National University of Singapore, Department of Biological Sciences, Singapore, 117558, Singapore.
Max Planck Institute for Ornithology, 82319, Seewiesen, Germany.
Sci Rep. 2019 Jun 12;9(1):8546. doi: 10.1038/s41598-019-44996-5.
Genetic isolation of populations over evolutionary time leads to the formation of independent species. We examined a pair of shorebirds - the Kentish Plover Charadrius alexandrinus and the enigmatic White-faced Plover C. dealbatus - which display strong plumage differentiation, yet show minimal genetic divergence based on previous mitochondrial and microsatellite work. Two scenarios may lead to this situation: (1) they represent clinal or poorly diverged populations with limited genomic differentiation despite substantial plumage variation, or (2) they are diverging taxa at the cusp of speciation, with ongoing limited gene flow obliterating signals of differentiation in traditional genetic markers. We compared the genotypes of 98 plovers (59 Kentish Plovers, 35 White-faced Plovers and 4 genomic hybrids) sampled in eastern Asia and Europe using ddRADSeq to harvest over 8000 genome-wide SNPs. In contrast to previous studies, our analyses revealed two well defined genomic clusters, with limited hybridization and a narrow contact zone. We also uncovered significant differences in bill length and further sex-specific differences in size, which may signal differences in mate choice between Kentish and White-faced Plovers. Our results support the hypothesis that this shorebird duo is on the verge of speciation.
遗传隔离导致种群在进化过程中形成独立的物种。我们研究了一对滨鸟——黑腹滨鹬 Charadrius alexandrinus 和神秘的白脸滨鹬 C. dealbatus，它们表现出强烈的羽色分化，但根据先前的线粒体和微卫星研究显示，它们的遗传分化很小。这种情况可能有两种原因：（1）尽管存在大量的羽色变异，但它们代表具有有限基因组分化的连续或分化不足的种群；（2）它们是处于物种形成边缘的分化分类群，持续的有限基因流使传统遗传标记的分化信号消失。我们使用 ddRADSeq 比较了东亚和欧洲 98 只滨鸟（59 只黑腹滨鹬、35 只白脸滨鹬和 4 只基因组杂种）的基因型，共获得了 8000 多个全基因组 SNPs。与先前的研究相比，我们的分析揭示了两个定义明确的基因组聚类，杂交有限，接触区狭窄。我们还发现了喙长的显著差异，以及大小的进一步性别特异性差异，这可能表明黑腹滨鹬和白脸滨鹬在择偶方面存在差异。我们的研究结果支持了这样一种假设，即这种滨鸟对即将发生物种形成。
