Lund University.

Several published reviews of selection gradients that have been estimated field populations
have failed to show that stabilizing selection is a the predominant mode of selection on
microevolutionary time scales. Instead these reviews have shown that stabilizing and
disruptive selection are equally common in nature. Two major explanations have been put
forward to resolve this apparent discrepancy between these selection gradients on
microevolutionary time scales, and the macroevolutionary assumption that stabilizing
selection should predominate and lead to evolutionary stasis: (1) Low statistical power (2) and
fluctuating selection. However, few studies have been replicated over several generations and
with high sample sizes, and even fewer have attempted verify that stabilizing selection is
indeed operating on macroevolutionary time scales. Here we will present the results of a
multi-season selection study of two congeneric damselfly species (“demoiselles”; Calopteryx
splendens and C. virgo), using large sample sizes and replicated estimates across years and
populations. Additionally, macroevolutionary trends on body size within the suborder
Zygoptera (damselflies) will be presented and compared to the patterns of selection in extant
populations. Finally, I will address other sources of low power within selection studies,
namely low recapture probabilities can affect the results of natural selection studies in field
populations.

Sex in space: what changes? (51738)

Hanna Kokko, Anna Harts, Luke Holman, Lisa Schwanz.

University of Zurich; Australian National University; University of New South Wales.

No-one who travelled from afar to the ESEB disputes that environments vary spatially. Still,
many topics in evolutionary ecology are modelled assuming one panmictic population. I will
discuss two cases where this tradition can make us miss intriguing and important phenomena.
The first question considers spatial variation with dispersal in the context of the lek paradox.
A spatial selection mosaic is sometimes seen to be ‘bad’ and sometimes ‘good’ for female
choice for genetic benefits: bad because it disrupts signal reliability; good because it prevents
female choice from being too efficient for its own good (by depleting variation). We will
show the need to proceed beyond simplistically discrete GxE worlds to find out how often
“good > bad” in this context. The second question: is there an a priori reason to expect that
alleles that benefit one particular sex are favoured when there is sexual antagonism? One
might think ‘no’ in diploid species because approximately ½ of gene flow operates through
males, the other ½ through females. Our modelling shows, however, that a fundamental
asymmetry between female and male importance as determinants of demography can change
this conclusion – but only when there is spatial variation in habitat quality.
# Using a landscape genomic analysis to detect selection by climate in natural populations of a Mexican endemic oak, Quercus rugosa (51733)

Karina Martins, Paul Gugger, Jesus Llanderal Mendoza, Antonio Gonzalez-Rodrigues, Ken Oyama, **Victoria Sork**.

*Ecology and Evolutionary Biology, University of California; Department of Biology, Federal University of São Carlos; Centro de Investigaciones en Ecosistemas, UNAM; Institute of the Environment and Sustainability, University of California.*

Climate places strong selective pressure on local populations. In tree species with extensive gene flow, it is not clear the extent to which climate creates locally adapted populations. By using a landscape genomics analysis of geographic patterns of genome-wide single nucleotide polymorphisms (SNPs), DNA sequence data can be used to test the hypothesis that tree populations are locally adapted to climate. Our goal to find evidence of local adaptation to climate and identify specific loci under selection by surveying DNA fragments spread throughout the genome of Quercus rugosa. We sampled adult leaf tissue from 105 trees in 17 localities across Mexico, extracted DNA, and used the genotyping-by-sequencing (GBS) method to generate SNPs from thousands of “random” 100-bp fragments. We controlled for background demographic history using covariance matrices and then correlated individual SNP genotypes with specific climate variables using the Bayesian approach implemented in Bayenv2. After aligning our fragments to a Quercus lobata reference draft genome, we generated 8,383 SNPs. Several SNPs were correlated with climate variables, usually variables associated with precipitation. We conclude that landscape genomics provides an effective tool to find evidence for selection in natural populations of nonmodel species, and for providing excellent information about the genome-wide genetic structure.

# The evolutionary history of Cochlearia (Brassicaceae) in Central Europe: Population- and phylogenomics of a cold relic in a warming world (51728)

Marcus Koch, **Eva Wolf**.

*COS Heidelberg, Heidelberg University.*

The genus Cochlearia represents an isolated evolutionary lineage that diverged from its Mediterranean sister clade during the Miocene and since that did not underwent any significant speciation until Pleistocene glaciation and deglaciation cycles. During the Pleistocene approximately 20 taxa evolved within a polyploid complex, with most of the species closely associated with cold-characterized habitats. Similar eco- and phenotypes of varying ploidy levels emerged and are scarcely distributed all over Europe and the Circumarctic. One sub-group of species is occurring mostly along coastal lines and a second sub-group is highly restricted to mountain and high elevation/altitude regions. The proposed project aims to unravel the evolutionary history of the various species, subspecies and cytotypes on a high-resolution-scale in space and time. The resulting evolutionary-systematic framework will lay the ground to study in particular hypotheses on parallel evolution and
adaptation to cold environments with its respective characteristics and types of habitats (e.g. bedrock types, elevation, etc.).

# Effects of environmental heterogeneity on phenotypic and genetic variance components in a tree swallow population (51696)

**Audrey Bourret**, Dany Garant.

*Université de Sherbrooke.*

Despite numerous reports of selection on heritable traits in wild populations, expected evolutionary responses are often absent. Different causes for this stasis are suggested, including undescribed fluctuating selection and unstudied factors influencing phenotypic/genetic variance components. Heterogeneous environmental conditions, in space and/or in time, can affect both selective pressures and trait heritabilities in wild populations and thus reduce our capacity to predict evolutionary changes. Here, we will use data from a long-term study of Tree swallow (Tachycineta bicolor) in southern Québec (Canada) to assess the effects of environmental heterogeneity on phenotypic and genetic variance components of several traits. This study system, followed since 2004, is composed of 400 nest boxes equally distributed within 40 farms in a highly heterogeneous agricultural landscape. Previous studies in this population reported patterns of fluctuating selection in direction and/or strength for morphological and reproductive traits over space and time. Our analyses will assess the importance of phenotypic and genetic variance components across these scales and provide predictions on the evolutionary potential of these traits in this population. Our results will thus contribute to a better understanding of the environmental effects on evolutionary processes in the wild.

# Evolutionary Origin of Antimicrobial Peptide (AMP) Resistance in Firmicutes Bacteria (51678)

**Sonja Grath**, Helge Feddersen, Susanne Gebhard.

*Department of Biology II, University of Munich (LMU), Planegg-Martinsried, Germany;*
*Department of Biology and Biochemistry, University of Bath, United Kingdom.*

To combat the alarming rate of antibiotic resistance, antimicrobial peptides (AMPs) are seen as promising new drugs. However, AMP resistance already exists in many bacteria, including important pathogens. We focus on BceAB-like transport systems, which mediate AMP resistance in a wide range of Gram-positive bacteria. Here, we present a highly interdisciplinary approach that combines bioinformatic analyses of the evolutionary origin of BceAB-like transporters with experimental work on the structure and function of these proteins. Protein domains – the evolutionary, functional and structural building blocks of
proteins – are the modules on which evolution acts. Bce-like transporters possess two FtsX domains of unknown function, which also occur in other resistance transporters found in most bacterial phyla. To gain insights into the relationship and evolution of the diverse group of FtsX-domain transporters, we studied their domain arrangements. Computational analyses of FtsX domains showed that the two domains in BceAB-like transporter have diverged from one another, which is a good indication of the evolution of separate functions. Our approach is aimed to gain insights that can ultimately lead to the development of new stochastic models for the evolution of antibiotic resistance in general or of new drugs that counteract this resistance.

# Domestication of Lima bean (Phaseolus lunatus L.) and its adaptation (51660)

**Maria Chacon**, Jaime Martinez-Castillo.

*Universidad Nacional de Colombia; Centro de Investigación Científica de Yucatán.*

Lima bean is an ancient crop widely distributed in Mesoamerica and the Andes. Three wild gene pools with disjunct distributions are recognized: the Andean one distributed on the western slope of the Andes in Ecuador and northern Peru, the Mesoamerican I located in central-western Mexico, and the Mesoamerican II distributed from southern Mexico to northern Argentina, always on the eastern slope of the Andes. Humans domesticated Lima beans in at least two separate events: once in Mexico from wild populations of the gene pool MI, and a second event in the Andes of Ecuador-northern Peru. Both domestication events resulted in strong founder effects and in a group of landraces that although share many domestication traits, also differ in many morphological characteristics and in their adaptation to diverse agroecological conditions. In this study, we applied Genotyping by Sequencing in a set of wild and domesticated individuals of Lima bean representative of its geographical distribution in the Americas for two purposes: identify genomic regions associated with climate adaptation and with the adaptive syndrome of domestication. The present results contribute to our understanding of the adaptation processes of wild species to new environments during domestication and the origin of traits of agricultural importance.

# Genetic structure and signature of selection in a cyanobacterial lichen symbiosis (51646)

**Silke Werth**, Hörður Guðmundsson, Zophonías Oddur Jónsson, Ólafur Sigmar Andrésson.

*Institute of Plant Science, University of Graz, Austria; Life and Environmental Sciences, University of Iceland, Iceland.*

Lichens represent a textbook example of mutualistic symbiosis. For green-algal lichens, evidence is mounting that the ecological niche of the lichen-forming fungi is shaped by
associations with green-algal strains that are locally adapted to specific ecological and climatic conditions. These green-algal associations are frequently highly specific, with lichen-forming fungi associating with one or few green-algal taxa. Cyanobacterial symbioses represent about 10% of the lichens. Cyanobacterial lichen symbioses frequently show low specificity, with local strains being present in a lichen that are frequently more closely related to free-living or bryophyte-associated cyanobacteria than to the cyanobacterial strains occurring in the same lichen, collected from another site. Here, we compare the genetic structure among P. membranacea and its Nostoc photobiont based on ddRAD tag sequences. We found differences in genetic structure among lichen symbionts, with the fungus showing less isolation by distance than its associated cyanobacteria. Finally, we detect outlier RAD tag loci in both symbionts and relate these to the bioclimatic factors and environmental conditions of the sites to evaluate whether either one of the partners exhibits signatures of selection.

## Long term sperm competition radically alters male success (51630)

Tom Price, **Paulina Giraldo-Perez**, Paul Herrera, Nina Wedell.

*University of Liverpool; University of Vienna; University of Exeter.*

Competition between sperm from more than one male within females has major evolutionary impacts. However, research has typically focused on females that store sperm for a short time. In nature, females from many insects and reptiles store sperm overwinter or summer, and some may store sperm for decades. Here we investigate sperm competition in the fruit fly *Drosophila pseudoobscura*. We show that sperm competition that occurs over winter has radically different outcomes to the short term sperm competition seen in the summer. Moreover, overwintering duration greatly increases the cost of carrying an ejaculate, with high death rates among females that have mated with particular male genotypes. We suggest that many of the puzzles of reproductive physiology may turn out to be adaptations to long term sperm storage and competition.

## Resistance and tolerance towards parasites in a polymorphic insect (51645)

Beatriz Willink, Erik I. Svensson.

*Lund University.*

The role on biotic conflicts promoting the buildup of distinct genetic clusters is widely appreciated in evolutionary biology. Evolutionary arms races propelled by parasitism and sexual conflict can be driven to a halt through the evolution of alternative phenotypic strategies governed by or linked to a few major loci. In the pond damselfly *Ischnura elegans* (*Common Bluetail*) sexual conflict over mating rates is involved in the maintenance of female genetic colour morphs via frequency-dependent male-mating harassment. However, several
other traits differ between these discrete morphs. These damselflies are parasitized by water
mites (Arrenurus spp.) whose abundance and pathogenicity may vary largely across
populations and years. We analyzed how parasite loads effected female fecundities over a
decade and across a dozen populations in southern Sweden. Resistance and tolerance are
integrated differently in the two most common morphs: male coloured females suffered from
higher parasitism but their egg production was largely insensitive to mites, whereas the other
morph carried fewer parasites but their fecundity was more severely affected by the parasite
loads. Our results are in line with the theoretical tenet that negative correlational selection
operates to couple resistance and tolerance, resulting in alternative adaptive peaks of these
sympatric morphs.

Evolutionary Potential of Ectoparasitism by Mites (51750)

Michal Polak, Joshua Benoit.

University of Cincinnati.

Knowledge of the fitness costs of parasitism and the genetic basis of host defensive traits are
critical components of our ability to predict evolutionary response to parasitism. We studied
the evolutionary potential of ectoparasitism by mites in two species of Drosophila hosts, D.
nigrospiracula and D. melanogaster, which occur naturally in the North American Sonoran
Desert and in Taiwan, respectively. We demonstrate significant fitness costs of
ectoparasitism, including damage to host lifespan and reproduction. Both host species
responded to laboratory artificial selection for increased resistance, demonstrating significant
additive genetic variation for defense. Flies resistant to one species of mite exhibited cross-
resistance to the other, indicating that resistance may be a broad-based multiple-parasite
defensive phenotype, as seen in certain other animal, plant and microbial systems. We
performed RNA-seq analyses to characterize acute responses to ectoparasitism. Parasitized
flies exhibited over 600 genes with differential expression compared to controls. Among flies
exposed to mites but that evaded parasitism, 13 genes were upregulated while 27 were
downregulated. Among upregulated genes, some are involved in gluconeogenesis and amino
acid metabolism, suggesting shifts in metabolic processes resulting from defensive activities.
This transcriptional characterization identifies potentially variable genes serving as substrate
for evolutionary response under parasite-mediated selection.

Coevolution between the red flour beetle and Bacillus thuringiensis bacteria:
transcriptome analysis of host defence after experimental evolution (51782)

**Barbara Milutinovic**, Jennifer Greenwood, Kevin Knoblich, Philip Rosenstiel,
Daniela Esser, Hinrich Schulenburg, Joachim Kurtz.
Institute of Science and Technology Austria; Institute for Evolution and Biodiversity
(University of Münster); Institute of Clinical Molecular Biology (CAU Kiel); Zoological
Institute (CAU Kiel).

Host-parasite interactions are ideal systems for studying fast coevolutionary processes. We performed a laboratory evolution experiment using an oral infection system of the red flour beetle Tribolium castaneum and the entomopathogenic bacterium Bacillus thuringiensis. We were specifically interested in distinguishing coevolution-specific patterns from patterns resulting from the adaptation to a non-changing antagonist. For this, we used such an experimental design where the antagonists were either adapting reciprocally to each other ('coevolution' treatment), or to a non-changing, ancestral parasite or host genotype, respectively ('evolution' treatments). We found that after only seven host generations, parasite virulence was increased in the 'coevolution' treatment, but not in the parasite 'evolution' treatment, where some replicate lines of the parasite even showed reduced virulence. By contrast, the hosts evolved to increased resistance in both 'coevolution' and 'evolution' treatments. Using RNA sequencing, we studied the transcriptomes of the evolved hosts upon infection to find out to what extent differences in the regulation of host defences might be responsible for the fast (co-) evolutionary responses of the hosts. To detect evolved differences in host defences shaped by the differing selection pressures we compared transcriptome responses of the selected hosts upon infection and will report our first results.

Poster session A - GEN 2000

Contemporary evolution of immunity in invasive species: the case of the domestic mouse (Mus musculus domesticus) and of the black rat (Rattus rattus) in Senegal. (51810)

**Christophe Diagne**, Khalilou Bâ, Carine Brouat, Nathalie Charbonnel, Ambroise Dalecky, Mamoudou Diallo, Emmanuelle Gilot-Fromont, Laëtitia Husse.

Centre de Biologie pour la Gestion des Populations (CBGP) Montpellier, FRANCE; IRD-BIOPASS/CBGP (Dakar, SENEGAL); Département de Biologie animale (FST/UCAD, Dakar, SENEGAL); LPED UMR 151 IRD, Marseille FRANCE; VetAgroSup / LBBE (Lyon, FRANCE).

Biological invasions provide unique opportunity for studying adaptive evolution over contemporary time scales. The recently refined “evolution of increased competitive ability” (EICA) theory predicts that invasive populations are likely to favour less expensive antibody-mediated immunity at the expense of costly cell-mediated one, what would increase their competitive ability.

We tested this hypothesis by comparing immune responses of invasive (Mus musculus domesticus, Rattus rattus) and native (Mastomys erythroleucus) rodents along invasion routes in Senegal. We estimated several components of immunity, including humoral pathways (natural antibodies and complement) and inflammation (haptoglobin).

We found significant differences in immune investment between native and invasive rodents, as well as between anciently established and wave-front populations of invasive species. Surprisingly, inflammatory responses were found to increase in wave-front populations of both invaders, whereas an increase in humoral responses was only detected in M. m.
domesticus. These results are compatible with some patterns observed when studying parasite
communities (helminths, bacteria) along invasion routes, which highlighted higher infection
risks for invasive hosts in wave-front populations. Experimental immune challenges are in
progress to decipher whether these changes in immune investments may be explained by
selection or plasticity.

Poster session A - GEN 2000

A targeted proactive response to prevent disease outbreaks in ant societies
(51870)

Christopher D Pull, Simon Tragust, Mark JF Brown, Sylvia Cremer.

IST Austria; University of Regensburg, 93040 Regensburg, Germany; Current address: University of Bayreuth, 95447 Bayreuth, Germany; Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK.

Infectious diseases will have represented a major challenge during the evolution of sociality,
given that close contact with conspecifics is a key transmission route for many pathogens. To
prevent epidemics, societies have evolved mechanisms to reduce pathogen exposure, and to
prevent transmission when infections do occur. The most efficient way to block transmission
is to break the infectious cycle of the pathogen.

Here we show how ants alter their behavioural response, from the initial intensive care of pathogen-exposed colony members, to a colony-level disease-containment strategy, when an individual becomes fatally infected. Crucially, we found that the ants responded proactively towards infected colony members, inhibiting pathogen replication early during the infection cycle, before they became a source of infection to others. The ants achieved this through the very early detection of sick individuals, before they displayed outward signs of disease, followed by destructive mechanical and chemical disinfection, which inhibits pathogen growth.

Thus, although this defensive strategy does not cure the sick colony member, it has a
beneficial effect at the colony level, avoiding further infections that may otherwise lead to an
epizootic.

Poster session A - GEN 2000

Parasitism as a driver of age-specific mortality in Asian Elephants (Elephas
maximus) (51896)

Carly Lynsdale, Hannah Mumby, Khyne U Mar, Virpi Lummaa.

University of Sheffield.
Parasitism has long been proposed to drive trade-offs between host investment in reproduction and survival. In natural populations, hosts vary in their ability to resist or succumb to parasite infection and the extent to which such infection impacts upon host health and reproductive fitness. Determining the causes of variation in resistance and the consequences of infection for different individual hosts is key in understanding host-parasite evolution.

We investigated the effect of parasitism as a driver of age specific mortality in a population of semi-captive Asian elephants (Elephas maximus) employed in logging camps across Myanmar. First, using a longitudinal database encompassing elephant life-history, health and reproductive data (n= ~2,350), we determined variation in causes of host mortality across different ages and any sex differences therein. Second, we linked parasite-caused mortality at different ages to individual reproductive history across previous life.

This research highlights the importance of host variation in parasitic resistance and susceptibility, providing data on effects of parasitism on elephant mortality and reproduction across a lifetime. Through determining individuals for which infection may be a particular risk, we provide important insights for the conservation, welfare and management practices of Asian elephants.

Poster session A - GEN 2000

# Protein evolution of Toll-like receptors 4, 5 and 7 within Galloanserae birds (51898)

Michal Vinkler, Hana Bainova, Josef Bryja.

