On Feb. 11, 2015, researchers announced they had sequenced the genomes of all 15 species of Darwin’s finches, which revealed a key gene responsible for the diversity in the birds’ beaks. The study, published in Nature, also redrew the family tree of these iconic birds, whose facial variations helped Charles Darwin to formulate his theory of natural selection.

The researchers found extensive evidence for interspecific gene flow throughout the radiation. Hybridization has given rise to species of mixed ancestry. A 240 kilobase haplotype encompassing the ALX1 gene that encodes a transcription factor affecting craniofacial. development is strongly associated with beak shape diversity across Darwin’s finch species as well as within the medium ground finch (Geospiza fortis) a species that has undergone rapid evolution of beak shape in response to environmental changes.

The ALX1 haplotype has contributed to diversification of beak shapes among the Darwin’s finches and thereby, to an expanded utilization of food resources.