Borioikon Poliakov, 1881; Cuniculus Wagler, 1830 [not of Brisson, 1762, Gronovius, 1763, or Mayer, 1790]; Misothermus Hensel, 1855; Tylonyx Schulze, 1897.
Dicrostonychini. Dicrostonyx was initially grouped with other lemmings following Millerís (1896) classic Lemmi-Microti division (e.g., Ellerman, 1941; Hinton, 1926; Ognev, 1963; Simpson, 1945). A large and diverse information base, however, requires its tribal separation from the true lemmings (Lemmini) and suggests that the cladistic origin of Dicrostonyx dates to the earliest radiation of arvicolines (Carleton, 1981; Chaline and Graf, 1988; Conroy and Cook, 1999; Gromov and Polyakov, 1977; Hinton, 1926a; Hooper and Hart, 1962; Kretzoi, 1969; Mezhzherin et al., 1995; Modi, 1987, 1996). Various aspects of taxonomy, karyology, distribution, and ecology are summarized by Stenseth and Ims (1993). Pliocene-Pleistocene changes in molar complexity traced by Agadzhanyan (1986); Quaternary fossils place the generic occurrence in North America far to the south of its present distribution, e.g., in Wyoming, Iowa, and Maryland (Graham and Lundelius, 1994; Mead and Mead, 1989).
The simple viewpoint of a single circumpolar species, D. torquatus, as advocated by Ognev (1963) and Rausch (1953, 1963), was unsettled by karyological and breeding studies in recent decades that implied a geographically partitioned superspecies complex (Chernyavskii and Kozlovskii, 1980; Gileva, 1983; Krohne, 1982; Rausch, 1977; Rausch and Rausch, 1972). The occurrence of collared lemmings in quite different tundra biotopes (e.g., see Youngman, 1975) alone disputed the existence of a single species within North America. Later authorities either have listed the North American karyotypic variants as species (Baker et al., 2003b; Corbet and Hill, 1991; Honacki et al., 1982; Jones et al., 1986, 1997; Musser and Carleton, 1993); or continued to recognize most as subspecies of D. groenlandicus, retaining only D. exsul on St. Lawrence Isl and D. hudsonius on the Ungava Peninsula as separate (Hall, 1981); or modified Hallís treatment to yield two New World species, D. hudsonius and D. groenlandicus, the latter embracing exsul and vinogradovi on Wrangel Isl (Jarrell and Fredga, 1993).
The kinds of studies needed to settle this indecision emerged in the 1990s (Borowik and Engstrom, 1993; Eger, 1995; Ehrich et al., 2000; Engstrom et al., 1993; Fedorov et al., 1999a; Van Wynsberghe and Engstrom, 1992). While the framework for taxonomic understanding is thus much improved, straightforward declarations of synonymy of studied taxa would help much to signal systematic conclusions. As indicated in 1993, the specific recognition of D. groenlandicus, D. hudsonius, D. richardsoni, and D. unalascensis is defensible on morphological grounds, and such an interpretation is generally consistent with these recent research contributions. The distinctiveness of other North American taxa, namely kilangmiutak and rubricatus, has not been sustained by this body of research, which points to their synonymy under D. groenlandicus (Eger, 1995; Ehrich et al., 2000). We continue to provisionally retain as species D. nelsoni and D. nunatakensis (specimens of latter not seen), examples of which have yet to be critically addressed in the on-going systematic review of Dicrostonyx; nor is the evidence for merging D. vinogradovi as another form of D. groenlandicus, as advanced by Jarrell and Fredga (1993), sufficiently convincing to date.