Both genitalia evolve faster than the non-genital traits (p<0.01), and the male
genitalia evolves two times faster than the female genitalia (p<0.01). We show for the first
time that both genitalia may evolve at quite distinct rates in a coevolutionary scenario, which
is consistent with a delayed response of the female genitalia.

Sex related transcriptome differences of the protogynous hermaphrodite red
porgy, Pagrus pagrus (52746)

**Alexandros Tsakogiannis**, Tereza Manousaki, Nikos Papandroulakis, Constantinos
C. Mylonas, Costas S. Tsigenopoulos.

*Hellenic Centre for Marine Research (H.C.M.R.) Crete ; Department of Biology, University of Crete, Greece.*

Teleost fish show an extraordinary diversity in terms of reproductive styles. Specifically in the Sparidae family, the full spectrum of sexual reproduction modes is observed. This exceptional variety of sexual mechanisms and the presence of hermaphroditism or gonochorism even in closely related species turn Sparidae into an ideal system for understanding the processes leading to sex differentiation. In red porgy, Pagrus pagrus, a protogynous hermaphrodite and economically important member of the family, we performed whole transcriptome sequencing of gonad and brain tissues to identify the gene toolkit and explore the properties of genes exhibiting sex-related expression profiles. The wealth of information coming through RNA sequencing in fish of different sex sheds light into the molecular mechanisms shaping the sex differentiation process. These genes were compared to known sex-related candidates from other teleosts and sparids like the rudimentary hermaphrodite Diplodus puntazzo.

Evolving reproduction: from sexual genomic recombination to asexual genome
stability. (52823)

Margarida Sofia Nobre, Anja Herrmann, Bernhard Schmid, Ueli Grossniklaus.

*Institute of Plant Biology, University of Zürich; Institute of Evolutionary Biology and Environmental Studies, University of Zürich.*

The natural genetic variation that makes evolution possible can be attributed to the
recombination events during gametogenesis and fusion of maternal and paternal genomes
after fertilization. Through sexual reproduction, the allelic combination of an offspring that is
better suited to its particular environment is the basis of agricultural selection, the production
of superior hybrids that result in crops of higher fitness and yield.
But sexual reproduction of hybrids introduces new recombinations and variation, and ultimately dispersal of the hybrid phenotypical traits. Apomixis, the asexual reproduction through the formation of clonal seeds, circumvents recombination and forms an embryo without fertilization.

In Arabidopsis thaliana, mutants have been identified that show unreduced embryo sacs, derived either from a developmentally altered megaspore mother cell or from an adjacent cell, which is the first step towards the production of clonal offspring. We aim to compare the sequence, expression patterns and levels of these genes with Arabidopsis' closest apomictic relative, Boechera. Evolutionary analysis of the differences in these genes between Arabidopsis and Boechera species will tell us whether they are indeed involved in the deregulation of the sexual pathway that leads to naturally occurring apomixis; and whether they can be manipulated to induce apomictic development in agriculturally relevant crops, thus preserving hybrid vigour through generations.

Poster session A - MAX 414

## Ecological differentiation and the maintenance of sex (52900)

**Stephanie Meirmans.**

*University of Bergen.*

There is evidence for ecological differentiation between many related sexual and asexual organisms. Well known is the broad pattern of geographical parthenogenesis, where asexuals occur in relatively more marginal and resource-poor habitats than their sexual relatives. Less known is the much more varied and detailed evidence that has been found on a species-specific level. In principle, such ecological differentiation could reduce competition between the two reproductive types and thus help to maintain sex within those species. So far, however, it is not yet clear whether and to which degree this really is the case. Here, I will review existing theoretical models (including older, half-forgotten ones) together with the existing empirical evidence from nature and lab in order to better assess the importance of ecological differentiation to maintain sex. I will also suggest some rigorous ways in which one could further test this issue.

