bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional types in the Bromeliaceae: relationships with drought‐resistance traits and bioclimatic distributions
Authors: Males Jamie , Griffiths Howard 
Published: May 2017

Summary

Neotropical Bromeliaceae occupy an exceptional diversity of habitats. The five principal functional types, which are defined by innovations such as Crassulacean acid metabolism (CAM), epiphytism, the tank growth form and neoteny, display distinct ecological water‐use strategies.

The contribution of putative drought‐resistance traits to the ecological differentiation of functional types has not previously been assessed, despite growing interest in the importance of these traits in other plant groups.

We formulated a set of hypotheses to be tested through a major survey of 376 bromeliad species (over 10% of the entire family) representing different functional types and ecologies. We quantified four drought‐resistance traits: osmotic potential at full turgor (πo), saturated water content (SWC), water mass per unit area (WMA) and dry leaf mass per unit area (LMA). For a subset of 308 species, relationships between drought‐resistance traits and species bioclimatic envelopes were also analysed.

Saturated water content, WMA and LMA were closely inter‐correlated, and there was weaker coordination with πo, but the four traits differed significantly between functional types. Species of different functional types occupied distinct areas of bioclimatic space, and the relationships mapping drought‐resistance trait values into bioclimatic space also varied between functional types.

We conclude that divergences in drought‐resistance trait values form an integral part of the evolution of functional type distinctiveness and climatic niche differentiation in this megadiverse tropical plant family.

This study demonstrates how rapid, taxonomically extensive quantification of plant functional traits can provide important insights into the evolution of ecological diversity.

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Optimal running speeds when there is a trade‐off between speed and the probability of mistakes
Authors: Amir Abdul Nasir Ami Fadhillah , Clemente Christofer J. , Wynn Melissa L. , Wilson Robbie S. 
Published: May 2017

Summary

Do prey run as fast as they can to avoid capture? This is a common assumption in studies of animal performance, yet a recent mathematical model (Wheatley et al. Integrative and Comparative Biology, 55, 1166–1175; ) of escape behaviour predicts that animals should instead use speeds below their maximum capabilities even when running from predators. Fast speeds may compromise motor control and accuracy of limb placement, particularly as the animal runs along narrow structures like beams or branches. Mistakes decrease speed and increase the probability of capture.

We tested several key assumptions and predictions of Wheatley et al.'s () model using wild‐caught northern quolls (Dasyurus hallucatus), a squirrel‐sized marsupial carnivore. We quantified the speeds of quolls as they traversed beams of differing width and expected animals should balance the benefits of higher speeds against the increased probability of mistakes when selecting speeds.

We first explored whether the probability of mistakes when running along a beam increased at faster running speeds (speed‐accuracy trade‐off) and when the difficulty of a task was greater (narrower beam). In addition, we quantified the costs of locomotor mistakes to test the assumption that mistakes decreased overall running speed. Finally, we tested whether individual northern quolls modulated their running speeds when moving on narrow beams, which would decrease the probability of making catastrophic mistakes.

We found quolls were more likely to make mistakes when running faster and on the narrower beam. Locomotor mistakes increased the total time needed to traverse the entire beam, and each mistake decreased average escape speed by around 50%, representing a substantial cost for slips or trips. To circumvent the costs of these mistakes, quolls voluntarily reduced speeds in situations when they are more likely to make a mistake (i.e. narrower beams), thereby allowing them to decrease the total time it took to traverse the beam.

Our data provide support for the assumptions and predictions of Wheatley et al.'s () model of optimal escape speeds, and suggest that animals optimize rather than simply maximize speeds when running along challenging substrates. Our work provides a foundation for understanding the movement behaviour of animals when their objective is to escape predatory attacks, and demonstrates that animals should select their escape strategy based on how both the speed of movement and motor control affect task success.

