Subgenus Akodon, A. mollis species group (Hershkovitz, 1990c). Recognized as a species since its description (Cabrera, 1961; Gyldenstolpe, 1932; Moojen, 1952). Most strongly differentiated, based on cytochrome b sequences, of six Brazilian Akodon species examined by Geise et al. (2001). The single example of A. serrensis studied by D’Elía et al. (2003) is genetically (cytochrome b) most similar to Thaptomys nigrita, a finding that recommends expansion of sampling and review of the taxon’s assignment within Akodon proper.
New records of sympatry with A. cursor reported by Hershkovitz (1998), who amplified the discrimination of these two morphologically similar species (also see Liascovich and Reig, 1989). Karyotypic and morphometric separation from A. paranaensis illuminated by Christoff et al. (2000) and from A. reigi by González et al. (1998); strong genetic (cytochrome b) divergence from members of A. cursor species group confirmed by Geise et al. (2001). Hershkovitz (1990c) listed leucogula as a species, but Christoff et al. (2000) demonstrated its synonymy under A. serrensis and uncovered no basis for subspecific recognition. Morphometric variation in a local sample (Paraná, Brazil) investigated by Kosloski (1997), whose finding of two distinct phenetic groupings may relate to one of the species recently described from the region (e.g., A. paranaensis or A. reigi).