Data from: Evolution of male and female genitalia following release from sexual selection

Despite the key functions of the genitalia in sexual interactions and fertilization, the role of sexual selection and conflict in shaping genital traits remains poorly understood. Seed beetle (Callosobruchus maculatus) males possess spines on the intromittent organ, and females possess a thickened reproductive tract wall that also bears spines. We investigated the role of sexual selection and conflict by imposing monogamous mating on eight replicate populations of this naturally polygamous insect, while maintaining eight other populations under polygamy. To establish whether responses to mating system manipulation were robust to ecological context, we simultaneously manipulated life history selection (early/late reproduction). Over 18-21 generations, male genital spines evolved relatively reduced length in large males (i.e., shallower static allometry) in monogamous populations. Two non-intromittent male genital appendages also evolved in response to the interaction of mating system and ecology. In contrast, no detectable evolution occurred in female genitalia, consistent with the expectation of a delayed response in defensive traits. Our results support a sexually antagonistic role for the male genital spines, and demonstrate the evolution of static allometry in response to variation in sexual selection opportunity. We argue that further advances in the study of genital coevolution will require a much more detailed understanding of the functions of male and female genital traits.尽管生殖器在性互动与受精过程中承担核心功能，但性选择与性冲突在塑造生殖器性状演化中的作用仍未得到充分阐释。绿豆象（Callosobruchus maculatus）的雄性交配器带有棘突，雌性的生殖道壁增厚且同样分布有棘突。本研究将该天然一夫多妻制昆虫的8个重复种群强制实施单配制交配，同时将另外8个种群维持在一夫多妻制条件下，以此探究性选择与性冲突的演化作用。为验证交配系统操控的演化响应是否在不同生态背景下具有稳健性，我们同时对生活史选择（早期/晚期繁殖）进行了操控。经过18至21代的演化，单配制种群中的体型较大雄性个体的生殖器棘突长度相对缩短（即静态异速生长斜率变浅）。此外，两种非插入式雄性生殖器附肢也会响应交配系统与生态环境的交互作用而发生演化。与之形成鲜明对比的是，雌性生殖器未出现可检测到的演化，这与防御性性状演化响应存在延迟的预期相符。本研究结果支持雄性生殖器棘突具有性拮抗作用的假说，并证实了静态异速生长可随性选择机会的变化发生演化。我们认为，若要在生殖器协同演化研究领域取得进一步突破，需对雌雄生殖器性状的功能开展更为细致深入的解析。