Department of Herpetology, American Museum of Natural History, New York, NY, USA; Richard Gilder Graduate School, American Museum of Natural History, New York, NY, USA.
Department of Biological Sciences, State University of New York at Buffalo, Buffalo, NY, USA.
Mol Phylogenet Evol. 2023 Sep;186:107844. doi: 10.1016/j.ympev.2023.107844. Epub 2023 Jun 9.
North American Thamnophiini (gartersnakes, watersnakes, brownsnakes, and swampsnakes) are an ecologically and phenotypically diverse temperate clade of snakes representing 61 species across 10 genera. In this study, we estimate phylogenetic trees using ∼3,700 ultraconserved elements (UCEs) for 76 specimens representing 75% of all Thamnophiini species. We infer phylogenies using multispecies coalescent methods and time calibrate them using the fossil record. We also conducted ancestral area estimation to identify how major biogeographic boundaries in North America affect broadscale diversification in the group. While most nodes exhibited strong statistical support, analysis of concordant data across gene trees reveals substantial heterogeneity. Ancestral area estimation demonstrated that the genus Thamnophis was the only taxon in this subfamily to cross the Western Continental Divide, even as other taxa dispersed southward toward the tropics. Additionally, levels of gene tree discordance are overall higher in transition zones between bioregions, including the Rocky Mountains. Therefore, the Western Continental Divide may be a significant transition zone structuring the diversification of Thamnophiini during the Neogene and Pleistocene. Here we show that despite high levels of discordance across gene trees, we were able to infer a highly resolved and well-supported phylogeny for Thamnophiini, which allows us to understand broadscale patterns of diversity and biogeography.
北美 Thamnophiini （束带蛇、水蛇、褐蛇和沼泽蛇）是一个生态和表型多样化的温带蛇类群，代表 10 个属的 61 个物种。在这项研究中，我们使用∼3700 个超保守元件（UCEs）对代表所有 Thamnophiini 物种 75%的 76 个样本进行了系统发育树估计。我们使用多物种合并方法推断系统发育，并使用化石记录对其进行时间校准。我们还进行了祖先区域估计，以确定北美主要生物地理边界如何影响该组的广泛多样化。虽然大多数节点都表现出很强的统计支持，但跨基因树的一致数据分析揭示了很大的异质性。祖先区域估计表明，Thamnophis 属是这个亚科中唯一跨越西部大陆分水岭的分类群，尽管其他分类群向南扩散到热带地区。此外，基因树分歧的水平在生物区域之间的过渡带总体上更高，包括落基山脉。因此，西部大陆分水岭可能是塑造 Neogene 和更新世 Thamnophiini 多样化的一个重要过渡带。在这里，我们表明，尽管基因树之间存在高度的不和谐，但我们能够推断出一个高度解决和支持良好的 Thamnophiini 系统发育，这使我们能够理解多样性和生物地理学的广泛模式。
