COLLEGE STATION, Texas – Long and pointy, short and blunt, large and prominent: these are just a few of the beak variations of Darwin’s finches. Beaks are not only highly variable among species, but also they are shaped by evolution. In a study published in Science, a research team led by Leif Andersson, professor at the Texas A&M; College of Veterinary Medicine & Biomedical Sciences and Uppsala University in Sweden, has discovered a gene-HMGA2-affecting the variation in beak size in Darwin’s finches.
Previously, the team discovered that the ALX1 gene affects beak shape, specifically whether the beak is pointed or blunt. Both studies help unveil the genetic basis of the beak variation in Darwin’s finches and further explain this iconic example of evolutionary adaptation.
“Our data shows that beak morphology is affected by many genes, as is the case for most biological traits,” Andersson said. “However, we are convinced that we now have identified the two loci with the largest individual effects that have shaped the evolution of beak morphology among Darwin’s finches.”
Aptly named, Darwin’s finches greatly influenced Charles Darwin’s theory of evolution through natural selection. The finches descended from a common ancestor, which arrived in the Galápagos Islands about two million years ago. Since then, the finches have evolved into 18 species, differing in body size, beak shape, song, and feeding behavior. Variations in beak size and shape allow the different species to consume different foods, such as insects, seeds, and nectar.
Specifically, the researchers compared the medium ground finch and the large ground finch on Daphne Major Island in the Galápagos. The average beak size in the medium ground finch was reduced following a drought because birds with a large beak could not compete well with the large ground finch. Having two different beak sizes allowed the two species to use different food sources, reducing competition for a single food source. The team now demonstrates that the HGMA2 gene played a prominent role in this rapid evolution.
The HMGA2 gene is known to play a role in body size in dogs and horses as well as height in humans.
“The HMGA2 gene regulates the expression of other genes, but the exact mechanism how it controls beak size in Darwin’s finches or human stature is unknown,” Andersson said. “It is very fascinating that this gene pops up in many different species as a gene affecting growth. In humans is also a gene affecting dysregulated cell growth in cancer, and it is clear that more research to better understand the function of the gene is well justified.”
“Dr. Andersson’s research is not limited to discovering genes, but extends deeply into the biology of inheritance and adaptation,” says Evelyn Tiffany-Castiglioni, head of the Department of Veterinary Integrative Biosciences at Texas A&M; University. “This new paper is an elegant example of how the function of a gene can play a role in survival of a bird lineage when the environment changes. It will undoubtedly shed light in future on how this gene and others influence growth and body size of important domestic animal species.”
Andersson has been a Texas A&M; University Institute for Advanced Study (TIAS) Faculty Fellow-one of the nationally and internationally renowned scholars invited by the Institute to come to the campus for extended stays to teach, conduct research, and interact with Texas A&M; students and faculty.