Data from: 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.

复杂的性二态性状（sexually dimorphic traits）普遍被认为是经由雌性偏好、雄性间竞争或二者共同作用的性选择（sexual selection）演化而来。橙喉镖鲈（Etheostoma spectabile）是一种两性异色鱼类（sexually dichromatic fish），其雌性个体对雄性的体型或体色并无偏好。本研究设置多只雄性自由竞争与雌性交配的实验情境，以此检验该物种的相关性状是否会影响个体繁殖成功率（reproductive success）。研究结果显示，雄性体色的品质与丰富度均与维持雌性接触权、作为首要雄性（首个参与交配的个体）完成产卵的更高成功率显著相关。与之相对，偷袭交配行为（sneaking behavior）与体色特征几乎不存在相关性。综上，橙喉镖鲈的雄性繁殖体色或可印证，种内竞争（intrasexual competition）是推动雄性装饰性状（male ornaments）演化的主导因素。