Molecular phylogeny and taxonomy of subgenus Eothenomys (Cricetidae: Arvicolinae: Eothenomys) with the description of four new species from Sichuan, China

The systematics of the subgenus Eothenomys (Cricetidae: Arvicolinae) is controversial because of the morphological similarity among species and the incomplete sampling of taxa. Here, we gather specimens of Oriental voles from throughout their distributions. We sequence and analyse two mitochondrial and three nuclear gene segments. A principal components analysis serves to evaluate morphological variation among taxa of the subgenera Eothenomys and Ermites. Our analyses support recent revisions on the systematics of Eothenomys as follows: (1) Eothenomys melanogaster colurnus requires elevation to a valid species; (2) subgenus Eothenomys includes the species Eothenomys colurnus, E. cachinus, E. eleusis, E. fidelis, E. melanogaster, E. miletus and an unidentified taxon; (3) Eothenomys melanogaster libonotus and E. miletus confinii are junior synonyms of E. cachinus; Eothenomys melanogaster kanoi is a junior synonym of E. colurnus; and (4) one unidentified taxon of subgenus Eothenomys and three unidentified taxa of subgenus Ermites constitute new species, which we describe as Eothenomys shimianensis sp. nov., E. jinyangensis sp. nov., E. meiguensis sp. nov. and E. luojishanensis sp. nov., respectively. Our analyses indicate that the teeth of Oriental voles present extensive heteromorphosis. A species of subgenus Eothenomys from an isolated area may possess two or three tooth patterns. The three unidentified species of subgenus Ermites are ecological sky-island species whose origins are attributable to rapid adaptive evolution caused by ecosystem isolation.