Research Update: Conservation biology

The cheetah, spotted embodiment of feline grace and power, races across African plains. The pocket gopher, small and squat, scurries among tunnels in the American West. Unbeknownst to either cheetah or gopher, research at UCSC has unveiled a common bond between them--and has bolstered one side of a hot cheetah debate.

That bond is remarkable genetic similarity between individuals within each species. Many scientists suspect that one reason behind the decline of cheetahs is their lack of genetic variation--a degree of sameness close to that seen in inbred laboratory mice. Key evidence came from a surprising 1985 experiment in which unrelated captive cheetahs accepted skin grafts from each other, a sign that their immune systems were genetically almost identical. However, in recent years some ecologists have questioned the validity of that work.

The UCSC study provides an independent check. Graduate students M. A. Sanjayan and Kevin Crooks used pocket gophers in the first attempt to repeat the 1985 experiment on wild animals. Just as with the cheetahs, gophers in populations with little genetic variation accepted skin grafts from one another. However, gophers from a population with higher genetic diversity rejected skin grafts from their neighbors--an experimental control that the 1985 study lacked.

These results led Sanjayan and Crooks to conclude that the cheetah study was accurate. Consequently, cheetahs and other genetically impoverished species, such as California sea otters and elephant seals, may have little variability among their immune systems and thus may be more vulnerable to outbreaks of disease.

"Genetic variation is the stuff of evolution," says Sanjayan. "It allows a population to adapt effectively to changes in the environment. You exist at a price if you have low genetic variation. It's like having lots of clones of yourself."

Sanjayan and Crooks presented their work in August at a meeting of the Ecological Society of America and in the June 13 issue of the journal Nature.

-ROBERT IRION

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