*Department of Zoology, Charles University in Prague; Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic.*

Toll-like receptors (TLRs) belong among essential activators of vertebrate immunity. We analysed interspecific variability in coding sequences of three TLRs (bacterial-sensing: TLR4, TLR5 and viral-sensing: TLR7) within the Galloanserae bird clade (13 species). The investigated TLRs are interspecifically invariant in their tertiary structures but vary in some of their physiochemical properties, mainly in the predicted surface electrostatic potential distribution. The predicted ligand-binding features of avian proteins (mainly TLR4 and TLR5) were distinct from their fish and mammalian counterparts and variable within the Galloanserae clade. We have identified 20 positively selected sites and 79 evolutionarily non-conservative sites, several of which were located in close topological proximity to the ligand-binding sites reported for mammalian and fish TLRs. Most of these functionally relevant positively selected sites were found in TLR5. In viral-sensing TLR7 the variability seems to be functionally far more conservative than the variability in the bacterial-sensing TLRs. Our results suggest that avian TLRs might be differentially adapted to pathogen-derived ligand recognition than the corresponding TLRs in mammals and we have found signatures of positive selection even within the Galloanserae lineage itself.
**Individual multilocus heterozygosity at immune gene loci but not microsatellites influences roe deer natal dispersal (51957)**

Cécile Vanpé, Lucie Debeffe, Maxime Galan, Mark Hewison, Jean-Michel Gaillard, Emmanuelle Gilot-Fromont, Nicolas Morellet, Erwan Quéméré.

LBBE - CNRS; CEFS - INRA; CBGP - INRA; VetAgro-sup - Université Lyon 1.

Most previous studies on immune genes have focused on immunological defence, pathogen resistance, mate preference, or kin recognition. Although both immune function and pathogen infestation, which are associated with immune gene diversity, have been found to influence dispersal decisions, no study has yet investigated the influence of immune genes on dispersal. Here, we filled the gap by investigating the effect of individual heterozygosity at five immune gene loci (from the Major Histocompatibility Complex and encoding Toll-Like Receptors) on roe deer natal dispersal. We showed that dispersal propensity was affected by immune gene diversity, with a body-mass dependent effect likely linked to pathogen-mediated selection through over-dominance, whereas individual multilocus heterozygosity at 12 putatively neutral microsatellite markers did not affect natal dispersal. Overall, in support of the body-condition dependent dispersal hypothesis, dispersal propensity increased with both body mass and immune gene diversity. However, very light roe deer with low immune gene diversity dispersed much more than expected from their size. We suggest these poor quality individuals exhibited an emergency life-history tactic to escape a heavily infested environment associated with poor fitness prospects. Our results have potentially important consequences in terms of population genetics and demography, and improve our knowledge of host-pathogen evolution.

**The QRS (Quantification of Representative Sequences) pipeline for amplicon sequencing: Case study on within population ITS1 sequence variation in a microparasite infecting Daphnia. (51964)**

Enrique Gonzalez Tortuero, Jakub Rusek, Adam Petrusek, Sabine Giessler, Dimitrios Lyras, Sonja Grath, Federico Castro Monzon, Justyna Wolinska.

Department of Ecosystem Research, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB); Berlin Centre for Genomics in Biodiversity Research (BeGenDiv); Department of Biology II, Ludwig Maximilians University, Munich; Department of Ecology, Faculty of Sciences, Charles University in Prague.

Next Generation Sequencing (NGS) platforms are replacing traditional molecular biology protocols like cloning and Sanger sequencing. However, accuracy of NGS platforms has rarely been measured when quantifying relative frequencies of genotypes or taxa within populations. Here, we compared results generated by 454 amplicon sequencing with the results obtained from Sanger sequencing of cloned PCR products. Specifically, we focused on sequence variation of the first internal transcribed spacer (ITS1) region of the nuclear ribosomal DNA of the ichthyosporean Caullerya mesnili, a microparasite that commonly
infects water fleas (Daphnia). Caullerya samples were obtained from seven spatially isolated
host populations, some of which were sampled across different years (16 population samples
altogether). In order to analyse 454-generated sequence data, we developed a bioinformatic
pipeline – Quantification of Representative Sequences (QRS) – that clusters slightly varying
sequences into representative variants and determines the frequency of these variants per
population sample. Overall, there was a good correspondence in absolute frequencies of ITS1
variants obtained from Sanger and NGS sequencing; consequently, the respective analyses of
molecular variance (AMOVA) resulted in similar amounts of genetic variance partitioned
across spatial and temporal components. Our results support the usefulness of amplicon
sequencing data for studies of within-population structure.

Variation of vector competence in Culicoides sonorensis (51979)

Ramiro Morales-Hojas, Rhiannon Silk, Malcolm Hinsley, Irina Armean, Paul Kersey, Simon Carpenter, Mark Fife.

*The Pirbright Institute; European Bioinformatics Institute.*

Culicoides species include major vectors of livestock disease agents such as Bluetongue (BTV), Schmallenberg and African Horse sickness viruses. Understanding the genetics of virus transmission is a fundamental step towards controlling these diseases. As in the case for other vector-borne diseases, this task can be greatly facilitated by the availability of a genome sequence, however the closest phylogenetic species to the biting midges for which complete annotated genomes are available are the mosquitoes, which have a divergence of more than 200 million years. With the aim of understanding the genetic basis of vector competence in C. sonorensis, the North American vector of BTV, we have de novo sequenced the first genome for this group of vector species. Using this genome as reference, we have studied the differences in gene expression between individuals that are susceptible to virus infection and are, thus, vector competent, and those that are refractory to infection and are not capable of BTV transmission. The differences observed will help understanding the evolution of Culicoides-BTV interactions and the relevance of genetic variation in vector species for arbovirus transmission. This information will be central to control BTV transmission and its range expansion.

Why Sexually Transmitted Bacteria Tend to Cause Infertility: An
Evolutionary Hypothesis (51988)

Péter Apari, Joao Dinis De Sousa, Viktor Müller.

Eötvös Loránd University; Katholieke Universiteit Leuven.
Extending earlier work we argue that the tendency of sexually transmitted infections (STIs) to cause infertility is likely to reflect an evolutionary adaptation of the pathogens. We use an evolutionary perspective to understand how STI pathogens may benefit from reducing fertility in the host, and what clues the mechanisms of pathogenesis can offer to the evolution of this ability.

We survey three lines of evidence. First, we present a compilation of recent epidemiological and clinical data to illustrate the breadth and magnitude of the problem; second, we draw on sociological and behavioural data to argue that infertility can destabilize partnerships and thereby increase promiscuity—which facilitates the transmission of STI pathogens; and third, we review the pathomechanisms of STI induced infertility, and demonstrate that most of these mechanisms have a specific targeted effect on fertility, which is strong indication that the mechanisms have evolved specifically for their role in infertility.

Our evolutionary framework also provides clues to why STI induced infertility tends to affect female host more than male hosts, and suggests specific medical interventions.

Poster session A - GEN 2000

Ants do drugs to fight disease (51990)

Nick Bos, Liselotte Sundström, Siiri Fuchs, **Dalial Freitak**.

*Centre of Excellence in Biological Interactions, University of Helsinki and University of
Jyväskylä; Centre of Excellence in Biological Interactions, University of Helsinki.*

Parasites are everywhere, and if anything in life is certain, it is that at one point, you are going
to get infected. One way to fight infection is self-medication, which occurs when an organism
consumes biologically active compounds to clear or inhibit an infection. Self-medication can
either be therapeutic or prophylactic, depending on the health status of the organism when it
consumes the biologically active compounds. Here, we show for the first time that ants
selectively consume harmful substances (Reactive Oxygen Species, ROS) upon exposure to a
fungal pathogen Beauveria bassiana, yet avoid these in the absence of infection. This
increased intake of ROS, while harmful to healthy ants, leads to higher survival of infected
ants. The fact that ingestion of this medicine carries a fitness cost in the absence of pathogens
rules out compensatory diet choice as the mechanism, and provides the first conclusive
evidence that social insects engage in therapeutic self-medication. They have a sense of what
they eat, and can modulate their choice of food in response to environmental challenges such
as pathogens, resulting in a fine-tuned interaction between pathogens and host.

Poster session A - GEN 2000

Steady state and induced immunity among castes of Formica exsecta (52105)

Dimitri Stucki, Liselotte Sundström, Dalial Freitak.
Probably the most striking feature of eusocial insects is the separation into distinct castes, each of which specialize in different aspects of colonial performance. As a consequence gynes, males and workers which perform different tasks follow different life history trajectories. While the short-lived males and long-lived gynes only leave the colony for reproduction, workers experience frequent contact with the surrounding environment. In addition, depending on their task some workers stay closer around the nest (nurses) or spread further outdoors (foragers). Thus, each caste and worker class encounters pathogens at a different frequency, which might influence demands on individual immune defenses. We examined the differences in steady state immunity and expression of immunity after challenge with Beauveria bassiana in males, gynes and two worker classes of Formica exsecta. Using gene expression data for ten genes we found a clear separation between castes in steady state gene expression patterns. The response in gene expression to infection with B. bassiana was distinct between gynes and males but not between nurses and foragers or sexuals and workers in general.

# The Impact of Parasite Mediated Selection on the Host's Genetic and Phenotypic Diversity at the Metapopulation Level (52123)

**Andrea P. Kaufmann**, Ebert Dieter.

Theory suggests that parasite mediated selection varying in space and time is capable of maintaining diversity in disease related traits. Studying parasite mediated dynamics in natural populations has proven challenging because it is difficult to disentangle the relative roles of natural selection, migration, drift and mutation in shaping the genetic structure of a subdivided population. In this project we aim to uncover signatures of spatially fluctuating, parasite mediated selection in a natural metapopulation of Daphnia magna. We hypothesize that the polymorphism in disease related traits of the host can be explained by the dynamic metapopulation structure of the host and the parasite. The spatial variation in the presence and absence of a microsporidian parasites leads to fluctuating selection for and against (if there is a cost of resistance) resistance, respectively. As a consequence hosts evolve specific adaptation to the parasites, which is costly and hence lost in uninfected populations. To test this hypothesis we compare among population variation in neutral marker allele frequencies and quantitative trait divergence and correlate the infection status of local populations (infected or uninfected) with the measured phenotypes to infer local adaptation of the host to the parasite, simultaneously inferring a measure of the cost of resistance.
Use, effectiveness and variability of external immune defense in ants (52148)

Simon Tragust.

*University of Bayreuth.*

Antimicrobial secretions delivered to the environment play a major role in several host-parasite interactions. Although they are generally not viewed as an integral part of the immune system of an organism, these compounds improve an organism's survival and manipulate the microbial community surrounding the organism. It has recently been proposed to that these secretions play an underappreciated selective force in shaping the evolution of insect immune systems. However variability in the susceptibility of different pathogen strains to antimicrobial secretions as well as variability in the effectiveness of antimicrobial secretions within and among species has seldom been shown, despite the fact that it represents the raw material for (co)evolution and might shed new light on the evolution of virulence. Using the recently described external immune defense trait of formic acid as cleaning agent against entomopathogenic fungi I will investigate the universality and variability of this cleaning agent within the formic acid carrying ant subfamily Formicidae as well as the possibility of entomopathogenic fungi to adapt to formic acid.

Poster session A - GEN 2000

MULTIDIMENSIONAL MANIPULATION OF HOST BEHAVIOUR
EXPLAINS THE ECOLOGICAL SUCCESS OF A SOCIAL PARASITE
(52149)

Evelien Jongepier, Isabelle Kleeberg, Susanne Foitzik.

Johannes Gutenberg University Mainz.

Manipulative parasites influence interspecific interactions and thereby the composition of
communities. Yet, how evolutionary dynamics govern the ecological success of these
parasites is still poorly understood. Manipulative parasites frequently alter multiple host traits
and here we test the hypothesis that variation in host resistance to this multidimensional
manipulation drives the parasites' ecological success. We quantified parasite-induced
behavioural alterations in 16 populations of two hosts of the social parasitic ant
Protomognathus americanus. We thereby covered the entire range of these Temnothorax ants,
including non-parasitized populations. We demonstrate that the parasite can manipulate its
hosts along two, interrelated behavioural axes, and that these manipulations promote parasite
survival and prevalence. Hence, the multidimensional manipulation can explain the parasite's
ecological success, whereas initial variation in the host's constitutive defences, which are
target of the manipulation, cannot. Our findings underline the importance of host
manipulation for the ecological and evolutionary dynamics between hosts and parasites.

Poster session A - GEN 2000
# Host age modulates parasite within-host competition (52190)

Rony Izhar, Frida Ben-Ami.

Tel Aviv University.

Among the most striking differences among hosts within most populations is host age, which is a key epidemiological factor, but there is very little data on how age-dependent effects impact ecological and evolutionary dynamics of host and parasite populations. Using two clones of the water flea Daphnia magna and two clones of its bacterial parasite Pasteuria ramosa, we examined how host age at exposure interacts with multiple infections to influence the expression of parasite virulence and lifetime transmission potential. We further analyzed the competitive outcome of multiple infections in different host age groups. We found that multiply-infected hosts were more susceptible to infection and suffered higher mortality than singly-infected hosts. As host age increased competition shifted from coinfection, where both parasite clones succeeded in producing transmission stages, to superinfection, where one of the parasite clones was excluded. Thus, the host population age structure could serve as a limiting factor for parasite strain coexistence. Our results emphasize that the outcome of within-host competition is influenced by the complex interplay between host demography and the ecology of host and parasite populations, and present a call for incorporating age-dependent epidemiological parameters into stage-structured theory and virulence modeling.

Poster session A - GEN 2000

# Local adaptation between malaria and its bird hosts: an experimental approach (52242)

Tania Jenkins, Jessica Delhaye, Philippe Christe.

Dept Ecology and Evolution.

The virulence and dynamics of malaria parasites can depend on whether they coevolve with their vertebrate hosts. Previous studies have investigated the spatial and genetic patterns of malaria and have suggested that coevolution is likely. However, experimental data demonstrating local adaptation, a signature of coevolution, is needed in order to confirm this hypothesis. We tested for local adaptation between the great tit, Parus major, and its malaria parasites by conducting a reciprocal transplant experiment in the field, where we exposed individuals from two populations of great tit to Plasmodium parasites. We were therefore able to assess the extent of host adaptation to their local parasites. We present three main findings: i) there was low support for local adaptation. However, the direction of the effect was more consistent with one of host adaptation and hosts appeared better able to resist foreign parasites; ii) there were site-specific effects of malaria infection on the hosts and iii) there was a sex-bias in infection success. These data represent one of the few experimental studies of parasite-host local adaptation using a natural malaria system. These results may have consequences on the ecology and evolution of vector-transmitted parasites and on the evolution of host defense traits.
# Variation in Toll-like receptor 4 in closely related passerine species adapted for different environments (52243)

Tereza Králová, Michal Vinkler, Hana Bainová, Arild Johnsen, Jan T. Lifjeld, Josef Bryja, Tomáš Albrecht.

Institute of Vertebrate Biology, The Czech Academy of Sciences, Brno, Czech Republic;
Department of Botany and Zoology, Faculty of Science, Masaryk University, Brno, Czech
Republic; Department of Zoology, Faculty of Science, Charles University in Prague, Prague,
Czech Republic; National Centre for Biosystematics, Natural History Museum, University of
Oslo, Oslo, Norway.

Toll-like receptors (TLRs) are designed to optimally bind conservative microbe-associated
molecular patterns (MAMPs). These proteins, therefore, evolve under strong diversifying
selection. It has been repeatedly shown that even MAMPs are structurally variable and this
may be particularly true for structures originating from pathogens occurring at different
latitudes. According to one of the hypotheses, tropical and migratory birds are exposed to
higher pathogen diversity than their closely related sedentary species, and thus they may also
be expected to exhibit higher variability in immune receptors. In this contribution we focused
on genetic variability in Toll-like receptor 4 (TLR4) which binds, amongst other ligands,
lipopolysaccharides from outer membranes of Gram-negative bacteria to trigger the immune
response. Here, we present our result on intra- and interspecific comparison of TLR4 ligand-
binding region sequence variation in closely related passerine species from tropical
(Cameroon, Nigeria) and temperate zone (Czech Republic, Norway). We assessed 15
unrelated individuals per species to evaluate the differences in TLR4 variability and ongoing
selection using 46 species from 26 passerine families. The acquired information provides us
with unique insight into the evolutionary effects acting on this genes in different
environments.

# The Genetic Basis of Behavioral Coevolution: Adaptations in Socially Parasitic Slavemakers and Their Hosts (52258)

Austin Alleman, Barbara Feldmeyer, Daniel Elsner, Susanne Foitzik.

Johannes Gutenberg-Universität Mainz.

In the ant genus Temnothorax, socially parasitic, slavemaking behavior has evolved multiple
times independently. Results of phenotypic studies suggest that slavemakers and hosts, which
tend to be closely related species, engage in evolutionary arms races, coevolving through
reciprocal adaptations. Aside from morphological differences, the behavior and activity
patterns vary markedly between slavemaker and host workers. Slavemaker workers do not
participate in normal worker chores and display raiding activity only during a few weeks in
summer. Conversely, host workers carry out a number of different tasks, including brood care,
foraging, and, during slavemaker raiding season, nest defense. However, the genetic basis of
raiding and defensive behavior, including the primary genes involved in the ongoing
coadaptation of these systems, remains unknown. Through transcriptome analysis of three
host and three slavemaker species, we will investigate three primary objectives: a) to elucidate
the genetic basis of differential behavior patterns within a species, b) the general evolution of
slavemaker raiding and host defensive behavior, and c) search for selective signatures
involved in parasite-host differentiation. We will report on genes and functional groups
responsible for a specific behavioral pattern, their consistency across species, as well as
selective signatures of parasite-host coevolution.

Poster session A - GEN 2000

MIXED DIETS – THE KEY TO A HEALTHY LIFE? (52263)

Franziska Dickel, Johanna Mappes, Dalial Freitak.

Centre of Excellence in Biological Interactions, University of Jyväskylä; Centre of Excellence
in Biological Interactions, University of Jyväskylä; Centre of Excellence in Biological
Interactions, University of Jyväskylä and University of Helsinki.

The uptake of secondary metabolites can increase the ability to combat an infection.
Therapeutic self-medication describes the insect's ability to actively change their diet,
ingesting possibly toxic plants after encountering an infection. Most of the studies so far have
focused on the short term effect of a single diet post infection, rather than looking at the
mixed food in long term. Also, even if the consumption of a harmful substance is increasing
the probability to survive an infection, how is this affecting the long-term fitness of the
insect?

To test this we used larvae of the polyphagous Wood tiger moth, Parasemia plantaginis, fed them with three different food plants (Plantago major, Taraxacum sect. ruderalia, Lactuca sativa) and infected them with a bacterial pathogen, Serratia marcescens. We found that a combination of diet 1- harmful plant and diet 2- nutrient rich plant provides the highest medication effect and furthermore guarantees a normal larval development. Steady state immunity is upregulated in response to the most harmful plant. This indicates that the change of food plants is essential in increasing the ability to survive bacterial infections, but also the combination of several diets is the key for long-term fitness.

Poster session A - GEN 2000

Evolution of immune responses and parasitoid virulence in a spatial context
(52273)

Peter Hambäck, Lisa Fors, Ulrich Theopold, Robert Markus.

Dept Ecol. Env. and Plant Science, Stockholm university; Dept of Molecular Life Sciences, Stockholm university.
In polyphagous parasitoid species, the ability to successfully parasitize hosts may vary between host species and depending on community context, potentially causing population divergence and speciation. Causes for host race formation and speciation are however poorly understood in parasitoid species and deserves further attention. In a system with a eulophid parasitoid (Asecodes parviclava) and three leaf beetle species (Galerucella sp), we found that hosts vary in their ability to encapsulate parasitoid eggs from weak encapsulation (G. calmariensis) to efficient encapsulation (G. pusilla). Encapsulation was shown to involve at least three cell types in the hemolymph and particularly one type was differentially induced among host species. We also found differences among parasitoid populations in parasitism success. Parasitoids hatching from G. pusilla had much higher success rate than parasitoids hatching from G. calmariensis when attacking G. pusilla larvae. This ability was particularly obvious when using parasitoids from some localities, suggesting local adaptation in parasitoid virulence. The differences in parasitoid success rate was also apparent in cytological studies, where induction in several cell types was surpressed when parasitized by a highly virulent parasitoid. We believe that this system is at an early stage of speciation, conclusions that are also supported by genetic studies.

