Deconstructing the high-Andean sigmodontine Abrothrix andina (Rodentia, Cricetidae): taxonomic insights from northwestern Argentinean and western Bolivian populations

Abrothrix andina is traditionally regarded as a widespread Andean sigmodontine rodent, with several nominal forms described from Argentinean, Chilean, and Peruvian populations considered junior synonyms. Recent studies, however, have demonstrated that topotypes of the Argentinean nominal form Akodon gossei, are deeply divergent from the Peruvian Akodon andinus polius, challenging their proposed conspecificity. In this study, cytochrome b sequences from samples attributed to A. andina from the provinces of Jujuy (including topotypes of the nominal form Akodon jucundus), Salta, and Tucumán (Argentina), and Oruro (Bolivia) were phylogenetically analyzed. The results suggest that the sequence from Tucumán corresponds to Abrothrix gossei, while sequences from Jujuy, Salta, and Oruro cluster with those from northern Chile (referred to the nominal form Hesperomys dolichonyx) and southern Peru, constituting a clade resolved as part of Abrothrix olivacea. These findings highlight an emerging taxonomic and nomenclatural scenario. Although the definitive analysis of typical A. andina from the central Chilean Andes remains pending, the available evidence strongly supports the synonymization of the nominal forms cinnamomea, dolichonyx, jucundus, and polius under A. olivacea. Furthermore, it is likely that A. andina itself should also be included in this synonymy. Conversely, Abrothrix gossei merits recognition as a distinct species, sister to A. olivacea, with a range extending from Mendoza to, at least, Tucumán in Argentina.