In many species, males exhibit phenotypic plasticity in sexually selected traits when exposed to social cues about the intensity of sexual competition. To date, however, few studies have tested how this plasticity affects male reproductive success. We initially tested whether male mosquitofish, Gambusia holbrooki (Poeciliidae), change their investment in traits under pre- and postcopulatory sexual selection depending on the social environment. For a full spermatogenesis cycle, focal males were exposed to visual and chemical cues of rivals that were either present (competitive treatment) or absent (control). Males from the competitive treatment had significantly slower-swimming sperm but did not differ in sperm count from control males. When two males competed for a female, competitive treatment males also made significantly fewer copulation attempts and courtship displays than control males. Further, paternity analysis of 708 offspring from 148 potential sires, testing whether these changes in reproductive traits affected male reproductive success, showed that males previously exposed to cues about the presence of rivals sired significantly fewer offspring when competing with a control male. We discuss several possible explanations for these unusual findings.

中文翻译：

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响应竞争对手的生殖投资变化降低了男性生殖成功率。

在许多物种中，雄性暴露于有关性竞争强度的社会线索时，在性选择的性状上表现出表型可塑性。然而，迄今为止，很少有研究测试这种可塑性如何影响男性生殖成功。我们最初测试了雄性蚊子是否属于Gambusia holbrooki（Poeciliidae），根据交往环境选择在交配前和交配后进行性状改变的投资。在完整的精子发生周期中，雄性雄性会暴露于存在（竞争性治疗）或不存在（对照）竞争对手的视觉和化学线索。竞争性治疗的男性精子游游速度明显慢，但与对照组男性相比，精子数量没有差异。当两个雄性竞争一个雌性时，与对照雄性相比，竞争性治疗雄性的交配尝试和求爱表现也显着减少。此外，对来自148个潜在父亲的708个后代进行了父子关系分析，测试了这些生殖特征的变化是否影响了男性的生殖成功，研究表明，与对照雄性竞争时，以前受到竞争对手存在线索的雄性所生的后代数量明显减少。我们讨论了这些不寻常发现的几种可能解释。