# How are coevolutionary trajectories affected by variable environments?
(52275)

Franziska Brunner, Jaime Anaya-Rojas, Blake Matthews, Christophe Eizaguirre.

Queen Mary University of London; Swiss Federal Institute of Aquatic Research and Technology.

Host-parasite interactions are strongly affected by their environmental context. Differences in such context dependence between populations can occur in two different ways: differences in molecular host responses between populations reflect adaptation to a local optimum whereas different patterns of variation within populations can reveal different levels of genetic diversity and/or how phenotypic plasticity has evolved in each of them.

Using experiments performed with different three-spined stickleback ecotypes and their monogenean parasite Gyrodactylus gasterostei we examined how eutrophication – a major environmental factor affecting stickleback habitat – alters parasite success and molecular host responses on the gene expression level. We found that eutrophication has opposite effects on parasite success between host ecotypes. We also show that host gene expression response to eutrophication is population specific in both mean expression levels and variation within ecotypes. Together, these findings show that ecological conditions can rapidly alter both directional selection and plasticity within a host-parasite system. Both aspects can have an important impact on coevolutionary trajectories.

# Uncovering host defense strategies: bacterial infection in Drosophila melanogaster (52283)
In principle hosts can employ two strategies to limit parasite load. Resistance, a host's ability to limit pathogen load, has been well studied. While tolerance, a host's ability to limit damage caused by a parasite, a phenomenon well documented in the plant literature, is less well understood in animals. Previous work on resistance and tolerance in animals focuses primarily on host survival or health rather than on fitness measures or life history traits like fecundity. Reproduction for insects like Drosophila melanogaster is costly, so it is reasonable to predict a tradeoff in egg and offspring production in response to bacterial infection, depending on the defense strategy employed by the host. Here we aimed to assay resistance and tolerance in response to dietary restriction by limiting protein intake and to characterize bacterial infection pathology at the individual level. Because infectious diseases are not always lethal we chose to test the effect of two non-lethal, persistent bacteria. A low protein diet translated into lower egg production and decreased resistance, but tolerance was unaffected. We uncovered considerable individual variation in resistance despite controlled conditions. Future experiments will reveal the long-term impacts of infection and the underlying causes of individual variation.

# The relationship between host oxidative stress and Plasmodium infection in the canary, Serinus canaria (52320)

**Jessica Delhaye**, Fabrice Lalubin, Philippe Christe.

Inter-individual variation in parasite susceptibility exists among hosts. However, the underlying mechanisms driving these inequalities are still poorly understood. The release of pro-oxidants is known to play a key role in the fight against pathogens with potential harmful side-effects for hosts in terms of oxidative stress. Pro-oxidant and antioxidant compounds have been shown to affect Plasmodium development. In this study, we experimentally infected canaries, Serinus canaria with two Plasmodium strains, P.relictum and P. polare to investigate the link between Plasmodium infection and host oxidative stress. We monitored the infection dynamic in terms of changes in parasite intensity and host oxidative stress, measuring both pro-oxidant production and antioxidant defence traits. We looked at the effect of oxidative stress prior to infection on subsequent Plasmodium development as well as the effect of infection on oxidative stress. One component of oxidative stress prior to infection affected subsequent Plasmodium development. We further found that infection status, parasitaemia and Plasmodium strain affected oxidative stress during the course of infection. These results support that initial oxidative stress can play a role in affecting host susceptibility and that Plasmodium infection can also impose a further physiological stress on the host.
# Coinvasion and Coinfection: evolution and adaptation in two invasive parasites infecting blue mussels (52369)

Marieke E. Feis, K. Mathias Wegner.

*Alfred Wegener Institute; Alfred Wegener Institute.*

Biological invasions of parasites offer ideal opportunities to study coevolution in nature – especially when hosts are faced with repeated invasions of parasites. Such coinvasions not only lead to selection on the host but also to selection on parasites arising from direct competition. Here, we present data from a crossed coinfection experiment using two closely related copepod parasites that have invaded the Eastern Atlantic, infecting mussels. One is the specialist Mytilicola intestinalis that invaded from the Mediterranean Sea in the 1930ies and the other one is the generalist Mytilicola orientalis that invaded from Japan in the 1990ies. This system thus offers the opportunity to study host-parasite interactions along a gradient of different coevolutionary timescales and host specificity. Here we report the first results of this experiment on the phenotypic level focussing on the balance and trade-offs between host and parasite traits, i.e. infectivity – virulence for parasites and virulence - tolerance for hosts. We find different interactions along these trade-offs between both interactions. We also find that the generalist new invader is outcompeting the old invader.

Poster session A - GEN 2000

# Gene diversity of Major histocompatibility complex (MHC) class IIβ alleles of Scandinavian anuran species (52376)

*Maria Cortazar Chinarro, Ella Z. Lattenkamp, Yvonne Meyer-lucht, Anssi Laurila, Jacob Höglund.*

*Uppsala University. Animal Ecology Department.*

Gene diversity of Major histocompatibility complex (MHC) class IIβ alleles of Scandinavian anuran species.

Amphibian populations face a multitude of threats, including habitat degradation, environmental change and infectious disease such as those caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd) or Ranavirus, among others. Major histocompatibility complex (MHC) class II genes play key roles in the vertebrate immune system response. MHC loci are the most polymorphic genes ever reported which are used by vertebrates to withstand newly emerging diseases. The proposed mechanism for why MHC is so polymorphic is balancing selection ultimately caused by parasites and pathogens. MHC Class II molecules bind to chopped up particles of bacteria and macroparasites that have been engulfed by macrophages. When MHC molecules present these particles on the cell surface of the macrophages, antibody production against the disease is induced. Using the Miseq sequencing platform and 10 different microsatellites markers, we investigated the patterns of genetic diversity and differentiation of five species of frogs along a latitudinal gradient in Sweden. For one species, the moor frog (Rana arvalis), preliminary results show low gene
diversity at northern and southern latitudes and high gene diversity at intermediate latitudes.

Poster session A - GEN 2000

# Disentangling genetic and parental effects in determining immune function in a simultaneously hermaphroditic snail (52420)

Otto Seppälä, Laura Langeloh.

Eawag / ETH Zürich.

Parasites are an ubiquitous selective force in natural populations. Evolutionary change in defence traits, such as immune function, requires additive genetic variance in them. However, also parental (especially maternal) effects can be important in determining the strength of immune function, which could affect their evolution by altering the phenotypes on which selection can act. Therefore, understanding the relative role of genetic background and parental effects in determining expression of immune traits is highly important. We investigated variation in constitutive immune defence traits in a simultaneously hermaphroditic snail Lymnaea stagnalis. We compared phenoloxidase-like and antibacterial activity of snail haemolymph across pairs of full-sib families, each pair sharing the same two parents (i.e. same genetic background) but in reversed sex roles. We found that the variation in immune defence traits was largely dependent on the genetic background of snails (i.e. families sharing the same genetic background were often similar, but differed from families with different genetic backgrounds). However, also parental effects played a role indicated by differences between families in some of the family pairs. This suggests that parental effects (possibly due to immune priming) can add to evolution of defence traits against parasites.

Poster session A - GEN 2000

# Microbiota plays a role in oral immune priming in Tribolium castaneum (52476)

Momir Futo, Joachim Kurtz.

Institute for Evolution and Biodiversity.

Animals are inhabited by a diverse community of microorganisms. The relevance of such microbiota is increasingly being recognised in a broad spectrum of species, ranging from sponges to primates, revealing various beneficial roles microbes can play. The red flour beetle Tribolium castaneum represents a well-established experimental model organism for studying questions in ecology and evolution, however, the relevance of its microbial community is still largely unknown. T. castaneum larvae orally exposed to inactivated bacterial components of the entomopathogen Bacillus thuringiensis tenebrionis showed increased survival upon a subsequent challenge with this bacterium. We explored the role of microbiota for oral immune priming in this species. To investigate whether T. castaneum microbiota plays a role
in this phenomenon, we established a protocol for raising germ-free larvae and subsequently
tested whether they differ in their ability to mount such a priming response. Here we
demonstrate that larvae, which lack their microbiota, show decreased survival upon secondary
challenge with bacterial spores, compared to animals which still had, or were allowed to
regain their microbiota before priming. Although the exact mechanism of oral immune
priming is still unclear, we here suggest that the microbiota plays a crucial role in oral
immune priming in this species.

# Not all MHC alleles are equal: different characteristics of MHC Class I alleles among song birds (52497)

Emily O'Connor, Maria Strandh, Jan-Åke Nilsson, Dennis Hasselquist, Helena Westerdahl.

Lund University.

Molecules of the Major Histocompatibility Complex (MHC) play a key role in protecting animals against infection by helping to determine which pathogens can be presented to the immune system for elimination. Song birds (i.e., passerines) appear to possess a larger number of MHC genes than most other animals. However, very little is currently known about potential differences in characteristics and functions among these gene copies which could influence the number of pathogens they recognise.

We have used next generation amplicon sequencing to investigate MHC class I alleles for 12 candidate songbird species spanning the passerine radiation from each of the following families: Passeridae, Muscicapidae, Acrocephalidae, Sylviidae, Phylloscopidae and Paridae.
We found three different MHC allele lengths with a strong phylogenetic signature in the distribution of these sequences among species. In some species these length differences were associated with evidence for different selection pressure. Furthermore, in species from Passeridae, Acrocephalidae and Paridae there were groups of alleles with strikingly little variation. This is counter to expectations for classical MHC genes where selection from a diverse pathogen fauna is expected to generate high allelic polymorphism.

Potential implications for pathogen recognition of the observed differences in allele
characteristics among species will be discussed.

# Use of Concanavalin A in skin-swelling test of immune responsiveness facilitates interpretation of the measurement in rodents (52532)

Barbora Bílková, Tomáš Albrecht, Milada Chudíčková, Vladimír Holáň, Jaroslav Piálek, Michal Vinkler.
Skin-swelling test is a widely used method to quantify immune responsiveness of free-living
animals in immunoecological studies. This test is based on measuring magnitude of tissue
swelling in the time after injection of an artificial inflammatory stimulant, most commonly
phytohaemagglutinin (PHA). However, given the complexity of the immune response,
interpretation of the test results is not completely clear. The aim of our study was to improve
the test protocol to facilitate interpretation of the skin-swelling data. In mice, we compared
cellular immune response to PHA and an alternative pro-inflammatory stimulant
Concanavalin A (ConA). We measured magnitude of the tissue swelling and compared it with
intensity of infiltration of blood cells into the tissue in a 72-hour time frame. Our results show
that the response to ConA and PHA differs in time. ConA induces grater swelling with greater
cellular activity and higher pro-inflammatory cytokine expression than PHA. Furthermore, after
ConA injection, the magnitude of the swelling is positively associated with the cellular
activity. Considering also the molecular binding specificity of the two lectins, we conclude
that ConA is a more suitable stimulant for the skin-swelling test in rodents than PHA.

Evolution of specific resistance against bacterial infection: Based on
genetically hard-wired or phenotypically plastic defences? (52582)

Kevin Knoblich, Robert Peuß, Joachim Kurtz.

Insect immune systems can provide their host with pathogen-specific protection, either via
genetically hard-coded or acquired responses (genetic and phenotypic specificity,
respectively). So far the evolution of phenotypic specificity is not well understood, in
particular during the process of genetic adaption to a pathogen. Therefore, we experimentally
selected the Coleoptera Tribolium castaneum for its ability to survive an infection with either
one of four closely related strains of Bacillus thuringiensis or one of the two Gram-negative
bacteria Lactococcus lactis and Pseudomonas fluorescence. Selection regimes consisted of
immune priming (using heat-killed bacteria) followed by septic challenge (with the same
bacteria as for priming, but alive). After 11 generations, we performed a full-factorial priming
and challenge experiment to discriminate whether genetically hard-wired or phenotypically
plastic immune specificity responded to selection. We found that the beetles evolved a
slightly increased resistance for five out of the six bacteria species or strains. Resistance was
specific for the bacterial species and even strain, i.e. there was no cross-resistance towards the
other bacteria. Survival of the infection was not strongly affected by the priming treatment.
This suggests that in this host-pathogen system, resistance evolution might mostly rely on
genetically hard-wired rather than acquired defence components.
# Host-mutualist and host-parasite coevolution in tripartite interactions (52586)

**Charlotte Rafaluk**, Kayla King.

*University of Oxford.*

Host-parasite coevolution can drive rapid reciprocal adaptation. Several host-parasite coevolution experiments have been carried out to date demonstrating reciprocal coevolutionary change under laboratory conditions. In nature, however, hosts and parasites coexist in complex ecological communities, with different kinds of interaction taking place between different species pairs within the community. In communities where hosts and their parasites coexist, species that decrease the negative impacts caused by parasites to hosts, termed defensive mutualists, may have important effects on the dynamics of host-parasite coevolution. Additionally, coevolution is also likely to occur between the defensive mutualist and the host which may feedback in turn to effect host-parasite coevolution. In order to test whether host-parasite coevolutionary dynamics differ when a protective mutualist is present and to assess how hosts and mutualists coevolve, we are carrying out a coevolution experiment with: 1) treatments allowing a host species, *Caenorhabditis elegans* to coevolve with a parasite species, *Staphylococcus aureus*, in the presence and absence of an evolutionarily static defensive mutualist, *Enterococcus faecalis*; and 2) treatments allowing *C. elegans* to coevolve with a defensive mutualist, *E. faecalis*, in the presence and absence of an evolutionarily-static parasite, *S. aureus*.

Poster session A - GEN 2000

# Differential expression of MHC genes in three species of sparrows indicates conserved functional differences (52589)

**Anna Drews**, Maria Strandh, Lars Råberg, Helena Westerdahl.

*Lund University.*

The Major Histocompatibility Complex, MHC, is an important component of the vertebrate immune system. MHC enables recognition of foreign antigens which triggers an immune response. MHC genes are highly variable and this variation is thought to be maintained by host-parasite interactions. Songbirds have a larger number of MHC genes than most vertebrates. However the individual function of these multiple copies are to a large extent unknown. We have therefore studied gene expression of different MHC gene copies, as a first estimate of their relative importance in the immune system, in three species of sparrows; house sparrows, tree sparrows and Spanish sparrows. All three species had a similar MHC organization containing MHC alleles with low variability. This group of alleles was significantly separated from all the remaining MHC alleles which were highly variable. We hypothesized that these alleles with low variability would be expressed to a lower degree than the other alleles. We used massively parallel amplicon sequencing to determine relative expression of the alleles. Not all alleles were expressed equally; the low variability alleles were expressed to a significantly lower degree. This conserved differential gene expression pattern among species suggests that there are MHC genes of different functions in sparrows.
# Interactions among co-infecting bacterial strains and fluke genotypes shape disease virulence (52654)

Katja-Riikka Louhi, Lotta-Riina Sundberg, Jukka Jokela, **Anssi Karvonen**.

University of Jyväskylä, Department of Biological and Environmental Science, Jyväskylä, Finland.; Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.; ETH Zurich, Institute of Integrative Biology, Zürich, Switzerland.

It is common that several parasite or pathogen genotypes of the same or different species co infect a single host individual. Such co infection can intensify competition for host resources, favoring more competitive strains that are more virulent to the host. Here, we present the first evidence that the genetic identity of the co-infecting partners largely determines the virulence of co infections between bacterial strains and parasitic fluke genotypes, to a degree that the outcome cannot be predicted from the virulence of respective single infections. By measuring the overall disease virulence of single bacterial strains, single fluke genotypes, and combinations of reciprocal co infections, we demonstrate that co infection caused higher than predicted virulence and infection intensity in most strain genotype combinations, but not in all. We conclude that predicting the overall disease virulence may be much more complex than previously acknowledged, making it necessary to consider how genetic interactions among co infecting parasites affect disease dynamics and host health in different host parasite systems.

# Acquired host responses erode advantages of co-infection by multiple parasite genotypes (52658)

Ines Klemme, Katja-Riikka Louhi, Anssi Karvonen.

University of Jyväskylä.

Co-infections by multiple parasite genotypes or species are common and have important implications for host-parasite evolution through within-host interactions. Typically, these infections take place sequentially and thus, co-infection dynamics may be shaped by host immune responses targeted against previous infections. However, our understanding of these processes is limited. Here, we investigated whether acquired host resistance affects interactions between co-infecting parasite genotypes of the trematode eye-fluke Diplostomum pseudospathaceum, infecting one of its intermediate hosts, the rainbow trout Oncorhynchus mykiss. We show that simultaneous attack of two genotypes facilitates parasite establishment in immunologically naïve hosts, which is in accordance with previous results. More importantly, we show that sequential infection and immune priming of the host erode this facilitation in infection, thus significantly altering the interactions between co-infecting
genotypes. Our results may have significant implications for the evolution of co-infections
and parasite transmission strategies.

Poster session A - GEN 2000

Defence by AMP synergies against variable parasites (52677)

Monika Marxer, **Paul Schmid-Hempel**.

ETH Zurich; ETH Zurich.

In the model system of the bumblebee, Bombus terrestris and its trypanosome parasite, Crithidia bombi, parasite populations are highly variable. We studied how hosts can defend themselves despite having genetically fixed immune repertoires. We show experimentally that variation in the concentrations of the expressed genes for anti-microbial peptides (AMPs) can keep different strains of the parasites specifically in check. This defence by "synergistic cocktails" is an efficient and flexible strategy of defence against variable and quickly changing parasites. Some evolutionary implications are discussed.

Poster session A - GEN 2000

MHC and Borrelia in bank voles: Divergent allele advantage (52732)

Kristin Scherman, Martin Andersson, Helena Westerdahl, Lars Råberg.

*Department of Biology, Lund University.*

Parasite-mediated selection is generally invoked to explain the extreme allelic diversity found
in the vertebrate Major Histocompatibility Complex (MHC). Balancing selection may operate
either in the form of heterozygote advantage, or through the interaction of pathogens and
specific MHC alleles. Moreover, heterozygotes with minimal overlap in antigen recognition
should be selected for according to the divergent allele advantage hypothesis. Selection for
divergence can also work on multiple genes favouring individuals that recognise a wider
range of antigens. We surveyed allelic polymorphism at the MHC class II DQB gene in wild
bank voles (Myodes glareolus) hosting Borrelia afzelii, a multi-strain infection causing Lyme
disease in humans. Screening more than 500 individuals and a subset of families on DQB
made it possible to group alleles from four loci in a haplotypic framework. We tested 12
different DQB haplotypes for associations with Borrelia. We found two significant
associations between DQB haplotype and infection prevalence: one associated with resistance
and the other with susceptibility. We found no evidence for heterozygote advantage but the
average pairwise amino acid divergence (p-distance) was higher for voles with the protective
haplotype than other voles. Conversely, voles with the susceptible haplotype had less
divergent genotypes than other voles.
# Transcriptomic response to pathogen challenges in leaf-cutting ants (52737)

Morten Schiøtt, Sze Huei Yek, Jacobus J. Boomsma.

University of Copenhagen.