Poster session A - MAX 414

## Sex, salamanders and dimorphism (52923)

**Alexander Kupfer, Sandra Renner, Sandy Reinhard.**

*State Museum of Natural History Stuttgart, Germany; Institute of Systematic Zoology and Evolutionary Biology, University of Jena, Germany.*

The salamanders of the family Salamandridae (Amphibia: Caudata) are highly suitable for studying inter- and intraspecific patterns of sexual size dimorphism (SSD) because they exhibit an extraordinary diversity of reproductive modes including oviparity and viviparity
combined with variable morphologies and body shapes. A diverse array of species
representing different mating systems and life histories have been analysed morphometrically.
We have also studied the ontogeny of sexual dimorphic traits by including age data and
finally we have integrated the most recent phylogenetic hypothesis to follow the evolution of
particular morphological traits. Our comparative multidimensional analysis will help to
understand the scenario behind the evolution of sexual dimorphism in a phylogenetically
ancient vertebrate group.

Evolutionary genomics of sex determination in the common frog Rana
temporaria (51673)

Wen-Juan Ma, Nicolas Perrin.

University of Lausanne.

Despite sex determination being a fundamental process in all sexually reproducing organisms,
the underlying mechanisms are surprisingly labile across taxa. Contrasting with the classic
view that recombination between X and Y chromosomes is entirely suppressed and the Y
highly degenerated, sex chromosomes in amphibians are generally undifferentiated, due to
high sex chromosome turnover rate and/or occasional X-Y recombination. This makes
amphibians ideal to investigate the evolution of sex determination.

Previous studies of the common frog (Rana temporaria) have provided evidence for both
genetic and epigenetic components to sex determination, showing that the two mechanisms
can coexist both between and within populations (Rodrigues et al. 2013, 2014). In this project,
we aim to investigate the genomic basis of sex determination in R. temporaria, by combining
approaches of candidate gene and temporal dynamics of genome-wide gene expression in a
range of developmental stages. We show that allelic polymorphism of the candidate gene
Dmrt1 is strongly associated with phenotypic gender in a population with genetic sex
determination, but not in a population with epigenetic sex determination. The ongoing project
on temporal dynamics of genome-wide gene expression and methylation pattern will provide
further insights in understating the genetic and epigenetic basis of sex determination in the
common frog.

Faster-Z evolution of gene expression in birds (51687)

**Rebecca Dean**, Peter Harrison, Alison Wright, Fabian Zimmer, Stephen Montgomery,
Judith Mank.

University College London.

The elevated rate of evolution of sex chromosomes (Fast-X or Fast-Z Evolution) can result
from positive selection in the heterogametic sex or from non-adaptive consequences of
reduced effective population size. Recent work in birds suggests that Fast-Z of coding
sequence is due to relaxed purifying selection, however gene sequence and expression are
often subject to distinct evolutionary pressures. We tested for Fast-Z in gene expression using
next-generation RNA-sequencing data from multiple avian species. Similar to studies of Fast-
Z in coding sequence, we also recover clear signatures of Fast-Z in gene expression, however
our data indicate that Fast-Z in expression is due to positive selection acting primarily in
females. In the soma, where gene expression is highly correlated between the sexes, we
detected Fast-Z in both sexes. In the gonad, where inter-sexual correlations are much lower,
we detected Fast-Z for gene expression in females, but crucially not in males. Taken together,
our results indicate that Fast-Z is the product of positive selection acting on recessive
beneficial alleles in the heterogametic sex. These results indicate that the adaptive potential of
Z chromosome expression may be much greater than that of coding sequence.

Testing hypothesis of sex-chromosome degeneration using bryophytes as a
model system (51777)

Linley Jesson, Cody Parker, Stuart McDaniel, Stefan Rensing.

University of Marburg; University of New Brunswick; University of Florida.

