Microtus mexicanus (Saussure, 1861) . Rev. Mag. Zool. Paris, Ser. 2, 13:3.

TYPE LOCALITY: Mexico, Puebla, Volcan de Orizaba .

DISTRIBUTION: Highly dissected in mountains from extreme S Utah and SW Colorado, USA, south in Sierra Madrés through interior Mexico to C Oaxaca.

STATUS: U.S. ESA and IUCN - Endangered as M. m. hualpaiensis; IUCN - Indeterminate as M. m. navaho.

SYNONYMS: fulviventer, fundatus, guadalupensis, hualpaiensis, madrensis, mogollonensis, navaho, neveriae, phaeus, salvus, subsimus.

COMMENTS: Interspecific affinities unclear: affiliated with Microtus sensu stricto, in particular M. californicus, by Anderson (1959, 1960); associated with members of subgenus Pitymys by Hooper and Hart (1962); genic similarity to M. montanus and M. pennsylvanicus disclosed by Moore and Janecek (1990); also see Hoffmann and Koeppl, 1985); chromosomal banding data uninformative (Modi, 1987). Morphometric, electrophoretic, and karyotypic variation among isolated populations in southwestern USA studied by Wilhelm (1982). Musser (1964) reduced fulviventer to a subspecies of M. mexicanus .