Sylvaemus group. A close relative of A. mystacinus, which has been considered the sole member of Karstomys, although Musser et al. (1996) placed it in their Sylvaemus Group, a relationship weakly to strongly corroborated by allozymic studies (Filippucci et al., 2002; Mezhzherin, 1997a) and phylogenetic analyses of nuclear IRBP and mtDNA cytochrome b and 12S rRNA sequences (Michaux et al., 2002a, in press). Described as a species and listed that way by Ellerman (1941) but subsequently treated as a subspecies of A. mystacinus (Ellerman and Morrison-Scott, 1951; Corbet, 1978c; Musser and Carleton, 1993; Pavlinov et al., 1995a). Based on morphology and biochemical genetic variation data, Mezhzherin (1997a) separated epimelas as a species separate from A. mystacinus, an action supported by phylogenetic analyses of protein electrophoresis of 28-38 gene loci (Filippucci et al., 2002) and mtDNA cytochrome b and 12S rRNA sequences (Michaux et al., 2002a). That the Balkan epimelas was a different species than the Anatolian mystacinus was indicated in Mitchell-Jones et al. (1999), and the basic discriminatory data was provided earlier by Storch (1977; who also wrote the account in Mitchell-Jones et al., 1999) who documented the significant differences between the two in occlusal patterns of M1 and M2 (posterior cingulum is free in most epimelas, but coalesced with cusp t8 in mystacinus); we verified these contrasts in series from Greece, Montenegro, and Turkey in USNM. Karyotype of Macedonian sample recorded and compared with published karyotypes from other regions (Zima et al., 1997a, as mystacinus). Greek samples of A. epimelas (recorded as mystacinus), A. sylvaticus, and A. flavicollis contrasted using data from electrophoretic and immunological sources (Fraguedakis-Tsolis et al., 1983).

Apodemus epimelas may represent a population of A. mystacinus that dispersed across a Pleistocene Bosporous land bridge (between Balkan Peninsula and Turkish Thrace plus NW Anatolian Turkey) 20,000-10,000 years before present and achieved genetic isolation after post-Pleistocene sea level rise reconnected the Black and Marmara Seas through the Bosporous channel (Hosey, 1982). Michaux et al. (2002a) suggested the isolation of Balkan and Near East groups of A. mystacinus and the subsequent differentiation of A. epimelas resulted from late Pliocene or early Pleistocene cooling intervals associated with low population densities.