Darwin’s inspiration for evolutionary theory came from his observations of the fascinating creatures inhabiting the Galápagos archipelago and Cocos Island. Darwin noted that the finches in particular had specific adaptations, allowing them to inhabit different niches of the islands and to eat different types of foods. The birds have become a symbol of Darwin’s genius, but how would his ideas hold up to DNA evidence, in the era of genetic testing?
A group of scientists, led by Texas A&M‘s Dr. Leif Andersson of the Veterinary Medicine & Biomedical Sciences, collaborating with Uppsala University in Sweden, has published a study in the journal Nature confirming and adding to Darwin’s classification of the finches. This occurred on February 11th, the day before the 206th anniversary of Charles Darwin’s birth.
The beaks of the finches were of particular interest to Darwin, since changes in the size and shape of the beak allowed different finches to eat either insects, seeds, nectar from cactus flowers, or even blood from marine iguanas inhabiting the Galápagos.
Sangeet Lamichhaney, a Ph.D. student at Uppsala University and shared first author on the paper remarked, “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.”
Lamichhaney continued, “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.”
“The most thrilling and significant finding was that genetic variation in the ALX1 gene is associated with variation in beak shape not only between species of Darwin’s finches but also among individuals of one of them, the medium ground finch,” Andersson said.
“During our field work on the Galápagos we have observed many examples of hybridization between species of Darwin’s finches but the long-term evolutionary effects of these hybridizations have been unknown,” said Peter and Rosemary Grant of Princeton University, a married team who are world experts on the finches, and have lived and worked on the Galápagos for over 40 years.
“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,” Grant remarked.
“This is a very exciting discovery for us since we have previously shown that beak shape in the medium ground finch has undergone a rapid evolution in response to environmental changes,” Rosemary Grant said. “Now we know that hybridization mixes the different variants of an important gene, ALX1.”
“This is an interesting example where mild mutations in a gene that is critical for normal development leads to phenotypic evolution,” Andersson said. “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.”