After the introduction of a new species of finch, a hybrid finch variant developed closed breeding, meaning that it is a separate species - the first ever seen example.
Finches in the Galapagos Islands have evolved into a new species, which is the first example ever seen by scientists, effectively making the theory of evolution an empirically measurable theory. Prior, the theory primarily relied on fossil records and species hybridisation, though an existing species had never been observed evolving into an entirely new species.
After decades of hybridisation, a group of finches on the Daphne Major island in the Galapagos Island chain developed closed breeding.
The various groups of finches in the Galapagos had been aptly named ‘Darwin’s finches’ to commemorate Charles Darwin, the famous scientist who developed his theory of evolution by way of natural selection after spending time on the islands, one of the most biologically diverse places in the world, and observing the species, especially the finches which he wrote about extensively in his personal journals.
Scientists note that in 1981, a male large cactus finch that is believed to have come from the nearby island of Espanola, mated with a native finch on Daphne Major and produced offspring.
"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," Princeton zoology professor Peter Grant told Phys.org.
This gave rise to a population of finches, about 30 of them, that are distinctively different in appearance and behavior on the island of Daphne Major. This population has been called the ‘Big Bird’ group by zoologists and researchers.
Professors Rosemary and Peter Grant of Princeton University collaborated with Prof Leif Andersson of Sweden's Uppsala University to genetically analyze the mixed-species population, and published their findings in Science journal on Nov. 23.
“From the second generation onwards the lineage bred endogamously, and despite intense inbreeding, was ecologically successful and showed transgressive segregation of bill morphology,” they wrote. “This example shows that reproductive isolation, which typically develops over hundreds of generations, can be established in only three.”
This is a remarkable observation which is demonstrated by the fact that native females do not recognize the mating calls of the new species, which is a form of behavioral isolation, meaning that the two species can no longer breed and are distinct.
"The surprise was that we would expect the hybrid would start to breed with one of the other species on the island and be absorbed,” Andersson told the BBC. “We have confirmed that they are a closed breeding group."
Even more remarkably, hybrid species have been long believed to be sterile, meaning that they are unable to reproduce and become a viable species, however this observation demonstrates that it is possible.
Ironically, the discovery was published on the eve of the anniversary of the publication of Charles Darwin’s magnum opus titled "On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life", which was released in 1859 and largely inspired by his time on the Galapagos Islands.