Population genetics reveal Myotis keenii (Keen’s myotis) and Myotis evotis (long-eared myotis) to be a single species

Abstract: Recognizing delineations of gene flow among groups of animals can be challenging, but necessary for conservation and management. Of particular importance is the identification of species boundaries. Several physical and genetic traits have been used with mixed success to distinguish Myotis keenii (Merriam, 1895) (Keen’s myotis) and Myotis evotis (H. Allen, 1864) (long-eared myotis), but it is unclear whether species distinction is biologically warranted. We generated 12-14 microsatellite loci genotypes for 275 long-eared Myotis representing 4 species -- M. keenii, M. evotis, Myotis septentrionalis (Trouessart, 1897) (northern myotis), and Myotis thysanodes Miller, 1897 (fringed myotis) -- from across northwestern North America, and 23 Myotis lucifugus (Le Conte, 1831) (little brown myotis) as outgroup. Population genetics analyses revealed four well defined groups (species): M. septentrionalis, M. thysanodes, M. lucifugus and a single group comprising M. keenii and M. evotis. We document high rates of gene flow within M. evotis/keenii. Cytochrome b gene (mtDNA) sequencing failed to resolve morphologically identifiable species. We highlight the importance of geographically thorough investigation of genetic connectivity (nuclear markers) when assessing taxonomic status of closely related groups. We document a morphometric cline within M. evotis/keenii that may in part explain earlier analyses that led to the description of the smaller-bodied M. keenii (type locality Haida Gwaii). We conclude that M. keenii does not qualify as a genetic or biological species.

摘要：识别动物类群间的基因流界限颇具挑战性，但对于物种保护与管理而言却至关重要。其中，物种边界的界定尤为关键。此前已有多项形态与遗传性状被用于区分凯氏鼠耳蝠（Myotis keenii, Merriam, 1895, Keen’s myotis）与长耳鼠耳蝠（Myotis evotis, H. Allen, 1864），但相关研究结果良莠不齐，目前仍不清楚二者的物种区分是否具备生物学合理性。
本研究为采自北美西北部的275只长耳鼠耳蝠类群样本生成了12~14个微卫星位点（microsatellite loci）的基因型数据，所涉类群涵盖4个物种：凯氏鼠耳蝠、长耳鼠耳蝠、北鼠耳蝠（Myotis septentrionalis, Trouessart, 1897, northern myotis）以及缨毛鼠耳蝠（Myotis thysanodes, Miller, 1897, fringed myotis）；同时以23只小棕鼠耳蝠（Myotis lucifugus, Le Conte, 1831, little brown myotis）作为外群（outgroup）。
种群遗传学分析结果显示，可明确区分出4个清晰的类群（即物种）：北鼠耳蝠、缨毛鼠耳蝠、小棕鼠耳蝠，以及由凯氏鼠耳蝠与长耳鼠耳蝠组成的单一类群。本研究证实，该复合类群内部存在高水平的基因流。
细胞色素b（cytochrome b）基因（线粒体DNA, mtDNA）测序未能区分形态学上可识别的物种。本研究强调，在评估近缘类群的分类学地位时，开展覆盖完整地理范围的遗传连通性（核标记）研究至关重要。
本研究还发现，凯氏鼠耳蝠/长耳鼠耳蝠复合类群存在形态渐变群，这或许可以部分解释此前的分析结果——此前的分析将体型较小的凯氏鼠耳蝠（模式产地位于夏洛特皇后群岛（Haida Gwaii））描述为独立物种。
本研究得出结论：凯氏鼠耳蝠并不具备作为遗传物种或生物学物种的资格。