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 the Galápagos archipelago. Scientists have identified a gene that explains variation in beak size within and among species

See the source article by following the link below: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 the Galápagos archipelago. Scientists have identified a gene that explains variation in beak size within and among species