Growth Factor Gene is Responsible for Bill Size in Finches

Growth Factor Gene is Responsible for Bill Size in Finches

Researchers at the University of California identified the trait responsible for evolutionary changes in the beak of finches.

Researchers spent several years investigating on the reason behind the varied sizes of beaks inPyrenestes ostrinus, a Cameroonian finch. Tom Smith, ornithologist and biologists, professor at UCLA as well as the founding director of the Center for Tropical Research, along with his colleagues identified differences of the finches’ beak size to the hardness of the seeds it eat. They found that larger beak was the dominant trait while smaller beaks were the recessive trait in finches, perfecting the theory of Gregor Mendel as 3:1 pattern in the offspring of dominant and recessive trait finches.

However, Princeton biologist Bridgett vonHoldt discovered that the ‘mega’ morph of the black-bellied seedcrackers finch, appears to result from an additional evolutionary step after the evolution of the large beaked finch. Using new technology to analyze the entire genome of the finch, vonHoldt compared the genes of the large-beaked birds to those of their smaller-beaked counterparts.

She observed that the gene IGF-1 was responsible for triggering growth of the beak of those finches. “In dogs, this is a giant gene, literally and figuratively,” she said. “It’s a growth-factor gene. In dogs, if you change how it’s expressed, with just a few genetic changes you can change a normal-sized dog into a dwarfed, teacup-sized dog.”

The researchers found that in finches only its bills were changing size, while the rest of the body remained unaffected due to the gene IGF-1. Smith found a third morph of these finches, which he called the “mega” variety, with an even bigger bill and a larger overall body size. The findings were published in the journal Nature Communications on November 19, 2018.