Sexual selection is believed to be responsible for the rapid divergence of male genitalia, which is a widely observed phenomenon across different taxa. Among mammals, the stimulatory role of male genitalia and female ‘sensory perception’ has been suggested to explain these evolutionary patterns. Recent research on house mice has shown that baculum (penis bone) shape can respond to experimentally imposed sexual selection. Here, we explore the adaptive value of baculum shape by performing two experiments that examine the effects of male and female genitalia on male reproductive success. Thus, we selected house mice (Mus musculus domesticus) from families characterized by extremes in baculum shape (relative width) and examined paternity success in both non-competitive (monogamous) and competitive (polyandrous) contexts. Our analyses revealed that the relative baculum shape of competing males influenced competitive paternity success, but that this effect was dependent on the breeding value for baculum shape of the family from which females were derived. Our data provide novel insight into the potential mechanisms underlying the evolution of the house mouse baculum and lend support to the stimulatory hypothesis for the coevolution of male and female genitalia.

This article is part of the theme issue ‘Fifty years of sperm competition’.

性选择被认为是男性生殖器快速分化的原因，这是一种在不同分类群中广泛观察到的现象。在哺乳动物中，男性生殖器和女性“感官知觉”的刺激作用被认为可以解释这些进化模式。最近对家鼠的研究表明，阴茎骨（阴茎骨）的形状可以对实验强加的性选择做出反应。在这里，我们通过进行两个实验来探索生殖器形状的适应性价值，这些实验检查男性和女性生殖器对男性生殖成功的影响。因此，我们选择了家鼠（Mus musculusdomesticus）来自以生殖器形状（相对宽度）极端为特征的家庭，并在非竞争性（一夫一妻制）和竞争性（一妻多夫）环境中检查了亲子关系的成功。我们的分析表明，竞争雄性的相对杆状结构影响了竞争性亲子鉴定的成功，但这种影响取决于产生雌性的家族的杆状结构的育种价值。我们的数据为家鼠生殖器进化的潜在机制提供了新的见解，并为男性和女性生殖器共同进化的刺激假设提供了支持。

本文是“精子竞赛五十年”主题刊的一部分。