Survival benefits and divergence of predator-induced behavior between pumpkinseed sunfish ecomorphs

Resource use is widely thought to influence adaptive phenotypicdivergence, whereas other ecological factors, such as predation,are frequently overlooked, particularly in studies of polyphenismin fishes. Juvenile pumpkinseed sunfish (Lepomis gibbosus) rearedwith predatory walleye (Sander vitreus) increase body depthand dorsal spine length, indicating that developmental responsesto predation can shape phenotype. Body form responses to thesame predator cues though have also evolutionarily divergedbetween sunfish ecomorphs that coexist in single lake populationsby inhabiting either littoral or pelagic habitats, suggestingthat predation risk varies between habitats. Here, we test ifprior exposure to predator cues influences the development ofbehavior in juvenile pumpkinseed sunfish, if behavioral responsesto the same predator cues vary between ecomorphs, and if inducedphenotypic variation affects survival under predation. Behaviordepended strongly on prior exposure to predator cues, but thiseffect varied between sunfish ecomorphs, indicating that ecomorphshave different responses to the same predator cues. Predator-inducedphenotypes had higher survival than control phenotypes undersimulated littoral but not pelagic conditions. Predator-inducedphenotypic responses are candidate-inducible defenses, and divergentresponses between ecomorphs suggest that they can evolve inresponse to selection imposed by differences in habitat-specificpredation risk.