Clethrionomys gapperi (Vigors, 1830) . Zool. J., 5:204.

TYPE LOCALITY: Canada, Ontario, between York (= Toronto) and Lake Simcoe .

DISTRIBUTION: Most of Canada from N British Columbia to Labrador, excluding Newfoundland; south in the Appalachians to N Georgia, in the Great Plains to N Iowa, and in the Rockies to C New Mexico and EC Arizona, USA.

SYNONYMS: arizonensis, athabascae, brevicaudus, carolinensis, cascadensis, caurinus, fuscodorsalis, galei, gaspeanus, gauti, hudsonius, idahoensis, limitis, loringi, maurus, nivarius, occidentalis, ochraceus, pallescens, paludicola, phaeus, proteus, pygmaeus, rhoadsii, rufescens, rupicola, saturatus, solus, stikinensis, uintaensis, ungava, wrangeli .

COMMENTS: Information on specific relationships somewhat contradictory. Interspecific hybrids of reduced fertility produced from laboratory crosses with Eurasian C. glareolus, which led Grant (1974) to view the two as semispecies of recent divergence. Others (Bee and Hall, 1956; Youngman, 1975) have suggested, without presentation of data, that gapperi and rutilus are conspecific. Based on biochemical data, Nadler et al. (1978) viewed Old World C. rufocanus as closely related to the gapperi-rutilus complex. Most highly variable in gastric morphology among species of Clethrionomys studied by Carleton (1981). See account of C. californiens for allocation of occidentalis and caurinus to C. gapperi . See Merritt (1981, Mammalian Species, 146).