See Kretzoi (1955, 1962, 1969) for family-group priority of Arvicolidae Gray, 1821, instead of Microti Miller, 1896. Although some have intentionally maintained the latter name (e.g., Repenning, 1992, 1998), a group concept of arvicoline rodents, recognized as Arvicolinae, actually had emerged long prior to Miller’s (1896) seminal monograph (e.g., Baird, 1857; Coues, 1874; Murray, 1866; Alston, 1876; Lataste, 1887). Carleton and Musser (1984) generally defined and reviewed the limits and contents of the subfamily. Hinton’s (1926a) classic monograph, although never completed, still remains the most authoritative systematic, morphological, and biogeographic review for many genera. Synthetic taxonomic treatments are available for broad regions, including the Palearctic (Agadzhanyan and Yatsenko, 1984; Corbet, 1978c, 1984; Ellerman and Morrison-Scott, 1951), Eurasia (Gromov and Erbajeva, 1995; Gromov and Polyakov, 1977; Ognev, 1963, 1964; Pavlinov and Rossolimo, 1987; Pavlinov et al., 1995a), Europe (Mitchell-Jones et al., 1999; Niethammer and Krapp, 1982a), and North America (Hall, 1981; Hall and Cockrum, 1953; Wilson and Ruff, 1999). Biochronology, paleogeography, and paleoecology of the arvicoline radiation comprehensively reviewed by Repenning (1990), Repenning et al. (1990, 1998), Fejfar and Repenning (1992), Montuire et al. (1997), and Chaline et al. (1999, and references therein). Dating of the early arvicoline phylogenesis, about 5-6 million years ago, is in reasonable agreement whether based on paleontological or molecular-clock perspectives (Chaline et al., 1999; Conroy and Cook, 1999).
The earliest indisputable arvicolines are represented by early Pliocene fossils in Holarctic North America, Europe and NW Asia (the primitive Prosomys; Chaline et al., 1999; Fejfar, 1990a; Repenning, 1998, 2003, as Promimomys). Southern Asia was not populated by voles until the late Pliocene, presumably derived from immigration of a European Mimomys stock (Kotlia, 1994; Kotlia and Koenigswald, 1992); early Pliocene dispersion of Mimomys to North America, via Beringia, important to the diversification of New World arvicolines (Repenning, 2003). Several independent lineages of cricetids with rooted, slightly hypsodont molars appeared in the late Miocene of Europe, Asia, and North America and survived into the Pleistocene in Europe; these "microtoid cricetids," such as Baranomys and Microtoscoptes, are believed to precede the appearance of true voles and were replaced by them (see review by Fejfar, 1999a). Although some have treated certain of these genera as Arvicolinae (e. g., Gromov and Polyakov, 1977; Kretzoi, 1969; Repenning, 1998; Repenning et al., 1990; Zheng and Li, 1990), most have recognized them as dentally progressive cricetids that exploited a graminivorous niche (see review by Chaline et al., 1999). Arvicolines are convincingly derived from a cricetid ancestral stock (Gromov and Polyakov, 1977; Kretzoi, 1955; Michaux et al., 2001b), yet whether their phylogenetic roots are embedded in the microtoid cricetids or another cricetid lineage is unknown. Chaline et al. (1999:242) summarized the uncertainty of the paleontological evidence: "there is a wide array of cricetids with arvicoline features but it is currently impossible to specify their involvement in the origin of arvicolines."
Broad, multispecies surveys have been undertaken on morphological and biochemical systems of arvicolines that bear on issues of their phenetic divergence and phylogenetic relationships. E.g., comparative and functional studies of the dentition (Abramson, 1993; Brunet-Lecomte and Chaline, 1992; Bustos, 2002; Contoli, 1993; Hinton, 1926a; Koenigswald, 1980, 1982; Miller, 1896); of the cranium (Courant et al., 1997; Gromov, 1990; Kratochvíl, 1982; Pietsch, 1980); of middle ear anatomy (Hooper, 1968; Pavlinov, 1984a); of cutaneous and subcutaneous glands (Quay, 1954, 1968; Sokolov and Dzhemukhadze, 1991); of the arterial system (Durán et al., 1998); of myology (Kesner, 1980, 1986; Repenning, 1968; Stein, 1986, 1987); of the digestive tract (Carleton, 1981; Quay, 1954; Vorontsov, 1979); of reproductive structures (Anderson, 1960; Hooper and Hart, 1962; Niethammer, 1972). Chromosomal comparisons, both standard and banded karyotypes, are prevalent in recent systematic studies (Ashley and Fredga, 1994; Burgos et al., 1989; Modi, 1987; Radosavlievic et al., 1990; Zagorodnyuk, 1990, 1991c; Zima and Kral, 1984a); especially see Zagorodnyuk (1992c), who tabulated chromosomal traits of 63 species of Arvicolini and discussed their taxonomic and geographic patterns. Molecular studies have broadly addressed phylogenetic questions, including allozyme variation (Chaline and Graf, 1988; Gill et al., 1987; Graf, 1982; Mezhzherin et al., 1993, 1995; Moore and Janecek, 1990), albumin evolution (Nikoletopoulos et al., 1992), and DNA, whether hybridization comparisons (Catzeflis, 1990; Catzeflis et al., 1987; Din et al., 1993), interspersed repetitive elements (Modi, 1996; Vanlerberghe et al., 1993), or mitochondrial and nuclear gene sequences (Conroy and Cook, 1999; Martin et al., 2000; Michaux and Catzeflis, 2000; Michaux et al., 2001b). Although morphological data has historically formed the foundation for defining Arvicolinae, this body of molecular data robustly supports the subfamily’s monophyly.
Notwithstanding the proliferation of family-group names, practically a one-to-one correspondence with recognized genera, suprageneric relationships remain somewhat ambiguous—e.g., compare the tribal contents of Ognev (1963), Hooper and Hart (1962), Kretzoi (1969), Gromov and Polyakov (1977), and Repenning (1992). The instability of tribal limits is mirrored in the irresolvable polytomies disclosed in phylogenetic evaluation of mitochondrial DNA sequences, suggesting rapid taxonomic diversification over a short time period (Conroy and Cook, 1999). In general, we follow McKenna and Bell (1997) for tribal affiliations (Table 1) and provide explanations for departures from their taxonomic scheme. We observe Ketzoi’s (1969) Myodini, type genus Myodes, for most arvicolines with rooted molars and simple molar patterns. In the following generic and specific remarks, therefore, readers should understand that wherever we use Myodes or Myodini the cited publications generally refer to Clethrionomys (or Evotomys) and Clethrionomyini.