Department of Biology, University of Miami, Coral Gables, Florida, 33146.
Evolution. 2019 Aug;73(8):1647-1662. doi: 10.1111/evo.13797. Epub 2019 Jul 22.
Examining what happens when two closely related species come into secondary contact provides insight into the later stages of the speciation process. The Zosteropidae family of birds is one of the most rapidly speciating vertebrate lineages. Members of this family are highly vagile and geographically widespread, raising the question of how divergence can occur if populations can easily come into secondary contact. On the small island of Kolombangara, two closely related nonsister species of white-eyes, Zosterops kulambangrae and Zosterops murphyi, are distributed along an elevational gradient and come into secondary contact at mid-elevations. We captured 134 individuals of both species along two elevational transects. Using genotyping-by-sequencing data and a mitochondrial marker, we found no evidence of past hybridization events and strong persistence of species boundaries, even though the species have only been diverging for approximately 2 million years. We explore potential reproductive barriers that allow the two species to coexist in sympatry, including premating isolation based on divergence in plumage and song. We also conducted a literature review to determine the time it takes to evolve complete reproductive isolation in congeneric avian species/subspecies in secondary contact (restricted to cases where congeneric taxa are parapatric or have a hybrid zone), finding our study is one of the youngest examples of complete reproductive isolation studied in a genomic context reported in birds.
研究两个密切相关的物种在二次接触时会发生什么，可以深入了解物种形成过程的后期阶段。鸟类的 Zosteropidae 科是脊椎动物谱系中最快形成物种的谱系之一。该科的成员高度迁徙且地理分布广泛，这引发了一个问题，如果种群很容易发生二次接触，那么分歧是如何发生的。在科伦班加拉小岛上，两种密切相关的非姐妹种白眼鸟，Zosterops kulambangrae 和 Zosterops murphyi，分布在海拔梯度上，并在中海拔处发生二次接触。我们在两条海拔横切线上捕获了这两个物种的 134 个个体。使用基于测序的基因分型和线粒体标记，我们没有发现过去杂交事件的证据，并且物种边界的持续存在很强，尽管这两个物种仅在大约 200 万年前才开始分化。我们探讨了允许两个物种在同域共存的潜在繁殖障碍，包括基于羽毛和歌声差异的交配前隔离。我们还进行了文献综述，以确定在二次接触中同属鸟类物种/亚种中完全生殖隔离进化所需的时间（仅限于同属分类单元并置或存在杂交区的情况），发现我们的研究是鸟类中在基因组背景下研究的最年轻的完全生殖隔离例子之一。
