Paul Baker

Animal Life

Article Summary 2

4-17-98

The tiny pocket gopher is providing the first evidence in more than a decade that members of wild populations with little genetic variability can accept skin grafts from each other. The findings by researchers in Michael Soule’s lab at the University of California-Santa Cruz lend support to long-standing cheetah studies. Stephen O’Brien, a researcher at the National Cancer Institute, and his colleagues discovered in the 1980's that unrelated cheetahs accepted skin grafts from each other, a sign that the animals lacked genetic variation, thus making their immune systems alike. The O’Brien team hypothesized that this genetic uniformity might account for the high juvenile mortality and other breeding problems seen in the big cats and that it could put them at increased risk for disease. O’Brien’s work was dismissed by some because of his choice of control; instead of staying within the species, O’Brien grafted skin from domestic cats onto the cheetahs. To test the relationship between genetic variation and immune response in wild populations, Sanjayan and Kevin Crooks compared three pocket gopher populations. The results showed one population always rejected grafts from other members of their home population; the other two populations had almost no genetic variation, and the animals from each of these populations consistently accepted skin grafts from other members of their respective groups. They did, however, reject skin grafts from animals outside their population. Sanjayan cautions that, even though their study suggests that the results from the cheetah graft were a real phenomena, it does not validate the hypothesis that genetic uniformity is necessarily a threat. He points out that gopher populations with low genetic variability are thriving in the wild. "The pocket gopher is a good mammalian surrogate for animals like the cheetah that are at risk," say Sanjayan. "Its range of genetic variation provides within-species control."