Intrasexual competition underlies sexual selection on male breeding coloration in the orangethroat darter, Etheostoma spectabile .

Elaborate, sexually dimorphic traits are widely thought to evolve under sexual selection through female preference, male-male competition, or both. The orangethroat darter ( Etheostoma spectabile ) is a sexually dichromatic fish in which females exhibit no preferences for male size or coloration. We tested whether these traits affect individual reproductive success in E. spectabile when multiple males are allowed to freely compete for a female. The quality and quantity of male coloration were associated with greater success in maintaining access to the female and in spawning as the primary male (first male to participate). On the other hand, sneaking behavior showed little correlation with coloration. Male breeding coloration in E. spectabile may therefore demonstrate how intrasexual competition can be a predominant factor underlying the evolution of male ornaments.