Semenov Georgy A, Scordato Elizabeth S C, Khaydarov David R, Smith Chris C R, Kane Nolan C, Safran Rebecca J
Department of Ecology & Evolutionary Biology, The University of Arizona, Tucson, AZ, USA.
Institute of Systematics and Ecology of Animals, Novosibirsk, Russia.
Mol Ecol. 2017 Nov;26(22):6430-6444. doi: 10.1111/mec.14376. Epub 2017 Nov 1.
Phenotypic differentiation plays an important role in the formation and maintenance of reproductive barriers. In some cases, variation in a few key aspects of phenotype can promote and maintain divergence; hence, the identification of these traits and their associations with patterns of genomic divergence is crucial for understanding the patterns and processes of population differentiation. We studied hybridization between the alba and personata subspecies of the white wagtail (Motacilla alba), and quantified divergence and introgression of multiple morphological traits and 19,437 SNP loci on a 3,000 km transect. Our goal was to identify traits that may contribute to reproductive barriers and to assess how variation in these traits corresponds to patterns of genome-wide divergence. Variation in only one trait-head plumage patterning-was consistent with reproductive isolation. Transitions in head plumage were steep and occurred over otherwise morphologically and genetically homogeneous populations, whereas cline centres for other traits and genomic ancestry were displaced over 100 km from the head cline. Field observational data show that social pairs mated assortatively by head plumage, suggesting that these phenotypes are maintained by divergent mating preferences. In contrast, variation in all other traits and genetic markers could be explained by neutral diffusion, although weak ecological selection cannot be ruled out. Our results emphasize that assortative mating may maintain phenotypic differences independent of other processes shaping genome-wide variation, consistent with other recent findings that raise questions about the relative importance of mate choice, ecological selection and selectively neutral processes for divergent evolution.
表型分化在生殖隔离的形成和维持中起着重要作用。在某些情况下，表型几个关键方面的变异可以促进和维持分化；因此，识别这些性状及其与基因组分化模式的关联对于理解种群分化的模式和过程至关重要。我们研究了白鹡鸰（Motacilla alba）白亚种和黑背亚种之间的杂交，并在一条3000公里的样带上对多个形态性状和19437个单核苷酸多态性（SNP）位点的分化和基因渗入进行了量化。我们的目标是识别可能导致生殖隔离的性状，并评估这些性状的变异如何与全基因组分化模式相对应。只有一个性状——头部羽毛图案——的变异与生殖隔离一致。头部羽毛的转变很陡峭，发生在其他方面形态和基因均一的种群中，而其他性状和基因组祖先的渐变中心距离头部渐变中心超过100公里。野外观察数据表明，社会配对按头部羽毛进行选型交配，这表明这些表型是由不同的交配偏好维持的。相比之下，所有其他性状和遗传标记的变异都可以用中性扩散来解释，尽管不能排除微弱的生态选择。我们的结果强调，选型交配可能独立于塑造全基因组变异的其他过程来维持表型差异，这与最近的其他发现一致，这些发现对配偶选择、生态选择和选择性中性过程在分歧进化中的相对重要性提出了质疑。