Social insects can be expected to experience a high selection pressure on their immune system, as their social lifestyle is prone to ease the spread of diseases. This is especially true for leaf-cutting ants due to their large colony size and the monoclonality of their fungal symbiont. Paradoxically genome sequencing projects have revealed that social hymenopterans such as the honey bee have fewer known immune genes than e.g. fruit flies, which may be attributed to social immunity of social insect colonies. Alternatively social insects may have evolved immune genes not known from insect model species. We examined the behavioural and gene expression (using RNA-seq) response in leaf-cutting ants after challenging both the ants and their fungal symbiont with either an ant pathogen (Metarhizium brunneum) or a fungus-garden pathogen (Escovopsis weberi). While the behavioural response by the ants was largely independent of pathogen identity, the gene expression response showed clear differences, and only inoculations with Metarhizium caused a large increase in the expression of known immune genes. Inoculations with Metarhizium also caused a pronounced upregulation of several genes of unknown function. These putative immune genes are currently being functionally analysed using RNAi knock-down methods and immune assays of heterologously expressed proteins.

# Distribution of protective symbiont in natural populations (52749)

Mélanie LECLAIR, Jean-Christophe SIMON, Yannick OUTREMAN.

Université Rennes 1; INRA; Agrocampus-Ouest.

A majority of species maintains associations with symbiotic microorganisms. They can change the ecology and evolution of their hosts by inducing a variety of effects on phenotype. Symbionts are most often heritable; phenotypes induced by symbiotic associations can be transmitted to subsequent generations. The obtained phenotypes can appear very beneficial for the host: some microbial symbionts allow their host to access a new food resource or be protected against their natural enemies. Although very beneficial, these symbiotic associations are sometimes poorly represented or absent in some natural populations. Our goal is to understand why a beneficial trait conferred by a symbiotic association is not spread in all host populations.

To answer this question, the biological model used was the pea aphid and its optional bacterial symbiont leading to many phenotypic effects including protection against natural enemies. The distribution of these symbionts in different specialized populations of aphids was analyzed via numerous field surveys. Two major effects on the distribution of the symbionts, a priori beneficial, were tested: interactions between symbionts and properties of the host environment as pressure of natural enemies.
Our study reveals that distribution of the symbionts in natural populations is affected by many
ecological and evolutionary factors and doesn't respond to a simple relationship 'profit-
fixing'.

Poster session A - GEN 2000

# Is There An Association Between Haemosporidian Parasite Infection And Toll-Like Receptor (TLR) Genotype? (52759)

Haslina Razali, Shinichi Nakagawa, Terry Burke.

*University of Sheffield; University of Otago.*

There is an enormous advantage to being polymorphic in the immune genes such as the major histocompatibility complex and toll-like receptors (TLRs) loci because this increases the chance of combating mutliple pathogens. TLRs are part of the first line of defence in the immune system. In humans, TLR4 and TLR7 have been found to be associated with malaria. We tested whether TLR polymorphism in house sparrows (Passer domesticus) has been shaped by local pathogenic pressure. We hypothesized that different malaria strains exert different selection pressures on the TLRs. Testing for infection with haemosporidian parasites, such as malaria, may result in false negatives, especially using PCR detection methods. The advent of next-generation sequencing enables more accurate detection and identification of haemosporidian parasites. Initial analyses detected two major malarial strains in the north and south islands of New Zealand. We screened seven TLR loci in this house sparrow population and report our results on their association with malaria infection.

Poster session A - GEN 2000

# Superinfection and the coevolution of parasite virulence and host recovery
(52802)

Sara Kada, Sébastien Lion.

CEFE, UMR 5175 CNRS, 1919 route de Mende, 34293 Montpellier Cedex 5 France;
Université de Montpellier 2.

Parasite strategies of host exploitation may be affected by host defence strategies and multiple infections. In particular, within-host competition between multiple parasite strains has been shown to lead to higher virulence. However, little is known on how multiple infections could affect the coevolution between host recovery and parasite virulence. Here, we extend a coevolutionary model introduced by van Baalen [1] to account for superinfection. When the susceptibility to superinfection is low, we recover van Baalen's results and show that there are two potential evolutionary endpoints: one with avirulent parasites and poorly defended hosts, and another one with high virulence and high recovery. However, when the susceptibility to superinfection is above a threshold, only the outcome where both virulence and defence are high remains. We discuss how different parasite and host strategies (facilitation, competitive
exclusion) as well as demographic and environmental parameters, such as host fecundity or
various costs of defence, may affect the interplay between multiple infections and host-
parasite coevolution.

Poster session A - GEN 2000

An examination of Dscam1 in the light of immunity, fecundity and behaviour
(52864)

**Robert Peuß**, Kristina U. Wensing, Luisa Woestmann, Hendrik Eggert, Barbara Milutinović, Marlene Sroka, Jörn P. Scharsack, Joachim Kurtz, Sophie A.O. Armitage.

Institute for Evolution and Biodiversity, University of Münster; Department of Biosciences, Faculty of Biological and Environmental Sciences, University of Helsinki; : Institute of Science and Technology Austria.

Dscam1 (Down syndrome cell adhesion molecule 1), has important neuronal functions and seems to play a role in immunity as well, which is however less -well understood. We took an integrative approach to understand more about the roles that Dscam1 plays in fitness-related contexts in Drosophila melanogaster and Tribolium castaneum. At present there is a lack of consensus on the conditions under which Dscam1 expression changes after exposure to pathogens. We therefore tested whether exposure to the same bacteria species affects Dscam1 expression in two model insect species in a similar way. We found no short-term modulation of Dscam1 expression after septic or oral bacteria exposure. Furthermore we hypothesized, if Dscam1 is involved in immunity, RNAi-mediated knockdown and subsequent bacterial exposure might result in reduced T. castaneum survival, but this was also not the case. Since Dscam1 is vital for nervous system development and is also expressed in the reproductive system we predicted that there may be a behaviour and fecundity cost to the knockdown. Indeed, Dscam1 knockdown as larvae resulted in significant changes in adult behaviour and fecundity-related traits. Our results take a step towards understanding more about the role of Dscam1 in immunity, fecundity and behaviour.

Poster session A - GEN 2000

Ecological factors dictate the degeneration of induced immunity in the spider
mite Tetranychus urticae (52886)

**Gonçalo Matos**, Nicky Wybouw, Nelson E. Martins, Maria Riga, John Vontas, Miodrag Grbic, Thomas van Leewen, Sara Magalhães, Élio Sucena.

Instituto Gulbenkian de Ciência, Oeiras, Portugal; CE3C, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal; Laboratory of Agrozoology, Faculty of Bioscience Engineering, Ghent, Belgium; Faculty of Applied Biotechnology and Biology, University of Crete, Crete, Greece; Department of Biology University of Western Ontario, Canada; IBED,
University of Amsterdam, Amsterdam, The Nederlands; Departamento de Biologia Animal, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal.

The genome of the spider mite Tetranychus urticae, is missing important elements of the canonical Drosophila immune pathways necessary to fight bacterial infections. Thus, the spider mite may rely on different mechanisms to mount an immune response or may have lost this response to pathogen aggression.

We compared the consequences of bacterial infection in the spider mite that feeds on virtually aseptic plant cell contents, to infection in Sancassania berlesei, a litter-dwelling mite. Whereas in S. berlesei infections are kept under control, T. urticae does not mount a response and dies from uncontrolled bacterial proliferation. Furthermore, in accordance with their different ecologies, spider mites harbour three orders of magnitude fewer commensal bacteria than S. berlesei.

We postulate that life-history has driven the loss of induced immune responses in T. urticae and is convergent with other arthropods with which it shares ecological conditions.

Poster session A - GEN 2000

# Endosymbiont-mediated immune protection in a novel host species (52915)

Tânia Paulo, Vitor G. Faria, Alexandre B. Leitão, Élio Sucena.

Instituto Gulbenkian de Ciência; Universidade de Lisboa, Faculdade de Ciências, Departamento de Biologia Animal, Lisbon, Portugal.

Host-symbiont relations are a key class of interactions present in natural populations. Drosophila melanogaster hosts several species of symbionts, such as Wolbachia, a gram-negative endosymbiont of arthropods, known to manipulate the host's reproductive system for its own advantage. Yet, beneficial effects of Wolbachia infection have been unveiled also, namely that it confers protection to viral infection in D. melanogaster.

Our first objective is to determine whether the viral protection conferred by the Wolbachia strain carried by Drosophila would operate in a novel host, the parasitoid wasp Leptopilina boulardi. Secondly, we wish to determine whether this protection can occur upon horizontal transmission from a Wolbachia-infected D. melanogaster host to the wasp host.

We screened parasitoid wasps for horizontal transmission of one of two Wolbachia strains (wMel-like and wMel_CS) and infected them with Drosophila C Virus through systemic and oral routes. We estimate the maintenance of the distinct protective effects of different Wolbachia strains in its novel host. We will also determine if wasps can act as viral vectors between Drosophila hosts.

In sum, this work will highlight the immediate ecological and evolutionary consequences that Wolbachia presence may confer to a novel host upon a naturally occurring event of horizontal transmission.

Poster session A - GEN 2000
**Local specialists and global generalists : understanding parasite diversification**
**patterns within host communities at different spatial scales. (51657)**

Karen McCoy.

CNRS.

The parasitic environment is often both strongly spatially-structured and highly heterogeneous, and particularly so when parasites exploit a wide range of host species within local communities. At the scale of their global distribution, such parasites are often classified as host generalists, only to find that they are in fact composed of a series of local host specialists. Such is the case for the cosmopolitan seabird tick, Ixodes uriae. This ectoparasite commonly exploits colonial seabirds across the temperate and polar regions of both hemispheres. Host race formation has occurred multiple times across its worldwide distribution, with clear signatures of local adaptation to different host types within the local seabird community. Here, we use genetic markers and simulation modeling to explore the relative roles of selection and drift in the diversification process by retracing host colonization patterns at regional scales. We quantify both the frequency and direction of local host divergence events at the within-colony scale in three isolated regions of its distribution and place our results within the context of its historical phylogeography. Our results illustrate how understanding the origin of parasite diversity at different spatial scales can help us predict the evolution patterns in a changing world.

Poster session A - GEN 2000

**Linking morphologic and genetic divergence with host use in the tropical tick**
**complex, Ornithodoros capensis sensu lato. (51659)**

Marlene Dupraz, Céline Toty, Valérie Noël, Jean-Pierre Dujardin, Thierry Boulinier,
Karen McCoy.

Université Montpellier; IRD; CNRS.

Vector-borne diseases are often the result of a complex transmission cycle where a vector transmits a pathogen through numerous reservoir host species; the epidemiology of the pathogen being a consequence of host use by the vector. Vector-host interactions can be intense and host use by the vector is not always directly related to host availability. In order to understand pathogen transmission cycles, it is therefore essential to understand the local structure of vector populations within host communities. Soft ticks of the Ornithodoros capensis complex exploit colonial seabirds in tropical-subtropical areas across the globe. Morphological resemblances among species and a lack of genetic data have limited our ability to clarify the local and global phylogenetic positions of the species of this complex. Here, we link phenotypic and genetic data to understand geographical distributions and host relationships within this complex. We test whether host use is always accompanied by the same phenotypic changes and, if these changes are associated with patterns of genetic divergence. We find that strong host associations, closely linked to genetic structure, exist across the complex suggesting that speciation in the group has been strongly shaped by host adaptation and that geography plays only a secondary role.
# Phylogenetic patterns in species diversity (51760)

Eric Lewitus, Helene Morlon.

Institut de Biologie, Ecole Normale Supérieure.

Our understanding of any biological phenomena is guided by our ability to identify what is universal and what is specific. In the particular case of species diversity, identifying features of diversification universal to all clades and specific to certain clades could allow us to derive a general model of the evolution of species richness. Here, we introduce a method based on phylogenetic trees — trees defining species relationships over evolutionary time — that allows such an identification. We treat phylogenies as graphs and characterize them by the spectrum of the graph Laplacian. This allows us to quantitatively and visually compare phylogenies both across and within clades and to identify features of diversification universal to all clades and specific to certain clades. Because biological systems are most aptly explained by the distribution of their parts, graph theory is, in general, well suited for deciphering the organization of biological networks. The spectrum of the graph Laplacian is shown here, in its application to phylogenetic trees, to be particularly useful in identifying evolutionary patterns in species diversity. We illustrate our approach with birds and mammals.

# Resistance to invasive congener's pollen in Japanese dandelion: reproductive character displacement in response to biological invasion? (51761)

Daisuke Kyogoku.

Kyoto University.

Japanese dandelion, Taraxacum japonicum, has declined in abundance in the last several decades due to the invasion of common dandelion, T. officinale. The decline is thought to be due to reproductive interference; seed production of T. japonicum, which is self-incompatible, is reduced by T. officinale pollen even when sufficient amount of compatible pollen is pollinated. However, recently I found a place where T. japonicum is apparently recovering from population decline. The recovery of T. japonicum population suggests the evolution of resistance to T. officinale pollen. In a preliminary experiment, I found that the seed production of T. japonicum in that population was not affected by T. officinale pollen, a consistent result with my prediction. T. japonicum may be being evolutionarily rescued by the evolution of resistance to heterospecific pollen. To make the hypothesis testing vigorous, the same experiment needs to be performed in other sites both where T. japonicum population is recovering and where it is not.
# Correlation of the intraspecific diversity patterns of benthic invertebrates with the microbial community functioning (51843)

**Katerina Vasileiadou**, Christina Pavloudi, Anastasis Oulas, Giorgos Kotoulas, Christos Arvanitidis.

IMBBC-HCMR; *Biology Department, University of Patras; Department of Biology, Faculty of Sciences, University of Ghent; Department of Microbial Ecophysiology, Faculty of Biology, University of Bremen.*

Transitional water ecosystems host a number of habitats with temporally and spatially variable conditions, thus they can be very useful in understanding the mechanisms affecting population establishment. Samples were collected from lagoons located in Amvrakikos Gulf (Western Greece). These ecosystems are characterized by increased hypoxia and high concentrations of hydrogen sulfide, which is produced by sulfate-reducing bacteria. It has been suggested that burrowing polychaetes may cause substantial changes in oxygenation and redox potential of surficial and burrow-lining sediments, that may have a significant effect on the bacterial assemblages. The polychaete Nephtys hombergii is one of the most abundant species found in the lagoons. A fragment of the mitochondrial DNA (COI gene) was analyzed from this species. Sediment DNA was extracted and processed through next generation sequencing of a region of the dissimilatory sulfite reductase (dsr) gene, which is found in sulfate reducing bacteria.

The C-score index was used to quantify patterns of taxa co-occurrence. The observed values for this index were significantly different from that of simulated assemblages suggesting that the patterns of species co-occurrence do not arise by chance and that the genetic diversity of benthic assemblages may be driven by the microbial community functions.

# Interlopers or welcome guests? The role of non-protective invertebrates in an ant-plant mutualism (52066)

**Joyshree Chanam**, MS Sheshshayee, Srinivasan Kasinathan, Amaraja Jagdeesh, Kanchan A. Joshi, Renee M. Borges.

*National Centre for Biological Sciences, Bangalore; University of Agricultural Sciences, GVK, Bangalore; Indian Institute of Science, Bangalore.*

How a symbiosis originates and is maintained is an important evolutionary question. Symbioses in myrmecophytes (plants providing shelter for ants) are believed to be maintained by protection and nutrition provided by specialist plant-ants in exchange for nesting spaces (domatia) and nourishment offered by ant-plants. In the unspecialised ant-plant Humboldtia brunonis (Fabaceae), which offers extrafloral nectar to ants, only some plants have domatia. These domatia are occupied mostly by non-protective ants and invertebrates, especially
arboreal earthworms; protection mutualism with ants is restricted to a small part of the plant's geographical range. Stable isotope analysis showed that 8% (earthworms) to 17% (protective or non-protective ants) of nitrogen of plant tissue nearest the domatium came from domatia-inhabitants. 15N-enriched feeding experiments with domatia-inhabitant ants demonstrated nutrient flux from domatia-inhabitants to nearby plant modules from domatia-bearing branches. This study is the first to demonstrate nutritive role of non-protective ants and non-ant invertebrates, hitherto referred to as interlopers, in an unspecialised myrmecophyte. This suggests that even in the absence of specialised ant-plant protection mutualism, nutritional benefits conferred by domatia-inhabitants can explain fitness benefits of bearing domatia, and thus might have had a role in the origin and maintenance of this symbiosis.

**Interspecific interactions influence contrasting spatial genetic structures in
two closely related damselfly species (52112)**

**Aapo Kahilainen**, Inka Keränen, Katja Kuitunen, Janne S. Kotiaho, K. Emily Knott.

*Department of Biological and Environmental Science, University of Jyväskylä; Department of*
*Mathematical Information Technology, University of Jyväskylä; Natural History Museum,*
*University of Jyväskylä.*

Spatial genetic structure (SGS) is largely determined by colonization history, landscape and ecological characteristics of the species. Therefore, sympatric and ecologically similar species should exhibit similar SGSs, potentially enabling prediction of the SGS of one species from that of another. On the other hand, due to interspecific interactions, ecologically similar species could have different SGSs. We explored the SGSs of the closely related Calopteryx splendens and Calopteryx virgo within Finland and related the genetic patterns to characteristics of the sampling localities. We observed different SGSs for the two species. Genetic differentiation within short distances in C. splendens suggests genetic drift as an important driver. However, we also observed indication of previous gene flow (revealed by a negative relationship between genetic differentiation and increasing potential connectivity of the landscape). Interestingly, genetic diversity of C. splendens was negatively related to density of C. virgo, suggesting that interspecific interactions influence the SGS of C. splendens. In contrast, genetic differentiation between C. virgo subpopulations was low and only exhibited relationships with latitude, suggesting high gene flow, colonization history and range margin effects as the drivers of SGS. The different SGSs of the two species caution indirect inferences of SGS based on ecologically similar surrogate species.

**Invasion triggers rapid phenotypic evolution in a native freshwater snail
species (52277)**

**Elodie Chapuis**, Thomas Lamy, Jean-Pierre Pointier, Philippe Jarne, Patrice David.
A successful invasive species and a closely related native species occupying similar niches may coexist in a community through niche or character displacement. We here evaluate whether the invasion of the metacommunity of freshwater snails from Guadeloupe (Lesser Antilles) by Physa acuta is associated with a modification in life-history traits in the related species Aplexa marmorata, or in the invader itself. We study 21 populations of A. marmorata and 16 of P. acuta, which have been in contact with the other species from zero to eleven years. Reproduction, growth and survival were measured under common garden conditions. Our analyses show that several traits have changed in the native species as a result of fast evolution while the invasive species was hardly affected. Our analysis also indicates that local changes in the environment or in the snail community do not explain these modifications. These results therefore show that bioinvasions may trigger fast phenotypic evolution. They also are of interest for theories of species interaction and community assembly.

# Spatial genetic structures of strongly interacting species at different trophic levels in a fragmented landscape (52426)

Abhilash Nair, Christelle Couchoux, Saskya van Nouhuys.

University of Helsinki; Cornell University.

The genetic structures of species that interact trophically are interrelated, and differ depending on resource specialization and dispersal behaviour. The Glanville fritillary butterfly, Melitaea cinxia, lives as a metapopulation in the Aland islands, Finland. The butterfly hosts multiple parasitoid species at different trophic levels. Its caterpillars are parasitized by a specialist parasitoid wasp, Hyposoter horticola, which itself is parasitized by the specialist hyperparasitoid wasp, Mesochorus stigmaticus. Studying the genetic differentiation of these strongly interacting species helps us to understand the influence of landscape fragmentation on demographic histories and evolution of spatial genetic structure in mulitrophic communities. The host butterfly populations are highly differentiated spatially and genetically in this fragmented landscape, with a high number of genetic clusters (n=27). In contrast, the parasitoids, which depend on the host butterfly and inhabit the same landscape, have weak spatial genetic structure (FST = 0.02-0.06) and fewer genetic clusters (n=3-8), with the hyperparasitoid having less structure than the primary parasitoid. This is expected because the parasitoids are much more dispersive than the host butterfly, resulting in weaker spatial genetic differentiation. They are however, constrained by the population dynamics and dispersal limitation of the host butterfly in the fragmented landscape

# Viral diversity in ant communities (52459)

Matthias, Alois Fürst, Thomas Eder, Thomas Rattei, Sylvia Cremer.
Viruses are important infectious pathogens, regularly causing epidemics in societies, whether human or social insect. While research has made considerable progress in understanding viral infections in vertebrate societies, our knowledge in social insects is nearly exclusive to honey bees as important pollinators and fire ants, a serious pest species. Almost all studies available focus on single viral infections rather than multiple viruses present in a host population, taking the pathogen community into account. In this study we explore the natural viral component communities, different virus species populating a single host species, of three host ant species from three different subfamilies across various sampling sites. Next generation sequencing allows us to catch the whole viral diversity within the sampled host populations. We will highlight conserved viral community patterns within single host species across our sampling sites. For a deeper understanding of natural host pathogen systems the new techniques at hand offer valuable insights into complex ecological communities like multi-host multi-pathogen systems.

