Genetic Study Of Darwin’s Finches Sheds Light On Evolutionary History Of Species

A team of scientists has conducted the genome sequencing of Darwin’s finches, and have identified a gene, which is responsible in shaping beaks of different sizes within and among species. In a study, published Wednesday in the journal Nature, scientists said that Darwin’s finches constitute an ideal model for studies of the process of new species creation as well as adaptive evolution.

According to the scientists, the common ancestors of Darwin’s finches arrived on the Galapagos islands, a group of 19 islands situated in the Pacific Ocean about 621 miles from the South American continent, nearly two million years ago. Ever since that happened, Darwin’s finches have evolved into 15 recognized species featuring different body size, beak shape, song and feeding behavior.

“We have now sequenced 120 birds including all known species of Darwin’s finches, as well as two closely related species in order to study their evolutionary history,” Sangeet Lamichhaney, a PhD student in Uppsala University in Sweden, and the study’s co-author, said in a statement. “Multiple individuals of each species were analyzed and for some species birds from up to six different islands were sampled to study variation within and between islands.”

Scientists found that gene flow between species has played a significant role throughout the evolutionary history of the Darwin’s finches. Scientists also detected hybrid species that were the result of the combination between a warbler finch and the common ancestor of tree and ground finches, a process that is believed to have occurred about a million year ago.

“Now we can safely conclude that interspecies hybridization has played a critical role in the evolution of the finches, and has contributed to maintaining their genetic diversity,” Peter Grant of Princeton University in New Jersey, and the study’s co-author, said in the statement.

Working with DNA samples collected by Grant and his wife B. Rosemary Grant, researchers identified a gene that influences beak shape by comparing the genomes of the 120 birds, all members of the 15 species of Darwin's finches. Further analysis helped researchers find another gene, called “ALX1,” which had previously been identified in humans and mice as being associated with the formation of facial features.

“This is an interesting example where mild mutations in a gene that is critical for normal development leads to phenotypic [observable] evolution,” Leif Andersson, a professor of functional genomics at Uppsala University, the Swedish University of Agricultural Sciences, and Texas A&M University, and the study’s lead author, said in a statement.

According to Andersson, the most interesting finding of the study was that the ALX1 gene varied not only between species of Darwin’s finches, but also among individuals from the same species. For example, the medium ground finch includes some birds with both blunt and pointed beaks.

In addition, the study also helps scientists better understand how genes are transferred from one species to another when individuals from two closely related species mate.

"I would not be surprised if it turns out that mutations with minor or minute effects on ALX1 function or expression contribute to the bewildering facial diversity among humans," Andersson said.