University of Western Australia, Western Australia, Australia.
Evolution. 2012 Apr;66(4):1138-53. doi: 10.1111/j.1558-5646.2011.01509.x. Epub 2011 Dec 6.
It is generally accepted that postcopulatory sexual selection drives rapid divergence of genital morphology among isolated populations. The mode of selection operating upon genitalia can be explored by comparing patterns of population divergence in genetic and genitalic traits. We collected Antichiropus variabilis millipedes from eight localities across the species range. Levels of among-population genetic divergence, at microsatellite loci, and the mitochondrial COI gene were very high. Following geometric morphometric analyses, genital morphology was also found to be highly divergent among the populations surveyed, whereas head morphology had not diverged as markedly. However, pairwise comparisons of F(ST) and P(ST) showed that among-population divergence in both genital and head shape was significantly lower than that experienced by neutral genetic markers. Our results suggest that the genitalia of A. variabilis are currently experiencing a period of stabilizing selection, the mode of selection expected for genitalia that function in species recognition via a "lock-and-key" mechanism. Our results demonstrate that although genital morphology can clearly diverge among genetically isolated populations, divergence is not necessarily as rapid as commonly argued, and continuous directional sexual selection may not always underpin the evolutionary divergence of male genitalia.
普遍认为，交配后性选择驱动着生殖器形态在隔离种群中的快速分化。通过比较遗传和生殖器特征的种群分歧模式，可以探究作用于生殖器的选择模式。我们从物种分布范围内的八个地点采集了 Antichiropus variabilis 千足虫。在微卫星基因座和线粒体 COI 基因上，种群间遗传分化水平非常高。经过几何形态测量分析，我们还发现，在所调查的种群中，生殖器形态高度分化，而头部形态则没有明显分化。然而，成对的 F(ST)和 P(ST)比较表明，生殖器和头部形状的种群间分化明显低于中性遗传标记所经历的分化。我们的研究结果表明，A. variabilis 的生殖器目前正经历着稳定选择的时期，这是一种通过“锁和钥匙”机制在物种识别中起作用的生殖器所预期的选择模式。我们的研究结果表明，尽管生殖器形态可以在遗传隔离的种群中明显分化，但分化并不一定像通常所说的那么迅速，并且连续的定向性选择不一定总是支持雄性生殖器的进化分化。
