Gyllenhaal Ethan F, Brady Serina S, DeCicco Lucas H, Naikatini Alivereti, Hime Paul M, Manthey Joseph D, Kelly John, Moyle Robert G, Andersen Michael J
Department of Biology and Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico, USA.
Department of Biological Sciences, Texas Tech University, Lubbock, Texas, USA.
Syst Biol. 2025 Apr 15. doi: 10.1093/sysbio/syaf023.
Secondary contact between previously allopatric lineages offers a test of reproductive isolating mechanisms that may have accrued in isolation. Such instances of contact can produce stable hybrid zones-where reproductive isolation can further develop via reinforcement or phenotypic displacement-or result in the lineages merging. Ongoing secondary contact is most visible in continental systems, where steady input from parental taxa can occur readily. In oceanic island systems, however, secondary contact between closely related species of birds is relatively rare. When observed on sufficiently small islands, relative to population size, secondary contact likely represents a recent phenomenon. Here, we examine the dynamics of a group of birds whose apparent widespread hybridization influenced Ernst Mayr's foundational work on allopatric speciation: the whistlers of Fiji (Aves: Pachycephala). We demonstrate two clear instances of secondary contact within the Fijian archipelago, one resulting in a hybrid zone on a larger island, and the other resulting in a wholly admixed population on a smaller island. We leveraged low genome-wide divergence in the hybrid zone to pinpoint a single genomic region associated with observed phenotypic differences. We use genomic data to present a new hypothesis that emphasizes rapid plumage evolution and post-divergence gene flow.
先前异域分布的谱系之间的二次接触为可能在隔离过程中积累的生殖隔离机制提供了一个检验。这种接触情况可以产生稳定的杂交带——在那里生殖隔离可以通过强化或表型替代进一步发展——或者导致谱系合并。正在进行的二次接触在大陆系统中最为明显，在那里亲本类群的稳定输入很容易发生。然而，在海洋岛屿系统中，亲缘关系密切的鸟类物种之间的二次接触相对较少。当在相对于种群规模足够小的岛屿上观察到时，二次接触可能是一种近期现象。在这里，我们研究了一组鸟类的动态，它们明显广泛的杂交影响了恩斯特·迈尔关于异域物种形成的基础研究：斐济的啸鹟（鸟纲：厚头啸鹟属）。我们在斐济群岛内展示了两个明确的二次接触实例，一个在较大岛屿上形成了杂交带，另一个在较小岛屿上形成了完全混合的种群。我们利用杂交带中全基因组低分化来确定一个与观察到的表型差异相关的单一基因组区域。我们利用基因组数据提出了一个新的假说，该假说强调羽毛的快速进化和分化后的基因流动。