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Conspecific and not performance‐based attraction on immigrants drives colony growth in a waterbird
Authors: Tenan Simone , Fasola Mauro , Volponi Stefano , Tavecchia Giacomo 
Published: May 2017

Abstract

Local recruitment and immigration play an important part in the dynamics and growth of animal populations. However, their estimation and incorporation into open population models is, in most cases, problematic. We studied factors affecting the growth of a recently established colony of Eurasian spoonbill (Platalea leucorodia) and assessed the contribution of local recruits, i.e. birds born in the colony, and immigrants, i.e. birds of unknown origin, to colony growth.

We applied an integrated population model that accounts for uncertainty in breeding state assignment and merges population surveys, local fecundity and individual longitudinal data of breeding and non‐breeding birds, to estimate demographic rates and the relative role of recruitment and immigration in driving the local dynamics. We also used this analytical framework to assess the degree of support for the ‘performance‐based’ and ‘conspecific attraction’ hypotheses as possible mechanisms of colony growth.

Among the demographic rates, only immigration was positively and significantly correlated with population growth rate. In addition, the number of immigrants settling in the colony was positively correlated with colony size in the previous and current year, but was not correlated with fecundity of the previous year.

Our results suggest that the variation in immigration affected colony dynamics and that conspecific attraction likely triggered the relevant role of immigration in the growth of a recently formed waterbird colony, supporting the need of including immigration in population analysis.
Reproductive performance of resident and migrant males, females and pairs in a partially migratory bird
Authors: Grist Hannah , Daunt Francis , Wanless Sarah , Burthe Sarah J. , Newell Mark A. , Harris Mike P. , Reid Jane M. 
Published: May 2017

Abstract

Quantifying among‐individual variation in life‐history strategies, and associated variation in reproductive performance and resulting demographic structure, is key to understanding and predicting population dynamics and life‐history evolution. Partial migration, where populations comprise a mixture of resident and seasonally migrant individuals, constitutes a dimension of life‐history variation that could be associated with substantial variation in reproductive performance. However, such variation has rarely been quantified due to the challenge of measuring reproduction and migration across a sufficient number of seasonally mobile males and females.

We used intensive winter (non‐breeding season) resightings of colour‐ringed adult European shags (Phalacrocorax aristotelis) from a known breeding colony to identify resident and migrant individuals. We tested whether two aspects of annual reproductive performance, brood hatch date and breeding success, differed between resident and migrant males, females and breeding pairs observed across three consecutive winters and breeding seasons.

The sex ratios of observed resident and migrant shags did not significantly differ from each other or from 1:1, suggesting that both sexes are partially migratory and that migration was not sex‐biased across surveyed areas.

Individual resident males and females hatched their broods 6 days earlier and fledged 0.2 more chicks per year than migrant males and females on average. Resident individuals of both sexes therefore had higher breeding success than migrants.

Hatch date and breeding success also varied with a pair's joint migratory strategy such that resident–resident pairs hatched their broods 12 days earlier than migrant–migrant pairs, and fledged 0.7 more chicks per year on average. However, there was no evidence of assortative pairing with respect to migratory strategy: observed frequencies of migrant–migrant and resident–resident pairs did not differ from those expected given random pairing.

These data demonstrate substantial variation in two key aspects of reproductive performance associated with the migratory strategies of males, females and breeding pairs within a partially migratory population. These patterns could reflect direct and/or indirect mechanisms, but imply that individual variation in migratory strategy and variation in pairing among residents and migrants could influence selection on migration and drive complex population and evolutionary dynamics.
Gut microbial communities of American pikas (Ochotona princeps): Evidence for phylosymbiosis and adaptations to novel diets
Authors: Kohl Kevin D. , Varner Johanna , Wilkening Jennifer L. , Dearing M. Denise 
Published: May 2017

