Sylvaemus group. Reviewed by Storch (1977) and Niethammer (1978a), who included krkensis as a subspecies; that form, however, is a color phase of A. sylvaticus (see that account). Usually regarded as sole member of subgenus Karstomys, but included in a Sylvaemus Group by Musser et al. (1996); placed in subgenus Karstomys of genus Sylvaemus by Mezhzherin (1997a) and Pavlinov et al. (1995a), but in an "Apodemus group" by Liu et al. (2004). Electrophoretic analyses of allozyme variation indicated A. mystacinus (and A. epimelas) to be a distinct species justifiably placed within subgenus Sylvaemus (Britton-Davidian et al., 1991; Filippucci, 1992; Filippucci et al., 2002; Gemmeke, 1980; Mezhzherin et al., 1992). Data from nuclear IRBP and mtDNA cytochrome b and 12S rRNA sequences also indicated weak affinity with Sylvaemus (Michaux et al., 2002a), as did analyses of cytochrome b haplotype divergences (Reutter et al., 2003), but not complete mtDNA cytochrome b sequences (Liu et al., 2004). Vorontsov et al. (1989) provided chromosomal data in context of defining species of Apodemus in the Caucasus. Formerly included the Balkan epimelas, which is now treated as a separate species (see that account). Sequences from mtDNA cytochrome b and D-loop and the IRBP nuclear gene identified two distinct clades within A. mystacinus, one occupying NW and E Turkey, and the Near East, the other inhabiting SW Turkey and the island of Crete (Michaux et al., in press).

Remains of A. mystacinus were uncovered from subfossil cave deposits in S and E Anatolia (Corbet and Morris, 1967; Kock et al., 1972) as well as middle Pleistocene (Storch, 1975) and Holocene (Besenecker et al., 1972) sediments on the Aegean island of Khios. Fossils are also common in middle Palaeolithic assemblages from Lebanon (Kersten, 1992) and date back to middle Pleistocene in other parts of the Levant (Tchernov, 1968, 1986, 1992, 1994).