UC Santa Cruz

Many prey species display behavioral responses to environmental cues from predators. Organisms can inherit fixed behavioral responses to certain predators as a result of evolutionary history with a predator. Developmental plasticity allows individuals to associate predation risk with environmental cues experienced in their lifetimes and respond behaviorally. However, the interactive effects of evolution and plasticity on shaping immediate antipredator behavior is not well known. Here we show that evolution and developmental plasticity affect antipredator behavior of western mosquitofish (Gambusia affinis) through altered food intake in response to predation risk imposed by largemouth bass (Micropterus salmoides). Results show that the effects of evolutionary history and developmental plasticity are substitutive – mosquitofish show a similar level of feeding if they originated from ponds with largemouth bass (evolutionary history) or if they originated from ponds lacking largemouth bass but have been exposed to bass cues during development (developmental plasticity). Mosquitofish lacking both evolutionary history and developmental cues from the predator did not show a behavioral response. For populations lacking an evolutionary history with bass, developmental exposure to the predator was required to induce a behavioral response. In contrast, populations with an evolutionary history with bass displayed antipredator behavior regardless of whether they had been exposed to bass cues during development. Our results suggest a progression of anti-predator feeding responses of prey from no behavioral response, to an inducible response, to a fixed response. This sequence may shift the cascading ecosystem effects of predators introduction from density-mediated to behaviorally-mediated via plasticity to behaviorally mediated via evolution over time.