Abstract

Gut microbial communities provide many physiological functions to their hosts, especially in herbivorous animals. We still lack an understanding of how these microbial communities are structured across hosts in nature, especially within a given host species. Studies on laboratory mice have demonstrated that host genetics can influence microbial community structure, but that diet can overwhelm these genetic effects.
We aimed to test these ideas in a natural system, the American pika (Ochotona princeps). First, pikas are high‐elevation specialists with significant population structure across various mountain ranges in the USA, allowing us to investigate whether similarities in microbial communities match host genetic differences. Additionally, pikas are herbivorous, with some populations exhibiting remarkable dietary plasticity and consuming high levels of moss, which is exceptionally high in fibre and low in protein. This allows us to investigate adaptations to an herbivorous diet, as well as to the especially challenging diet of moss.
Here, we inventoried the microbial communities of pika caecal pellets from various populations using 16S rRNA sequencing to investigate structuring of microbial communities across various populations with different natural diets.
Microbial communities varied significantly across populations, and differences in microbial community structure were congruent with genetic differences in host population structure, a pattern known as “phylosymbiosis.”
Several microbial members (Ruminococcus, Prevotella, Oxalobacter and Coprococcus) were detected across all samples, and thus likely represent a “core microbiome.” These genera are known to perform a number of services for herbivorous hosts such as fibre fermentation and the degradation of plant defensive compounds, and thus are likely important for herbivory in pikas. Moreover, pikas that feed on moss harboured microbial communities highly enriched in Melainabacteria. This uncultivable candidate phylum has been proposed to ferment fibre for herbivores, and thus may contribute to the ability of some pika populations to consume high amounts of moss.
These findings demonstrate that both host genetics and diet can influence the microbial communities of the American pika. These animals may be novel sources of fibre‐degrading microbes. Last, we discuss the implications of population‐specific microbial communities for conservation efforts in this species.
The role of rare morph advantage and conspicuousness in the stable gold‐dark colour polymorphism of a crater lake Midas cichlid fish
Authors: Torres‐Dowdall Julián , Golcher‐Benavides Jimena , Machado‐Schiaffino Gonzalo , Meyer Axel 
Published: May 2017

Abstract

Genetically based stable colour polymorphisms provide a unique opportunity to study the evolutionary processes that preserve genetic variability in the wild. Different mechanisms are proposed to promote the stability of polymorphisms, but only few empirical examples have been documented, resulting in an incomplete understanding of these mechanisms.

A remarkable genetically determined stable colour polymorphism is found in the Nicaraguan Midas cichlid species complex (Amphilophus cf. citrinellus). All Midas cichlids start their life with a dark‐grey coloration (dark morph), but individuals carrying the dominant “gold” allele (c. 10%) lose their melanophores later in life, revealing the underlying orange coloration (gold morph). How this polymorphism is maintained remains unclear. Two main hypotheses have been proposed, both suggesting differential predation upon colour morphs as the proximate mechanism. One predicts that the conspicuous gold morph is more likely to be preyed upon, but this disadvantage is balanced by their competitive dominance over the dark morph. The second hypothesis suggests a rare morph advantage where the rarer gold morph experiences less predation. Empirical evidence for either of these mechanisms is still circumstantial and inconclusive.

We conducted two field experiments in a Nicaraguan crater lake using wax models simulating both morphs to determine predation pressure upon Midas cichlid colour morphs. First, we tested the interaction of coloration and depth on attack rate. Second, we tested the interaction of fish size and coloration. We contrasted the pattern of attacks from these experiments to the predicted predation patterns from the hypotheses proposed to explain the colour polymorphism's stability.

Large models imitating colour morphs were attacked at similar rates irrespectively of their position in the water column. Yet, attacks upon small models resembling juveniles were directed mainly towards dark models. This resulted in a significant size‐by‐colour interaction.

