Does Intraspecific Size Variation in a Predator Affect Its Diet Diversity and Top-Down Control of Prey?

It has long been known that intraspecific variation impacts evolutionary processes, but only recently have its potential ecological effects received much attention. Theoretical models predict that genetic or phenotypic variance within species can alter interspecific interactions, and experiments have shown that genotypic diversity in clonal species can impact a wide range of ecological processes. To extend these studies to quantitative trait variation within populations, we experimentally manipulated the variance in body size of threespine stickleback in enclosures in a natural lake environment. We found that body size of stickleback in the lake is correlated with prey size and (to a lesser extent) composition, and that stickleback can exert top-down control on their benthic prey in enclosures. However, a six-fold contrast in body size variance had no effect on the degree of diet variation among individuals, or on the abundance or composition of benthic or pelagic prey. Interestingly, post-hoc analyses revealed suggestive correlations between the degree of diet variation and the strength of top-down control by stickleback. Our negative results indicate that, unless the correlation between morphology and diet is very strong, ecological variation among individuals may be largely decoupled from morphological variance. Consequently we should be cautious in our interpretation both of theoretical models that assume perfect correlations between morphology and diet, and of empirical studies that use morphological variation as a proxy for resource use diversity

Species Interactions Alter Evolutionary Responses to a Novel Environment

Adaptation to a novel environment is altered by the presence of co-occurring species. Species in diverse communities evolved complementary resource use, which altered the functioning of the experimental ecosystems

Common garden experiments in the genomic era : new perspectives and opportunities

PdV was supported by a doctoral studentship from the French Ministère de la Recherche et de l’Enseignement Supérieur. OEG was supported by the Marine Alliance for Science and Technology for Scotland (MASTS)The study of local adaptation is rendered difficult by many evolutionary confounding phenomena (e.g. genetic drift and demographic history). When complex traits are involved in local adaptation, phenomena such as phenotypic plasticity further hamper evolutionary biologists to study the complex relationships between phenotype, genotype and environment. In this perspective paper, we suggest that the common garden experiment, specifically designed to deal with phenotypic plasticity has a clear role to play in the study of local adaptation, even (if not specifically) in the genomic era. After a quick review of some high-throughput genotyping protocols relevant in the context of a common garden, we explore how to improve common garden analyses with dense marker panel data and recent statistical methods. We then show how combining approaches from population genomics and genome-wide association studies with the settings of a common garden can yield to a very efficient, thorough and integrative study of local adaptation. Especially, evidence from genomic (e.g. genome scan) and phenotypic origins constitute independent insights into the possibility of local adaptation scenarios, and genome-wide association studies in the context of a common garden experiment allow to decipher the genetic bases of adaptive traits.PostprintPeer reviewe

Transgenerational selection driven by divergent ecological impacts of hybridizing lineages

Dynamic interactions between ecological conditions and the phenotypic composition of populations likely play an important role in evolution, but the direction and strength of these feedbacks remain difficult to characterize. We investigated these dynamics across two generations of threespine sticklebacks from two evolutionary lineages undergoing secondary contact and hybridization. Independently manipulating the density and lineage of adults in experimental mesocosms led to contrasting ecosystem conditions with strong effects on total survival in a subsequent generation of juveniles. Ecosystem modifications by adults also varied the strength of selection on competing hybrid and non-hybrid juveniles. This variation in selection indicated (1) a negative eco-evolutionary feedback driven by lineage-specific resource depletion and dependence and (2) a large perfor- mance advantage of hybrid juveniles in depleted environments. This work illustrates the importance of interactions between phenotype, population density and the environment in shaping selection and evolutionary trajectories, especially in the context of range expansion with secondary contact and hybridization

Linking the evolution of habitat choice to ecosystem functioning: Direct and indirect effects of pond-resproducing fire salamanders on aquatic - terrestrial subsidies.

Reinhardt T, Steinfartz S, Paetzold A, Weitere M. Linking the evolution of habitat choice to ecosystem functioning: Direct and indirect effects of pond-resproducing fire salamanders on aquatic - terrestrial subsidies. Oecologia. 2013;173(1):281-291

Multiple‐batch spawning as a bet‐hedging strategy in highly stochastic environments : an exploratory analysis of Atlantic cod

Stochastic environments shape life‐history traits and can promote selection for risk‐spreading strategies, such as bet‐hedging. Although the strategy has often been hypothesised to exist for various species, empirical tests providing firm evidence have been rare, mainly due to the challenge in tracking fitness across generations. Here, we take a ‘proof of principle’ approach to explore whether the reproductive strategy of multiple‐batch spawning constitutes a bet‐hedging. We used Atlantic cod (Gadus morhua) as the study species and parameterised an eco‐evolutionary model, using empirical data on size‐related reproductive and survival traits. To evaluate the fitness benefits of multiple‐batch spawning (within a single breeding period), the mechanistic model separately simulated multiple‐batch and single‐batch spawning populations under temporally varying environments. We followed the arithmetic and geometric mean fitness associated with both strategies and quantified the mean changes in fitness under several environmental stochasticity levels. We found that, by spreading the environmental risk among batches, multiple‐batch spawning increases fitness under fluctuating environmental conditions. The multiple‐batch spawning trait is, thus, advantageous and acts as a bet‐hedging strategy when the environment is exceptionally unpredictable. Our research identifies an analytically flexible, stochastic, life‐history modelling approach to explore the fitness consequences of a risk‐spreading strategy and elucidates the importance of evolutionary applications to life‐history diversity.peerReviewe