Theories of the Evolution of Dioecy

Abstract

In this chapter, I shall review theoretical models of the evolution of dioecy from hermaphroditism. I hope to show why theoretical ideas have been important, and why we cannot work in a purely ecological context, considering only fertility advantages of phenotypes, but must include genetic aspects of the breeding systems if we are not to be misled in our conclusions. I shall argue that both ecological and genetic factors are of central importance, and that we should not view the reasons for the evolution of unisexuality as having to be either constraints of resource availability or else inbreeding avoidance, but rather should see that both kinds of factors must play a part. To understand this evolutionary process, we should therefore not attempt to rule out one or the other type of factor, but should instead try to get empirical evidence that will help us to assess their relative importance. At the end of the chapter, I will briefly review some of this evidence.