Predation and the evolution of prey behavior: an experiment with tree hole mosquitoes

We tested for facultative changes in behavior of an aquatic insect in response to cues from predation and for evolution of prey behavior in response to experimental predation regimes. Larvae of the tree hole mosquito Aedes triseriatus reduced filtering, browsing, and time below the surface in response to water that had held a feeding larva of the predator Toxorhynchites rutilus. We subjected experimental A. triseriatus populations to culling of 50% of the larval population, either by T. rutilus predation or by random removal. After two generations of laboratory culling, behavior of the two treatment groups diverged. Aedes triseriatus in control-culled lines retained their facultative shift from filtering to resting, but tended to lose the response of reduced browsing below the surface in water that had held a feeding predator. Predator-culled lines lost their facultative response of reduced filtering in water that had held a feeding predator and evolved toward more time resting and less time filtering in both water that had held a feeding predator and water that had held only A. triseriatus. Predator-culled lines retained their facultative response of reduced browsing below the surface in water that had held a feeding predator. Two field populations and their reciprocal hybrids responded similarly to cues from predation and did not differ in their evolutionary response to experimental culling. We conclude that consistent presence or absence of predation can select rapidly for divergence in prey behavior, including facultative behavioral responses to predators.