The evolutionarily stable strategy for secondary sexual characters

We determine the evolutionarily stable strategy (ESS) for secondary sexual characters assuming they are subject to both sexual selection and viability selection. We express the parental investment in terms of the time for mating, parental care, and other variables. The ESS value of the trait varies with the length of mating time and the viability selection. The predictions agree with die published comparative studies and experimental data. The correlations between mating system and sexual dimorphism can be explained either by the differences in mating time or by differences in viability costs. [Behav Ecol 1991; 2: 16-20]