Small songbirds in the Galapagos islands known as Darwin’s finches are the subject of new research that is studying evolution and the shaping of beaks. Although it is more than 150 years since Charles Darwin proposed the theory of evolution, the small finches that helped shape his thinking are still in the process of evolving. Scientists have now identified the gene involved.
The paper, published in the journal Science last Thursday, describes a severe drought that struct the Daphne Major Island a decade ago and left the finches in fierce competition over scarce seeds. Two species, the medium ground finch and the large ground finch were left in a battle for seeds. Smaller seeds were left to the birds with smaller beaks, who thrived as the larger finches died off due to scarce food supplies. The tendency for smaller beaks continues today.
The researchers found that beak size variations are due to the HMGA2 gene. The genomes of the birds that survived the drought have variations of that gene that are associated with smaller beaks. The variation of the gene that causes larger beaks is not extinct, and there are currently 18 different species of finches across the Galapagos islands.
Leif Andersson, an animal geneticist from Uppsala University in Sweden and leader of the new study, says that different ecological pressures may lead to a resurgence of larger-beaked birds, through the process of natural selection. It will depend on which birds can best forage for food and reproduce.
A gene involved in the beak shape of Darwin’s birds was also identified by the researchers last year. Variations of the ALX1 gene relates to either pointed or blunt beaks.
Andersson says that Darwin’s finches are “a model for evolutionary biodiversity on Earth.” Different lineages of these little birds diverged in order to take advantage of different resources on the islands. Differently shaped and sized beaks would have allowed the finches to eat different seeds.
Interestingly enough, the HMGA2 gene is the same part of the genome that is associated with the stature of humans.