Degeneration of one sex-chromosome has independently happened in mammals, birds, insects, and flowering plants. What causes this? In organisms with diploid determination of sex expression two key features influence degeneration: sheltering of non-functional genes on the heterogametic sex chromosome by the other sex chromosome, and a lack of recombination in the sex determining regions. However in other organisms, such as bryophytes, sex is expressed at the haploid phase, allowing us to separate the effects of sheltering vs. recombination. To examine this, we are using sex-linked markers in a polyploid series of the bryophyte Atrichum, where haploid females are determined by a single U chromosome and haploid males by a V. Deleterious mutations in genes expressed in the haploid phase do not have an homologous chromosome to shelter the expression of mutations, but can be masked in the diploid phase. Furthermore, in polyploid Atrichum bivalent pairing of homologous sex chromosomes should result in the potential of masking of deleterious alleles by genes on a homeologous chromosome. However, polyploids can be hermaphroditic or strictly dioecious suggesting changes in potential for recombination. These contrasts allow a broader understanding of the factors influencing the evolution of sex chromosomes.

Sex-chromosome differentiation and ‘sexual races’ in the common frog (Rana
temporaria) (51825)

Nicolas Rodrigues, Yvan Vuille, Jon Loman, Nicolas Perrin.

University of Lausanne; Rana Konsult, Sweden.
Sex-chromosome differentiation was recently shown to vary among common-frog populations in Fennoscandia, suggesting a trend of increased differentiation with latitude. By rearing families from two contrasted populations (respectively from northern and southern Sweden), we show this disparity to stem from differences in sex-determination mechanisms rather than in XY-recombination patterns. Offspring from the northern population display equal sex ratios at metamorphosis, with phenotypic sexes that correlate strongly with paternal LG2 haplotypes (the sex chromosome); accordingly, Y haplotypes are markedly differentiated, with male-specific alleles and depressed diversity testifying to their smaller effective population size. In the southern population, by contrast, a majority of juveniles present ovaries at metamorphosis; only later in development do sex ratios return to equilibrium. Even at these later stages, phenotypic sexes correlate only mildly with paternal LG2 haplotypes; accordingly, there are no recognizable Y haplotypes. These distinct patterns of gonadal development fit the concept of 'sexual races' proposed in the 1930's, with our two populations assigned to the 'differentiated' and 'semi-differentiated' races respectively. Our results support the suggestion that 'sexual races' differ in the genetic versus epigenetic components of sex determination. Analyzing populations from the 'undifferentiated race' with high-density genetic maps should help to further test this hypothesis.

Poster session A - MAX 414

## Suppression of X chromosomal gene expression in the male germline of Drosophila melanogaster (51880)

Eliza Argyridou, John Parsch.

Ludwig-Maximilians-Universität München.

When sex chromosomes determine sex, their ploidy differs between males and females. In the XY system, males are hemizygous for the X chromosome. This exposes the X chromosome to unique selective forces that cause it to evolve differently from the autosomes. Previous studies of D. melanogaster have shown that the expression of testis-specific genes residing on the X chromosome is suppressed in the male germline. However, it is not clear whether this phenomenon is restricted to the male germline or if it occurs in other tissues. To examine the extent of the suppression, we compared the expression of X-linked and autosomal reporter genes expressed specifically in various tissues, including male accessory gland, ovary, and Malpighian tubule. The reporter genes were integrated randomly into the genome, resulting in multiple, independent lines with the insertion on either the X chromosome or an autosome. Our preliminary results provide no evidence for suppression of X-linked gene expression in the female germline or in somatic tissues, suggesting that the mechanism is specific to the male germline.

