Scientists spotted some evolution in action. A team of scientists identified a gene that explains variation in beak size among Darwin's finches. In fact, it's this gene that contributed to a rapid shift in beak size of the medium ground finch following a drought.
Darwin's finches are a classic example of adaptive radiation. These finches, from the Galapagos Islands, all evolved from a single common ancestor that arrived in the area about 2 million years ago. As years passed, this finch evolved into 18 distinct species that differed in size, beak shape, song and feeding behavior.
A previous study showed that the ALX1 gene controlled beak shape. Now, though, scientists identified a new gene that impacts beak shape, known as HMGA2.
HMGA2 has previously been associated with a variation in body size in dogs and horses. It's actually a trait that's affected by hundreds of genes. Now, though, scientists found it also affects the beak shape of finches.
"We previously documented that the average beak size of the medium ground finch population became smaller during this drought due to a high mortality among individuals with large beaks because they could not compete well with the large ground finch," said Peter and Rosemary Grant, researchers that carried out fieldwork on the Galapagos during a 40-day period. "Now we have demonstrated that the HMGA2 locus played a critical role in this evolutionary shift and that natural selection acting on this gene during the drought is one of the highest yet recorded in nature."
In fact, this gene is likely what allowed the birds to evolve so rapidly in response to changes in climate. By diversifying, birds were able to survive. With that said, researchers are still studying exactly how the HMGA2 gene regulates the expression of other genes and how it controls beak size.
"It's very fascinating that this gene pops up in many different species as a gene affecting growth, and in humans also as a gene affecting dysregulated cell growth in cancer," said Leif Andersson of Sweden's Uppsala University and leader of the new study. "It is clear that more research to better understand the function of this gene is well justified."
The findings were published in the edition of the journal Science.
