Lemmini. Nominative genus of Miller's (1896) classic tribe Lemmi, then including Dicrostonyx (see that account). Distinctiveness still recognized within a tribe, including Myopus and Synaptomys, a clade believed to represent an early line of arvicoline evolution (Abramson, 1993; Carleton, 1981; Chaline and Graf, 1988; Graf, 1982; Gromov and Polyakov, 1977; Hinton, 1926a; Hooper and Hart, 1962; Jarrell and Fredga, 1993; Koenigswald, 1980). The monophyly of true lemmings, excluding Dicrostonyx, is also supported by recent cladistic evaluations of allozymes (Mezhzherin et al., 1995), nuclear repetitive DNA elements (Modi, 1996), and mitochrondrial DNA sequences (Conroy and Cook, 1999). Myodes Pallas, 1811, usually placed in the synonymy of Lemmus (e.g., Hall, 1981; Hinton, 1926a; Miller, 1896), is the oldest name for Clethrionomys (see that account); also see account of Myopus, once treated as a subgenus of Lemmus.
Old World taxa covered by Corbet (1978, 1984), Gromov and Polyakov (1977), Pavlinov and Rossolimo (1987), and Gromov and Erbajeva (1995); biology, distributions, and taxonomic arrangements of New and Old World species summarized by Stenseth and Ims (1993). Fossil history reviewed by Koenigswald and L. D. Martin (1984) and Fejfar and Repenning (1998); zoogeography discussed by Rausch and Rausch (1975b). All sampled Lemmus have 2n = 50, with autosomes similar to those in Synaptomys (Jarrell and Fredga, 1993; Zima and Kral, 1984a). In an important series of reports, Fedorov (1999) and Fedorov et al. (1999a, b) assessed mitochondrial DNA variation among co-occurring samples of Lemmus and Dicrostonyx to explore circumpolar phylogeographic patterns and discussed the geographic incongruence of genetic differentiation within the two lemming genera.
The alpha taxonomy of true lemmings is complicated. The genus is clearly more diverse than the single Holarctic species proposed by Sidorowicz (1960, 1964). Two (Pokrovski et al., 1984; Rausch and Rausch, 1975b), three (Musser and Carleton, 1993; Pavlinov and Rossolimo, 1987), four (Gromov and Erbajeva, 1995; Honacki et al., 1982; Jarrell and Fredga, 1993; Pavlinov and Rossolimo, 1998; Pavlinov et al., 1995a), or five (Corbet and Hill, 1991) species have been recognized, and the senior names employed and synonymies allocated among them are inconsistent or contradictory. We distill this information and evidence supplied in recent studies as the basis for recognizing five allopatric species.