Radiation Revised

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Science  16 Aug 2002:
Vol. 297, Issue 5584, pp. 1095
DOI: 10.1126/science.297.5584.1095d

With their diverse bill shapes and ecological habits, Darwin's finches—13 species from the Galápagos Islands and 1 from Cocos Island—serve as a classic example of adaptive radiation. Understanding the evolution of the group and its morphologies has been handicapped by a lack of agreement about these finches' closest living relatives.

Burns et al. analyzed cytochrome b mitochondrial DNA sequences from the finches, sister taxa, and potential outgroups within the finch-tanager tribe. Darwin's finches form a clade within a larger, well-supported monophyletic group of species that build domed nests. Most of these close relatives are endemic to Caribbean islands and not found in South America. The relatives have a diversity of bill morphologies and feeding behaviors similar to those of Darwin's finches, and this diversity also evolved rapidly. The parallel courses may reflect strong selection as birds colonized islands with vacant niches, a developmental-genetic architecture inherited from the common ancestor, or both. In any case, it appears that the key change in the clade's history occurred before its arrival in the Galápagos. — ShJS

Evolution56, 1240 (2002).

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