Poster session A - MAX 414

## Extreme X-chromosomal enrichment of genes with male-biased expression in the Drosophila melanogaster brain (51892)
Genes expressed differently between males and females (sex-biased genes) often show a non-random distribution in the genome, particularly with respect to the sex chromosomes. Previous studies of Drosophila melanogaster found a general paucity of male-biased genes on the X chromosome in comparisons of whole flies or body segments containing reproductive organs. To better understand the chromosomal distribution of sex-biased genes in various tissues, we used a common framework to analyze high-throughput data comparing male and female gene expression in individual tissues, composite structures, and whole flies. In the brain, we find a strong, highly significant enrichment of male-biased genes on the X chromosome. Weaker enrichment of X-linked male-biased genes is seen in the head, suggesting that most of this signal comes from the brain. In all other tissues, there is either no departure from the random expectation or a significant paucity of male-biased genes on the X chromosome. The brain and head also differ from other tissues in that their male-biased genes are significantly closer to binding sites of the dosage compensation complex. We propose that the interplay of dosage compensation and sex-specific regulation can explain the observed differences between tissues and reconcile disparate results reported in previous studies.

# Sex determination in Silene: male and female heterogamety (51972)

**Bohuslav Janousek**, Veronika Slancarova, Jitka Zluvova, Roman Gogela, Jana Zdanska, Bengt Oxelman, Alex Widmer, Boris Vyskot.

*Institute of Biophysics, Brno, Czech Republic; University Gothenburg, Gothenburg, Sweden; ETH Zürich, Zürich, Switzerland.*

The plant genus Silene (namely section Melandrium) has become a model for evolutionary studies of sex chromosomes and sex-determining mechanisms in plants. In spite of this, the subsection Otites, that includes even more dioecious species then section Melandrium, remained neglected for a long time. Studies in S. colpophylla and Silene otites show that dioecy and the sex chromosomes in these species (subsection Otites) evolved independently from those in S. latifolia (section Melandrium) and we have further found that the sex-determining system in S. otites, a species closely related to S. colpophylla, is based on female heterogamety, a sex determination system that is unique among the Silene species studied to date. Our phylogenetic data suggest that a switch from XX/XY sex determination to a ZZ/ZW system (or vice versa) probably must have occurred in the subsection Otites. This is the first report of two different types of heterogamety within one plant genus of this mostly non-dioecious plant family. Current availability of high throughput sequencing technologies enables us to study evolution of these sex determining systems in detail and to compare the results obtained in the subsection Otites with the results obtained in the section Melandrium.
**Transition in sexual system and sex chromosome evolution in the tadpole shrimp Triops cancriformis (51998)**

**Africa Gomez**, Thomas C. Mathers, Robert L. Hammond, Ronald Jenner, Jennifer Atkins.

*University of Hull; University of Leicester; Natural History Museum.*

Transitions in sexual system and reproductive mode may affect the course of sex chromosome evolution, for instance by altering the strength of sexually antagonistic selection. However, there have been few studies of sex chromosomes in systems where such transitions have been documented. The European tadpole shrimp, Triops cancriformis, has undergone a transition from dioecy to androdioecy (a sexual system where hermaphrodites and males coexist), offering an excellent opportunity to test the impact of this transition on the evolution of sex chromosomes. To identify sex-linked markers, to understand mechanisms of sex determination and to investigate differences between sexual systems, we carried out a genome-wide association study using Restriction-site Associated DNA sequencing (RADseq) of 47 males, females and hermaphrodites from a dioecious and an androdioecious population. We analyzed 22.9 Gb of paired-end sequences and identified and scored >3,000 high coverage genomic RAD markers. Marker presence/absence, SNP association, and read depth identified 52 candidate sex-linked markers. We show that sex is genetically determined in T. cancriformis, with a ZW system conserved across dioecious and androdioecious populations and hermaphrodites likely having evolved from females. Results indicate that the structure of the sex chromosomes differs strikingly, with a larger sex-linked region in the dioecious population.

