Often considered conspecific with Yellow-breasted Brush-finch (Atlapetes latinuchus), and both were originally considered part of a wider complex that included also Vilcabamba Brush-finch (Atlapetes terborghi) and Black-faced Brush-finch (Atlapetes melanolaemus), although recent studies suggest that various components of this group may not be each other's closest relatives. It has been suggested that all of these the species, and also Slaty Brush-finch (Atlapetes schistaceus), are related in a complex manner, with yellow coloration lost or gained in a leap-frog pattern, such that taxa which do not look alike may in fact be closely related to each other. One specimen of present species from La Paz exhibits dark scalloping on breast, approaching Black-faced Brush-finch (Atlapetes melanolaemus). It is unclear if this is a variation in nominate subspecies or due to gene flow between the two species. Name "Buarremon melanops" refers to specimens apparently assignable to nominate form of present species.
The following 2 subspecies are recognised:
rufinucha (Lafresnaye & D'Orbigny, 1837) - Subtropical zone of Andes of La Paz and Cochabamba, in west-central Bolivia.
carrikeri Bond & Meyer de Schauensee, 1939 - Andes of Santa Cruz, in central Bolivia.
BirdLife International Species Factsheet