Genetic and environmental contributions to the impact of a range-expanding predator on aquatic ecosystems.

Global change is altering biodiversity locally and globally and subsequently affecting the dynamics of communities and ecosystems. Biodiversity can be impacted both at the interspecific (i.e., species composition of communities) and at the intraspecific (evolutionary modification of phenotypic traits through selection or plasticity) levels. Changes in intraspecific diversity have been demonstrated to generate evolutionary feedbacks acting on ecological dynamics. Quantifying the role of intraspecific trait variation, global change and their interactions on ecological dynamics is of utmost importance. Here, we used the range-expanding dragonfly Crocothemis erythraea as a model species to test the relative effects of intraspecific trait variation in larvae and thermal conditions on the dynamics of freshwater community and ecosystem functioning. Using experimental mesocosms, we manipulated intraspecific trait variation arising from genetic (G), early developmental environment (EE ) and late developmental environment (EL ) contributions in a full factorial design. We showed that intraspecific trait variation arising from genetic effects has the strongest consequences on community and ecosystem dynamics relative to trait variation driven by the thermal environment (EE and EL ). Importantly, the ecological effects of trait variation due to genetic effects were partly modulated by thermal conditions (G × EL , and to a lesser extent G × EE interactions) and varied among ecological response variables. For instance, the strongest G × EL effects were observed on primary productivity and zooplankton dynamics. Trait variation driven by plasticity related to early or late developmental environments has an overall weak effect on ecological dynamics. Intraspecific trait variation induced by genetic effects can affect ecological dynamics (evo-to-eco dynamics) more strongly than variation induced by the developmental environment. However, they likely interact to modulate the structure of communities and the functioning of ecosystems, highlighting the strong context (environmental) dependency of evo-to-eco dynamics.