Beak size matters as Darwin’s finches continue to evolve

Beak size matters as Darwin’s finches continue to evolve

Researchers witness evolutionary process first hand. PHOTO: Peter R. Grant

A team of biologists living and working in the Galapagos Islands have witnessed the evolution written about by Charles Darwin first hand, in the very finches Darwin noted in his time spent in the area, according to the Washington Post.

Peter and Rosemary Grant were doing research on Daphne Major Island, which is home to two species of birds, some cacti, and very little else, some ten years ago when a drought devastated the area, resulting in a food shortage for the birds.  They noted the smaller-beaked medium ground finches were living longer than their larger-beaked family members.  Over the period of about a year, the couple noted the beak size of the medium ground finches had shrink noticeably.

The Grants were able to determine by looking at the DNA of the surviving birds as well as those who perished, the survivors were more likely to have a version of the HMGA2 gene that led to developing smaller beaks.  In other words, the small-beak variation of the gene saved the birds.

In finches, the HMGA2 gene appears to be a primary factor in determining beak size, but the gene also appears in dogs, horses and even humans, playing a part in the body size and stature of each animal.  Exactly how it works it not yet understood, but the Grants believe what they have witnessed during the drought period is likely one of the most fascinating examples of natural selection ever noted.

The Grants, both emeritus professors at Princeton University, and their colleagues at Uppsala University in Sweden, published a study last year that reported on the sequencing of the DNA of 120 birds to study the amount of variation between them.  In that work, they were able to determine the birds had been evolving, interbreeding and responding to their environment for over two million years, since their first ancestors arrived on the islands.

The couple have even witnessed a hybridization event themselves, when in the 80s, a bird that had migrated to the area and which they named Big Bird, mated with an established inhabitant medium ground finch, and produced an offspring that has now produced seven generations.  They stopped short of saying the hybrid is a new species, because they fear the line will die off due to “fitness problems.”

The Grants published their findings in the journal Science earlier this week.



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