Predator-induced dispersal and the evolution of conditional dispersal in correlated environments.

It is widely accepted that organisms adjust their dispersal propensity to local population density, but there has been no analysis of how they should react to changes in environmental conditions that reduce local density. We take the case of delayed predator-induced dispersal (PID) in aphids to explore in which way current environmental conditions may be utilized as an appropriate signal for dispersal decisions. In aphids, the presence of predators triggers the production of winged offspring that may later leave the plant and shift their center of activity permanently. Using individual-based simulations as well as analytical approximations, we explore under which conditions PID is likely to evolve. We demonstrate that this requires substantial temporal correlation in predation risk and weak competition among prey; these conditions may be fulfilled in the aphid system. We discuss the analogy between the specific case of PID and the evolution of conditional emigration in the face of spatiotemporally correlated deterioration in reproduction or survival.