Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario M5S 3B2, Canada.
Evolution. 2012 Jan;66(1):40-54. doi: 10.1111/j.1558-5646.2011.01411.x. Epub 2011 Aug 24.
Animal genitalia show two striking but incompletely understood evolutionary trends: a great evolutionary divergence in the shape of genitalic structures, and characteristic structural complexity. Both features are thought to result from sexual selection, but explicit comparative tests are hampered by the fact that it is difficult to quantify both morphological complexity and divergence in shape. We undertake a comparative study of multiple nongenitalic and male genital traits in a clade of 15 water strider species to quantify complexity and shape divergence. We show that genital structures are more complex and their shape more divergent among species than nongenital traits. Further, intromittent genital traits are more complex and have evolved more divergently than nonintromittent genital traits. More importantly, shape and complexity of nonintromittent genital traits show correlated evolution with indices of premating sexual selection and intromittent genital traits with postmating sexual selection, suggesting that the evolution of different components of genital morphology are shaped independently by distinct forms of sexual selection. Our quantitative results provide direct comparative support for the hypothesis that sexual selection is associated with morphological complexity in genitalic traits and highlight the importance of quantifying morphological shape and complexity, rather than size in studies of genital evolution.
生殖器结构的巨大进化分歧和特征结构的复杂性。这两个特征被认为是由性选择产生的，但由于难以量化形态复杂性和形状的分歧，明确的比较测试受到阻碍。我们对 15 种水黾物种的一个分支进行了非生殖器和雄性生殖器特征的比较研究，以量化复杂性和形状分歧。我们表明，与非生殖器特征相比，生殖器结构在物种间更复杂，形状更具分歧性。此外，插入性生殖器特征比非插入性生殖器特征更复杂，进化更具分歧性。更重要的是，非插入性生殖器特征的形状和复杂性与婚前性选择的指标呈相关进化，而插入性生殖器特征与交配后性选择呈相关进化，这表明生殖器形态不同组成部分的进化是由不同形式的性选择独立塑造的。我们的定量结果为性选择与生殖器特征的形态复杂性相关的假设提供了直接的比较支持，并强调了在研究生殖器进化时量化形态形状和复杂性而不是大小的重要性。
