Harrison Hugo B, Berumen Michael L, Saenz-Agudelo Pablo, Salas Eva, Williamson David H, Jones Geoffrey P
Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD, Australia.
Division of Biological and Environmental Science and Engineering, Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.
Mol Ecol. 2017 Oct;26(20):5692-5704. doi: 10.1111/mec.14279.
Coral reefs are highly diverse ecosystems, where numerous closely related species often coexist. How new species arise and are maintained in these high geneflow environments have been long-standing conundrums. Hybridization and patterns of introgression between sympatric species provide a unique insight into the mechanisms of speciation and the maintenance of species boundaries. In this study, we investigate the extent of hybridization between two closely related species of coral reef fish: the common coral trout (Plectropomus leopardus) and the bar-cheek coral trout (Plectropomus maculatus). Using a complementary set of 25 microsatellite loci, we distinguish pure genotype classes from first- and later-generation hybrids, identifying 124 interspecific hybrids from a collection of 2,991 coral trout sampled in inshore and mid-shelf reefs of the southern Great Barrier Reef. Hybrids were ubiquitous among reefs, fertile and spanned multiple generations suggesting both ecological and evolutionary processes are acting to maintain species barriers. We elaborate on these finding to investigate the extent of genomic introgression and admixture from 2,271 SNP loci recovered from a ddRAD library of pure and hybrid individuals. An analysis of genomic clines on recovered loci indicates that 261 SNP loci deviate from a model of neutral introgression, of which 132 indicate a pattern of introgression consistent with selection favouring both hybrid and parental genotypes. Our findings indicate genome-wide, bidirectional introgression between two sympatric species of coral reef fishes and provide further support to a growing body of evidence for the role of hybridization in the evolution of coral reef fishes.
珊瑚礁是高度多样化的生态系统，众多亲缘关系密切的物种常常共存于此。在这些高基因流环境中，新物种如何产生并得以维持，一直是长期存在的难题。同域物种之间的杂交和基因渗入模式，为物种形成机制和物种边界的维持提供了独特的见解。在本研究中，我们调查了两种亲缘关系密切的珊瑚礁鱼类——普通珊瑚鳟（豹纹鳃棘鲈）和斑颊珊瑚鳟（黑点鳃棘鲈）之间的杂交程度。我们使用一组互补的25个微卫星位点，从第一代和后代杂种中区分出纯合基因型类别，在从大堡礁南部近岸和中陆架珊瑚礁采集的2991条珊瑚鳟样本中识别出124个种间杂种。杂种在各珊瑚礁中普遍存在，可育且跨越多个世代，这表明生态和进化过程都在维持物种屏障。我们详细阐述这些发现，以研究从纯合个体和杂种个体的ddRAD文库中获得的2271个单核苷酸多态性（SNP）位点的基因组渗入和混合程度。对回收位点上的基因组渐变分析表明，261个SNP位点偏离了中性渗入模型，其中132个显示出与有利于杂种和亲本基因型选择一致的渗入模式。我们的研究结果表明，两种同域珊瑚礁鱼类在全基因组范围内存在双向渗入，并为杂交在珊瑚礁鱼类进化中的作用这一越来越多的证据提供了进一步支持。
