Beyond beefalo

  • Beefalo, a heavily hybridized bison/cow bred for meat.

  • Gates, C.C., Freese, C.H., Gogan, P.J.P. and Kotzman, M. (eds. and comps.) (2010). American Bison: Status Survey and Conservation Guidelines 2010. Gland, Switzerland: IUCN.

By the end of the 19th century, North America's many millions of bison were reduced to just a few hundred. They've since recovered to around a half million, most raised as livestock and crossbred with cattle. Now conservationists manage over 60 herds, such as the one at the American Prairie Reserve in Montana, to restore the bison's genetic integrity and ecological function. But new technology is revealing cattle DNA even in herds identified as purebred a few years ago. James Derr at Texas A&M University, who has genotyped over 35,000 bison, says it ranges from miniscule traces to heavy hybridization. "It's hard to prove a bison herd is free of cattle genes. All herds may have some hybrids," he says. The American Prairie Reserve bison await results from recent genetic tests. If they are found to carry cattle DNA, how much is acceptable? Manager Bryce Christensen says, "A lot of conservation herds will be trying to figure (that) out this year."

Anonymous says:
Sep 16, 2010 12:30 PM

    Bison aren't the only indigenous animals whose modern DNA shows evidence of mingling with a related species.

    Earlier this year, I happened upon an engaging book by Mark Anders Halverson -- An Entirely Synthetic Fish: How Rainbow Trout Beguiled America and Overran the World.

    It's an interesting tale -- even to a non-angler like me -- and it's well told. Part of the story is the modern effort to restore the native trout of the Rocky Mountains -- the cut-throat -- to its original habitats where it had been supplanted, over the years, by imported rainbows.

    But it turns out that even in the most remote, isolated streams of Montana, there are no pure cut-throats. Even the best strains contain about 2 percent rainbow DNA.

    In this case, though, as opposed to the bison, the intermingling might be natural, because there's a slight overlap in their original ranges; once upon a time, not so long ago, rainbows and cut-throats might have spawned in some of the same streams.

    But it does raise questions about whether genetic purity is even possible for some species, as well as some speculation that precise modern DNA analysis might be telling us more than we really want to know.

Anonymous says:
Sep 20, 2010 09:42 AM
Thanks for adding this, Ed. Yes, it seems many apparently purebred species carry recent or remnant DNA from other species. One of my sources for this story even directed me to a paper that describes how some humans carry remnant DNA from neanderthals! Read the paper "Neanderthal DNA lives on ... in some of us" here: http://cosmiclog.msnbc.msn.[…]-dna-lives-on-in-some-of-us
Anonymous says:
Sep 20, 2010 11:30 AM
So perhaps the message here is that "purity" may not be as inherently valuable as we think it is. Living systems are dynamic, in part because they cross-pollinate like this.

--Associate Editor Sarah Gilman