Data from: A tradeoff between precopulatory and postcopulatory trait investment in male cetaceans

Mating with multiple partners is common across species, and understanding how individual males secure fertilization in the face of competition remains a fundamental goal of evolutionary biology. Game theory stipulates that males have a fixed budget for reproduction that can lead to a trade-off between investment in precopulatory traits like body size, armaments, and ornaments, and postcopulatory traits such as testis size and spermatogenic efficiency. Recent theoretical and empirical studies have shown that if males can monopolize access to multiple females, they will invest disproportionately in precopulatory traits and less in postcopulatory traits. Using phylogenetically controlled comparative methods, we demonstrate that across 58 cetaceans, species with the most prominent sexual dimorphism in size, shape, teeth, tusks, and singing invest significantly less in relative testes mass. In support of theoretical predictions, these species tend to show evidence of male contests, suggesting there is opportunity for winners to monopolize access to multiple females. Our approach provides a robust data set with which to make predictions about male mating strategies for the many cetacean species for which adequate behavioral observations do not exist.

跨各类物种而言，与多位配偶交配的现象极为普遍；解析雄性个体在竞争环境中如何成功获得受精机会，始终是进化生物学的核心研究命题。博弈理论指出，雄性的繁殖资源预算固定，这会使其在交配前性状（precopulatory traits，如体型、争斗武器与装饰结构）与交配后性状（postcopulatory traits，如睾丸大小与生精效率）之间形成资源权衡。近期的理论与实证研究表明，若雄性能够垄断与多位雌性的交配权，其将向交配前性状投入不成比例的资源，而对交配后性状的投入则相对减少。本研究采用系统发育控制比较方法（phylogenetically controlled comparative methods），对58种鲸类（cetaceans）开展分析后发现：那些在体型、形态、牙齿、獠牙与鸣唱方面存在显著性二态性（sexual dimorphism）的物种，其相对睾丸质量（relative testes mass）的投入显著更低。这一结果与理论预测相符，这类物种往往存在雄性争斗行为，提示获胜者有机会垄断与多位雌性的交配权。本研究构建了一套可靠的数据集，可用于预测那些尚未获得充足行为观测数据的多数鲸类物种的雄性交配策略。