Microtus umbrosus Merriam 1898

Wilson, Don E. & Reeder, DeeAnn, 2005, Order Rodentia - Family Cricetidae, Mammal Species of the World: a Taxonomic and Geographic Reference (3 rd Edition), Volume 2, Baltimore: The Johns Hopkins University Press, pp. 955-1189 : 1019

Microtus umbrosus Merriam 1898

Microtus umbrosus Merriam 1898 , Proc. Biol. Soc. Wash., 12: 107.

Type Locality: México, Oaxaca, Mt Zempoaltépec, 8200 ft (2500 m).

Vernacular Names: Zempoaltepec Vole.

Distribution: Cerro Zempoaltépec, 1800-3000 m, NC Oaxaca, México.

Conservation: IUCN – Lower Risk (lc).

Discussion: Type species and sole member of Orthriomys , a taxon typically identified as a subgenus of Microtus ( Anderson, 1959; Bailey, 1900; Hall and Cockrum, 1953; R. A. Martin, 1995; Zagorodnyuk, 1990). Nonbanded karyotype reported by Cervantes et al. (1994), who noted its agreement with the complement hypothesized as ancestral for Arvicolinae . Viewed as cladistically basal to other North American pitymyines (subgenera Herpetomys , Pedomys , and Pitymys ) based on phylogenetic study of molar traits ( R. A. Martin, 1995); more removed from pitymyine species according to mitochrondrial gene sequences and weakly associated with M. chrotorrhinus ( Conroy et al., 2001) . Conroy et al. (2001) suggested that M. umbrosus represents an independent invasion of southern latitudes, the other consisting of species related to M. pinetorum , subgenus Pitymys ( M. guatemalensis , M. oaxacensis , M. quasiater ). See Frey and Cervantes (1997, Mammalian Species, 555).