UNIFYING GENETIC MODELS FOR THE EVOLUTION OF FEMALE CHOICE.

A best-of-N rule of female mating preferences can give rise to lines of unstable equilibria in a two-locus haploid model of sexual selection. Under the best-of-N rule, which corresponds to choice at a lek, male fitnesses can exhibit a form of positive frequency-dependence that is not seen under fixed-relative-preference rules (Kirkpatrick, 1982). This positive frequency-dependence can be strongly destabilizing. Lande's (1981) criterion for the stability of the equilibria in quantitative-genetic models of sexual selection applies exactly and in general to the related family of simple population-genetic models. This offers some insight into the workings of these models and greatly simplifies their analysis.