DNA Reveals New Bird Species in America's Heartland

By Cat Lazaroff

DENVER, Colorado, December 8, 2000 (ENS) - Thanks to DNA evidence, the United States has a new species of bird today. Genetic testing is now being used to prove - and challenge - the distinctiveness of species around the U.S.

The Gunnison sage-grouse, which is about the size of a chicken, is not a bird that would be easy to overlook. But it took technology powerful enough to examine its individual genes to discover that this bird of western prairies is unique.

Gunnison sage-grouse

A male Gunnison sage-grouse in mating display (Photo courtesy U.S. Geological Survey)
The new grouse species is recognized in the December issue of the ornithology journal "Wilson Bulletin," which includes a discussion of the genetics research that conclusively proved the species designation.

Comparing the DNA of wildlife species is a relatively new way of uncovering distinct species. In the past, scientists had to rely on evidence like coloration and behavior to determine whether two populations came from different species.

Historically, scientists had believed that the newly named Gunnison sage-grouse, found in the sagebrush ecosystem of southwestern Colorado and southeastern Utah, was the same species as the greater sage-grouse, which is found in northern Colorado and throughout 11 western states and two Canadian provinces.

But over the years, differences in body size and unique plumage and behaviors led scientists to question this kinship.

"Compiling the evidence needed to formally designate a new species is no easy task," said Dr. Jessica Young of Western State College of Colorado, a member of the research team that worked on the sage-grouse problem.

The ultimate test of a species has always been whether the two animals could - or would - interbreed. That determination has been based on evidence like geographic location and mating behavior. Populations that live far apart, or use different mating calls, are unlikely to interbreed.

The researchers used powerful DNA markers to determine whether gene flow, or interbreeding, had occurred between the two groups of sage grouse.

comparison

Plumage comparison between the greater (left) and Gunnison (right) sage-grouse (Photo courtesy USGS)
"We discovered that gene flow between the two grouse was absent and that the two groups were too distantly related to be considered the same species," said Dr. Sara Oyler-McCance, a conservation geneticist with the U.S. Geological Survey.

The studies also confirmed that most populations of the Gunnison sage-grouse are geographically and genetically isolated from each other, with low genetic diversity, factors that can contribute to species decline or extinction.

Scientists have used historical documents and interviews to estimate that the Gunnison sage-grouse, named for the area of Colorado where it was discovered, was once several orders of magnitude more abundant than it is at present, and that the species occurred over a much larger geographic area.

These small grouse, with their penchant for eating sage, are now restricted to isolated populations in Colorado and Utah with a total population of less than 5,000. Some populations are quite small, fewer than 150 breeding birds, and several former populations have become extirpated since 1980.

FROM GROUSE TO WHALES

Unique species are often singled out for unique protections. Just the knowledge that a dwindling wildlife population is found nowhere else on earth can be enough to prompt conservation actions by public and private groups.

In January 2000, the U.S. Fish and Wildlife Service was petitioned to protect the Gunnison sage-grouse - already recognized as a distinct population - under the federal Endangered Species Act because of concern that the species is at risk of extinction due to habitat loss, fragmentation and degradation. That petition gains strength from the new genetic research, which proves conclusively that the birds are distinct from their more common cousins.

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Right whale (Photo courtesy National Marine Fisheries Service)
Less than a month ago, the world gained a new whale species, when DNA research revealed that right whales living in the North Pacific Ocean are genetically unique. Genetic research by the Bronx Zoo based Wildlife Conservation Society, American Museum of Natural History, and other organizations ferreted out DNA differences between this population and North Atlantic right whales.

"There is very little recent information about the North Pacific right whale, other than sporadic sightings, and the fact that it has been hard hit by illegal hunting," said Wildlife Conservation Society (WCS) researcher Dr. Howard Rosenbaum, lead author of a study . "What is known is that this animal numbers perhaps a few hundred individuals throughout their entire range in the North Pacific and should therefore be a top conservation priority."

Both of the recognized species are now listed as endangered under the Convention on International Trade of Endangered Species of Fauna and Flora (CITES). Rosenbaum believes that these new findings will help guide changes to the federal Endangered Species Act, which now recognizes just one species of right whale occurring in U.S. waters.

THE FLIP SIDE

But the DNA double helix can be a double edged sword. In September, California developers used DNA research to challenge federal protections for the threatened California gnatcatcher.

A study published in the October edition of "Conservation Biology" showed little difference between the California gnatcatcher and its common Mexican cousins.

gnatcatcher

The California gnatcatcher is darker colored than its Mexican cousins (Photo courtesy USFWS)
"Put simply, based on [DNA] data, northern populations do not appear to constitute a unique component of gnatcatcher biodiversity," the study concludes.

Among the biologist authors of the report was Jonathan Atwood, who reported a decade ago that the California and Mexican populations were distinct enough to be considered separate subspecies. That study was the primary evidence that the USFWS used in designating the California gnatcatcher as threatened under the Endangered Species Act.

Developers used the new study to argue that the two populations are so similar that no special measures - including the preservation of vanishing coastal scrublands - were necessary to protect dwindling California populations.

The U.S. Fish and Wildlife Service (USFWS) was then facing a court ordered deadline to designate critical habitat for the California gnatcatcher by September 30. The USFWS had proposed protecting almost 800,000 acres for the tiny birds, one of the largest critical habitat designations ever made.

"Clearly, the designation of 800,000 acres of habitat no longer can be justified if there is no subspecies, and the species itself is not threatened with extinction," wrote Laer Pearce, executive director of the Coalition for Habitat Conservation, a developer funded group. The delay is warranted, Pearce wrote, even "putting aside questions regarding whether the gnatcatcher should be delisted given this information."

gnatcatcher

The California gnatcatcher lives only in dwindling patches of coastal scrubland (Photo by Arnold Small, courtesy USFWS)
The USFWS asked for a two week extension on the critical habitat designation deadline, to allow the agency to complete its lengthy and complex final rule. The agency said its request was not based on the genetic study, which "contributes no information that is relevant to the critical habitat decision," said Michael Spear, USFWS California/Nevada operations manager.

In mid-October, the USFWS went ahead and designated 513,650 acres of land in southern California as critical habitat for the endangered California gnatcatcher.

"The Service designated only those lands that we determined are essential to the species' conservation, based on the best scientific evidence currently available," said Spear.

The Coalition criticized the agency's decision as ignoring scientific evidence.

HOW DISTINCT IS A SPECIES?

The USFWS is likely to face similar challenges to Endangered Species Act listing and critical habitat designations in the future. With many species - humans and chimpanzees, for example - separated from each other by just a handful of genes, and no clear rules regarding DNA species evidence, the U.S. and the world could stand to gain dozens of new species as the new technology is applied to a growing number of cases.

At the same time, arguing genetic similarity could prove a powerful tool in the hands of those who have a vested interest in opposing protections for inconvenient pockets of wildlife.