Galapagos Finch Flies to Distant Island, Mates With Birds There, Forms New Species

A large cactus finch, like the one who grandfathered a new species. Wildlife Travel on Flickr

Darwin's finches are icons of evolution. Now, researchers have discovered how quickly they can evolve into a new species: with the help of an outside bird, a new species can develop in as little as two generations.

Finches on the Galapagos Islands represent many species, but are collectively known as "Darwin's finches." Their isolation makes them ideal to study, and researchers at Princeton University and Uppsala University have been focusing on the birds in the small Galapagos island of Daphne Major.

They noted that a bird from another island had flown to Daphne Major 36 years ago. Students at the island took a blood sample of the new bird, who was larger and had a different song than the native birds, and identified him as a large cactus finch.

He then mated with other birds on the island, fathering hybrid fledglings. Those hybrids were able to mate with each other, and in spite of the severe inbreeding, the resulting offspring thrived. Scientists have sequenced their blood and found that they are a genetically distinct species from the medium ground finches that are native to Daphne Major. The study was published in the journal Science.

This is especially surprising because evolution is known as extremely gradual change over time. As environmental pressures select for an animal with certain traits, such as an ideal beak shape, more and more of the population will have that trait. But in this case, all it took was a stranger bird and a lot of incestuous mating.

However, they're not the first new species to form from hybridization. Many animals today have a genetic history of hybridizing, borrowing genes from similar species' to form new populations. In fact, hybrid "coywolves" and "grolar bears" could be the future of coyote, wolf, grizzly, and polar bear populations.

It's also surprising to someone who may define "species" by their inability to create fertile offspring with members of other species'. However, there are many different definitions of "species," and the lines are blurry in the scientific community.

In the case of the new finch species, their isolation from other birds was tantamount. The male large cactus finch was unable to fly home, being too far away, otherwise he might have chosen a member of his own species to mate with. His offspring, too, were isolated, and because their songs were different than the native birds, they were more likely to just mate with each other than to seek out native sexual partners.

Evolution isn't always as gradual as we thought, and a single foreign bird can change everything.