We suggest that gold Midas cichlids experience a rare morph advantage as juveniles when individuals of this morph are extremely uncommon. But this effect is reduced or disappears among adults, where gold individuals are relatively more common. Thus, the interaction of rare morph advantage and conspicuousness, rather than either of those factors alone, is a likely mechanism resulting in the stability of the colour polymorphism in Midas cichlids.
Desynchronizations in bee–plant interactions cause severe fitness losses in solitary bees
Authors: Schenk Mariela , Krauss Jochen , Holzschuh Andrea 
Published: May 2017

Abstract

Global warming can disrupt mutualistic interactions between solitary bees and plants when increasing temperature differentially changes the timing of interacting partners. One possible scenario is for insect phenology to advance more rapidly than plant phenology.

However, empirical evidence for fitness consequences due to temporal mismatches is lacking for pollinators and it remains unknown if bees have developed strategies to mitigate fitness losses following temporal mismatches.

We tested the effect of temporal mismatches on the fitness of three spring‐emerging solitary bee species, including one pollen specialist. Using flight cages, we simulated (i) a perfect synchronization (from a bee perspective): bees and flowers occur simultaneously, (ii) a mismatch of 3 days and (iii) a mismatch of 6 days, with bees occurring earlier than flowers in the latter two cases.

A mismatch of 6 days caused severe fitness losses in all three bee species, as few bees survived without flowers. Females showed strongly reduced activity and reproductive output compared to synchronized bees. Fitness consequences of a 3‐day mismatch were species‐specific. Both the early‐spring species Osmia cornuta and the mid‐spring species Osmia bicornis produced the same number of brood cells after a mismatch of 3 days as under perfect synchronization. However, O. cornuta decreased the number of female offspring, whereas O. bicornis spread the brood cells over fewer nests, which may increase offspring mortality, e.g. due to parasitoids. The late‐spring specialist Osmia brevicornis produced fewer brood cells even after a mismatch of 3 days. Additionally, our results suggest that fitness losses after temporal mismatches are higher during warm than cold springs, as the naturally occurring temperature variability revealed that warm temperatures during starvation decreased the survival rate of O. bicornis.

We conclude that short temporal mismatches can cause clear fitness losses in solitary bees. Although our results suggest that bees have evolved species‐specific strategies to mitigate fitness losses after temporal mismatches, the bees were not able to completely compensate for impacts on their fitness after temporal mismatches with their food resources.
Towards a mechanistic understanding of the effect that different species of large grazers have on grassland soil N availability
Authors: Liu Chen , Wang Ling , Song Xuxin , Chang Qing , Frank Douglas A. , Wang Deli , Li Jing , Lin Haijiao , Du Feiyue 
Published: May 2017

Abstract

Herbivore grazing has major effects on soil nutrient dynamics in a variety of grassland ecosystems. Previous studies have examined how large herbivores as a group affect nutrient cycling, but little information is available on how assemblages of different herbivore species may influence nutrient cycling, and whether herbivore assemblage effects are influenced by plant community characteristics (e.g. composition, diversity) of the grazed grassland.

We conducted a 5‐year, replicated grazing experiment to test the effects of different large herbivore assemblages (cattle grazing, sheep grazing, combined cattle and sheep grazing, no grazing) under moderate grazing intensity on soil nitrogen (N) mineralization rate in two types of grassland communities (high forbs/high diversity and low forbs/low diversity) in meadow steppe habitat of northeast China. Moreover, we examined two distinctly different pathways that herbivores could influence soil N availability: directly through urine and dung deposition and indirectly by shifting grassland species composition (i.e. the grass: forb ratio), thereby the quality of plant litter available to soil decomposers.

We found that grazer effects on soil N availability (indexed with anion and cation adsorption strips) depended on herbivore assemblage, and the herbivore assemblage effects varied in the two types of grasslands. In one type of grassland characterized by low diversity, grazing by each of the herbivore assemblages enhanced soil N availability compared to the ungrazed plots, and mixed species (cattle and sheep) grazing had a greater effect than single species grazing. In high diversity grassland, single species herbivore grazing significantly increased soil N availability, but mixed grazing had no effect.

