Evolutionary change in metabolic rate of Daphnia pulicaria in response
to the invasive predator Bythotrephes longimanus
Abstract
Metabolic rate is a trait that can be hypothesized to evolve in response
to a change in predation. In the current study, we address this question
by utilising an invasive event by the predatory zooplankton Bythotrephes
longimanus in Lake Mendota, Wisconsin, US. This invasion dramatically
impacted the prey Daphnia pulicaria, causing a ~60%
decline in their biomass. Using a resurrection ecology approach, we
compared the metabolic rate of D. pulicaria clones originating from
prior to the Bythotrephes invasion with that of clones having evolved in
the presence of Bythotrephes. We observed a 7.4% reduction in metabolic
rate among post-invasive clones compared to pre-invasive clones. This
change is in the opposite direction to what might be expected to evolve
in response to increased predation. The evolution of a lower metabolic
rate may instead be due to a habitat shift in the prey species into
deeper and less productive waters and associated changes in the optimal
metabolic rate.