Department of Biological Sciences, San Diego State University, San Diego, CA, United States.
Department of Evolution, Ecology, and Organismal Biology, Speith Hall, University of California, Riverside, CA, United States.
J Hered. 2023 Nov 15;114(6):625-636. doi: 10.1093/jhered/esad044.
Gene flow can affect evolutionary inference when species are undersampled. Here, we evaluate the effects of gene flow and geographic sampling on demographic inference of 2 hummingbirds that hybridize, Allen's hummingbird (Selasphorus sasin) and rufous hummingbird (Selasphorus rufus). Using whole-genome data and extensive geographic sampling, we find widespread connectivity, with introgression far beyond the Allen's × rufous hybrid zone, although the Z chromosome resists introgression beyond the hybrid zone. We test alternative hypotheses of speciation history of Allen's, rufous, and Calliope (S. calliope) hummingbird and find that rufous hummingbird is the sister taxon to Allen's hummingbird, and Calliope hummingbird is the outgroup. A model treating the 2 subspecies of Allen's hummingbird as a single panmictic population fit observed genetic data better than models treating the subspecies as distinct populations, in contrast to morphological and behavioral differences and analyses of spatial population structure. With additional sampling, our study builds upon recent studies that came to conflicting conclusions regarding the evolutionary histories of these 2 species. Our results stress the importance of thorough geographic sampling when assessing demographic history in the presence of gene flow.
基因流会影响物种抽样不足时的进化推断。在这里，我们评估了基因流和地理采样对杂交蜂鸟 Allen's hummingbird（Selasphorus sasin）和 rufous hummingbird（Selasphorus rufus）的种群推断的影响。利用全基因组数据和广泛的地理采样，我们发现存在广泛的连通性，尽管 Z 染色体在杂交区以外的基因渗入受阻，但基因渗入远超出 Allen's × rufous 杂交区。我们检验了 Allen's、rufous 和 Calliope（S. calliope）蜂鸟的物种形成历史的替代假说，并发现 rufous hummingbird 是 Allen's hummingbird 的姊妹分类群，而 Calliope hummingbird 是外群。与形态学和行为差异以及空间种群结构分析相反，一个将 Allen's hummingbird 的 2 个亚种视为单一混合种群的模型比将亚种视为不同种群的模型更能拟合观察到的遗传数据。随着更多的采样，我们的研究建立在最近的研究之上，这些研究对这 2 个物种的进化历史得出了相互矛盾的结论。我们的结果强调了在存在基因流的情况下评估种群历史时，全面地理采样的重要性。
