University of Alaska Museum, 907 Yukon Drive, Fairbanks, AK 99775, USA; Department of Biology and Wildlife, University of Alaska Fairbanks, PO Box 756100, Fairbanks, AK 99775, USA; University of Kentucky, Department of Biology, 101 T. H. Morgan Building, 675 Rose St, Lexington, KY 40508, USA.
University of Alaska Museum, 907 Yukon Drive, Fairbanks, AK 99775, USA; Department of Biology and Wildlife, University of Alaska Fairbanks, PO Box 756100, Fairbanks, AK 99775, USA; Sam Noble Oklahoma Museum of Natural History, 2401 Chautauqua Ave, Norman, OK 73072, USA.
Mol Phylogenet Evol. 2019 Oct;139:106564. doi: 10.1016/j.ympev.2019.106564. Epub 2019 Jul 19.
New World thrushes in the genus Catharus are small, insectivorous or omnivorous birds that have been used to explore several important questions in avian evolution, including the evolution of seasonal migration and plumage variation. Within Catharus, members of a clade of obligate long-distance migrants (C. fuscescens, C. minimus, and C. bicknelli) have also been used in the development of heteropatric speciation theory, a divergence process in which migratory lineages (which might occur in allopatry or sympatry during portions of their annual cycle) diverge despite low levels of gene flow. However, research on Catharus relationships has thus far been restricted to the use of small genetic datasets, which provide limited resolution of both phylogenetic and demographic histories. We used a large, multi-locus dataset from loci containing ultraconserved elements (UCEs) to study the demographic histories of the migratory C. fuscescens-minimus-bicknelli clade and to resolve the phylogeny of the migratory species of Catharus. Our dataset included more than 2000 loci and over 1700 variable genotyped sites, and analyses supported our prediction of divergence with gene flow in the fully migratory clade, with significant gene flow among all three species. Our phylogeny of the genus differs from past work in its placement of C. ustulatus, and further analyses suggest historic gene flow throughout the genus, producing genetically reticulate (or network) phylogenies. This raises questions about trait origins and suggests that seasonal migration and the resulting migratory condition of heteropatry is likely to promote hybridization not only during pairwise divergence and speciation, but also among non-sisters.
新大陆鸫属的鸫类是小型、食虫或杂食性鸟类，被用于探索鸟类进化中的几个重要问题，包括季节性迁徙和羽色变化的进化。在鸫属中，一个强制性长距离迁徙的分支（Catharus fuscescens、Catharus minimus 和 Catharus bicknelli）的成员也被用于异域物种形成理论的发展，这是一种扩散过程，其中迁徙谱系（在其年度周期的某些部分可能发生在异地或同域）尽管基因流水平较低，但仍会发生分歧。然而，对鸫属关系的研究迄今为止仅限于使用小型遗传数据集，这些数据集对系统发育和种群历史的分辨率都很有限。我们使用包含超保守元件（UCEs）的多个基因座的大型多基因座数据集来研究迁徙的 C. fuscescens-minimus-bicknelli 分支的种群历史，并解决鸫属迁徙物种的系统发育。我们的数据集包括超过 2000 个基因座和超过 1700 个可遗传的基因分型位点，分析结果支持我们的预测，即在完全迁徙的分支中存在基因流和分歧，所有三个物种之间都存在显著的基因流。我们对属的系统发育与过去的工作不同，它将 C. ustulatus 放在了不同的位置，进一步的分析表明，整个属都存在历史基因流，产生了遗传上的网状（或网络）系统发育。这引发了关于特征起源的问题，并表明季节性迁徙和由此产生的异地繁殖条件不仅可能在成对的分歧和物种形成过程中促进杂交，而且可能在非姐妹物种之间也促进杂交。
