Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia, Crawley 6009, Australia.
Collections and Research, Western Australian Museum, Welshpool 6106, Australia.
Proc Biol Sci. 2024 Jan 31;291(2015):20232883. doi: 10.1098/rspb.2023.2883.
Animal genitalia are thought to evolve rapidly and divergently in response to sexual selection. Studies of genital evolution have focused largely on male genitalia. The paucity of work on female genital morphology is probably due to problems faced in quantifying shape variation, due to their composition and accessibility. Here we use a combination of micro-computed tomography, landmark free shape quantification and phylogenetic analysis to quantify the rate of female genital shape evolution among 29 species of millipedes, and their coevolution with male genitalia. We found significant variation in female and male genital shape among species. Male genital shape showed a stronger phylogenetic signal than female genital shape, although the phylogenetic signal effect sizes did not differ significantly. Male genital shape was found to be evolving 1.2 times faster than female genital shape. Female and male genital shape exhibited strong correlated evolution, indicating that genital shape changes in one sex are associated with corresponding changes in the genital shape of the other sex. This study adds novel insight into our growing understanding of how female genitalia can evolve rapidly and divergently, and highlights the advantages of three-dimensional techniques and multivariate analyses in studies of female genital evolution.
动物生殖器被认为会因性选择而迅速且不同地进化。生殖器进化的研究主要集中在雄性生殖器上。由于女性生殖器的组成和可及性问题，对女性生殖器形态的研究很少，这可能是由于在量化形状变化方面面临的问题。在这里，我们使用微计算机断层扫描、无标记形状量化和系统发育分析相结合的方法，量化了 29 种千足虫的雌性生殖器形状的进化速度及其与雄性生殖器的协同进化。我们发现，在物种之间，雌性和雄性生殖器的形状存在显著差异。与雌性生殖器形状相比，雄性生殖器形状表现出更强的系统发育信号，尽管系统发育信号效应大小没有显著差异。雄性生殖器形状的进化速度比雌性生殖器形状快 1.2 倍。雌性和雄性生殖器形状表现出强烈的相关进化，表明一个性别的生殖器形状变化与另一个性别的生殖器形状相应变化有关。这项研究为我们不断加深理解女性生殖器如何能够迅速且不同地进化提供了新的见解，并强调了三维技术和多变量分析在女性生殖器进化研究中的优势。
