image: The most characteristic feature of Darwin's finches is the diversification of beak morphology that has allowed these species to expand their utilization of food resources in Galápagos, here illustrated by the gray warbler finch (Certhidea fusca) that has a small, pointed beak and feeds on insects; the common cactus finch (Geospiza scandens) that has a large, pointed beak and feeds on medium-sized seeds and cactus pollen; and the large ground finch (Geospiza magnirostris) that has a large, blunt beak and feeds on large seeds. Variation in beak morphology among these species is determined by the action of many gene variants but two genes with particularly important effects have now been identified, HMGA2 that affects beak size and ALX1 that controls beak shape. HMGA2*L and HMGA2*S promote the development of large and small beaks, respectively, while ALX1*P and ALX1*B are associated with the development of pointed and blunt beaks, respectively. This material relates to a paper that appeared in the April 22, 2016 issue of Science, published by AAAS. The paper, by S. Lamichhaneyat Uppsala University in Uppsala, Sweden, and colleagues was titled, "A beak size locus in Darwin's finches facilitated character displacement during a drought." view more
Credit: Photo © B. Rosemary Grant