Re-evaluation of species limits in the genus Atlapetes based on mtDNA sequence data

Brush-finches of the genus Atlapetes present a complicated pattern of differentiation along the Andes. Forms with different colours may replace each other sharply at different altitudes on the same slopes, in similar humid habitats on different slopes or on adjacent humid and semi-humid slopes. In the current classification, grey and yellow-and-green species are placed in different groups, and similar-coloured populations replacing each other in corresponding ecological zones on different slopes are ranked as subspecies of the same species. However, Remsen and Graves have suggested that different-coloured forms inhabiting adjacent mountains could be representatives of the same species with different pigment saturations, rather than competing species. The relationships between and within Atlapetes species are assessed based on mtDNA sequence data. Three main branches are demonstrated, comprising southern (Bolivian, northwest Argentinean), central (south and central Peruvian) and northern/western species. Clearly, the traditional groupings based on plumage colours did not demonstrate evolutionary trajectories in the genus. The data also show that many forms, currently ranked as subspecies, are genetically more divergent than sympatric species. Species rank is suggested for several forms hitherto treated as subspecies of geographically disjunct species.