**Unique evolutionary features of the pseudoautosomal region of the Ectocarpus UV sex chromosomes (52079)**

**Agnieszka Lipinska**, Remy Luthringer, Alexandre Cormier, Akira Peters, Denis Roze, Mark Cock, Susana Coelho.

*Sorbonne Universités, UPMC Univ Paris 06, Station Biologique de Roscoff, Roscoff, France; Bezhin Rosko, 29250 Santec, France.*

While the processes shaping the evolution of sex chromosomes are increasingly well understood in diploid organisms, haploid sex determination systems (U/V) have been understudied. We have recently sequenced and analysed the sex determining region of the model brown alga Ectocarpus (Ahmed et al. 2014). In Ectocarpus, sex is expressed in the gametophyte generation, during the haploid phase of the life cycle, and both the female (U) and the male (V) sex chromosomes contain non-recombining regions. Using experimental and theoretical approaches, we have investigated here the extensive pseudoautosomal regions (PARs) that border the SDR on the Ectocarpus sex chromosome. We show that recombination events are unevenly distributed along the PARs, and reveal the distinct evolutionary features of this region, that include accumulation and accelerated evolution of not only sex-biased genes but, remarkably, of genes differentially expressed during the gametophyte versus sporophyte generation of the life cycle (generation-biased genes). In agreement with our
experimental data, theoretical models predict that the evolution of the PAR in haploid sex
determining systems may be shaped by generation-antagonism, provided that different
selection pressures act on males and females.

Partial inactivation of the chicken Z chromosome is a response to selection for dosage compensation (52104)

Fabian Zimmer.

University College London.

The loss of gene content on the non-recombining Y or W chromosome results in a reduction
in gene dose for the heterogametic sex. For dosage sensitive genes, reduced gene dose leads to
selection in the heterogametic sex for dosage compensation. However up-regulation in the
heterogametic sex to balance gene dose effects can lead to hyper-transcription in the
homogametic sex. We recently investigated the status, mechanism and consequences of
dosage compensation in chicken using RNA-Seq data from multiple somatic and gonadal
tissues. Our results reveal the conflict between the heterogametic and homogametic sexes
over dosage compensation. We show that a subset of highly expressed genes on the Z
chromosome are dosage compensated in females (the heterogametic sex). These same genes
show allele-specific expression in males, indicating that they are partially activated in the
homogametic sex. This results in a system of Z inactivation analogous to X inactivation in
mammals, although the system has not spread to the entire Z chromosome. Our findings
indicate that the combination of partial Z inactivation and gene-by-gene dosage compensation
results effective dosage compensation for dosage sensitive genes in chicken, and that sex
chromosome inactivation in the homogametic sex may be a common consequence of dosage
compensation.

Characterization of Northern pike (Esox lucius, Esociformes, Teleosts) master sex determining gene and evolution of sex determination in Esociformes (52161)

Qiaowei Pan, Ayaka Yano, Jennifer Anderson, Julien Bobe, Laurent Journot, John Postlethwait, Manfred Schartl, Amaury Herpin, Yann Guiguen.

INRA, Laboratoire de Physiologie et Génomique des Poissons; MGX (Montpellier Genomix); University of Oregon; University of Wuerzburg.

The understanding of the evolution of sex determination (SD) in vertebrates is limited by the
scarcity of known SD genes. Although in mammals SRY is highly conserved as the master
SD gene, the recent discovery of new SD genes in fish reveals an important diversity of
genetic sex determination systems. Following the identification in Salmoniformes of sdY, as a
novel SD gene in vertebrates, we expanded our studies into its sister group Esociformes.
Using a transcriptomic approach we identified in Esox lucius a duplicated copy of an
autosomal gene that could act as a strong candidate master SD gene. This gene was found to
be expressed only in the testis and is unique to the male genome which is in agreement with
the known XX/XY SD system of E.lucius. Subsequent functional targeted inactivation of this
gene resulted in male to female sex reversal, providing a first and strong functional proof of
its role as a master SD gene. We are currently examining whether this sex determining gene is
conserved in closely related species within this family and exploring the potential diversity of
SD systems and their evolution in more distant species of Esociformes.

Poster session A - MAX 414

Modeling the evolution of recombination in sex chromosomes (52188)

Elisa Cavoto, Nicolas Perrin, Jérôme Goudet, Samuel Neuenschwander.

University of Lausanne.

