Adaptive feeding across environmental gradients and its effect on population dynamics

This paper analyzes a consumer's adaptive feeding response to environmental gradients. We consider a consumer-resource system where resources are dist ributed among many discrete resource patches, Each consumer exhibits a feed ing morphology allowing it to remove resources from a patch down to some th reshold density (or level) before having to seek resources elsewhere. Assum ing consumers trade off resource extraction with patch access and predation , we show that for a given environment there often exists a single evolutio narily stable feeding threshold and it is an evolutionary attractor. We the n investigate how the population dynamics of the resource and the consumer change as the environment changes. Two cases are considered: (i) all consum ers exhibit a fixed feeding threshold that is adaptive for an intermediate environment; and (ii) the consumer population adapts and adopts the evoluti onarily stable feeding threshold associated with the current environment. I n less harsh environments (i.e., environments where consumers experience a lower risk of predation, or environments where resource patches are more ab undant) the adaptive consumer population is predicted to evolve so that res ources within a patch are depleted to lower densities. We show that the cha nge in consumer density due to environmental change can be rather different depending on whether or not the population can adapt. In some situations w e observe that when the consumer's environment becomes harsher, the consume r population may increase in density before a rapid crash to extinction. Th is result has implications for monitoring and managing a population, (C) 20 00 Academic Press.