The finches of the Galápagos islands (Archipiélago de Colón) have an important place in the history of biology. It was the study of finches that led to Darwin’s work on natural selection. The Galápagos Islands today, together with their surrounding waters, form an Ecuadorian province, a national park, and a biological marine reserve.
New research has found that the variations in beak among the species of Galápagos finches is the result of a single gene that has been shaped through interbreeding between different species. To show this, scientists sequenced the full genomes of 120 birds representing the 14 defined Galápagos finch species, a related species from nearby Cocos Island, and two other related species from the Caribbean. By comparing the genomes of two species with blunt beak with those from two pointy-beaked species, biologists revealed 15 genomic regions that were linked to the shape of the beak.
The most important finding was that there were two variants of a single gene called ALX1. This gene had an ancestral version associated with pointed beaks and a derived variant correlated with blunt beaks. Commenting on this finding, lead researcher Dr. Leif Andersson of Uppsala University explained to the BBC: “There are multiple genes that contribute. But we think that ALX1 is one of the most important, if not the most important factor that has changed on the island.”
The fascinating thing about the ALX1 gene is that when it mutates in humans, the mutation can lead to cleft palate and skull malformation With the gene and finches, variations were apparent not only among species but within them, as well. These differences revealed that recent and rapid changes in the usually blunt shape of the medium ground finch beak were the result of interbreeding with other finch species.
The genomic data raised some questions about current species classifications. Two species: the sharp-beaked ground finch (Geospiza difficilis) and the large cactus finch (Geospiza conirostris) were found to have been wrongly classified. In addition, a new species was found. The end result was that the total number of Galápagos finch species was actually 17 rather than the assumed number of 14.
The study was undertaken by scientists based at the Uppsala and Umeå Universities in Sweden and from Princeton University. The findings have been published in the journal Nature. The research paper is “Evolution of Darwin’s finches and their beaks revealed by genome sequencing.”
