Biotic interactions structure zooplankton metacommunity dynamics following a summer heatwave

Despite the key role of biotic interactions in structuring ecological communities, their influence is often overlooked in predictions of how communities respond to environmental change.Here, we present an experimental test of hypotheses based on metacommunity theory about how abiotic responses, biotic interactions and dispersal determine the response of ecological communities to abiotic perturbations.We established experimental zooplankton metacommunities that included a temperature gradient among local communities in each metacommunity.Metacommunities were exposed to one of three dispersal rate treatments.After four weeks, differences in community composition were explained by temperature and this spatial structure was strongest in metacommunities with lower dispersal.A midsummer natural heatwave shifted all communities toward heat-tolerant taxa and when conditions cooled, communities diverged into compositional states that were no longer explained by the temperature and dispersal treatments.Although our experimental design did not allow us to directly assess the influence of biotic interactions, these results are consistent with the hypothesis that biotic interactions resulted in post-heatwave dynamics that prevented the reestablishment of the temperature structured pre-heatwave community composition.These results highlight the need to better account for biotic interactions in the theories that guide our expectations for how ecological communities respond to environmental change.