Akodontini (S Andean clade). An assemblage of species whose level of taxonomic recognition has come full circle: early employed as a genus (Gyldenstolpe, 1932; Thomas, 1916); later viewed as subgenus of Akodon (Cabrera, 1961; Ellerman, 1941; Musser and Carleton, 1993; Reig, 1978, 1981, 1987) or even a full synonym of Microxus (Hershkovitz, 1966c); and recently reinstated to genus based on congruence of morphological, karyological, and genetic traits that set it apart from typical Akodon (Apfelbaum and Reig, 1989; Barrantes et al., 1993; Gallardo et al., 1988; Smith and Patton, 1993, 1999; Spotorno et al., 1990). See Reig (1987), Spotorno et al. (1990), and Barrantes et al. (1993) for a review of the treatment of Abrothrix and its specific contents. Sister genus to the long-clawed akodonts (Chelemys, etc.) according to cladistic interpretations of allozymic and cytochrome b data (Barrantes et al., 1993; D’Elía, 2003; D’Elía et al., 2003; Smith and Patton, 1993, 1999).
Working with N species of the S Andean clade (i.e., jelskii and andinus), Patton et al. (1989; and later Smith and Patton, 1991, 1993, and Patton and Smith, 1992) conveyed their genetic divergence and cladistic separation by employing the local genus-group taxon Chroeomys (type species in Perú). Described as a genus (Thomas, 1916c), Chroeomys, like Abrothrix, was afterwards conventionally viewed as a subgenus of Akodon (Cabrera, 1961; Ellerman, 1941; Gardner and Patton, 1976; Reig, 1987) until the studies of Patton and Smith. Although Smith and Patton (1999) have continued to recognize Chroeomys as a genus (including jelskii but not andinus which they returned to Abrothrix), their own gene-sequence analyses consistently nest jelskii among species of Abrothrix, not basal to them. These results, together with the persuasive body of evidence cited above, recommend the junior synonymy of Chroeomys.