Evolutionary change in metabolic rate of Daphnia pulicaria following
invasion by the predator Bythotrephes longimanus
Abstract
Metabolic rate is a trait that may evolve in response to the direct and
indirect effects of predator-induced mortality. Predators may indirectly
alter selection by lowering prey densities and increasing resource
availability or by intensifying resource limitation through changes in
prey behaviour (e.g. use of less productive areas). In the current study
we quantify evolution of metabolic rate in the zooplankton Daphnia
pulicaria following an invasive event by the predator Bythotrephes
longimanus in Lake Mendota, Wisconsin, US. This invasion has been shown
to dramatically impact D. 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, and
discuss the potential roles of direct and indirect selection in driving
this change.