‘White-eyes’ Form New Species Faster than Any Other Bird

A family of island-dwelling birds form new species faster than any other known bird, according to a University of Kansas researcher who used modern genetic techniques to answer an 80-year-old question about how fast new bird species can form.

New data show that birds in the family Zosteropidae — commonly known as white-eyes for the ring of white feathers around their eyes — have formed new species faster than any known bird.

Some island-dwelling white-eyes have long been dubbed “great speciators” for their apparent ability to rapidly form new species across geographies where other birds show little or no diversification, said Rob Moyle, ornithology curator at KU’s Biodiversity Institute and an author of a study of white-eyes published the week of Jan. 26.

Moyle, along with Chris Filardi of the American Museum of Natural History; Catherine Smith of the University of Washington; and Jared Diamond of the University of California-Los Angeles, has been able to reconstruct key aspects of these birds’ evolutionary history using genetic analyses. The authors used DNA sequences and a variety of analytical methods to determine that most of the family speciated at rates among the fastest of any known vertebrate.

More than 100 species in the family have spread across vast regions from Asia to Africa and to far-flung islands. Despite this ability to disperse over long distances, some species remain separated by water gaps as narrow as 2.2 kilometers and yet show no inclination to cross.

“As we started to compile the data, we were shocked,” said Moyle. “White-eye species from across the family’s range had strikingly similar gene sequences, indicating a recent origin and incredibly rapid diversification.”

The authors of the study, published in the prominent journal Proceedings of the National Academy of Sciences, assert that traits of white-eyes may have helped them diversify. These include sociability and the ability to survive in a variety of habitats. Some species also may have become more sedentary and unwilling to cross narrow water gaps.

The idea of “great speciators” has been gestating for nearly 80 years. Ernst Mayr and Diamond coined the term after they had observed birds in the Solomon Islands. Each island the men visited had a different white-eye species, whereas the species of other birds did not vary across the archipelago. They proposed that the variation was driven by traits intrinsic to white-eyes.

“I am delighted to see this molecular evidence supporting ideas that I had only been able to guess at over the last several decades,” said Diamond, a professor in the geography department at UCLA. “I know that Ernst Mayr, if he had still been alive, would have been delighted at this confirmation 78 years after he visited the Solomons.”