The interplay between genetic and learned components of behavioral traits

This article considers the evolution of behavioral traits that have both a genetic basis and can be modified. The modifications considered concern an adaptive (learnt) response to environmental influences. In theory, the evolution of such traits may lead to two extreme outcomes; one where the trait becomes genetically fixed (and phenotypically invariable) and the other where it is entirely shaped by environmental influences. Between these extremes lies a spectrum of traits containing a genetic component, but also, to differing degrees, a modifiable component. We review theory considering how learning may affect the genetic evolution of a behavioral trait (commonly referred to as the Baldwin effect). We claim behavioral interactions in tritrophic systems, such as the responses of natural enemies to herbivore-induced plant volatiles, provide an excellent model system to study the Baldwin effect and we illustrate this with recent findings on the searching behavior of the predatory mite Phytoseiulus persimilis.