Brown Richard P, Paterson Steve, Risse Judith
School of Natural Sciences & Psychology, Liverpool John Moores University, Liverpool, United Kingdom
Department of Integrative Biology, University of Liverpool, Liverpool, United Kingdom.
Genome Biol Evol. 2016 Dec 31;8(11):3618-3626. doi: 10.1093/gbe/evw268.
Geographical variation among contiguous populations is frequently attributed to ecological divergence or historical isolation followed by secondary contact. Distinguishing between these effects is key to studies of incipient speciation and could be revealed by different genomic signatures. We used RAD-seq analyses to examine morphologically divergent populations of the endemic lizard (Gallotia galloti) from the volcanic island of Tenerife. Previous analyses have suggested ecological and historical causes to explain the morphological diversity. Analyses of 276,483 single nucleotide polymorphisms (SNPs) from >20 Mbp of the genome revealed one genetically divergent population from Anaga, a region associated with divergent mtDNA lineages in other Tenerife endemics. This population also has a high number of private alleles, and its divergence can be explained by historical isolation. Bayesian outlier analyses identified a small proportion of SNPs as candidates for selection (0.04%) which were strongly differentiated between xeric and mesic habitat types. Individual testing for specific xeric-mesic selection using an alternative approach also supported ecological divergence in a similarly small proportion of SNPs. The study indicates the roles of both historical isolation and ecological divergence in shaping genomic diversity in G. galloti However, north-south morphological divergence appears solely associated with the latter and likely involves a relatively small proportion of the genome.
相邻种群之间的地理差异通常归因于生态分化或历史隔离以及随后的二次接触。区分这些影响是研究初期物种形成的关键，并且可以通过不同的基因组特征来揭示。我们使用简化基因组测序（RAD-seq）分析来研究来自特内里费火山岛的特有蜥蜴（加那利蜥蜴）形态上有差异的种群。先前的分析已经提出了生态和历史原因来解释这种形态多样性。对来自基因组超过20兆碱基的276,483个单核苷酸多态性（SNP）进行分析后发现，来自阿纳加的一个种群在基因上存在差异，该地区与特内里费其他特有物种中不同的线粒体DNA谱系相关。这个种群也有大量的私有等位基因，其差异可以用历史隔离来解释。贝叶斯离群值分析确定了一小部分SNP作为选择候选基因（0.04%），这些基因在干旱和湿润栖息地类型之间有强烈差异。使用另一种方法对特定的干旱-湿润选择进行个体测试，也支持了一小部分SNP中存在生态分化。该研究表明历史隔离和生态分化在塑造加那利蜥蜴基因组多样性中都起到了作用。然而，南北形态差异似乎仅与后者相关，并且可能只涉及基因组中相对较小的一部分。