One of the key factors involved in the evolution of sex chromosomes is the interaction
between the evolution of a sex antagonistic trait and the accumulation of deleterious
mutations. These two processes affect recombination in opposite directions. A sex
antagonistic variant arising on a sex chromosome favors the arrest of recombination; as a
consequence, deleterious mutations accumulate, generating an opposite selective force
favoring recombination. Using individual based simulations, we explore the interaction of
these two processes in a finite sexual population. We vary the strength of selection on a sex
antagonistic trait and the genetic load due to deleterious mutations, and track the evolution of
recombination. We find that when the sex antagonistic effect is strong, recombination is
heavily repressed in males, independently of the genetic load, while in the absence of the sex
antagonistic trait, sex chromosomes recombine freely. Surprisingly, the transition between
these two opposite states is not gradual, and always occurs for a specific strength of sex
antagonistic selection, largely independent of how many and how deleterious the mutations
are. These results will be discussed in the light of existing theories for sex chromosome
evolution.

Poster session A - MAX 414

Evolution of the guppy sex chromosomes (52217)

Alison Wright, Felix Breden, Niclas Kolm, Judith Mank.

University College London; Simon Fraser University; Uppsala University.

Early coloration genetics research in the guppy revealed that many colouration genes are Y-linked, and these findings formed the basis of Fisher's theory of sex chromosome evolution nearly a century ago. In order to characterize the degree of differentiation and population variation in sex chromosome evolution, we sequenced the genomes of male and female P.
reticulata and P. parae, two closely related species. Our de novo genome assembly has a total length of 685,443 kbp and consists of 135,564 scaffolds with an N50 and N90 of 14,019 and 2,403 respectively.

# Does female meiotic drive affect the evolution of multiple sex chromosomes in amniote vertebrates? (52486)

**Martina Johnson Pokorna**, Marie Altmanova, Lukas Kratochvil.

*Faculty of Science; Charles University in Prague; Institute of Animal Physiology and Genetics, The Academy of Sciences of the Czech Republic.*

The difference in the involvement of sex-specific sex chromosomes in female meiosis subjected to the female meiotic drive under male versus female heterogamety is theoretically well known. Essentially, the male-specific Y chromosome is not involved in female meiosis and is therefore sheltered against the effects of the female meiotic drive affecting the X chromosome and autosomes. Conversely, the Z and W sex chromosomes are both present in female meiosis. Non-random segregation of these sex chromosomes may be a consequence of their rearrangements leading to the emergence of multiple sex chromosomes. We hypothesize that under female heterogamety, where both sex chromosomes are involved in female meiotic drive, this would result in a biased sex ratio, which should be penalized by selection. Therefore, the emergence of multiple sex chromosomes should be less constrained in the lineages with male rather than female heterogamety. Our broader phylogenetic comparison across amniotes fully supports this prediction. We suggest that our results are consistent with the widespread occurrence of female meiotic drive in amniotes.

# Comparisons of introgression at sex-linked vs. autosomal markers in secondary hybrid zones of two anuran systems with XY-sex determination (52527)

Christophe Dufresnes*, Jörn Frederik Gerchen*, Tomasz Majtyka, Stuart J.E. Baird, Maria Ogielska, Nicolas Perrin, **Matthias Stöck**.

*University of Lausanne, Dep. Ecology and Evolution, Lausanne, Switzerland; Leibniz-Institute of Freshwater Ecology & Inland Fisheries (IGB), Müggelseedamm 301, D-12587 Berlin; Dep. Evol. Biology & Conserv. of Vertebrates, Wroclaw University, Poland; Research Facility Studenec, Inst. of Vertebrate Biology, Acad. Sciences of the Czech Republic, Brno.*

