A NEW SPECIES WHICH APPEARS IN TWO GENERATIONS

«Charles Darwin would have loved to read this research», the authors say. For four decades, Rosemary and Peter Grant, an adorable couple of scientists from Princeton University (New Jersey, USA), are studying the finches that live in the remote Galapagos Islands in the Pacific Ocean. They are the birds that inspired the father of the theory of evolution in the nineteenth century and it seems that they still have a lot to teach us about it. Researchers have discovered a new species of finch on one of the islands, Daphne Major, which surprisingly originated in just two generations.

As explained in the journal "Science", the story began 36 years ago, when a strange bird came to Daphne Major. It was a male who sang an unusual song and whose body and beak were much larger than those of the three species of finches that already existed on the small island. "We did not see him fly from the sea, but we noticed his presence shortly after his arrival. It was so different from the other birds we knew was not born from an egg in Daphne Major, "recalls Peter Grant, professor of Zoology, Ecology and Evolutionary Biology.

The researchers took a blood sample and released the bird, which was later crossed with a female ground finch resident Geospiz fortis, which gave rise to a new species. "The novelty of this study is that we can follow the appearance of new species in nature," says Rosemary Grant, biologist at the Department of Ecology and Evolutionary Biology.

The Grant and his research team followed the new lineage for six generations, taking blood samples for use in genetic analysis. In the current study, researchers at the University of Uppsala in Sweden analyzed the DNA collected from the parent birds and their offspring over the years. In this way, they discovered that the original male parent was a large cactus finch of the Geospiza conirostris species from La Española, which is more than 100 kilometers southeast of the archipelago.

Probably, the pioneer male could not return to his distant home to mate with a female of his own species, so he chose to choose a mate from among the three species that were already living in Daphne Major. This reproductive isolation is considered a critical step in the development of a new species when two usually separate species are crossed.

The descendants were also isolated reproductively because their songs, used to attract potential partners, were unusual and failed to conquer the females of the resident species. The offspring differed in the size and shape of the beak, which is an important signal for the choice of their peers. As a result, the descendants mated with members of their own lineage, which the researchers called "Big Bird," strengthening the development of the new species.

The researchers assumed until now that the formation of a new species took a long time, but this lineage happened very fast, in only two generations. In addition, it is ecologically competitive, that is, thanks to its unique and differentiated peak, it competes for food and other resources with other species. And it behaves like any other finch. "A naturalist who came to Daphne Major without knowing that this lineage has recently emerged, would have recognized him as one of the four species on the island," says Leif Andersson, a professor at Uppsala University.

The 18 species of finches existing in the Galapagos come from a single ancestral species approximately one to two million years ago. Since then, they have diversified and changes in the shape and size of the beak have allowed them to use different sources of food, such as insects, seeds, nectar from cactus flowers, and even the blood of iguanas, all driven by natural selection. .

According to the authors, it is likely that new lineages such as "Big Bird" have originated many times during the evolution of Darwin's finches. Most have become 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 a way in which speciation occurs," Andersson adds.

So long after, the Galápagos finches continue to surprise us as if they were a great natural laboratory.

Fuente: ABC