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| With nearly 30 species, the Atlapetes brush-finches are one of the most species-rich genera in the New World sparrows (Passerellidae). Atlapetes is mainly distributed in highland forests from Mexico to north-western Argentina, with a few taxa in the foothills (<1000 m). Species diversity is highest in South America, because of high rates of local replacement but few cases of local co-occurrence, creating a mosaic of forms with different plumage colours. With the purpose of understanding phylogenetic and environmental determinants of trait evolution, we reconstructed a molecular phylogeny based on full ND2 mtDNA sequences, with focus on the core group of Andean Atlapetes species and related outgroups. Phylogenetic relationships revealed that most Andean species are closely related to a geographical neighbour, although these neighbours may often be phenotypically quite different, with yellow-plumaged species sister to grey-plumaged taxa. Biogeographic analyses suggest Mesoamerica as the area of origin for Atlapetes, which dispersed through the Panama Isthmus to the eastern Andean slope, then the western Andes and finally the southern Andes. Diversification in the genus was apparently influenced by the glacial cycles that affected the distribution of montane forests in the Neotropics, particularly during the last million years. Phenotypic plumage changes may be associated with ecological conditions, with black dorsum in the wettest areas and a pale dorsum in a group of closely related species in dry environments on the Pacific slope. Local sympatry and ecological segregation presumably does not lead to increased divergence in plumage signals or song. | |
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