White Eyes Claim Record for 'Fastest Bird Speciator'

Recent molecular studies have revealed that Zosteropidae—a family of birds commonly referred to as white eyes—diversify into new species faster than any other group of birds. Scientists estimate that every one million years, between 2.24 and 3.16 new species of white eye appears. The Zosteropidae family presently includes more than 100 species and the family is estimated to be between 4.46 and 5.57 million years old.

White eyes are so named for the white ring of feathers that encircles their eyes. The range of the white eye family extends from from Asia to Africa and into Oceania.

White eyes' tendency for rapid diversification first caught the attention of evolutionary biologists Ernst Mayr and Jared Diamond nearly 80 years ago when they visited the Solomon Islands. Mayr and Diamond observed that within geographical regions where other birds showed little or no diversification, white eyes were highly varied. Mayr and Diamond went on to suggest that white eyes may possess a set of inherent traits that made them 'great speciators'. Until recently, there was no way to test their hypothesis.

But with the advent of molecular genetics, the mechanism of speciation in white eyes could be explored in greater detail than ever before. A team of experts banded together to delve deeper into the mysteries of white eye speciation—the team included Christopher Filardi (Biodiversity Scientist for the Pacific Programs at the Center for Biodiversity and Conservation at the American Museum of Natural History), Rob Moyle (University of Kansas), Catherine Smith (Missoula, Montana), and Jared Diamond (University of California at Los Angeles).

That Jared Diamond was able to participate in this research was particularly significant—it enabled him to answer questions he had posed with Mayr nearly eight decades earlier:

"I am delighted to see this molecular evidence supporting ideas that I had only been able to guess at over the last several decades," says Diamond, a professor of 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."

The molecular evidence gathered by the team supports the 'great speciator' hypothesis proposed by Mayr and Diamond and suggests that there are indeed some inherent traits enabling white eyes to rapidly form new species. Such traits might include the ability of the species to survive in a wide variety of habitats, and the short time between generations when compared to other groups of birds.

Find out more:

• White Eyes Diversity Across a Hemispheric Range Faster than any Other Bird (American Museum of Natural History)
• 'Great speciators' explained: It's intrinsic (Eurekalert)

Photo © C. Filardi / CBC-AMNH. The splendid white-eye (Zosterops splendidus) is found only on the tiny island of Ranongga is one of seven species endemic to islands of the New Georgia Group, Solomon Islands.