Graylings (Thymallus) are among the less well-studied groups of salmonid fishes, especially across their Asian distribution range. Here we perform a comprehensive global review of their phylogeography, systematic diversity and range distributions, including biogeographic reconstruction and assessment of both conservation and taxonomic status of each species. Based on a mitogenomic phylogenetic analysis, three approaches to the delineation of molecular operational units, and evaluation of 15 a-priori defined species, we provide biological support for the recognition of 13 grayling species, plus two additional species tentatively. Several instances of paraphyly and its potential effect on systematic inferences are discussed. Overall, the genus displays increasing species diversity and decreasing range size from higher to lower latitudes and ancestral trait reconstruction supports an East Asian origin for extant diversity, most likely centred in the Amur River drainage. Europe’s colonization by Thymallus took place as early as the late Miocene, at least two colonisations of North America are supported, and multiple dispersal events likely took place into Western Siberia. The conservation status for the 15 taxa was estimated to be: 6 least concern, 1 near-threatened, 2 vulnerable, 3 endangered and 3 data deficient.

中文翻译：

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鳟鱼的全球系统多样性、范围分布、保护和分类评估（Teleostei：鲑科；胸腺属）

鳟鱼（Thymallus）是研究较少的鲑鱼群，尤其是在它们的亚洲分布范围内。在这里，我们对其系统地理学、系统多样性和范围分布进行了全面的全球审查​​，包括生物地理学重建以及对每个物种的保护和分类状态的评估。基于有丝分裂基因组系统发育分析、分子操作单元的三种划分方法以及对 15 个先验定义物种的评估，我们为 13 种鳟鱼物种的识别提供了生物学支持，另外还有两个暂时的物种。讨论了几个并列现象及其对系统推理的潜在影响。全面的，该属显示出从高纬度到低纬度增加的物种多样性和减小的范围大小，并且祖先特征重建支持现存多样性的东亚起源，最有可能集中在阿穆尔河排水系统。Thymallus 对欧洲的殖民化早在中新世晚期就发生了，至少有两次北美的殖民化得到支持，并且可能在西西伯利亚发生了多次扩散事件。15 个分类群的保护状况估计为：6 级最不受关注，1 级近危，2 级易危，3 级濒危，3 级数据不足。并且在西西伯利亚可能发生了多次传播事件。15 个分类群的保护状况估计为：6 级最不受关注，1 级近危，2 级易危，3 级濒危，3 级数据不足。并且在西西伯利亚可能发生了多次传播事件。15 个分类群的保护状况估计为：6 级最不受关注，1 级近危，2 级易危，3 级濒危，3 级数据不足。