**From mutualism to parasitism: variation of toxicity in communities of mimetic butterflies (52547)**

**Mónica Arias**, Johanna Mappes, Bastien Nay, Marianne Elias, Marc Théry, Violaine Llaurens.

UMR 7205. CNRS-MNHN. Institut de Systématique, Evolution et Biodiversité. Batiment d'entomologie. 45; University of Jyväskylä. Department of Biological and Environmental Science P.O. Box 35 FI-40014 Uni; UMR 7245. CNRS-MNHN. Molécules de Communication et Adaptation des Micro-organismes, 57 rue Cuvier; UMR 7179. CNRS-MNHN. MECADEV 1 avenue du petit château 91800 Brunoy (France).

Müllerian mimicry is the evolutionary convergence of several toxic species towards common warning signals and an example of mutualistic interactions driving species assemblage. Common local warning signals allow toxic species to share predator learning costs. However, such signals vary within natural communities, perhaps due to toxicity levels variation. Less defended species might weaken the protection brought by the shared signals, promoting new warning signals and associated mimetic communities. To investigate the role of toxicity variation in the warning signal diversity of the mimetic communities, we focused on toxic and brightly coloured neotropical butterflies from the genus Heliconius and a distantly related tribe, Ithominii. Several mimetic communities include several species from one or both clades. The Heliconius butterflies' toxicity relies on cyanogenic compounds, whereas Ithominii butterflies present pyrrolizidine alkaloids. A characterization of the compounds found in both clades and a dosage analysis were done, providing information about the toxicity levels variation among various phylogenetic distance species. Additionally, the toxicity variation effect on the rejection of different butterflies by predators, was tested through behavioural experiments with insectivorous wild caught birds (Parus major). Our results provide new insights on the effect of toxicity variation on species and colour pattern diversity of mimetic communities.
# Ploidy level and genome size influence angiosperm species distributions under different nutrient conditions. (52623)

**Maite Guignard**, Ilia Leitch, Richard Nichols, Rob Knell, Catalina-Andreea Romila, Andy MacDonald, Mark Trimmer, Andrew Leitch.

Queen Mary University of London; 2Jodrell Laboratory, Royal Botanic Gardens, Kew; Queen Mary University of London; Queen Mary University of London; Queen Mary University of London; Rothamsted Research; Queen Mary University of London; Queen Mary University of London.

Angiosperm species display a 2400-fold wide range in genome size and ploidy levels as high as 38 are estimated. Focusing on nitrogen (N) and phosphorus (P) availability, we hypothesize that ploidy and genome size influence angiosperm distributions and abundance under different nutrient regimes. Angiosperm genomes are strongly skewed towards small values, suggesting selection for small genomes. A potential source of selection is N and P availability, since large genomes are more costly in terms of the N and P needed to make nucleic acids. We analysed the impact of fertilizer treatments on angiosperm species with different genome sizes, ploidy levels, and Grime's C-S-R plant strategies, growing in the world's longest running ecological experiment, Park Grass (Rothamsted, UK).

Genome sizes of species growing on plots with N+P fertilizer were significantly higher than plants growing on control plots and plots with either N or P. Polyploids also increased most significantly with N+P fertilizer, in particular polyploids with a strong C (competitor) strategy. These results are consistent with the hypothesized influence of large genome size on plant abundance under macronutrient limitation. They also suggest that ploidy and genome size are functional traits which contribute to plant distributions, community composition, and plant responses under different nutrient conditions.

# Unraveling the role of host traits in predicting host parasite assemblages (52635)

**Alexander Hayward**, Masahito Tsuboi, Christian Owusu, Alexander Kotrschal, Josefina Zidar, Hanne Løvlie, Niclas Kolm.

Stockholm University; Uppsala University; Linköping University.

Parasites are common and abundant members of ecological communities. Additionally, parasites impose a range of host impacts, leading to major influences on community composition and function. However, despite their widely appreciated ecological and evolutionary significance, little is known about the factors that determine the great variation in parasite load observed among host species. Specifically, understanding remains lacking regarding the influence of host species traits, such as diet, body size, habitat usage, phylogeny
and mating system, on the abundance and diversity of parasites. To address this question, we sampled a wide range of Lake Tanganyika cichlid fishes, a model system in speciation research, and their gut macroparasites. This powerful approach, combining an extensive field sample with comparative evolutionary analysis, permits us to tease apart the relative influence of a large set of host traits on the abundance, diversity, prevalence and spread of parasites. Our findings suggest that the species richness of hosts occupying a habitat is the dominant factor in dictating differences in parasite diversity, abundance, and prevalence, while mating system explains skew in the distribution of parasites across individuals within a species. Our results provide unique new insights into the factors that govern variation in parasite assemblages across host species.

Poster session A - GEN 2000

# The distribution and phylogeography of an important pollinator parasite (52665)

Regula Schmid-Hempel, Paul Schmid-Hempel.

ETH Zürich.

Crithidia spp, especially C. bombi, are important parasites of bumblebees; in turn, bumblebees are key pollinators in temperate and cold areas. Work over the last decade has shown that Crithidia are more diverse than realized before and that they occur in most of the areas so far investigated, forming communities of co-shared parasites. Here, we report on the worldwide distribution and communities of these parasites. The findings have implications of the study of host invasions into different areas, e.g. South America, as well as for the problem of possible parasite spillovers as has been reported for several cases.

Poster session A - GEN 2000

# Rapid evolution alters natural microbial community structure (52683)

Pedro Gómez, K. McElroy, L. Xuan, S. Paterson, M.D. Sharma, A. Buckling.

Biosciences, University of Exeter, Penryn Campus. TR109FE, UK; Centre for Marine Bio-Innovation and School of Biotechnology and Biomolecular Sciences, UNSW, AUS; Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.

There is growing acceptance of the key role that evolution occurring over ecological time scales plays in shaping the structure and function of communities. However, while there are numerous demonstrations in laboratory settings, studies in natural communities have only reported effects when evolutionary change, although rapid, occurred over much longer time scales than the ecological time scales of the experiments. We determine whether and how rapid evolution of a single resident species affects the structure of a soil microbial community, where evolutionary and ecological changes occur over comparable time scales. We compared how the presence of ancestral or pre-adapted (for 48 days) populations of the soil bacterium
Pseudomonas fluorescens SBW25 affected the natural microbial community structure in soil-compost over 2 months. The pre-adapted P. fluorescens bacteria both reduced the density and altered the composition of the resident community, a key feature of the latter being a large reduction in the proportion of resident Pseudomonads – the species most related to the pre-adapted focal species. Our results show that evolution of a single microbial species over ecological time scales predictably alters natural community structure by outcompeting genetically (and presumably ecologically) similar species.

**Agricultural landscapes influence the repartition of traits on carabid beetles. (52748)**

**Alexia Marie**, Manuel Plantegenest.

*Agrocampus-ouest.*

The intensification of agriculture and its consequences on landscapes are considered as a major cause of biodiversity decline. The composition of landscape affects diversity of arthropods in particular through the diversity of available habitats. Indeed, a general trend that landscape heterogeneity is positively correlated with specific richness is well documented. On an applied point of view, this loss of biodiversity affects ecosystem services that it provided, especially, pest regulation service provided by natural enemies' diversity.

However, an approach based on species traits at the community level can highlight strategies that allow species to settle and to maintain themselves in an environment, and in the same time, identify filters that favor benefic traits for biological control.

During this study, we focused on carabid beetles which are considered as good natural enemies on several pests. The work consisted in finding links between landscape composition and traits at the community level. The beetles were trapped on 57 fields spread on 3 different regions of West of France. An analysis on fields according to their landscape characteristics showed an opposition between two agricultural systems: cereals farms and breeding farms. For each system, particular traits were found, showing an opposition between two strategies.

**Phylogeography and taxonomy of Arabidopsis halleri across its distributional range (52786)**

**Gabriela Fuxová**, Eliška Záveská, Filip Kolář, Magdalena Lučanová, Stanislav Španiel, Karol Marhold.

*Department of Botany, Faculty of Science, Charles University in Prague, Prague, Czech Republic; Institute of Botany, University of Innsbruck, Innsbruck, Austria; Natural History Museum, University of Oslo, Oslo, Norway; Institute of Botany, Academy of Sciences of the Czech Republic, Průhonice, Czech Republic; Institute of Botany, Slovak Academy of Sciences, Bratislava, Slovak Republic.*
Arabidopsis halleri comprises about five subspecies and represents an important model species for the study of heavy metal tolerance and phytoremediation. Nevertheless, the so far unclear evolutionary history and provisional taxonomy may hamper correct interpretation on the evolution of these important traits within the species.

A. halleri is a perennial, clonal and self-incompatible plant. Four subspecies tentatively recognised (A. halleri subsp. halleri, subsp. dacica, subsp. ovirensis, subsp. tatrica) are centred in Central Europe, while the last one, A. halleri subsp. gemmifera occurs in Japan and the Far East. Despite representatives of A. halleri are purely diploid (2n=16), a high morphological variation combined with geographic differentiation stand behind complex and still unresolved taxonomy of the group.

Using six microsatellite loci and AFLP's we aimed to reveal phylogeographic structure of this lineage and to find correlations with the results of morphological analyses. We collected 450 samples from 40 populations across its whole European range in the Carpathian Mountains, the Dinaric and Balkan Mountains, the Bohemian Massif, the Alps and comparative material of A. halleri subsp. gemmifera from Japan. Our results indicate simpler genetic structure with three main groups within the European area generally correlated with geographical distribution, not with the current taxonomic concept.

Poster session A - GEN 2000

# Evolution of a community of a multiple-strain tick-borne pathogen during 11 years: Is fitness a good predictor? (52836)

Jonas Durand, Maarten Voordouw.

*Laboratory of Ecology and Evolution of Parasites, University of Neuchâtel.*

Borrelia afzelii is a tick-borne spirochete that causes Lyme disease in humans. The polymorphic ospC gene of B. afzelii codes for the immunodominant outer surface protein C and is a useful strain-specific marker. Previous genetic studies on the ospC gene found a pattern of balancing selection. One explanation is that the host immune system targets common ospC groups, thereby reducing their frequency over time.

We examined the diversity of ospC groups in a local population ofIxodes ricinus ticks infected by B. afzelii (n=196) over 11 years (2000-2010). We used 454-sequencing to characterize the ospC community in each tick. We also used experimental infections of mice to estimate the intrinsic fitness of six B. afzelii ospC strains in the lab.

We found that the frequency distribution of the B. afzelii ospC groups was stable over the duration of the study. Our laboratory estimates of strain fitness explained over 65% of the variation in the strain-specific frequencies in the field. The pattern of genetic variation at the ospC locus suggested there was strong selection against intermediately divergent ospC alleles. Our results are consistent with theoretical models on how acquired immunity structures multi-strain pathogen populations.

Poster session A - GEN 2000
# The Role of Plant-Microbe-Insect interactions in driving rapid evolution using Medicago polymorpha as an experimental system (52990)

**Chandra Jack**, Maren Friesen.

*Michigan State University.*

Invasive plant species leave behind coevolved herbivores and competitors when they invade novel environments. In these new environments, they face new biotic conditions that they must adapt to in order to become established. This includes multitrophic interactions with microbes and insects. Historically, these interactions were studied in two group interactions (plant-microbe or plant-insect) (Biere and Tack 2013). Yet, evidence suggests that these interactions are driven either directly or indirectly by a third party and can alter ecological and evolutionary outcomes (Heath and Lau, 2011). Our work explores the role of simultaneously interacting with beneficial microbes and insect herbivores in the evolution of Medicago polymorpha, a small invasive legume, in novel environments to determine the importance of multitrophic level interactions on rapid evolution and the success of invasive species as they enter new territories.

Poster session A - GEN 2000

# Host-microbiota interactions during adaptation to different nutritional conditions in Drosophila melanogaster (51830)

**Berra Erkosar**, Sylvain Kolly, Jan Roelof van der Meer, Tadeusz Kawecki.

*DEE-UNIL; DMF-UNIL.*

In the last decade, Drosophila emerged as a model to study host-microbiota interactions. Compared to mammals, Drosophila has a relatively simple microbiota that is mainly composed of aero-tolerant species, belonging to Lactobacillales and Acetobacteraceae families, which were previously shown to influence host digestive function and/or metabolism, that in turn impacts hormonal pathways and juvenile growth. Our major aim is to identify the role of gut microbiota during evolutionary adaptation to different nutritional conditions. To do this, we use experimentally evolved Drosophila populations that are maintained in distinct diets over numerous generations. During this period, fly populations got adapted to their nutritive regime causing remarkable phenotypes in terms of life history traits. By performing microbiota transplants among populations that are kept in distinct nutritional regimes, we aim to understand better how microbiota evolves on different food sources and how it contributes to host phenotypes that emerged upon adaptation.

Poster session A - GEN 2000

# Can different biocontrol agents be combined to develop evolutionary-proof biocontrol method against Ralstonia solanacearum plant pathogen? (51897)
**Zhong Wei**, Xiaofang Wang, Ville Petri Friman, Yangchun Xu, Qirong Shen, Alexandre Jousset.

*Nanjing Agricultural University; UK-based University of York; Utrecht University.*

Ralstonia solanacearum (RS) is a notorious soilborne plant pathogen. It has been demonstrated that many biocontrol methods including interference competition and parasitic phages might efficiently suppress RS disease. However, the long-term effectiveness or combinatory effects of different biocontrol methods have been less studied. For example, it is possible that RS could rapidly evolve resistance to single biocontrolling bacteria or phages. However, it is less likely that RS would evolve resistance simultaneously to different biocontrol agents. Here we tested this directly in realtime co-evolution experiments where we cultured RS bacterium with antagonistic antibiotic-producing Bacillus amyloliquefaciences T-5 strain and RS-specific phage pQL2014 alone or in combination. Besides tracking population dynamics, we also measured RS resistance evolution against different biocontrol agents. Our results show that B. amyloliquefaciences T-5 strain offered relatively more long-term protection against RS, while bacteria evolved resistance to phage pQL2014 within 4 days. Surprisingly, phage selection constrained the inhibitory effect of B. amyloliquefaciences T-5 strain. Using multiple biocontrol agents simultaneously could thus potentially reduce the effectiveness of each single biocontrol agent. Applying different biocontrol agents sequentially will be discussed. This work provides an important step toward understanding the resistance evolution of R. solanacearum against different biocontrol agents.

Poster session A - GEN 2000

**More than just density: different paths to the evolution of larval competitive ability (51908)**

**Manaswini Sarangi.**

*JNCASR.*

In D. melanogaster, series of studies on adaptation to larval crowding has led to an understanding about enhanced competitive ability being strongly correlated with increase in feeding rate and waste tolerance. This has been shown to be at the expense of lowered food to biomass conversion efficiency. More recent studies from our laboratory suggest that there are alternative routes to the evolution of adaptation to larval crowding in Drosophila populations. We show that populations of D. melanogaster when subjected to extreme larval crowding evolve greater competitive ability by a combination of different suite of traits which includes faster egg to adult development and greater food to biomass conversion efficiency. This is in contrast to what had been seen earlier in similar selection experiments, that there was neither elevated feeding rate nor enhanced tolerance to nitrogenous waste in the culture. We did certain experiments in which we observed subtle changes in the ecology of laboratory-adapted Drosophila populations under slightly different maintenance regimes can potentially affect the suite of traits that evolve in response to chronic larval crowding. We discuss the findings in the perspective of how the balance of food availability and build-up of nitrogenous waste can potentially affect the fitness of different traits underlying competitive ability.
# Shape matters: lifecycle of cooperative patches promotes cooperation in bulky populations (51977)

**Dusan Misevic**, Antoine Frénoy, Ariel B. Lindner, François Taddei.

INSERM U1001, University Paris Descartes, Sorbonne Paris Cité.

Natural cooperative systems take many forms, ranging from one-dimensional cyanobacteria arrays to fractal-like biofilms. We use in silico experimental systems to study a previously overlooked factor in the evolution of cooperation, physical shape of the population. We compare the emergence and maintenance of cooperation in populations of digital organisms that inhabit bulky (100x100 cells) or slender (4x2500) toroidal grids. Although more isolated sub-populations of secretors in a slender population could be expected to favor cooperation, we find the opposite: secretion evolves to higher levels in bulky populations. We identify the mechanistic explanation for the shape effect by analyzing the lifecycle and dynamics of cooperator patches, from their emergence and growth, to invasion by non-cooperators and extinction. Because they are constrained by the population shape, the cooperator patches expand less in slender than in bulky populations, leading to fewer cooperators, less public good secretion, and generally lower cooperation. The patch dynamics and mechanisms of shape effect are robust across several digital cooperation systems and independent of the underlying basis for cooperation (public good secretion or a cooperation game). Our results urge for a greater consideration of population shape in study of the evolution of cooperation across experimental and modeling systems.

# Co-evolutionary constraint after the true domestication of fungal crops by attine ants (51980)

**Jonathan Z. Shik**, Ernesto Gomez, William T. Wcislo, Jacobus J. Boomsma.

Centre for Social Evolution, University of Copenhagen; Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Republic of Panama; Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Republic of Panama; Centre for Social Evolution, University of Copenhagen.

Unlike humans, attine ants receive all of their nutrition from a single food crop, obligately farming fungus for over 50 million years. Around 20 MYA, the attines domesticated a specialized fungal lineage capable of concentrating nutrients in special organs (staphylae with gongylidia). Despite this innovation, attine colony-farms remained small (100 workers) until 12 MYA when the genus Atta began using fresh-cut leaves as compost to produce massive fungus gardens sustaining millions of ants. Towards explaining this transition, we used geometric framework experiments to compare the nutritional ecology of two Panamanian rainforest attines: Atta colombica (industrial-scale farmer) and Trachymyrmex cornetzi
(small-scale sister lineage). We found that A. colombica produces faster-growing fungus that is more robust to nutritionally imbalanced compost. In contrast, T. cornetzi workers are extremely averse to harvesting substrate with excess protein because this induces fungus-garden collapse and constrains colony growth. Moreover, T. cornetzi (but not A. colombica) faces nutritional compromises between maximizing fungus growth (fueled by carbohydrates) and staphylae production (fueled by protein). Our results shed new light on how nutritional adaptations helped leaf-cutting ants overcome co-evolutionary constraints in selection for crop improvement and achieve symbiotic complementarity that gave rise to the most advanced societies of farming ants.

