Genetic structure and biogeographic history of the Bicknell’s Thrush/ Gray-cheeked Thrush species complex

Abstract We examined species limits, admixture, and genetic structure among populations in the Bicknell’s Thrush (Catharus bicknelli)–Gray-cheeked Thrush (C. minimus) species complex to establish the geographic and temporal context of speciation in this group, which is a model system in ecology and a high conservation priority. We obtained mitochondrial ND2 sequences from 186 Bicknell’s Thrushes, 77 Gray-cheeked Thrushes, and 55 individuals of their closest relative, the Veery (C. fuscescens), and genotyped a subset of individuals (n = 72) at 5,633 anonymous single nucleotide polymorphic (SNP) loci. Between-species sequence divergence was an order of magnitude greater than divergence within each species, divergence was dated to the late Pleistocene (420 kbp) based on Bayesian coalescence estimation, and a coalescent model (IMa) revealed almost no gene flow between species based on ND2. SNP data were consistent with mitochondrial results and revealed low levels of admixtur...摘要 本研究针对比克内尔鸫（Bicknell’s Thrush，*Catharus bicknelli*）-灰颊鸫（Gray-cheeked Thrush，*C. minimus*）物种复合体的种群开展分析，旨在阐明该类群物种形成的地理与时间背景——该类群既是生态学研究的经典模式系统，同时具有极高的保护优先级。研究共获取了186只比克内尔鸫、77只灰颊鸫，以及二者的近缘物种褐背鸫（Veery，*C. fuscescens*）的55个个体的线粒体ND2序列，并对其中72个个体进行了5633个匿名单核苷酸多态性（single nucleotide polymorphic, SNP）位点的基因分型。物种间的序列分化程度较各物种种内分化高出一个数量级；基于贝叶斯溯祖估计，该分化事件的发生时间可追溯至晚更新世（420 kbp）；依托IMa溯祖模型的分析表明，基于ND2序列可见物种间几乎不存在基因交流。单核苷酸多态性数据与线粒体DNA的分析结果一致，并揭示了低水平的基因混合……