Data from: Sex roles and mutual mate choice matters during mate sampling

The roles of females and males in mating competition and mate choice have lately proven more variable, between and within species, than previously thought. In nature, mating competition occurs during mate search, and is expected to be regulated by the numbers of potential mates and same-sex competitors. Here, we present the first study to test how a temporal change in sex roles affects mating competition and mate choice during mate sampling. Our model system (the marine fish Gobiusculus flavescens) is uniquely suitable because of its change in sex roles, from conventional to reversed, over the breeding season. As predicted from sex role theory, courtship was typically initiated by males and terminated by females early in the breeding season. The opposite pattern was observed late in the season, at which time several females often simultaneously courted the same male. Mate-searching females visited more males early than late in the breeding season. Our study shows that mutual mate choice and mating competition can have profound effects on female and male behavior. Future work needs to consider the dynamical nature of mating competition and mate choice if we aim to fully understand sexual selection in the wild.

近年来的研究证实，雌性与雄性在交配竞争及配偶选择中所扮演的角色，在物种类群间与物种种内均比以往认知更为多变。在自然情境中，交配竞争发生于配偶搜寻过程，其强度受潜在配偶数量与同性竞争者数量的调控。本研究首次开展实验，探讨性角色的时间动态变化如何作用于配偶取样阶段的交配竞争与配偶选择。本研究选用的模式物种为海洋鱼类双带缟虾虎鱼（Gobiusculus flavescens），该物种在繁殖季内会经历从传统性角色到反转性角色的转变，因此是本研究的绝佳实验体系。正如性角色理论的预测，繁殖季早期的求偶行为通常由雄性发起、雌性终结；繁殖季晚期则呈现完全相反的模式，此时常有多只雌性同时向同一只雄性展开求偶。繁殖季早期，参与配偶搜寻的雌性访问的雄性个体数量显著多于繁殖季晚期。本研究证实，双向配偶选择与交配竞争可对雌性及雄性的行为产生深远影响。若要全面理解野外情境中的性选择机制，后续研究需充分考量交配竞争与配偶选择的动态属性。