Poster session A - GEN 2000

## The simplicity and complexity of the attine ant gut microbiota: living within a symbiotic network (52071)

**Panagiotis Sapountzis**, Mariya Zhukova, Lars H. Hansen, Søren J. Sørensen, Morten Schiøtt, Jacobus J. Boomsma.

*Centre for Social Evolution, Department of Biology, University of Copenhagen; Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk.; Molecular Microbial Ecology Group, Department of Biology, University of Copenhagen.*

The attine fungus-growing ants are a monophyletic group that switched to an almost exclusive fungal diet ca. 50 MYA. They are a model of complex symbiosis and have several fungal and bacterial symbionts. We obtained comparative and functional gut-microbiome data for 19 Panamanian species, representing 8 genera, which are dominated by few bacterial species belonging mostly to the Alpha-Proteobacteria and Mollicutes. These bacteria are located in specific gut tissues with some being found intracellularly. Rhizobiales species were among the most abundant gut bacteria and mediated the acquisition of nitrogen via the expression of NifH proteins in the hindgut where they form a biofilm. Guts and surrounding organs of higher attine, and particularly leaf-cutting, ants harbor most of these bacteria, consistent with the symbiosis being protein-limited in spite of increasing specialization of the crop fungus over evolutionary time. The composition of the gut microbiota appears to be correlated with the presence or absence of a cuticular microbiome of actinomycete bacteria: attine species that maintain cuticular actinomycetes had more stable gut microbiomes, possibly because the antibiotics produced by these bacteria protect gut microbiomes against invasion by non-symbiotic bacteria.

Poster session A - GEN 2000

## Host genotype × environment interaction change the microbial community of Daphnia (52177)

Karen Sullam, **Samuel Pichon**, Tobias Schär, Dieter Ebert.

*University of Basel.*
The environmental conditions and genetic background are believed to shape the composition of host-associated microbiota. It is unclear if the environment or the host genotype has the predominant role in shaping the microbiota of the host and whether they interact in doing so. We evaluated the effect of environment (temperature), host genotype, and their interaction on the composition of microbiota by using the cyclic parthenogenetic freshwater crustacean Daphnia magna. We used 21 different clones of D. magna from a wide geographic range, reared at 20 and 28 °C, to focus on microbial diversity and the abundance of indicator taxa under different environmental conditions. Our analysis reveals strong genetic, temperature and G x E interaction effects on the microbiota of D. magna, including a shift in overall community structure. Additionally, the abundance of certain microbial constituents shift consistently at higher temperatures across clones, while others exhibit clone-specific characteristics and change minimally across temperature conditions. The disparity in reactions of microbes to different temperatures and clones highlights their complex interactions with the environment and their host. This work enables a better understanding of the genotypic and environmental controls and selective forces that shape the variation found within a host's microbiota.

Chemical warfare no solution against parasite attack: Tribolium castaneum
vs. Beauveria bassiana (52199)

Gerrit Joop, **Charlotte Rafaluk**, Yang Wentao, Andreas Mitschke, Philip Rostenstiel, Hinrich Schulenburg.

*University of Giessen; University of Oxford; University of Kiel.*

The beetle Tribolium castaneum disposes an extended external immune defence, in addition to the classical invertebrate immune defence, coming with broad antimicrobial properties. Here, we wanted to gain a better understanding of if and how this external defence responds upon contact with a parasite and how the two interact.

We conducted a coevolution experiment with the entomopathogenic fungus Beauveria bassiana, taking the host and the parasite perspective. In the host we measured levels of internal and external immune traits throughout the experiment and survival as a proxy of resistance against the fungus. In the parasite, we tested for fungal virulence towards the host as well as for potential resistance against the host's external secretion, combined with a transcriptomics approach.

While no obvious change in host external immunity or survival was observed as a consequence of host-parasite coevolution, we were able to show that B. bassiana increased in virulence during the course of coevolution, based on the fungal isolates evolving resistance to the external immune defences of T. castaneum.

Results present a rare example of an experimentally coevolved increase in virulence, where the exact barrier of host immune defence overcome by the parasite has been described, the external secretion of quinones.
# Heterosis in yeast increases with parental divergence and environmental stress (52247)

**Joana Bernardes.**

*Max Planck Institute for Evolutionary Biology.*

Reproduction between genetically different parents often leads to F1 offspring with enhanced traits, a concept known as heterosis. While the phenomenon itself can be easily described using familiar genetic concepts (dominance, over-dominance and epistasis), the underlying molecular mechanisms for heterosis are still unknown. We tested the genetic and environmental factors that influence the strength of heterosis, using a set of sequenced and phenotyped yeast strains. We accurately measured heterosis in 45 heterozygous F1 hybrids, by competing them with their homozygous parental strains. F1 hybrids were on average 4% fitter than their mean parent. Interspecific crosses were significantly fitter than the intraspecific crosses, thus genetic distance was positive correlated with the strength of heterosis. We then tested a representative interspecific F1 hybrid under a range of extreme environmental conditions to measure how the strength of heterosis was affected. We found an increase of heterosis under stress. Next we will use transcriptome data to test if there is a general molecular mechanism underlying heterosis at a multigenic level. For this, we will test if the hybrids may be able to preferential express certain alleles for a specific environment.

Poster session A - GEN 2000

# Stability and variation in the gut and fungus comb microbial communities in fungus-growing termites (52287)

**Saria Otani, Michael Poulsen.**

*University of Copenhagen.*

The higher termite subfamily, Macrotermitinae, domesticated a plant-degrading fungus, Termitomyces, 30MYA. The adoption of Termitomyces has shaped fungus-growing termite gut microbiotas to become different from those of other termites and predicts that the external fungus combs could inhabit specialised bacteria communities. Using 16S rRNA high-throughput sequencing, we investigated the bacterial community compositions in fungus-growing termites by analysing guts of nine termite species from the Ivory Coast, 33 different fungus combs from four termite species and four sites in South Africa over two years, and 134 gut samples from worker and soldier castes from four South African Macrotermitinae species. Forty-two bacteria form a core community in Macrotermitinae guts and this core is more similar to cockroach microbiotas than those of other termites, with signals of termite phylogenetic ancestry. Comb communities were non-random, more variable than gut microbiotas, and shaped by gut content and time, likely due to environmental fluctuations. Gut microbiotas are expected to be shaped by caste more than species or colony, as gut communities are influenced by caste-specific functions. These results imply the uniqueness of fungus-growing termite microbiotas; both in guts and fungus combs, and that variation exist among castes and different genera as finer adaptations to specific lifestyles.
# Eco-evolutionary dynamics of a predator-prey system provide insight into the paradox of enrichment (52416)

Gökçe Ayan, Lutz Becks.

Max Planck Institute for Evolutionary Biology.

Resource enrichment might cause destabilization of a predator-prey system. However, it might stabilize the system by accelerating coevolutionary dynamics and diversification due to increased population sizes of interacting species. Coexistence of different prey types might also stabilize the system via preventing the predator to overexploit a specific prey type. Here, we combine these aspects in ciliate-bacteria (predator-prey) microcosm experiments to test for coevolution with resource enrichment in homogeneous and heterogeneous environments. We followed the population dynamics, measured the diversification in the prey as well as important traits such as the prey's grazing resistance, and the predator's counter adaptation over time. We found that with resource enrichment the extinction of predator occurred when there was no diversification in the prey (i.e. in homogeneous environments), whereas coexistence of predator and prey lasted 60 days in heterogeneous environments. We also showed that the frequency of defended prey increased with increasing resource levels. All these suggest that selection by predator and diversity in prey populations affect the coexistence of the predator-prey and matter for stabilization of the interaction. Thus, an eco-evolutionary approach is needed to understand the role of resource enrichment and the importance of rapid evolution for resolving the paradox of enrichment.

# Predation and the evolution of multicellular groups in algae (52512)

Stefania Kapsetaki.

University of Oxford.

The major evolutionary transition from unicellular to multicellular life and, in particular, social group formation is a puzzling question in biological research. Why do single cells form a group? Defence against predation has been proposed to drive social group formation mainly on the basis of predators being unable to engulf large sized entities. However cells in some species remain in their unicellular state upon encounter with a predator, implying that there are also fitness costs to forming groups. We investigated how widespread predation pressure is as a driving force towards colony formation by using Ochromonas spp., Tetrahymena thermophila and Daphnia as predators and the algae Chlorella sorokiniana, Chlorella vulgaris and Scenedesmus obliquus as prey, giving rise to a total of nine different predator-prey combinations. Our results showed that in all combinations, apart from two cases, Ochromonas spp.-S.obliquus and T.thermophila-S.obliquus, the prey species formed colonies, though the hypothesis of there being a size advantage in forming a colony was only confirmed in the case
of T.thermophila-C.sorokiniana. Overall, in seven combinations we observed that predation pressure causes colony formation in the prey and potentially, ensuring high relatedness, can favour multicellularity.

Poster session A - GEN 2000

# Insects' detoxification mechanisms as target for antagonistic filamentous fungi? (52649)

**Monika Trienens**, Joachim Kurtz, Bregje Wertheim.

*Institute for Evolution and Biodiversity, University of Münster DE; Evolutionary Genetics, University of Groningen NL.*

Insects and microorganisms co-inhabit resources for feeding and development. Microorganisms often excrete detrimental substances, i.e. mycotoxins and antibiotics, into these resources, and co-occupants need to cope with these substances. To study the evolution of such coping mechanisms in insect-fungus interactions, we combined experimental evolution and transcriptomics.

We mimic co-infestation, using breeding sites of fruitflies, Drosophila melanogaster, and inoculate these with filamentous fungi, Aspergillus nidulans. To disentangle the fruitfly responses to the mere presence of fungi (e.g., alterations in substrate pH-level, amino acid import) from responses caused by mycotoxins, we forced fruitfly populations to develop in the presence of wild type fungus, toxin-impaired fungus, a pure mycotoxin or under control conditions. After several generations, the wild-type and mycotoxin-selected populations survived subsequent confrontations significantly better, while the mycotoxin-selected fruitflies did not show increased survival when confronted with wild-type fungus.

RNA-seq analysis of D. melanogaster larvae during confrontation revealed a small set of genes in first and second line detoxification mechanisms that were induced during mycotoxin confrontation, whereas exactly these mechanisms were down-regulated in both fungal strain confrontations. Mycotoxins elicit selection in insect-fungus interaction, yet are they the key mechanism?

Poster session A - GEN 2000

# The genotypic view of social interactions in multispecies microbial communities (52660)

**Sara Mitri**, Kevin Foster.

*University of Lausanne; University of Oxford.*

Microbes live in dense communities composed of different strains and species, where cells can affect the growth and survival of their neighbours both positively and negatively. Disentangling these social interactions is central to understanding the stability and productivity of these microbial communities that are ubiquitous in our lives. By combining
ecological and evolutionary theory, we have recently proposed a general null model, which we call the genotypic view. This states that cooperation will be under positive selection when cells are surrounded by identical genotypes at the loci that drive interactions, whereas different genotypes will typically compete, leading to the evolution of antagonistic phenotypes or spatial separation. I will begin by presenting the logic of the genotypic view, supported by a mathematical model. I will then discuss various theoretical and experimental methods we are currently developing to test these ideas within two relatively simple communities composed of five to seven microbial species. These include approaches to disentangle existing social interactions, and later to follow their evolutionary trajectory over larger time-scales.

Poster session A - GEN 2000

# Eco-evolutionary dynamics of Pepino mosaic virus (52679)

Pedro Gómez, M. Juárez, M.A. Sánchez-Pina, C. Alcaide, M.A. Aranda.

CEBAS- CSIC, Dpto Patología Vegetal, Murcia, Spain; Escuela Politécnica Superior de Orihuela, Universidad Miguel Hernández, Alicante, Spain.

While individual plants are often infected in nature with more than one related or unrelated virus, the extent to which mixed infections can modulate the evolutionary dynamics of these viruses is unclear. Pepino mosaic virus (PepMV) is an emerging RNA virus known to be one of the most important tomato pathogens worldwide. Phylogenetic analyses have shown that PepMV populations in Spain are composed of isolates of two types (PepMV-CH2 and PepMV-EU) that appear to be still co-circulating after 10 years from their first detection. This study addressed how viral interactions among both PepMV types and also with other tomato RNA virus (Cucumber mosaic virus; CMV) could affect their evolutionary dynamics. Combining a population genetics approach with biological analyses of these viruses in planta, our results showed that an antagonistic interaction between both PepMV types was host-nonspecific, as patterns of RNA viral accumulation in single and mixed infections in different hosts were similar, and neither was affected by the presence of CMV. Furthermore, microscopy preliminary results show that these viruses are able to infect the same cell types, and ultra-structural analysis by electron microscopy will reveal whether they are infecting the same cell, and therefore, competing for the same plant and/or viral resources.

Poster session A - GEN 2000

# The role of parasitins and environmental change in ecosystems during sticklebacks adaptive radiations (52735)

Jaime M. Anaya-Rojas, Franziska Brunner, Christophe Eizaguirre, Ole Seehausen, Blake Matthews.

Swiss Federal Institute of Aquatic Science and Technology ; University of Bern; Queen Mary University London and Ewag.
Ecosytems can be affected by both ecological and evolutionary changes, for instance, through changes in the nutrient levels or indirect trait-mediated effects. Theory suggests that different phenotypes have different effects on the environment, however, less is known about the role of other relevant ecological factors such as parasitism. In a large scale mesocosm experiment, we studied how parasite exposure and contrasting nutrient levels affect (I) the diet of a recently divergent lake-stream pair of sticklebacks and (2) prey-community structure and ecosystem dynamics. Parasites had strong effects on fish diet, particularly for lake fish. The ecosystem effects of parasites were weaker. At the prey-community and ecosystem processes level (e.g., nutrients concentration, and primary productivity) interactive effects were statistically significant. We concluded that parasites can affect ecosystem processes through changes in feeding behavior of sticklebacks (e.g. prey-preferences or feeding performance) in different ways depending on the nutrient level of the environment.

# Genome streamlining in bacteria evolving under high predation pressure (52804)

**Michael Baumgartner**, Stefan Roffler, Thomas Wicker, Judith Blom, Jakob Pernthaler.

*University of Zurich, Limnological Station; University of Zurich, Institute of plant biology.*

Predation by eukaryotic protists is a major mortality source for aquatic bacteria. Consequently, many species have developed phenotypic antipredator strategies to cope with this threat. Such mechanisms are costly in terms of resource allocation or cause other competitive disadvantages, and therefore, are expected to be under strong selection pressure. We set up a long-term predator-prey experiment with a bacterial freshwater isolate, Sphingobium sp. Z007 and the bacterivorous flagellate Poterioochromonas sp.. The prey bacterium forms increased proportions of inedible cell aggregates in the presence of the predator. Bacteria in pure culture and a bacteria-predator co-culture were maintained in oligotrophic medium and regular propagations for 200 days. In both treatments, bacteria exhibited a rapid phenotypic adaptation to the presence or absence of flagellates. Strains under continuous predation pressure showed higher proportions of aggregates, and this phenotype was also maintained when grown in the absence of a predator. Bacteria in pure culture lost their ability to form aggregates but showed higher efficiency in substrate usage. Three independent evolutionary lineages of strains exposed to predation showed pronounced genome streamlining, whereas this was never observed in the evolved pure cultures. We hypothesize that this adaptation helped the evolved strains to increase their growth efficiency despite the resource investment in predator defence.

# The genomic basis of phenotype variation in social myxobacteria isolated from nature (52889)

**Sébastien Wielgoss**, Gregory Velicer.
Analyzing genetic variation in nature is mandatory for better understanding the processes governing the evolution of phenotypes in natural populations. For microbes, however, data on how natural genetic diversity relates to phenotypic divergence are sparse, including the remarkably sophisticated social traits exhibited by the myxobacteria. For example, members of this bacterial cooperate upon starvation to engage in the formation of fruiting bodies within which only a small fraction of cells form stress-resistant spores. Fruiting bodies of the model organism Myxococcus xanthus harvested from soil are composed of clones among that are highly genetically related and harbor a surprisingly high degree of diversity in social phenotypes. However, the molecular basis of this extremely fine-scale social diversity is unknown. Here, by applying whole genome sequencing to dozens of clones derived from individual fruiting bodies from nature, we shed light on the genomic basis of natural social diversity. Based on experiments, we then set out to pinpoint the evolutionary forces that could explain the particular genetic and phenotypic variation within groups. We conclude that fruiting bodies could be viewed as natural analogs to laboratory colonies in experimental evolution settings in which individuals share a single recent common ancestor but have undergone micro-diversification.

# The outcomes of bacteriophage selection on the evolution of virulence in Klebsiella pneumoniae (52911)

**Anni-Maria Örmälä-Odegrip**, Harald Eriksson, Lauri Mikonranta, Pilvi Ruotsalainen, Sari Mattila, Ville Hoikkala, Anders Nilsson, Jaana Bamford, Jouni Laakso.

*University of Jyväskylä; Stockholm University; University of Helsinki.*

Bacterial viruses or bacteriophages are ubiquitous bacterial parasites that impose a strong selection pressure for bacterial phage-resistance. Phage-resistance is often associated with fitness costs on bacterial traits such as virulence in multicellular hosts. We studied whether there were associated costs for resistance against single or multiple phages on bacterial virulence, growth ability and biofilm formation in a clinical isolate of Klebsiella pneumoniae. We found that resistance against multiple phages was in general associated with lowered virulence, when measured in vivo with Galleria mellonella wax moth larvae. However, selection by two phages alone led to increased virulence, coupled with an increased growth rate in bacteria. Biofilm production was negatively correlated with virulence, whereas growth rate had a positive correlation with bacterial virulence across all treatments. Our findings suggest that the presence of multiple phages could select for bacterial virulence, possibly due to a trade-off between phage resistance and rate of replication. However, this is dependent on the identity of phages. This is the first study to report increased bacterial virulence associated with exposure to lytic bacteriophages. Our findings are of practical importance when developing phage therapy, the use of bacterial viruses in treating bacterial infections that are resistant to conventional antibiotics.
# ACQUIRED IMMUNITY AND CROSS-IMMUNITY EFFECTS ON SYSTEMIC AND CO-FEEDING TRANSMISSION OF A MULTI-STRAIN TICK-BORNE PATHOGEN. (52968)

Maxime Jacquet, Maarten Voordouw.

*Université de Neuchâtel.*

Tick-borne pathogens have multiple modes of transmission including systemic (host-to-tick) and co-feeding transmission. Co-feeding transmission can occur when ticks exchange pathogens by feeding at the same time on the same host. We tested whether Borrelia afzelii, which causes Lyme disease in Europe, can use co-feeding transmission to escape the acquired immune response in the vertebrate host, and how cross-immunity influences the fitness of cross-reactive strains.

Outer surface protein C (OspC) is a single-copy, polymorphic antigen of B. afzelii that induces a strong immune response in the vertebrate host. Mice were immunized with one of two variants of the OspC antigen: A3 or YU then challenged with the homologous or heterologous B. afzelii ospC strain via tick bite. Mice were infested with larval ticks to measure co-feeding and systemic transmission. Ticks were tested for infection prevalence and bacterial load using qPCR.

Acquired immunity against the rOspC antigens blocked both co-feeding and systemic transmission of the homologous but not the heterologous strains. Cross-immunity had no effect on transmission but reduced the spirochete load in the tick vector. Acquired immunity and cross-immunity against the immunodominant OspC antigen have important consequences for the fitness and evolution of multi-strain Borrelia populations.

# Evolution of male and female choice in promiscuous mating systems (51788)

Mikael Puurtinen, Lutz Fromhage.

*University of Jyväskylä; Centre of Excellence in Biological Interactions.*

While empirical studies have revealed that both males and females often exercise mate choice, theoretical understanding of systems where both sexes can evolve mate choice is limited. We studied the evolution mate choice in a system where females vary in fecundity and males in sperm production. Additionally, sperm availability limits female fertility, and ejaculate size affects males' success in sperm competition. The probability with which opposite sex individuals are accepted as mating partners is a freely evolving parameter for each sex. Both sexes can also evolve choosiness, the cost of which increases with increasing discrimination between individuals of different quality. We solve the model for evolutionarily stable combinations of male and female mate acceptance strategies, varying the costs of mating and choosiness. Results of the model show that while highest quality males and females mate most often, these patterns mostly result from lower mating activity and higher choosiness of low quality males who have less sperm and evolve to use it more prudently.
These results highlight the need for explicit evaluation of mate acceptance criteria of both sexes in empirical mating system studies, and caution against making unsubstantiated conclusions about the mechanisms underlying mating patterns.

