Conservation: The genome of the American West

James Derr has just eaten a large grass-fed-bison steak topped with onions, the banquet dinner at a meeting of the American Bison Society in Rapid City, South Dakota. As he sips his wine, conservationists and managers of nature reserves — some wearing Stetsons and some wearing polar fleeces — approach to pay their respects to the man who could be considered the godfather of the bison genome.

Derr, a geneticist, is trying to reverse more than a century of human interference with the American bison (Bison bison). Those shaggy symbols of the American West were driven to the brink of extinction in the last half of the nineteenth century and then saved on ranches and in zoos. But the conservation efforts came at a cost. Most of the bison alive today have cattle genes rattling around in their genomes, left over from early efforts to interbreed the two species.

Derr has almost single-handedly started a movement to preserve the original bison, complete with its unadulterated genome. He has managed to persuade everyone from federal officials to private conservation leaders that they should care about the cattle genes hiding in bison. And he is convinced that his approach — managing the genome rather than the animals — could be a model for conserving other large mammals.

Wildlife managers have considered the genetic diversity of animals for some time, and animals in captivity have often been bred to preserve genetic diversity. But those were blunt approaches. Now, armed with genomic tools, researchers are starting to look at specific sequences in the genome, and are raising questions about what the fundamental unit of conservation should be. Most people see preserving wildlife as a matter of saving individuals; if all the individuals die out, the species becomes extinct. But that reasoning looks simplistic when considered at the genomic level. If the genes of a species change enough — through interbreeding, for example — that species will cease to exist even if individuals that look something like the original continue to thrive.

Although some species interbreed naturally, humans have forced other mix-ups, and those are the cases that most worry Derr. "Species conservation is more than skin deep," he says. "It is more than how they look, it is how they are — that's the genome."

This purist approach has won converts, but other conservationists say that the bison is an exception, and that for many species, the situation is so dire that they don't have the luxury of worrying about a few stray genes from related species.

Where the buffalo roamed

The troubles facing bison are relatively recent. When explorers Meriwether Lewis and William Clark voyaged across the continent at the beginning of the nineteenth century, tens of millions of bison roamed in massive herds from the Mississippi to the Rockies, and from Mexico to the Arctic. By the end of the century bison numbers had dropped to a few hundred, courtesy of long-range rifles and professional hunters.

At this point, a few forward-thinking people decided that the bison should not be driven to extinction. Charles Goodnight, the famous Texas cattle rancher, and a handful of other people made room for the animal on their private ranches. In 1905, then US President Theodore Roosevelt and William Hornaday, head of the New York Zoological Society (now known as the Wildlife Conservation Society), founded the American Bison Society, which collected bison and established herds in a few reserves in Montana, Oklahoma and South Dakota. A small herd, perhaps 30 in number, was still roaming Yellowstone National Park. According to Derr, all the bison in the United States today — there are now up to a million of them, mostly on private ranches — can probably be traced back to fewer than 200 bison.

Half a century after those conservation efforts started, Derr saw his first bison. He was a boy, growing up in Enid, Oklahoma, just north of a small town named Bison. His father raised cattle, and Derr lived mostly outdoors, hunting and fishing. The bison that young Derr encountered on local ranches did not act like his father's cattle, and they left a lasting impression. "They are much more athletic, very smart and incredibly quick and strong," he says.

In college, Derr studied biology with an eye to being a wildlife manager. But he soon decided "that I could have a lot bigger impact if I worked in the lab". He switched to genetics and is now a professor at Texas A&M University in College Station. In the 1990s, he put together a proposal to study how the bison had passed through that 200-individual bottleneck with seemingly no ill effects. Unlike many other species that have bounced back from small numbers, bison have retained a decent level of genetic diversity.

"It is a pretty darn amazing story," says Derr. At their fewest, bison were preserved by people sprinkled throughout the continent. "Just by luck, it seems that they were able to preserve, with the few bison that they got, much of the genetic diversity that was in those areas."