Darwinfinkar: About the emergence of a new species

2017-11-28

The Darwinfinkar family on the Galapagos Islands is an iconic model for the appearance of different species on our planet. A group of researchers from Uppsala University and Princeton now report that they were able to document how a new species of these birds occurred. The new species developed after two different species of Darwin finches hybridized almost 40 years ago.

The observation of this art formation was done during field studies on the small island of Daphne Major, conducted by Rosemary and Peter Grant, Princeton University, for a period of 40 years. In 1981, they discovered a strange male who deviated from all other species on this island in terms of song and size. The male formed pairs with one of the field finches nesting on the island. This became the start of the development of the specific population that they named Big Birds because of their size. DNA sequence analysis now shows that the foreign male was a cactus fin that nestles on the island of Española, located more than 100 km southeast of Daphne Major.

"A critical step for the development of a new species is that it develops reproductive isolation or it will simply be absorbed by any existing species. This process is usually expected to require a relatively long time of genetic isolation, but in this case this developed for a few generations, says Rosemary and Peter Grant.

An important explanation why Big Birds so quickly formed its own population that did not hybridize with other species on Daphne Major was the unique song the strange male sang because the sons learn to sing as their fathers, and the daughters form pairs of males singing as their fathers. Another important reason is that Big Birds differs from all other species in terms of the beak's appearance, which is another important factor for the Darwin finches partner trap.

 All 18 different species of Darwin finches have evolved from a common origin that came to Galapagos 1-2 million years ago. Their development and, in particular, changes in the shape of the beak have meant that they have been able to specialize in different food resources. Another important component of a species formation process is that the new species can successfully compete with other species, as is the case with these Big Birds.

"It is very striking that when we compare the shape and size of the beak with Big Birds with other species, it clearly distinguishes itself from the three other species that breed on Daphne Major. This indicates that combinations of hereditary genes from the two hybridizing species along with natural selection contributed to the evolution of a beak shape that is unique and made Big Bird's competitive in the struggle for existence, explains Sangeet Lamichhaney, former PhD student at Uppsala University and now at Harvard University.

A classic definition of a species is that it "respects" species boundaries and if there is a hybridization between two species, the offspring are either not viable or sterile, the latter is the case for horse and donkey. In recent years, however, more and more scientific studies have documented a significant flow of flow between certain closely related species. The authors of this article have previously reported that there has been significant hybridization between different species of Darwin finches for thousands of years.

"The important discovery now is that hybridization between two different species of Darwin finches has given rise to a population that, after a few generations, emerges as a whole new species. If a biologist had come to Daphne Major and discovered Big Birds without knowing about their history then they would definitely have been classified as one of four species that nest on this island. The study illustrates the importance of long-term studies of natural populations, which made this discovery possible! says Leif Andersson at Uppsala University, SLU and Texas A & M University.

"It is very likely that new populations like Big Birds have occurred many times during the Darwin fines evolution. Most of these have died but some may have given rise to the species we find today when visiting Galápagos. We have no idea of ​​the future fate of Big Birds, but they obviously have all the prerequisites for being a successful species, and the study is a unique example of how a new species can occur. I am convinced that Charles Darwin would have read our article with great interest, "concludes Leif Andersson.

The study published in Science: S. Lamichhaney; F. Han; M. T. Webster; L. Andersson, B.R. Grant; P.R. Grant (2017) Rapid hybrid speciation in Darwin's finches, Science, DOI: 10.1126 / science.aao4593

Galápagos National Parks Service, The Charles Darwin Foundation, the National Science Foundation, Knut and Alice Wallenberg Foundation, as well as the Swedish Research Council have contributed to the project.


Linda Koffmar

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