Inter population variation in behaviour of native prey (Daphnia) mediates the impact of the invasive spiny water flea (Bythotrephes cederstromii) on plankton communities

Abstract

Population-level differences in predator trait expression influence predator impacts on prey species, altering ecological interactions and trophic dynamics. However, the effect of inter-population differences in prey traits on the impacts of predation on ecological communities remains poorly understood, especially for introduced predators where differences in prey traits could influence the outcome of biological invasions. We examined if differences in Daphnia vertical position influenced the impacts of the invasive predator Bythotrephes cederstromii on major zooplankton and algal groups. Our results show differences in Daphnia vertical position influenced Bythotrephes impacts on small cladocerans. Larger reductions in density were observed in mesocosms with greater proportion of hypolimnetic Daphnia. Larger increases in algal biomass were also observed in invaded mesocosms with greater proportion of hypolimnetic Daphnia. These results suggest that differences in Daphnia vertical position influence the magnitude and type of Bythotrephes impacts on zooplankton communities.