EVOLUTION OF ADAPTIVE VARIATION IN ANTIPREDATOR BEHAVIOR

In many species of fish, behaviour varies adaptively amongst populations in response to predation risk. One of the best examples is provided by the guppy, Poecilia reticulata, in Trinidad. Although separated by distances of a few km, or less, guppy populations vary in terms of predator assessment and avoidance, schooling, foraging behaviour, resource defence, female choice and mating tactics. We show that there are behavioural costs (such as lower levels of individual aggression and reduced female choice) associated with selection for a heightened antipredator response. In the majority of cases population variation in guppy behaviour can be clearly linked to the predation regime. Nevertheless, we have begun to uncover situations where there is behavioural divergence amongst populations apparently experiencing equivalent risk. We consider explanations for these differences including the possibility that they may be related to high levels of genetic divergence.