Climate has both ecological and evolutionary effects. Evolutionary responses to anthropogenic climate change can be surprisingly fast, and may thus commonly interact with ecological changes. Hence, an “eco-evolutionary dynamics” perspective, which aims to understand the contemporary bi-directional nature of ecological with evolutionary processes, may be required to accurately predict future ecological conditions under climate change. Evolutionary changes in key ecological players (e.g. foundation species, dominant species, and top predators) can have particularly strong community and ecosystem ecological consequences. Thus, a first step towards integrating ecological with evolutionary responses to climate change is understanding the interaction of community ecological responses with the evolutionary responses of ecologically-important species. Here, we use a common aquatic predator, western mosquitofish (Gambusia affinis), which was recently introduced from a common source to geothermal systems of varying temperature regimes, to understand how rapid evolutionary responses to higher temperatures may interact with ecosystem warming to determine community and ecosystem ecological conditions. We use second-generation common garden rearing of mosquitofish from one warm-source and one cool-source population 1) to test for evidence of evolutionary thermal adaptation, including changes to functional traits, and 2) to test for the ecological consequences of this potential adaptation in an experimental pond warming study.
Results/Conclusions
Common garden rearing showed rapid evolution of countergradient variation with response to temperature – cool-source mosquitofish grew faster than warm-source mosquitofish across all rearing temperatures. Warm-source fish therefore evolved a relatively smaller size-at-age, but also evolved a smaller size at maturity – a common ectotherm response to higher temperatures. Behavioral assays revealed warm-source fish evolved relatively bolder behavior. Finally, in a feeding assay, warm-source fish consumed relatively smaller zooplankton prey, independent of fish body size. In our experimental pond warming study, common-reared warm-source fish induced relatively stronger prey biomass suppression, and caused stronger prey community body size declines. Ponds with warm-source fish showed a temporary relative increase in phytoplankton, suggesting the consequences of recent predator evolution for prey can have cascading ecological consequences. Across many ecological and physicochemical response variables, there were few interactions between predator evolution and ecosystem temperature. However, warming and fish evolution additively decreased zooplankton body size with similar effect sizes. Our results suggest that thermal adaptation may be an important pathway by which climate warming can impact communities and ecosystems. Experiments that test the ecosystem effects of future climate warming using organisms adapted to current climate conditions may underestimate these effects.