Phylogeny of Darwin's finches as revealed by mtDNA sequences

Darwin's finches comprise a group of passerine birds first collected by Cha rles Darwin during his visit to the Galapagos Archipelago. The group, a tex tbook example of adaptive radiation (the diversification of a founding popu lation into an array of species differentially adapted to diverse environme ntal niches), encompasses 14 currently recognized species, of which 13 live on the Galapagos Islands and one on the Cocos Island in the Pacific Ocean. Although Darwin's finches have been studied extensively by morphologists, ecologists, and ethologists, their phylogenetic relationships remain uncert ain. Here, sequences of two mtDNA segments, the cytochrome b and the contro l region, have been used to infer the evolutionary history of the group. Th e data reveal the Darwin's finches to be a monophyletic group with the warb ler finch being the species closest;to the founding stock, followed by the vegetarian finch, and then by two sister groups, the ground and the tree fi nches. The Cocos finch is related to the tree finches of the Galapagos Isla nds. The traditional classification of ground finches into six species and tree finches into five species is not reflected in the molecular data. In t hese two groups, ancestral polymorphisms have not, as yet, been sorted out among the cross-hybridizing species.