Dominance hypothesis, faster X (Z), faster male and faster-heterogametic-sex theory may explain or contribute to Haldane's rule, stating that in interspecies crosses, the heterogametic sex (XY-males, ZW-females) suffers greater fitness depressions than the homogametic (XX, ZZ). For XY-systems under secondary contact (allopatric speciation), introgression at
autosomes should be greater than X-chromosomal and both should surpass Y-linked
introgression. However, in animals (including amphibians) with homomorphic, occasionally
recombining sex chromosomes, this rule remains poorly studied. Using classical and
transcriptome-based microsatellite markers, we study sex-linked vs. autosomal introgression.
Genome-wide versus linkage group-specific hybrid index estimates (HI) in a secondary
contact of tree frogs (Hyla arborea/H. orientalis) across Poland revealed stronger introgression
at randomly chosen autosomal vs. sex-linked markers. We currently test whether differential
introgression can also be observed in hybrid zones of Palearctic green toads
(B.siculus/B.balearicus/B.viridis) in Italy. We compare both systems and discuss alternative
hypotheses like sex-biased dispersal and hybrid zone movement. (*equal contribution).
Ackn.: C. Betto-Colliard, L. Bonato, A. Borzée, A. Brelsford, C. Dieterich, B. Janic, A.
Ogrodowczyk, W. Kloas, N. Novarini, S. Tamschick, M. Rybacki, J. Röhr, A. Sicilia, G.
Turrisi, P. Zielinski.

The genomics and genetics of male ornaments and sex determination
supergene in the Trinidadian guppy Poecilia reticulata (52567)

Axel Künstner, Margarete Hoffmann, Paloma Medina, Verena A Kottler, Detlef Weigel,
**Frank Chan**, Christine Dreyer.

Max Planck Institute for Developmental Biology, Tübingen, Germany; Max Planck Institute
for Evolutionary Biology, Plön, Germany; Lübeck Institute of Experimental Dermatology,
University of Lübeck; Friedrich Miescher Laboratory of the Max Planck Society, Tübingen,
Germany.

Attracting mates, to a male Trinidadian guppy, is of utmost evolutionary significance. Under
strong selection for male ornaments, theory predicts and genetic evidence supports that tight
linkage may evolve between genetic sex determination and male ornament loci to form a
"supergene". The guppy Poecilia reticulata has long been an outstanding ecological model
organism for studying sexual selection. Here we will present our work towards establishing
the guppy as a genomic evolutionary model organism. To discover parts of the genome
specific to the male, we have separately constructed male and female high-quality genome
assemblies from inbred Guanapo guppy siblings (approximately 760Mb; N50: female
5.38Mb; male 2.82Mb). We extend our previous genetic results showing that the guppy
linkage group 12 is the sex chromosome and we highlight its evolutionary turnover from
rearrangements and transposable element insertions. Combining transcriptomics, population
genetic and comparative genomics, we will discuss features of the male-specific genome and
potential candidates for the guppy sex determination locus. The genomic resources allow us to
consolidate past and current genetic mapping work on male pigment patterns, showing strong
yet incomplete linkage with sex determination. Our results herald an exciting new chapter for
this classical ecological model organism.
# Chameleons out of disguise: evolution of karyotypes and sex chromosomes (52611)

**Michail Rovatsos**, Martina Johnson Pokorná, Marie Altmanova, Lukáš Kratochvíl.

*Department of Ecology, Faculty of Science, Charles University in Prague, Prague, Czech Republic; Institute of Animal Physiology and Genetics, ASCR, Liběchov, Czech Republic.*

Chameleons are well-known, highly distinctive lizards characterized by their unique morphological and physiological traits. Despite the popularity of chameleons, their karyotypes and sex determination system have remained largely unstudied. We prepared metaphase chromosome spreads in both sexes from 13 species of chameleons. The karyotype of all individuals was studied by classical (conventional stain, C-banding) and molecular (comparative genomic hybridization, in situ hybridization with rDNA and telomeric sequences) cytogenetic approaches. Subsequently, we carried out phylogenetic analyses combining our results and previously published data. In contrast to most sauropsid clades, our results show an extensive chromosomal variability, even between closely related species of chameleons. Furthermore, we identified for the first time a ZZ/ZW sex determination system in the genus Furfifer, resolving the long-standing question of whether or not environmental sex determination exists in this group of chameleons. Together with recent findings in other reptile lineages, our work demonstrates that female heterogamety is widespread among amniotes, adding another important piece to the mosaic of knowledge on sex determination in amniotes needed to understand the evolution of this important trait.

