Conservation efforts rely on robust taxonomic assessments that should be based on critical assessment of interspecific boundaries, infraspecific variation, and potentially distinctive peripheral populations. The meadow vole (Microtus pennsylvanicus) is widely distributed across North America, including 28 morphologically defined subspecies and numerous isolated populations. Because some subspecies are of high conservation concern, we examined geographic variation across the range of the species to test existing infraspecific taxonomy in terms of local and regional diversification. We sequenced mitochondrial DNA (mtDNA) from 20 subspecies of M. pennsylvanicus and contextualized infraspecific variation through comparison of pairwise genetic distances derived from an extended data set of 63 species of Microtus. We found strong support for at least three divergent clades within M. pennsylvanicus, with observed intraspecific clade divergence exceeding that between several pairwise comparisons of sister species within Microtus. Six nuclear genes were then sequenced to test the validity of mtDNA structure and to further evaluate the possibility of cryptic, species-level diversity using Bayes factor species delimitation (BFD) analyses. BFD consistently and decisively supported multiple species based on the multilocus approach. We propose that taxonomic revision of the meadow vole is required, with the eastern clade now identified as M. pennsylvanicus (Ord 1815), the western clade as M. drummondii (Audubon and Bachman 1853), and the coastal Florida clade as M. dukecampbelli (Woods, Post, and Kilpatrick 1982). We suggest that such an arrangement would more closely reflect evolutionary history and provide critical context for further examination of distinctive southern peripheral populations that harbor novel evolutionary legacies and adaptive potential.

中文翻译：

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田鼠（Microtus pennsylvanicus）独特的外围种群的前途未卜

保护工作依赖于稳健的分类评估，该评估应基于对种间边界、种内变异和潜在独特外围种群的批判性评估。草甸田鼠 (Microtus pennsylvanicus) 广泛分布于北美洲，包括 28 个形态学定义的亚种和许多孤立的种群。由于某些亚种具有高度的保护关注，我们检查了该物种范围内的地理变异，以在当地和区域多样化方面测试现有的种下分类。我们对来自 M. pennsylvanicus 的 20 个亚种的线粒体 DNA (mtDNA) 进行了测序，并通过比较来自 63 个 Microtus 物种的扩展数据集的成对遗传距离来区分种下变异。我们发现 M. pennsylvanicus 中至少有三个不同的进化枝得到了强有力的支持，观察到的种内进化枝分歧超过了 Microtus 内姐妹物种的几个成对比较之间的差异。然后对六个核基因进行测序以测试 mtDNA 结构的有效性，并使用贝叶斯因子物种定界 (BFD) 分析进一步评估神秘的物种水平多样性的可能性。BFD 始终如一地果断地支持基于多位点方法的多个物种。我们建议需要对草甸田鼠进行分类学修订，东部进化枝现在被确定为 M. pennsylvanicus (Ord 1815)，西部进化枝为 M. drummondii (Audubon and Bachman 1853)，以及佛罗里达海岸进化枝为 M. dukecampbelli （伍兹、波斯特和基尔帕特里克，1982 年）。