# Disassortative mating in plants: paternity analysis of floral morphs within experimental populations (51831)

Violeta I. Simón-Porcar, Thomas R. Meagher, Juan Arroyo.

University of Stirling; University of St. Andrews; University of Seville.

Heterostyly enhances disassortative pollination between floral morphs through reciprocal placement of stigmas and anthers, and through a physiological heteromorphic incompatibility system which impedes within-morph fertilization. Which of these mechanisms is the main driver of disassortative mating in this polymorphism is object of debate. Stylar-dimorphism lacks reciprocal anther placement and hence disassortative mating could be compromised, particularly when there is not intra-morph incompatibility. Variable rates of disassortative mating along with differential female fecundity or siring success among floral morphs could lead to variation in morph ratio in this polymorphism.

We investigated mating patterns in Narcissus papyraceus, an intra-morph compatible species with dimorphic (long- and short-styled) and monomorphic (long-styled) populations in central and north regions of its range, respectively. We established experimental populations in both regions and exposed them to ambient pollinators. Using paternity analysis, we found high disassortative mating in most populations. Female fecundity of morphs was similar in all populations.

Our results provided evidence for the evolutionary stability of stylar dimorphism in N. papyraceus and reveal the central role of morphological reciprocity of sexual organs in promoting disassortative pollination, even when such reciprocity is imperfect. However, it is unclear what forces lead to complete loss of one of the morphs in some natural populations.

# A novel cost to sex allocation in the mostly monandrous wasp, Nasonia vitripennis (51840)

Rebecca Boulton, David Shuker.

University of St Andrews.

The near-ubiquity of polyandry is a crucial component of mating system evolution, yet there is much we still do not understand about the economics of polyandry. Females of the parasitoid wasp Nasonia vitripennis are “mostly monandrous” in the wild, but become increasingly polyandrous under laboratory culture. They have also been well-studied in terms of sex allocation, producing female-biased sex ratios in line with the predictions of local mate
competition (LMC) theory. Here we present the results of a series of experiments showing that the costs and benefits of multiple mating in this species are contingent on sex allocation under LMC. We show that harassment and multiple mating during oviposition results in the increased production of sons under conditions that instead favour female-biased sex ratios. We also find evidence that mating multiply with virgin but not with previously-mated males increases female fecundity. In the laboratory, LMC is low compared to the wild, increasing the abundance of virgin males and perhaps relaxing the sex allocation cost of harassment and mating. We discuss the relevance of these findings with regards to the laboratory evolution of polyandry, and the evolution of polyandry more generally.

Poster session A - GEN 2000

# Paradox of high outcrossing and no selfing syndrome despite no inbreeding depression after a loss of self-incompatibility (51884)

Marie Voillemot, **John R. Pannell**.

Unil; Unil.

Evolution toward selfing is one of the most frequent transitions to have occurred in flowering plants, and its causes, mechanisms and consequences continue to pose puzzles. Species that vary in their mating systems among populations offer ideal material to test hypotheses for the transition. A strong prediction is the evolution of high selfing rates and a syndrome of self-fertilization (low attraction to pollinator attraction and reward) in populations that evolve low inbreeding depression. The toadflax species, Linaria cavanillesii (Scrophulariaceae), which is endemic to south-eastern Spain, exhibits variation in self-incompatibility (SI) among populations, with some populations being SI and others having lost this outcrossing mechanism to become self-compatible (SC). Surprisingly, populations with SC individuals appear to maintain a high outcrossing rate, and their flowers do not show the typical evolution toward a full selfing syndrome. We present results of an inbreeding depression experiment that further shows that SC individuals display much lower inbreeding depression than their SI counterparts. We discuss the reasons for the combination of low selfing rates and low inbreeding depression despite the loss of SI.

Poster session A - GEN 2000

# Beauty in the eyes of the beholders: Color vision is tuned to mate preference in the Trinidadian guppy (Poecilia reticulata) (51886)

Ben Sandkam, C. Megan Young, Felix Breden.

Simon Fraser University.

A broad range of animals use visual signals to assess potential mates, and the theory of sensory exploitation suggests variation in visual systems drives mate preference due to sensory bias. Trinidadian guppies (Poecilia reticulata), a classic system for studying mate
choice evolution, provide a unique opportunity to test this theory by looking for co-variation
in visual tuning, light environment, and mate preferences. Female preference co-evolves with
male coloration, such that guppy females from 'low predation' environments have stronger
preferences for males with more orange/red coloration than do females from 'high predation'
environments. We found color vision also varies across populations, 'low' predation guppies
invest more of their color vision to detect red/orange coloration. In independently colonized
watersheds, guppies expressed higher levels of both LWS-1 and LWS-3 (the most abundant
LWS opsins) in 'low predation' versus 'high predation' populations at a time that corresponds
to differences in cone cell abundance. We also observed differences in the frequency of a
coding polymorphism between high and low predation populations. Together this shows the
variation underlying preference could be explained by simple changes in expression and
coding of opsins, providing important candidate genes to investigate the genetic basis of
variation in this model system.

The repeatability of mating failure in a polyandrous insect (51919)

Ginny Greenway, David Shuker.

University of St Andrews.

Sexually-selected post-copulatory traits combined with well-documented costs of mating
would be expected to maximise fertilisation success, yet high rates of mating failure (the lack
of production of offspring following copulation) are observed across multiple taxa. However
the mechanisms and causes of mating failure are not easy to isolate, typically being hard to
directly observe. For example, it is unclear if failures are stochastic occurrences between
incompatible mating partners or represent a persistent, meaningful phenotype on the part of
one or other sex. Here we test this in the seed bug Lygaeus simulans, by sequentially mating
families of males with randomly-allocated unrelated females and calculating the repeatability
of mating outcome for each individual male and family. Mating outcome was found to be
significantly repeatable within individual males but far less so between full-sib brothers.
Furthermore approximately a quarter of experimental males failed to father any offspring
given multiple opportunities to do so. We infer from the observed low levels of between-sib
repeatability that mating failure, in this species at least, represents a commonly occurring
male-associated and environmentally-influenced phenotype with low heritability. This may be
key to unravelling the evolution of polyandrous mating systems in both this species and more
generally.

Evolution of female multiple mating and sperm competition: co-evolutionary
feed-backs between female and male traits (51963)

Greta Bocedi, Jane M. Reid.
Explaining the evolution of costly polyandry remains a major challenge in evolutionary biology. Polyandry creates sperm competition, exerting strong selection on male allocation to sperm traits. Such male allocation may simultaneously affect female fitness, thereby imposing positive or negative selection on polyandry. However, the degree to which female polyandry and male allocation to sperm traits can drive co-evolution of both sexes' strategies has not been explicitly modelled and clear, empirically testable predictions are lacking. We used a genetically-explicit individual-based model to test the "sexually-selected sperm" (SSS) hypothesis, that polyandry evolves due to indirect selection stemming from positive genetic covariance with male sperm competitiveness. We show that the SSS process is unlikely to generally explain the evolution of costly polyandry. We then used a multi-trait model that allows simultaneous evolution of female mating interval and male allocation to sperm number versus longevity to test the hypothesis that co-evolutionary feed-backs between female mating interval and male sperm allocation can drive the evolution of costly polyandry assuming female sperm limitation. We demonstrate that depending on the cost of sperm and the degree of sperm limitation, sperm allocation driven by sperm competition can prevent males from overcoming sperm limitation, thereby driving evolution of polyandry.

# The impact of cuticular hydrocarbon profiles on mate attraction and reproductive isolation in two grasshopper species (Chorthippus biguttulus and C. mollis) (51970)

Jonas Finck, Sven Geiselhardt, Janine Kuntze, Monika Hilker, Bernhard Ronacher.

The attraction and identification of mating partners are major tasks in animals' lives. Many species uses multiple signals to increase reproductive success and to sustain reproductive isolation. Sympatrically occurring grasshoppers' species (genus Chorthippus) are morphologically and genetically similar. Acoustic signals serve as pre-zygotic barrier and are under sexual selection. On a close range scale, however, the acoustic signal has only a minor impact on the fertilization rate of Chorthippus females, suggesting that additional hybridization barriers exist, probably based on chemical cues. A GCMS analysis provided evidence that the cuticular hydrocarbon profiles of C. biguttulus and C. mollis exhibit species- and sex-specific differences. Behavioral tests demonstrated that males of C. biguttulus respond with a calling song to the odor of conspecific females but not to odors of heterospecific females. This behavior could be reproduced with males of the sibling species (C. mollis). Therefore, we conclude that grasshoppers use chemical signals to identify mating partners and that multiple hybridization barriers evolved to prevent gene exchange.
# Are females always better? Sex ratio variation and population genetic diversity affect the female advantage in gynodioecious Plantago coronopus (51973)

Sascha van der Meer, Thomas Sebrechts, Nicholas Lund, Hans Jacquemyn.

KU Leuven.

Gynodioecy is a reproductive system in which hermaphrodites and females co-occur within a population. Theoretically this polymorphism can only be maintained when females have a reproductive advantage over hermaphrodites.

In this study, we examined how sex ratio variation and population genetic diversity affected the female advantage in 27 populations of Plantago coronopus. We hypothesized that: 1) females produce more seeds than hermaphrodites and seed production is related to population sex ratio, 2) seeds of females have higher germination rates, 3) females are genetically more diverse than hermaphrodites and therefore have a higher chance of establishing in stressful environments.

The studied populations showed large variation in sex ratios from 2 to 60% females. In contrast to our hypothesis, females had, on average, a reproductive disadvantage in terms of seed production (FA: 0.91), but this diminished when the percentage of females in the population was low. On the other hand, seeds of females were heavier and germinated better, most likely reflecting a trade-off between seed production and seed weight. Genetic analysis showed that females were genetically more diverse than hermaphrodites, suggesting that inbreeding avoidance as well as frequency dependent processes explain the occurrence and size of the female advantage in P. coronopus.

Poster session A - GEN 2000

# Selection and differentially expressed genes governing mixed mating in a plant (52003)

Maria Strandh, Jane Jönsson, William B. Walker III, Bengt Hansson, Josefin Madjidian, Mattias C. Larsson, Åsa Lankinen.

Lund University, Sweden; Swedish University of Agricultural Sciences (SLU) Alnarp, Sweden.

The evolutionary processes governing the large variation in mating system found in flowering plants are unclear. Using mixed-mating Collinsia heterophylla as a model we investigated population selfing rate variation in relation to environmental and floral trait variation and whether selection or genetic drift determine floral trait variation. Population selfing rates varied substantially. The best predictor of selfing rate was a negative association with dichogamy, 'stage of stigma receptivity'. Floral trait differentiation (PST) was substantially higher than neutral genetic differentiation (FST) in four estimated traits, suggesting that variation in floral traits is shaped by natural selection. Moreover, we report differential gene expression in self- vs outcross pollinations. The association between stage of stigma receptivity and selfing rate in C. heterophylla indicates that this floral trait is strongly linked with the mating system. The detected effect of natural selection acting on this trait and three additional mating-system related traits suggests that variability in mating system is not only
determined by genetic drift or by direct abiotic or biotic environmental factors. Determining
the evolutionary processes influencing levels of mixed mating and associated floral traits, as
well as mining the transcriptomes expressed in these pollinations provide important insights
to mating system function and evolution.

Poster session A - GEN 2000

Molecular evolution of freshwater snails with contrasted mating systems
(52046)

Concetta Burgarella, Philippe Gayral, Marion Ballenghien, Aurélien Bernard, Patrice David, Philippe Jarne, Sylvie Hurtrez, Nicolas Galtier, Sylvain Glémin.

Institut des Sciences de l'Evolution, UMR CNRS 5554, Université Montpellier II; Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS, Univ. François-Rabelais, Tours; CEFE/CNRS, Montpellier.

Selfing recurrently evolved from outcrossing in many groups, especially in flowering plants.
However, selfing species are of recent origin and less numerous than outcrossing ones.
Despite short-term advantages, selfing is supposed to be an evolutionary dead-end strategy:
selfing species experience reduced effective population size and recombination rates, which
decrease the efficacy of natural selection. Selfing species should thus go through higher
extinction rates because of reduced adaptive potential and/or genomic accumulation of
deleterious mutations. However, empirical evidences are only partly congruent with
theoretical expectations. Here we analyze coding sequence polymorphism, divergence and
expression levels of two groups of freshwater snails in which mating systems have been stable
for several millions of years. We report strongly reduced genetic diversity, decreased efficacy
of purifying selection, slower rate of adaptive evolution and weakened codon usage bias/GC-
biased gene conversion in the selfer Galba compared to the outcrosser Physa, in full
agreement with theoretical expectations. Our results demonstrate that self-fertilization, when
effective in the long run, is a major driver of population genomic and molecular evolutionary
processes. We also suggest that the particular ecology of Galba truncatula may buffer the
consequences of the genetic load, shedding new light on the dead-end hypothesis.

Poster session A - GEN 2000

The role of geographical and demographic factors in shaping floral morph
frequencies in the tristylous Lythrum salicaria at the southern edge of
distribution (52087)

Joana Costa, Sílvia Castro, João Loureiro, Spencer CH Barrett.

CFE, Centre for Functional Ecology and Department of Life Sciences, University of
Coimbra; Department of Ecology and Evolutionary Biology, University of Toronto.
Style morph frequencies in heterostylous populations are largely determined by a balance between stochastic forces and negative frequency-dependent selection. Investigation of morph frequencies at geographical range limits can provide new insights on the forces maintaining the floral polymorphism and the factors causing biased morph ratios. The aim of our study was to investigate floral morph frequencies at the southern European range of the tristylous self-incompatible perennial Lythrum salicaria L. (Lythraceae). Floral morph composition was assessed in 101 localities along a latitudinal transect from Galicia to Andalucia, Iberian Peninsula. Population size and morph frequencies were recorded for each population. Most populations of L. salicaria were trimorphic (90.10%) and isoplethic (68.75%). No consistent bias in floral morph frequencies across the sampled area was found. Population size was positively associated with latitude, i.e., smaller populations occurring towards the southern range limit. Despite the greatest variance in morph frequencies detected for smaller populations, a positive relation between population size and morph evenness was found. Our results provide evidence for the abundant centre distribution model and highlight the influence of finite population size and genetic drift on morph frequencies in a tristylous species which seems to be quite resilient to changes to the polymorphism.

# The evolution of reproductive isolation between two hybridizing dungfly species Sepsis cynipsea and S. neocynipsea (Diptera: Sepsidae) (52111)

**Athene Giesen**, Martin A Schäfer, Wolf U Blanckenhorn.

*Institute of Evolutionary Biology and Environmental Studies.*

Identifying traits contributing to reproductive isolation among species and their evolution challenges biological research. The evolution of sexual traits for mating and fertilization is interesting due to their role in the establishment of reproductive barriers to gene flow. It is necessary to characterize phenotypic differentiation, evolutionary and genetic processes underlying trait diversification that contributes to reproductive isolation. Only then we can understand the mechanisms of speciation, driven by pre- and postzygotic reproductive isolation.

To understand the underlying processes of speciation in two closely related, allopatrically and sympatrically occurring sister species Sepsis cynipsea and S. neocynipsea (genetic distance at COI gene < 2%), we investigated mating behavior and fitness measures (fecundity, hatching success) of hybrid offspring as an indicator of pre- and postzygotic barriers. We show successful hybridization, with lower hybridization rates between sympatric than between allopatric populations. Our data reveal prezygotic isolation with females discriminating more strongly against hetero-specific males in geographic areas of co-occurrence. These results indicate that this female resistance can be due to species recognition. Further we show greatly decreased copulation success for pure hybrid crosses and backcrosses, with male hybrid offspring being more sterile than females, indicating postzygotic isolation in accordance with Haldane's rule.
# Polyandry rates and reproductive success in a nuptial gift-giving dance fly
## Rhamphomyia longicauda (52115)

**Elizabeth J. Herridge**, Rosalind L. Murray, Deborah A. Dawson, Gavin J. Horsburgh, Terry Burke, Andre Gilburn, Darryl T. Gwynne, Luc F. Bussière.

*University of Stirling; University of Sheffield; University of Toronto at Mississauga.*

Females are rarely monogamous, but the processes that explain variation in polyandry are little understood, in part because few studies have measured selection on female mating frequency in the wild. In many species of dance fly, females obtain protein-rich nuptial gifts from males during courtship, and in many cases competition for these gifts involves elaborate female ornamentation which challenges theoretical arguments for the rarity and modesty of female ornaments. We use molecular markers to assess mating frequency among wild female long-tailed dance flies (Rhamphomyia longicauda) by probabilistically estimating the likeliest number of males contributing to the allele profiles of stored sperm. We compared mating frequency estimates to reproductive success as indicated by developing egg number and egg size. We consider how mating frequency, the proportion of multiply mated females, and egg maturation changes over the season, and use these measures to quantify how mating success mediates fecundity selection on ornamentation in the long tailed dance fly.

# Artificial selection in the context of contrasted mating system (52172)

**Elsa Noël**, Philippe Jarne, Violette Sarda, Sylvain Glémin, Patrice David.

CEFE ; ISEM ; .

Autogamous species are thought to adapt more slowly than allogamous ones and to go extinct more easily, for several reasons. (i) Self-fertilization leads to homozygosity and inefficient recombination. (ii) Self-fertilizing species have a lower effective population size and are more sensible to drift. (iii) Because of the magnitude of inbreeding depression, numerous families (and then genomes) are lost, by purge of the lethal genes they carry. The consequences are that they are suspected to have less standing variation and then a lower adaptive potential than outcrossing species.

In the lab, we have experimental lines of Physa acuta, a preferential outcrossing freshwater snail, able to self-fertilize if partners are missing. Two types of lines are evolving under two different mating systems, since around 30 generations: one “Control” line were the individuals reproduce in random mass mating (a proxy of panmixy), and one “Lack of partners” line, were individuals are isolated and forced to self-fertilize frequently. We decided to apply artificial selection on one morphological trait of those snails, in two contrasted mating systems treatments: (i) self-fertilization and (ii) random mass mating. The aim of this experiment is to see whether the response to selection differs between these two types of lines and these two reproduction treatments.
# Bottom-up effects of selection locally on outcross siring success shape the regional population genetic structure of an annual plant (52176)

**Luis Santos del Blanco**, John Pannell.

*University of Lausanne.*

In outcrossing plant populations, selection on siring success is expected to lead to the evolution of traits that enhance the production and effective dispersal of pollen locally. Indeed, such selection is probably the ultimate cause of a great many floral and inflorescence traits in angiosperms, including genetic polymorphisms such as dioecy and distyly. Importantly, local selection for siring success can have strong implications for population structure, because traits selected for high dispersal locally can also reduce genetic differentiation among population regionally. In the wind-pollinated plant Mercurialis annua, selection for enhanced siring success is probably responsible for the maintenance of males with females or hermaphrodites, whereas hermaphrodites are probably maintained by selection for self-fertilization when population densities are low. Here we show that variation in the maintenance of males among local populations strongly impacts on the regional genetic structure of the metapopulations to which they belong. Although metapopulation dynamics likely contribute to the population structure observed, we argue that competition for siring success locally has important knock-on effects on the metapopulation, too. Our study points to the possibility that the distribution of long-distance dispersal events may be shaped by the outcome of selection principally dispersal over short-distances.

# Frequency and life-history consequences of mixed mating in the freshwater snail Radix balthica (52185)

**Anja Bürkli**, Kirstin Kopp, Jukka Jokela.

*EAWAG, Swiss Federal Institute of Aquatic Science and Technology & ETH Zurich.*

Mixed mating describes the coexistence of self-fertilization (henceforth selfing) and outcrossing within individuals or populations, and might occur in almost half of the animals capable of selfing. Yet, our understanding of mixed mating is surprisingly limited.

