Conspecificity of Old (rutilus) and New World (dawsoni) populations advanced by Rausch (1953) and corroborated by subsequent studies (e.g., Nadler et al., 1976, 1978; Rausch and Rausch, 1975a). Phylogenetic interpretation of allozymes indicates that M. rutilus is most closely related to M. gapperi, the two forming a monophyletic group along with M. glareolus M. centralis but excluding M. rufocanus (Mezhzherin and Serbenyuk, 1992). Analyses of autosomes (Iwasa et al., 1999b) and mitochondrial and nuclear ribosomal DNA (Suzuki et al., 1999b; Wakana et al., 1996) also emphasize the phyletic distance between M. rutilus and M. rufocanus and its allies (M. andersoni, M. smithii, M. rex, M. regulus).

North American populations revised, as Clethrionomys dawsoni, by Orr (1945), and, as C. rutilus by Manning (1956). European populations reviewed by Henttonen and Peiponen (1982) and Mitchell-Jones et al. (1999); those in Russia and adjacent regions by Gromov and Erbajeva (1995). M3 variation and its systematic implications evaluated by Nakatsu (1982) for Japanese populations. Iwasa et al. (1999b) contrasted the sex chromosomes and pachytene synapses of Hokkaido M. rutilus with Hokkaido M. rufocanus and Japanese species of Eothenomys (here = Myodes); karyotypes of M. rutilus and M. rufocanus from Hokkaido are essentially identical and closely resemble mainland species of Myodes (Obara et al., 1995). Phylogeography of M. rutilus in NE Asia, and comparisons with M. rufocanus which has a similar geographic range, assessed by mitochondrial cytochrome b sequences (Iwasa et al., 2002). Occurrence on the Svjatoj Nos peninsula and isthmus in Lake Baikal documented by Reiter et al. (1995). In Hokkaido, Japan, M. rutilus occurs with M. rufocanus and M. rex (see those accounts and that of M. gapperi).