Data from: Molecular phylogeny of the marmots (Rodentia: Sciuridae): tests of evolutionary and biogeographic hypotheses

There are 14 species of marmots distributed across the Holarctic, and despite extensive systematic study, their phylogenetic relationships remain largely unresolved. In particular, comprehensive studies have been lacking. A well-supported phylogeny is needed to place the numerous ecological and behavioral studies on marmots in an evolutionary context. To address this situation, we obtained complete cytochrome (cyt) b sequences for 13 of the species and partial sequence for the 14th. We employed a statistical approach to both phylogeny estimation and hypothesis testing using parsimony and maximum likelihood based methods. We conducted statistical tests on a suite of previously proposed hypotheses of phylogenetic relationships and biogeographic histories. The cyt b data strongly support the monophyly of Marmota and a western montane clade in the Nearctic. The results are consistent with an initial diversification in North America followed by an invasion and subsequent rapid diversification in the Palearctic. These analyses reject the two major competing hypotheses of M. broweri's phylogenetic relationships: namely, that it is the sister species to camtschatica of eastern Siberia and that it is related closely to caligata of the Nearctic. The Alaskan distribution of M. broweri is best explained as a reinvasion from the Palearctic but a Nearctic origin can not be rejected. Several other conventionally recognized species groups can also be rejected. Social evolution has been homoplastic, with large colonial systems evolving in two groups convergently. The cyt b data do not provide unambiguous resolution of several basal nodes in the Palearctic radiation, leaving some aspects of pelage and karyotypic evolution equivocal.

旱獭属（Marmota）共包含14个物种，广布于全北界（Holarctic）；尽管已有大量系统性研究，但其系统发育关系仍未得到充分阐明，综合性研究尤为匮乏。为将众多针对旱獭的生态学与行为学研究置于进化研究框架之中，亟需构建得到稳健支持的系统发育树。为解决这一研究短板，我们获取了该属13个物种的细胞色素b（cytochrome b, cyt b）全序列，以及第14个物种的部分基因序列。我们采用基于简约法（parsimony）与最大似然法（maximum likelihood）的统计分析策略，同时开展系统发育推断与假说检验，并针对此前提出的一系列系统发育关系与生物地理历史假说进行了统计验证。细胞色素b数据强烈支持旱獭属（Marmota）以及新北界（Nearctic）西部山地分支的单系性。研究结果与“旱獭最初在北美发生分化，随后入侵古北界（Palearctic）并快速发生辐射演化”的演化假说相一致。本分析推翻了关于棕旱獭（Marmota broweri）系统发育关系的两大主流竞争性假说：其一为其与东西伯利亚的堪察加旱獭（Marmota camtschatica）互为姐妹群，其二为其与新北界的灰旱獭（Marmota caligata）亲缘关系密切。棕旱獭在阿拉斯加的分布格局，最合理的解释为其从古北界再次入侵北美，但“其起源于新北界”的假说亦无法被完全排除。多项此前被广泛认可的物种类群假说同样被本研究结果推翻。社会行为演化具有同塑特征，大型群居社群在两个类群中独立趋同演化形成。细胞色素b数据未能明确解析古北界辐射演化中的数个基部节点，使得部分关于被毛形态与核型演化的问题仍存在争议。