State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China.
Department of Life Science, National Taiwan Normal University, Taipei 116, Taiwan.
Mol Phylogenet Evol. 2020 Dec;153:106941. doi: 10.1016/j.ympev.2020.106941. Epub 2020 Aug 17.
Increasing evidence of post-divergence gene flow between taxa is shifting our understanding on the mode of speciation. A fundamental question arises concerning the circumstances under which strict allopatric speciation still holds true. Sky island populations might undergo reduced gene flow by niche conservatism to highland habitats and follow divergence in an allopatric manner. In this study, we tested this hypothesis in the sky island Grey-headed Bullfinch (Pyrrhula erythaca) species complex via statistical analyses of both genetic and ecological data. Results of coalescent-based analysis of multiple nuclear loci suggested that P. e. owstoni likely colonized Taiwan island during the severe mid-Pleistocene glacial climate followed by strictly allopatric divergence from P. e. erythaca distributed in Himalayas-Hengduan mountains and central North China. Results of ecological niche modeling suggested that their speciation may be attributed to the niche conservatism of these birds and the lack of a suitable ecological corridor during subsequent milder glacial episodes. In addition, we delimited the traditionally defined P. erythaca into two full species, P. erythaca in the Asian mainland and P. owstoni on the island of Taiwan, based on both genetic and behavioural evidences. These results suggest that ecology can have a dynamic role in allowing highland populations to expand their ranges and isolated by habitat barriers to diversify in a strictly allopatric manner.
越来越多的证据表明，分类单元之间存在扩散后的基因流，这正在改变我们对物种形成模式的理解。一个基本问题是，在何种情况下严格的异域物种形成仍然成立。由于高地生境的生态位保守性，岛屿上的种群可能会经历基因流减少，并以异域的方式发生分歧。在这项研究中，我们通过对遗传和生态数据的统计分析，检验了灰头凤头雀（Pyrrhula erythaca）物种复合体中天岛种群的这一假设。基于多个核基因座的分歧时间推断和基因流分析结果表明，分布于台湾岛的红头凤头雀（P. e. owstoni）可能是在中更新世剧烈冰期气候期间从喜马拉雅山脉-横断山脉和华北中部的分布区扩散而来的，之后与 P. e. erythaca 严格地异域分化。生态位模型的结果表明，它们的物种形成可能归因于这些鸟类的生态位保守性以及随后的冰川间冰期缺乏合适的生态走廊。此外，我们基于遗传和行为证据，将传统定义的红头凤头雀（P. erythaca）分为两个完全的物种，即分布在亚洲大陆的 P. erythaca 和分布在台湾岛上的 P. owstoni。这些结果表明，在随后的冰川间冰期，生态可以在允许高地种群通过生境障碍扩张其分布范围并以严格的异域方式多样化方面发挥动态作用。