Mixed linear modelling revealed that soil N availability was facilitated primarily by excreta additions to the soil and secondarily by the abundance of grasses.

Synthesis. Grazers increased soil N availability directly by adding readily accessible N in urine and dung to the soil. Herbivores indirectly influenced soil N availability by altering the plant composition (grass: forb cover). Both mechanisms contributed to the variation in how different herbivore assemblages affected soil N availability in the two grassland types.
The ‘golden kelp’ Laminaria ochroleuca under global change: Integrating multiple eco‐physiological responses with species distribution models
Authors: Franco João N. , Tuya Fernando , Bertocci Iacopo , Rodríguez Laura , Martínez Brezo , Sousa‐Pinto Isabel , Arenas Francisco 
Published: May 2017

Abstract

The loss of marine foundation species, in particular kelps at temperate latitudes, has been linked to climatic drivers and co‐occurring human perturbations. Ocean temperature and nutrients typically covary over local and regional scales and play a crucial role on kelp dynamics. Examining their independent and interactive effects on kelp physiological performance is essential to understand and predict patterns of kelp distribution, particularly under scenarios of global change.

Crossed combinations of ocean temperatures and availability of nutrients were experimentally tested on juveniles of the ‘golden kelp’, Laminaria ochroleuca, from the northwestern Iberian Peninsula. Eco‐physiological responses included: survival, growth and total N content. Results were embedded into a Species Distribution Model (SDM), which relates presence records and climatic and non‐climatic data to forecast distribution patterns of L. ochroleuca under different climate change scenarios.

Temperatures above 24.6°C were lethal irrespective of nutrients. Optimal growth of juvenile sporophytes occurred between 12 and 18°C and no nutrient limitation. The SDM, where ocean temperature was the main predictor of kelp distribution in line with temperature thresholds given by eco‐physiological responses, suggests a future expansion towards northern latitudes and a retreat from the southern limit/boundary of the current distribution.

Synthesis. Range‐shifting of the golden kelp can have severe ecological impacts at regional and local scales. The expansion or retraction of the species along the European coast seems to be modulated mainly by temperature, but nutrient availability would be a key to maintain optimal physiological performance. Our work highlights that the combination of empirical and modelling approaches is accessible to researchers and crucial to building more robust predictions of ecological and biogeographic responses of habitat‐forming species to forecasted environmental change.
Difference in shade tolerance drives the mixture effect on oak productivity
Authors: Toïgo Maude , Perot Thomas , Courbaud Benoit , Castagneyrol Bastien , Gégout Jean‐Claude , Longuetaud Fleur , Jactel Hervé , Vallet Patrick 
Published: May 2017

Abstract

Assessing how species productivity in mixtures is influenced by species shade tolerance (ST) and phylogeny would be helpful to improve our general understanding of the relationship between tree species diversity and productivity in forests.

We investigated the effects of differences in ST and phylogenetic distances (PDs) between pairs of species on the productivity of Quercus petraea growing in 18 mixtures in lowland temperate forests. We calculated the mixture effect as the difference in productivity of Q. petraea in mixed vs. pure stands. Our analyses were based on data from seven annual campaigns of the French National Forest Inventory covering 1,573 plots.

The mixture effect on Q. petraea productivity increased when the ST of the companion species decreased. Compared to its productivity in pure stands, Q. petraea productivity in mixed coniferous stands varied from −14.6% up to +39.6% as the ST of the companion species inversely varied from highest to lowest. With broadleaved companion species, the mixture effect varied from −10% up to +13.9% with decreasing ST. We found no effect of PD between Q. petraea and the companion species on the mixture effect.

Synthesis. Our results confirm that shade tolerance is an important driver of the diversity effect on productivity at species level in temperate forests and that phylogenetic distance is not a relevant proxy for species functional dissimilarity.