Darwin’s finches are seen evolving in real time on Galapagos creating an entirely new species
Around 36 years ago, a strange bird arrived on one of the Galapagos islands. He sang a different song to the other birds, and his body and beak were unusually large compared to all the other birds.
Soon the bird made himself at home, and despite their differences, he was able to woo one member of the island’s inhabitants. The two birds mated, and their offspring started a brand new species all in real time, in front of the scientists’ eyes. That species now has 30 members, according to a study published in Science.
Researchers at Princeton University and the University of Uppsala have been studying the finches on the Galapagos Islands in the Pacific Ocean for decades. In 1981, a graduate student noticed the newcomer because he was singing an unusual song and had a larger beak than the rest of the birds.
“The novelty of this study is that we can follow the emergence of new species in the wild,” said B. Rosemary Grant, a senior research biologist in the Department of Ecology and Evolutionary Biology at Princeton. “We were able to observe the pairing up of two birds from different species and then follow what happened to see how speciation occurred.”
The graduate student was on the Galapagos island called Daphne Major when he noticed the bird. “We didn’t see him fly in from over the sea, but we noticed him shortly after he arrived. He was so different from the other birds that we knew he did not hatch from an egg on Daphne Major,” said Peter Grant, who was also present when the bird was first discovered.
The scientist took a sample of blood from the bird before releasing him. The bird then went on to breed with a ground finch of the species Geospiz fortis, initiating a new lineage – which they named the Big Birds. The research team followed the new species for six generations, taking blood samples for genetic analysis.
In the latest study, researchers from Uppsala University studied DNA collected from the parent birds and their offspring at regular intervals. It turns out the original male parent was a large cactus finch of the species Geospiza conirostris from Española island, which is more than 100 kilometers (about 62 miles) from Daphne Major.
Because his home was so far away, he did not have the choice to go home. Instead, he settled on one of the three finch species on the island. This shows how important geographical isolation is when it comes to creating new species.
The offspring were also reproductively isolated because their song, which is used to attract mates, was unusual and failed to attract females from the resident species. Because of this, they mated with their own species.
Researchers had thought it took a long time to form a new species, but in this case it happened in just two generations.
“It is very striking that when we compare the size and shape of the Big Bird beaks with the beak morphologies of the other three species inhabiting Daphne Major, the Big Birds occupy their own niche in the beak morphology space,” said Sangeet Lamichhaney, a postdoctoral fellow at Harvard University and the first author on the study. “Thus, the combination of gene variants contributed from the two interbreeding species in combination with natural selection led to the evolution of a beak morphology that was competitive and unique.”
New lineages like the Big Birds have originated many times during the evolution of Darwin’s finches, the authors say. Most of these will have gone extinct, but some may have led to the evolution of contemporary species.
“We have no indication about the long-term survival of the Big Bird lineage, but it has the potential to become a success, and it provides a beautiful example of one way in which speciation occurs,” said Leif Andersson, a professor at Uppsala University.. “Charles Darwin would have been excited to read this paper.”