Poster session A - MAX 414

# Sex-chromosome homomorphy in Palearctic tree frogs proceeds from both turnovers and X-Y recombination (52631)

**Christophe Dufresnes**, Amaël Borzée, Agnès Horn, Matthias Stöck, Massimo Ostini, Roberto Sermier, Jérôme Wassef, Alan Brelsford, Nicolas Perrin.

*Department of Ecology & Evolution, University of Lausanne; Laboratory of Behavioral and Population Ecology, Seoul National University; Leibniz-Institute of Freshwater Ecology and Inland Fisheries.*

Contrasting with birds and mammals, poikilothermic vertebrates often have homomorphic sex chromosomes, possibly resulting from high rates of sex-chromosome turnovers and/or occasional X-Y recombination. Strong support for the latter mechanism was provided by four species of European tree frogs, which inherited from a common ancestor (~ 5 Mya) the same pair of homomorphic sex chromosomes (linkage group 1, LG1), harboring the candidate sex-determining gene Dmrt1. We tested sex linkage of LG1 across six additional species of the Eurasian Hyla radiation with divergence times ranging from 6 to 40 Mya. LG1 turns out to be sex linked in six out of nine resolved cases. Mapping the patterns of sex linkage to the Hyla phylogeny reveals several transitions in sex-determination systems, including one switch in heterogamety. Phylogenetic trees of DNA sequences along LG1 are consistent with occasional X-Y recombination in all species where LG1 is sex linked. Sibship analyses show that LG1 recombination is strongly reduced in males from most species investigated,
including some in which it is autosomal. This intrinsically low male recombination, together with the presence of important genes from the sex-determination cascade, might predispose LG1 to become a sex chromosome.

# Sequence and structural evolution of the feminizing X chromosome of African pygmy mice (Mus minutoides). (52865)

Pierre Boursot, Paul Saunders, Vladimir Bajic, Khalid Belkhir, Frederic Veyrunes.

*Institut des Sciences de l'Evolution.*

Sexual reproduction and dimorphism imply the evolutionary challenges of producing different phenotypes from a single genome, and dealing with the resulting genetic conflicts. The ways by which the differentiation of chromosomes with sex-linked transmission addresses this challenge is the object of intense theoretical and empirical research. Cases of recent modification of chromosomal sex-determination system are of particular interest in this framework. Two types of X chromosomes segregate in natural populations of the African pygmy mouse (Mus minutoides), one of which (designated X*) is feminizing. This switch to female-limited transmission must have had consequences on the evolution of the genetic information content of the non-recombining part of X* (the extent of which is yet unknown), with phenotypic effects attested by the observation of significant life-history trait differences (fertility and behavior) between XX, XX* and X*Y females. This system also induces bi-sexual transmission of the Y and must enhance male transmission of the X-specific genomic portion, given the observed high frequencies of X*. We present here a preliminary exploration of the correlates of these spectacular changes on the evolution of the structure and sequence of sex-chromosomes by comparing whole-genome shot-gun sequencing of the XX and X*Y genotypes.

# Developing sex markers for studying birds, sex ratios and chromosome rearrangements (52988)

Deborah Dawson, Gavin Horsburgh, Natalie dos Remedios, Terry Burke.

*University of Sheffield.*

In most bird species the sexes are morphologically indistinguishable. No sex-typing markers exist that can be used universally for all birds, and few of those applicable to a wider range of species can be multiplexed. Blood samples are often used for sex-typing birds; however, taking blood can cause stress and discomfort and requires training and appropriate permits. Therefore, less invasive sampling techniques are preferred, especially when studying endangered species – for example, using shed feathers, museum specimens and mouth swabs.