To document the frequency of mixed mating and its importance for reproductive fitness in the freshwater snail Radix balthica, I estimated within- and among-individual variation in selfing rates using microsatellite progeny arrays for both lab-laid and field-collected clutches. As selfing rates might show seasonality, e.g. driven by changes in mate availability, field clutches were obtained throughout reproductive season.

I then investigated the consequences of being selfed on life-history traits and parasite
infection rate in a large-scale field experiment. I placed selfed and outcrossed juveniles sharing the same mother in cages, either at the site of their grandparents or in a nearby deep-water habitat. After ten weeks, surviving snails were counted, measured, and screened for parasite infections. First results suggest that inbreeding depression in survival was considerable in both habitats, but not intensified in deep water where overall mortality was higher.

These rare datasets on mixed mating in a free-living population will help to understand the
ecological and evolutionary consequences of this fascinating mating system.

Poster session A - GEN 2000

Inbreeding depression and selective history in Noccaea caerulescens (52285)

Mathilde Mousset, Agnès Mignot, Ophélie Ronce, Christophe Petit, Marine Second, Pierre-Olivier Cheptou.

Institut des Sciences de l'Evolution de Montpellier; Centre d'Ecologie Fonctionnelle et Evolutive.

Inbreeding depression, a key driver of self-fertilization evolution, varies among species and populations, and can increase or decrease under stressful conditions. Few studies have attempted to disentangle the effects of stressful environmental conditions from those of selective history and adaptation to these conditions on the variation in inbreeding depression magnitude.

We here test whether adaptive history affects inbreeding depression in stressing conditions using the self-compatible and heavy-metal tolerant herb Noccaea caerulescens. This species harbors two ecotypes with different adaptation history to soil pollution: the non-metallicolous ecotype grows on regular soils whereas the metallicolous ecotype thrives on contaminated soils such as mine wastes. Metallicolous and non-metallicolous plants originating from outbred and inbred crosses from nine populations were grown in controlled conditions on contaminated and non-contaminated soils. Inbreeding depression was measured on vegetative and reproductive traits along the life cycle. We found that metallicolous plants often suffer from greater inbreeding depression than non metallicolous plants. Early survival of inbred progeny is greater than that of outbred progeny in most non-metallicolous populations on both soil contamination levels, revealing outbreeding depression within-populations. These findings are discussed in the context of variation of self-fertilization rate and adaptation history of the different ecotypes.

Poster session A - GEN 2000

Female mate sampling strategy based on acoustic signals of a field cricket:
implications for sexual selection (52333)

Diptarup Nandi, Rohini Balakrishnan.
Empirical studies on sexual selection in orthopterans and anurans have generally focused on measuring male mating success based on their acoustic signals by quantifying the variation in their signal components and by studying female preferences for the different signal components. However, little is known about how females in natural choruses sample males based on their acoustic signals in the process of choosing mates. Theoretical models of mate sampling have demonstrated significant differences in individual fitness returns for different sampling strategies. Moreover, studies on mate sampling strategies can further elucidate the relative importance of the two mechanisms of sexual selection: male-male competition and female mate choice. Thus, in this study we empirically investigated female mate sampling based on acoustic signals of males in a wild population of the field cricket species Plebeiogryllus guttiventris. We then used simulations to generate estimates of male mating success based on male trait distribution and their relative spacing in natural choruses, for the observed female mate sampling strategy and also for the different theoretical sampling strategies. We finally compared male mating success between the observed and the theoretical sampling strategies to infer the mechanisms of sexual selection acting on these acoustic signals.

# To each according to her... colour? Non-random male courtship effort in a viviparous fish with traditional sexual roles (52383)

Marcela Méndez-Janovitz, Constantino Macías Garcia.

Lower potential re-mating rates of females than of males lead to female mating selectivity, often based on male badges of quality. By definition such male displays are costly, and if they make every mating attempt too costly, males may also become selective, preferentially directing their mating efforts towards females with high reproductive value. We evaluated this possibility in Girardinichthys viviparus (Goodeidae), a matrotrophic fish whose stringent female mate choice is associated with costly male courtship. We found that males exposed to pairs of females devoted more courtship effort to the female whose flank had a more orange chroma, and to the one with wider abdominal distension -a direct indication of fecundity- even if this was the smaller of the pair. As we expected, male G. viviparus did not devote their courtship efforts randomly, but rather concentrated them on certain females; those with attributes that appear to indicate reproductive value. Yet males seemed to neglect the most obvious correlate of fecundity in viviparous fish; female size. This is probably because the mechanics of Goodeidae population promote size-assortative mating, thus variance in the size of available females is small for any given male, promoting the use of other indices of female quality.
# Measuring sexual selection: a more holistic model of reproductive life histories (52434)

**Jonathan Henshaw**, Karoline Fritzsche, Andrew Kahn.

*The Australian National University; Uppsala University.*

Sexual selection drives the evolution of some of nature's most spectacular traits, yet its measurement has proved difficult and controversial. Empirical studies are plagued by the problem of choosing appropriate target traits. Theoretical studies, on the other hand, have concentrated on a relatively narrow subset of naturally occurring patterns of sexual selection. This makes it difficult to draw general conclusions about how sexual selection covaries with mating system, sex roles, and other aspects of an organism's reproductive life history. We present a mathematical model that mirrors patterns of sexual selection across a wide range of biologically realistic life histories, incorporating variation in mating system, parental investment, mate choice and competition. We determine what common measures of sexual selection, such as the opportunity for sexual selection and the Bateman gradient, can tell us about the underlying biology and discuss their limitations. A recently defined measure, the 'maximum intensity of precopulatory sexual selection' s'max, performs better than other measures at tracking the actual strength of sexual selection across populations. We compare the predictions of our model to published empirical studies. Our study aims to synthesise insights from recent debates over measures of sexual selection.

Poster session A - GEN 2000

# Experimental evolution under manipulated sex ratios alters mating behaviour in two sex role reversed beetle species (52546)

**Karoline Fritzsche**, Isobel Booksmythe, Göran Arnqvist.

*Uppsala University.*

We examined how two beetle species with sex role reversed mating systems evolved in response to experimentally induced differences in sex ratio and food availability. In both species males transfer a large nutritious ejaculate during mating. Females actively court males for this direct benefit and males are choosy about whom they mate with. We let both species evolve under either male biased (125M:25F) or female biased (25M:125F) adult sex ratios and with either high or no food resources during adulthood. After 20 generations of evolution the two species showed very different adaptations. In one species males responded to elevated male-male competition under male-biased sex ratios by transferring more ejaculate per mating. In the other species, males surprisingly showed no measurable response to evolution. Females however responded to female-biased sex ratios by initiating courtship sooner and were more successful in gaining matings. Females of the second species that evolved under high food availability also increased their turning rates (a form of courtship effort). Our study provides direct evidence that closely related species can show very different evolutionary responses to the same selection pressures.
# Reproduction in social insects: what can superorganisms teach us about mating system evolution? (52548)

## Heikki Helanterä.

### University of Helsinki.

Social insect colonies have been for a long time likened to individual organisms or "superorganisms", and thus considered a prime example of a major transition in evolution, or a transition in individuality. However, this metaphor has not been exploited to its full potential, but has mainly been used as a mechanistic description of colony function. But what kind of organisms are they? Could superorganisms and their diversity allow testing evolutionary hypotheses about sex and reproduction in a novel way? In this work, I present an evolutionary framework in which to employ social insect diversity in novel independent tests of evolution of mating systems. I will discuss cases like evolution of anisogamy, evolution of separate sexes, and evolution of gamete dispersal. This approach will aim for a more thorough understanding of the general principles on the one hand, and idiosyncratic determinants on the other, of mating system evolution.

# A Drosophila-based screen for genes important to reproductive regulation in social insects (52613)

## Graham Thompson, Alison Camiletti.

### Western University.

For 50 years kin theory has provided a gene-based explanation for sociality, but for the most part we have yet to identify these genes. The burgeoning field of sociogenomics is bridging this gap between theory and discovery, but is limited by the genomic tools available for all but a few social insects. Here we show that we can use queen honeybee pheromone to 'trick' female Drosophila into a state of worker-like sterility. This remarkable observation potentially enables a Drosophila-based screen of mutant and transgenic lines responsive to queen pheromone. Preliminary screens reveal that the pseudo-social response from flies is mediated by mutations at the foraging locus as well as other loci previously implicated in honey bee worker sterility. Our results suggest deeply conserved elements of reproductive regulation in social and non-social insects. We further nominate new loci that seem to affect the fly's worker-like response to bee pheromone, including Or83b that is essential to insect olfaction and has a clear bee orthologue. Beyond screens, our novel Drosophila-based assay provides a framework for testing social gene function in situ using RNAi targeted knockdowns. We highlight the potential and limits for adopting non-social Drosophila as a model of social gene discovery.
# Contrasting patterns of inbreeding depression and hybrid vigor between small and large populations of Daphnia magna (52637)

**Christoph Haag**, Jennifer Lohr, Barbara Walser.

CNRS Montpellier, France; Univ. Hamburg, Germany; Univ. Fribourg, Switzerland.

The freshwater crustacean Daphnia magna shows a wide array of different breeding systems, including partially genetic sex determination, which favours outcrossing and which is found only in some populations. One factor that is thought to play a major role in determining the advantage of outcrossing is population size through its predicted effect on the magnitude of inbreeding depression. Here we test these predictions empirically and show that, among eight populations of Daphnia magna that strongly differ in size, strong inbreeding depression is consistently found for a number of life-history traits in large populations. Small populations, on the other hand, show only low or no inbreeding depression, suggesting that the load of deleterious mutations has either been purged or become fixed. To test for fixed load, we crossed individuals among nearby populations of similar size and found that outcrossing resulted in strong hybrid vigour in crosses between small, but not between large populations. This confirm the presence of fixed load in small populations. Overall, our results show that the fitness benefits of obligate outcrossing strongly depend on population size, suggesting that the amount of genetic drift is an important modulator of costs and benefits in breeding system evolution.

# Paternal care and paternity revisited (52738)

**Julia Schroeder**, Yu-Hsun Hsu, Isabel Winney, Mirre Simons, Shinichi Nakagawa, Terry Burke.

Max Planck Institute for Ornithology; University of Otago; University of Sheffield.

Whether and why male parents should adjust the amount of care they provide to young if the female partner is unfaithful has been discussed for more than two decades. While there is general agreement that such a relationship exists across species, empirical results for within-population effects are ambiguous. The problem partially lies in the difficulty to disentangle between-individual from within-individual processes. We use an exceptionally well-suited dataset on wild house sparrows (Passer domesticus) to revisit this problem. Females were repeatable in the proportion of extra-pair offspring they produced per brood, however, the repeatability was higher when they stayed with the same male. Individual males phenotypically adjusted paternal care to paternity only when they changed mates. We found no support for an association of this adjustment within pair bonds. The within-male paternal adjustment between-pairs was not affected by male age, offspring relatedness to the caring male, seasonality or the brood order. However, the paternal care adjustment was negatively associated with the number of annual extra-pair paternities the male gained with other
females. Our results support that social feedback may be driving paternity-parental care dynamics, allowing a better understanding of evolution female polygamy.

Poster session A - GEN 2000

# A protected polymorphism for shell colour in a natural population of a marine snail (52778)

Daniel Estévez, Emilio Rolán-Alvarez, **Juan Galindo**.

*University of Vigo.*

A well-established population of Littorina fabalis has been monitored since 1990, showing an apparently stable shell colour polymorphism. The analysis of mating pairs captured in the field across several years revealed a significant negative assortative mating (I_PSI = -0.4) for shell colour. This pattern could be produced by a mechanism of, negative frequency-dependent sexual selection based in shell colour. In order to test this prediction we estimated colour fitness with two alternative methods: by using 1) sexual selection plus viability estimates, and 2) inter-annual total fitness estimates. Both types of fitness estimates presented a significant (negative) correlation with colour frequency across samples of different years, providing a clear evidence for the polymorphism being maintained by frequency-dependent natural selection presumably caused by strong negative assortative mating. The evolutionary mechanisms (inbreeding avoidance or apostatic selection) able to cause the origin and maintenance of strong negative assortative mating are discussed.

Poster session A - GEN 2000

# Condition-dependent outcrossing in the filamentous fungus Aspergillus nidulans (52861)

Nicolas O. Rode, Sijmen Schoustra, Devin Arbuthnott, Rees Kassen, Howard Rundle.

*INRA-Montpellier; University of Wageningen; University of Washington; University of Ottawa.*

Recent theoretical models predict that facultatively sexual organisms should reproduce clonally when their fitness is high, but sexually when their fitness is low (condition-dependent sex).

Most empirical studies have been hampered by the difficulty of measuring simultaneously fitness along with sexual and asexual reproduction. For example, male fitness is notoriously difficult to estimate in most species. In facultatively sexual organisms, sexual reproduction virtually always produces sexual structures involved in spatial (or temporal) dispersal. Hence, disentangling condition-dependent sex from condition-dependent dispersal is almost impossible in most organisms.

In homothallic haploid organisms, selfed spores are genetically identical to asexual spores.
We investigated condition-dependent outcrossing in the filamentous fungus Aspergillus
nidulans, where sexual spores (both selfed and outcrossed) are enclosed within the same structures. This property allows ruling out condition-dependent dispersal as a possible alternative to condition-dependent outcrossing.

We competed different wild and lab strains in a single environment. We measured the investment in asexual reproduction, self-fertilization and outcrossing, along with absolute and relative fitness. Our results unravel the complex interactions between resource allocation to these different modes of reproduction and fitness.

Poster session A - GEN 2000

# Does self-fertilization enhance or reduce response to selection ? Empirical test in a freshwater snail. (52924)

Marie-Agnès Coutellec, Marc Collinet, Maïra Coke, Patrice David.

INRA, UMR ESE 0985; INRA, U3E; CNRS, CEFE.

Selfing as an evolutionary dead-end is a longstanding hypothesis, based on two main tenets: unidirectional evolution towards selfing through a purge process of the genetic load, and increased extinction rate due to low adaptive potential associated with selective interference in highly homozygous lineages. Although ancient, this hypothesis has been only recently started to be tested empirically. As a contribution to this endeavour, the present study focuses on the expected relative adaptability of selfing and outcrossing lines of an animal hermaphrodite (gastropod, Lymnaea stagnalis). The short-term response to selection was compared between enforced selfing and outcrossing, using lines set up from various natural populations and a pesticide as selective pressure vs benign conditions. In preferentially outcrossing species such as L. stagnalis, selfing is expected to lower the response to selection, due to high inbreeding depression. However, this species exhibits moderate inbreeding depression, which suggests a possible purge of part of the genetic load. Therefore, selfing may actually facilitate the response to selection. Nevertheless, after two generations, selfing lines are clearly more sensitive than outcrossing ones to the pesticide (weaker response to selection). Third-generation performances and subsequent inbreeding depression will be compared between selection regimes to get a more comprehensive picture (ongoing experiment).

Poster session A - GEN 2000

# Cooperative blood-feeding explains feeding aggregations in Phlebotomine Sandflies (51797)

Frédéric Tripet, Simon Clegg, Dia-Eldin Elnaiem, Richard Ward.

School of Life Sciences, Keele University, United Kingdom; LMVR/NIAID/NIH, Twinbrook Parkway, Rockville, MD, USA.
Given the importance that the evolution of cooperation bears in evolutionary biology and social sciences, extensive theoretical work has focused on identifying conditions that promote cooperation among unrelated individuals despite potential cheating individuals. In insects, cooperative interactions typically occur amongst related individuals and are explained by kin selection. Here we provide evidence that in Lutzomia longipalpis, a small biting fly vector of leishmaniasis in the New world, cooperative bloodfeeding in groups of unrelated individuals results in a strong decrease in saliva expenditure. Feeding in groups significantly affected the timing and duration of the flies' bloodmeal and resulted in greatly enhanced egg production. The benefits of feeding aggregations were particularly strong when flies fed on older hosts suggesting that flies were able to overcome the stronger immune response of pre-sensitized hosts. Our results demonstrate that, in Lutzomyia longipalpis, feeding cooperatively maximizes the effects of salivary components injected into hosts to facilitate blood intake and to counteract the host immune response. As a result, cooperating sandflies enjoy enormous fitness gains. This constitutes the first functional explanation for feeding aggregations in hematophagous insects and a rare example of cooperation in a non-social insects species. The evolution of cooperative group feeding in sandflies may have important implications for the epidemiology of leishmaniasis.

**Transitioning from pathogen to mutualist: the evolution of vertical transmission (51855)**

**Devin Drown, Michael Wade.**

*University of Alaska Fairbanks; Indiana University.*

We investigate the coevolution of transmission mode and virulence in host-symbiont interactions using population genetic models. Vertical transmission enhances the genetic fidelity of the host-symbiont interaction and directly affects the efficiency of selection on host-symbiont gene combinations (inter-genomic epistasis). We find that the interaction between virulence and population genetic structure determines the evolutionary balance between a host-symbiont arms race and host-mutualist coevolution. It is well known from models of the evolution of sex that, with horizontal transmission, evolution drives an arms race, wherein hosts adapt to escape virulent pathogens and pathogens adapt toward discovering susceptible hosts. Conversely, with vertical transmission, the more likely host-symbiont mutualistic coevolution becomes with an attendant reduction in symbiont virulence. We find that, when mutation generates inter-genomic epistasis, modifiers increasing the degree of vertical transmission can hitchhike to fixation. Once an intermediate level of vertical transmission is established, mutualistic coevolution or ‘symbiont capture’ predominates. That is, the evolutionary stable state is mutualistic symbiosis rather than an escalating host-pathogen arms race.
# Tripartite network of an ant host, transposable elements and intracellular bacteria. (51987)

Antonia Klein, Lukas Schrader, Jan Oettler.

*University Regensburg, Germany.*

The evolution of eukaryotic organisms is often influenced by transposable elements (TEs) and microbial symbionts that confer novel traits to their hosts. Here I will describe the tripartite system of a Cardiocondyla obscurior ant host, associated (TEs) and intracellular endosymbionts which likely play a significant role in the invasive success of the host. One the one hand TEs contribute to high rates of genomic novelty as precursor for adaptive variation (Schrader et al 2014). On the other hand the newly described gut-associated endosymbiont ‘Candidatus Westeberhardia cardiocondylae’ might facilitate development under poor nutritional regimes. I will discuss these findings from a holistic perspective of an extended genotype of egalitarian cooperation partners in changing environments. Contrary to common belief, environmentally initiated novelties by “selfish” intragenomic or intracellular interaction partners may have great evolutionary potential, strongly advising against a simplified view of organismal evolution.

Poster session A - GEN 2000

# Co-evolution with natural enemies promotes probiotic activity in a plant-associated bacterium (52075)

Erqin Li, Peter Bakker, Alexandre Jousset.

*Utrecht University; Utrecht University; Utrecht University.*

Plants roots are colonized by mutualistic, free living microbes that provide essential functions such as antibiosis that inhibits pathogens. However, this system cannot be evolutionarily stable if the host plant only feeds the microbes, but does not dispose of mechanisms for specifically rewarding cooperators or punishing defectors. As a result, mutualistic bacteria rapidly lose their ability to produce antibiotics and turn into free-riders consuming host resources without providing services in return. However, thanks to a functional overlap between disease suppression and antipredator defense, presence of predators (protozoa) may prevent the decay of plant-microbe mutualism by counter-selecting defectors. Here we co-evolve Pseudomonas protegens CHA0, a model mutualistic bacterium inhibiting several plant diseases, in presence of ciliated protozoa. We show that co-evolution with protozoa not only prevents the apparition of defectors but also results in an enhanced expression of the traits linked to pathogen suppression. Our results reveal that natural enemies may be essential to maintain host-microbe mutualism and that a multitrophic evolutionary framework should be used to assess the costs and benefits of interkingdom cooperation.

Poster session A - GEN 2000