Data from: Predation-associated divergence of male genital morphology in a livebearing fish

Male genital morphology is remarkably diverse across internally fertilizing animals, a phenomenon largely attributed to sexual selection. Ecological differences across environments can alter the context of sexual selection, yet little research has addressed how this may influence the rapid, divergent evolution of male genitalia. Using the model system of Bahamas mosquitofish (Gambusia hubbsi) undergoing ecological speciation across blue holes, we used geometric morphometric methods to test (i) whether male genital shape (the small, approximately 1 mm long, distal tip of the sperm-transfer organ, the gonopodium) has diverged between populations with and without predatory fish and (ii) whether any observed divergence has a genetic basis. We additionally examined the effects of genetic relatedness and employed model selection to investigate other environmental factors (i.e. interspecific competition, adult sex ratio and resource availability) that could potentially influence genital shape via changes in sexual selection. Predation regime comprised the most important factor associated with male genital divergence in this system, although sex ratio and some aspects of resource availability had suggestive effects. We found consistent, heritable differences in male genital morphology between predation regimes: Bahamas mosquitofish coexisting with predatory fish possessed more elongate genital tips with reduced soft tissue compared with counterparts inhabiting blue holes without predatory fish. We suggest this may reflect selection for greater efficiency of sperm transfer and fertilization during rapid and often forced copulations in high-predation populations or differences in sexual conflict between predation regimes. Our study highlights the potential importance of ecological variation, particularly predation risk, in indirectly generating genital diversity.体内受精动物的雄性生殖器形态呈现出显著的多样性，这一现象在很大程度上可归因于性选择（sexual selection）。不同环境间的生态差异能够改变性选择的作用情境，但目前鲜有研究探讨这类差异如何影响雄性生殖器的快速趋异演化。本研究以栖息于蓝洞（blue holes）中并经历生态物种形成的哈氏食蚊鱼（Gambusia hubbsi）作为模式系统，采用几何形态测量法（geometric morphometric methods）开展两项检验：其一，对比存在捕食性鱼类与不存在捕食性鱼类的种群间雄性生殖器形态——即长约1毫米的精子传递器官（交合突（gonopodium）的远端尖端）——是否已发生趋异；其二，观测到的形态趋异是否具有遗传基础。此外，本研究还分析了遗传亲缘关系的影响，并通过模型选择法探究了其他可能通过改变性选择进而影响生殖器形态的环境因素，具体包括种间竞争、成虫性比与资源可获得性。尽管性比与部分资源可获得性指标表现出潜在影响，但捕食环境是本系统中与雄性生殖器趋异关联最紧密的关键因素。研究发现不同捕食环境下的雄性生殖器形态存在稳定且可遗传的差异：与栖息在无捕食性鱼类蓝洞中的种群相比，与捕食性鱼类共存的哈氏食蚊鱼拥有更为修长的生殖器尖端，且软组织占比更低。我们推测，这一现象可能反映了高捕食压力种群中，针对快速且常为强迫式交配场景下精子传递与受精效率提升的选择，或是不同捕食环境间性冲突（sexual conflict）差异的体现。本研究凸显了生态变异——尤其是捕食风险——在间接驱动生殖器多样性产生方面的潜在重要性。