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DNA Fragments Yield Ivory-bill's Deep History

Researchers construct the ivory-bill's family tree


Ivory-billed Woodpecker, North America

Illustrations by John Schmitt (3)

According to the books, there is only one "Lord God Bird": the Ivory-billed Woodpecker. For years, many feared that it was extinct, both in the swampy forests of the southern United States and in the mountains of Cuba, the only other place ivory-bills have ever been found.

Now, after mining DNA from the toes of old woodpecker specimens, scientists have come up with new information showing that the similar-looking Cuban and North American ivory-bills are genetically distinct. The analyses, published in Biology Letters, could not resolve whether the North American ivory-bill's closest relative is the Cuban ivory-bill or the Imperial Woodpecker, a bigger and somewhat more distinctive species from Mexico. The authors suggest that Cuban and North American ivory-bills may be different enough to be considered two species.


Ivory-billed Woodpecker, Cuba

Conservation implications
There have been no confirmed sightings of Imperial Woodpeckers since the 1950s, and none of ivory-bills in Cuba since the 1980s. North American ivory-bills had vanished for 60 years and were only rediscovered in Arkansas, in 2004.

"Before the rediscovery in Arkansas, the main hope for ivory-bill conservation was in Cuba," said Martjan Lammertink, a Cornell Lab of Ornithology researcher and a coauthor of the study. "Showing these two birds are genetically distinct may bring renewed interest in the Cuban ivory-bill."

Irby Lovette, director of the Lab's Fuller Evolutionary Biology Program, said that the study shows the importance of the three woodpeckers as a group within their genus, Campephilus. "It's now clear that the two ivory-billed subspecies and the Imperial Woodpecker are each other's closest relatives. If we lose all three, we've lost a unique and spectacular group of woodpeckers," he said.

DNA analyses found that the similar-looking Cuban and North American ivory-bills are genetically distinct. Within the genus Campephilus, the genetic evidence places Ivory-billed and Imperial woodpeckers on their own branch of the family tree.


Imperial Woodpecker, Mexico



Clues to the past and future
Led by Robert Fleischer, head of the genetics program at the Smithsonian National Museum of Natural History, the researchers extracted DNA from specimens of Cuban and North American Ivory-billed Woodpeckers, some of which were collected as long as 145 years ago. Based on the differences in DNA, they concluded that ivory-bills in the two regions diverged from one another about one million years ago.

Theories about how Ivory-billed Woodpeckers made it to Cuba have included the possibility that Native Americans might have transported them to Cuba from the mainland as recently as 600 years ago. The new study suggests that the woodpeckers inhabited the island long before people ever got there.

In addition to revealing details about the ivory-bill's past, the DNA fragments may provide a forensic tool for future searches. "We can use the genetic sequences as a sort of bar code to compare DNA from material collected from the field—feathers or droppings, for example," Fleischer said.

Will field guides soon list two species of Ivory-billed Woodpeckers? Although the authors of the new study suggest that Cuban and North American ivory-bills should be considered separate species, the official decision rests with the American Ornithologists' Union Committee on Classification and Nomenclature.

Lovette, a member of the committee, said decisions to split or lump species are usually based on multiple lines of evidence. "The new data are intriguing, but place these birds in the gray zone. Some biologists would classify them as two species and others would retain them as just one," he said. "These results will likely initiate an interesting debate on how we should classify these birds."

 

For permission to reprint all or part of this article, please contact Laura Erickson, editor, Cornell Lab of Ornithology, 159 Sapsucker Woods Rd., Ithaca, NY, 14850. Phone: (607) 254-1114. email: lle24@cornell.edu

 
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