The Galápagos island birds known as Darwin's finches are famous as examples of how natural forces can drive the evolution of new species. Now Princeton University researchers have used genetic markers to describe the finches' first molecular family tree.
"This is one of the most important groups for our understanding of adaptive radiation," the process by which a species differentiates to fit different niches, says University of British Columbia evolutionary biologist Dolph Schulter. "It seems incredible that we've not had a molecular phylogeny by now" to match the phylogeny based on physical traits that was developed in the 1940s.
Described by Charles Darwin 140 years ago, the 14 species of finches vary widely. Classic finch types have short, stout beaks good for breaking seeds, while warblerlike species sport long, narrow beaks for insect eating.
Researchers have had little success verifying the finch family tree with allozymes or mitochondrial DNA, because the time scale of this radiation, less than 3 million years, is too short. But now evolutionary ecologist Kenneth Petren, with Peter and Rosemary Grant, have examined 16 microsatellite markers on genomic DNA drawn from the birds' blood. The markers "show variation on exactly the correct time scale" for distinguishing between species, says Petren. The new results, published in the 22 February Proceedings of the Royal Society B, also support the notion that the ancestor of all Darwin's finches resembled the pointy-beaked warbler finch.
