Salas Eva, Hobbs Jean-Paul A, Bernal Moisés A, Simison W Brian, Berumen Michael L, Bernardi Giacomo, Rocha Luiz A
Ichthyology Department California Academy of Sciences San Francisco CA USA.
Ecology and Evolutionary Biology Department University of California Santa Cruz Santa Cruz CA USA.
Ecol Evol. 2020 Feb 27;10(6):2813-2837. doi: 10.1002/ece3.6068. eCollection 2020 Mar.
Hybrid zones are natural laboratories for investigating the dynamics of gene flow, reproductive isolation, and speciation. A predominant marine hybrid (or suture) zone encompasses Christmas Island (CHR) and Cocos (Keeling) Islands (CKE), where 15 different instances of interbreeding between closely related species from Indian and Pacific Oceans have been documented. Here, we report a case of hybridization between genetically differentiated Pacific and Indian Ocean lineages of the three-spot dascyllus, (Rüppell, 1829). Field observations indicate there are subtle color differences between Pacific and Indian Ocean lineages. Most importantly, population densities of color morphs and genetic analyses (mitochondrial DNA and SNPs obtained via RADSeq) suggest that the pattern of hybridization within the suture zone is not homogeneous. At CHR, both color morphs were present, mitochondrial haplotypes of both lineages were observed, and SNP analyses revealed both pure and hybrid genotypes. Meanwhile, in CKE, the Indian Ocean color morphs were prevalent, only Indian Ocean mitochondrial haplotypes were observed, and SNP analysis showed hybrid individuals with a large proportion (~80%) of their genotypes assigning to the Indian Ocean lineage. We conclude that CHR populations are currently receiving an influx of individuals from both ocean basins, with a greater influence from the Pacific Ocean. In contrast, geographically isolated CKE populations appear to be self-recruiting and with more influx of individuals from the Indian Ocean. Our research highlights how patterns of hybridization can be different at scales of hundreds of kilometers, due to geographic isolation and the history of interbreeding between lineages.
杂交区是研究基因流动、生殖隔离和物种形成动态的天然实验室。一个主要的海洋杂交（或缝合）区涵盖圣诞岛（CHR）和科科斯（基林）群岛（CKE），在那里已经记录了来自印度洋和太平洋的近缘物种之间15次不同的杂交实例。在这里，我们报告了一例三点雀鲷（Rüppell，1829）的太平洋和印度洋遗传分化谱系之间的杂交情况。实地观察表明，太平洋和印度洋谱系之间存在细微的颜色差异。最重要的是，颜色形态的种群密度和遗传分析（线粒体DNA和通过RADSeq获得的单核苷酸多态性）表明，缝合区内的杂交模式并不均匀。在圣诞岛，两种颜色形态都存在，观察到了两个谱系的线粒体单倍型，单核苷酸多态性分析揭示了纯合子和杂交基因型。同时，在科科斯（基林）群岛，印度洋颜色形态占主导，只观察到印度洋线粒体单倍型，单核苷酸多态性分析显示杂交个体中很大一部分（约80%）的基因型属于印度洋谱系。我们得出结论，圣诞岛种群目前正接收来自两个大洋盆地的个体涌入，其中太平洋的影响更大。相比之下，地理隔离的科科斯（基林）群岛种群似乎是自我繁殖的，且有更多来自印度洋的个体涌入。我们的研究强调了由于地理隔离和谱系间杂交历史，杂交模式在数百公里尺度上可能会有所不同。
