Eberhard William G
Smithsonian Tropical Research Institute, and Escuela de Biología, Universidad de Costa Rica Ciudad Universitaria, Costa Rica.
Biol Rev Camb Philos Soc. 2004 Feb;79(1):121-86. doi: 10.1017/s1464793103006237.
Some recent models suggest a new role for evolutionary arms races between males and females in sexual selection. Female resistance to males is proposed to be driven by the direct advantage to the female of avoiding male-imposed reductions in the number of offspring she can produce, rather than by the indirect advantage of selecting among possible sires for her offspring, as in some traditional models of sexual selection by female choice. This article uses the massive but hitherto under-utilized taxonomic literature on genitalic evolution to test, in a two-step process, whether such new models of arms races between males and females have been responsible for rapid divergent evolution of male genitalia. The test revolves around the prediction that 'new arms races' are less likely to occur in species in which females are largely or completely protected from unwanted sexual attentions from males (e.g. species which mate in leks or in male swarms, in which males attract females from a distance, or in which females initiate contact by attracting males from a distance). The multiple possible mechanical functions of male genitalia are summarized, and functions of male genitalic structures in 43 species in 21 families of Diptera are compiled. Functions associated with intromission and insemination (e.g. seizing and positioning the female appropriately, pushing past possible barriers within the female, orienting within the female to achieve sperm transfer), which are unlikely to be involved in new arms races when females are protected, are shown to be common (> 50 % of documented cases). This information is then used to generate the new arms race prediction: differences in genitalic form among congeneric species in which females are protected should be less common than differences among congeneric species in which females are vulnerable to harassment by males. This prediction was tested using a sample of 361 genera of insects and spiders. The prediction clearly failed, even when the data were adjusted to take into account several possible biases. Comparative analyses within particular taxonomic groups also failed to show the predicted trends, as did less extensive data on other non-genitalic male display traits. Arms races, as defined in some recent models, seem to have been less important in male-female coevolution of genitalic structures than has been suggested. By elimination, alternative interpretations, such as traditional female choice, which do not predict associations between female protection from harassment and rapid divergent evolution, are strengthened.
一些近期模型表明，在性选择中，雄性与雌性之间的进化军备竞赛有了新的作用。与某些传统的雌性选择的性选择模型不同，雌性对雄性的抵抗被认为是由雌性避免雄性导致其后代数量减少的直接优势驱动的，而非为后代挑选潜在父亲的间接优势。本文利用大量但迄今未充分利用的关于生殖器进化的分类学文献，分两步来检验这种新的雄性与雌性之间的军备竞赛模型是否导致了雄性生殖器的快速分化进化。该检验围绕这样一个预测展开：在雌性基本或完全免受雄性不必要性关注的物种中（例如在求偶场或雄性群中交配的物种，其中雄性从远处吸引雌性，或者雌性通过从远处吸引雄性来发起接触），“新的军备竞赛”不太可能发生。总结了雄性生殖器多种可能的机械功能，并汇编了双翅目21个科43个物种中雄性生殖器结构的功能。与插入和授精相关的功能（例如恰当地抓住并定位雌性、推开雌性体内可能的障碍、在雌性体内定向以实现精子转移），在雌性受到保护时不太可能参与新的军备竞赛，而这些功能却很常见（超过50%的记录案例）。然后利用这些信息得出新的军备竞赛预测：在雌性受到保护的同属物种中，生殖器形态的差异应比雌性易受雄性骚扰的同属物种中的差异少见。使用361个昆虫和蜘蛛属的样本对这一预测进行了检验。即使对数据进行调整以考虑几种可能的偏差，该预测也明显不成立。特定分类群内的比较分析也未显示出预测的趋势，其他非生殖器雄性展示特征的较少数据也是如此。近期一些模型所定义的军备竞赛，在雄性与雌性生殖器结构的共同进化中似乎没有所认为的那么重要。通过排除法，诸如传统雌性选择等不预测雌性免受骚扰与快速分化进化之间关联的其他解释得到了强化。
