The impacts of global changes on ecosystems are shaped by evolution of organismal traits, plasticity and turnover in community structure. Ecological and evolutionary history can influence community responses to environmental change, though time scales of experimental studies are typically too short for such shifts to occur. Thus, the contributions of phenotypic selection within and among species to community resilience are largely unknown. To test if history alters community responses to environmental change, we conducted a plankton community transplant experiment. Our experiment is a community-level analog to a common garden, designed to measure the impact of the environment and genotype on the phenotype of an organism. We established communities of aquatic organisms originating from four types of lakes in the California Sierra Nevada mountains: all factorial combinations of alpine and sub-alpine elevations, with and without introduced trout predators. We grew these four types of plankton communities at three elevations crossed with the presence of fish predators in the experimental pond mesocosms. Our goal was to test the hypothesis that evolutionary and ecological history of elevation and fish predation would affect the contemporary population, community and ecosystem level responses of plankton to these same perturbations.
Results/Conclusions
We found that the response of communities to elevation and predators was contingent on the environment from which they originated. We expected that local adaptation would produce plankton with the highest fitness in their home environment, but this prediction was not supported. Instead, zooplankton that originated in lakes with fish obtained a higher total community biomass in the absence of fish than communities that were originally from fishless lakes. This pattern was largely driven by changes in Daphnia pulicaria biomass (increases in both abundance and body size) suggesting fish select for a faster intrinsic growth rate in Daphnia populations and this effect lasts for many generations. The history of fish predation played a greater role in contemporary community structure and response to environmental change than the history of elevation. Our experiment indicates that shifts in species composition and evolutionary history of populations along environmental gradients determine the aggregate response of communities to changes in predation and climate.