Résumé
Predator-prey interactions are key for the dynamics of many ecosystems. An
increasing body of evidence suggests that rapid evolution and co-evolution
can alter these interactions, with important ecological implications, by
acting on traits determining fitness, including reproduction,
anti-predatory defense and foraging efficiency. However, most studies to
date have focused only on evolution in the prey species, and the predator
traits in (co-)evolving systems remain poorly understood. Here we
investigated changes in predator traits after ~600 generations in a
predator-prey (ciliate-bacteria) evolutionary experiment. Predators
independently evolved on seven different prey species, allowing
generalization of the predator’s evolutionary response. We used highly
resolved automated image analysis to quantify changes in predator life
history, morphology and behavior. Consistent with previous studies, we
found that prey evolution impaired growth of the predator, although the
effect depended on the prey species. In contrast, predator evolution did
not cause a clear increase in predator growth when feeding on ancestral
prey. However, predator evolution affected morphology and behavior,
increasing size, speed and directionality of movement, which have all been
linked to higher prey search efficiency. These results show that in
(co-)evolving systems, predator adaptation can occur in traits relevant to
foraging efficiency without translating into an increased ability of the
predator to grow on the ancestral prey type.