Genetics and evolution of female choice

Abstract

Fisher's theory of the evolution of sexual selection by female choice depends crucially on the premise that the preference of females to mate with males of a specific genotype is itself genetic¹. In the polymorphic ladybird Adalia bipunctata, a genetically determined, non-assortative female preference for melanic males has been demonstrated². Models of the evolution of female choice show that the rate of evolution and the final outcome of this selection depend critically on the exact mode of inheritance of both the preferred character and the preference³. Here we describe experiments in which the level of preference has been raised by artificial selection over 14 generations. Resultant estimates of heritability are consistent with models in which one or a small number of genes control the preference. Analysis of the levels of preference in isofemale lines derived from the high preference stock shows a quadrimodal distribution in preference. These results are entirely consistent with the deduction that a single dominant gene controls female choice. We conclude that this complex behavioural strategy is based on simple genetics. Furthermore, the demonstration of a simple genetic basis to female mating preferences in A. bipunctata implies that sexual selection by female choice is not only important in the evolution of male sexual adornments in sexually dimorphic species, but may also maintain polymorphisms that are not sex-limited.