Individual behaviour and population dynamics: lessons from aphid parasitoids

An increasing number of researchers are studying behaviour in the hopes of understanding population dynamics or improving biological control efforts o f insect pests by natural enemies. However, it is unclear exactly how behav ioural studies will improve our understanding of these population level pro cesses. In this paper we argue that in order to understand population level processes, the problem must be approached from a population biology perspe ctive. A comprehensive understanding of certain behaviours will provide lit tle towards our understanding of host-natural enemy interactions. For examp le, using an aphid-parasitoid model, we examined the effect that a commonly studied behaviour, variance in host selection by aphid parasitoids, has on aphid-parasitoid population dynamics. Differential host selection does not qualitatively alter classic Nicholson-Bailey dynamics, but only results in quantitative differences in aphid-parasitoid population sizes. Irrespectiv e of the degree of aphid instar preference, a large increase in the number of aphids is followed by a large increase in the number of parasitoids, dec imating the aphid population. Thus, studying some behaviours, such as varia nce in host selection, will not contribute substantially to an understandin g of aphid-parasitoid population dynamics.