Well the gist of this NY Times piece is that they've been roaming around so much that they have interbred with cattle. The Times says that there are estimates that of the 300,000 bison in the US, only about 10,000 are genetically "pure" - don't carry genes from cattle. The Times makes this out to be a big problem calling for controlled breeding and the segregation of "pure' herds.
I was not aware of the issue, and when I passed this on to Steve his take was that it wasn't that big a deal:
"I knew of it. While keeping 'pure" herds pure is fine, I doubt it is as big a problem as is posed here. If they can eventually get them on the prairie with predators etc the "right' genes will sort themselves out, just as in the reintroduced eastern peregrine."
I was also interested to see that physical anthropologist John Hawks, a guy who knows lots more about genetics than I do, had weighed in on the matter and reached much the same conclusion as Steve:
"The whole idea of "genetic contamination" implies that there is something bad about this genetic introgression. But we can guess that the cattle genes don't intrinsically reduce fitness, since bison with cattle genes have been greatly increasing in numbers. And these introgressed herds are unlikely to be fixed for any cattle genes, so the original bison alleles still have every chance to compete with the cattle alleles. In other words, the cattle introgression has introduced variation into bison, some of which might be adaptive.
As you can tell, I'm not very sympathetic to the idea that we should prevent "genomic extinction" by insisting on some kind of genetic purity. It seems to me that we want to retain as much variation in our conserved populations as possible, so that they can adapt to changing climatic conditions in the future. We can't predict which alleles will be adaptive."
snip
"This seems like a good doctoral project for somebody: how do the introgressed bison compare behaviorally with "genetically pure" bison? And the all-important question: how does mean fertility compare between these herds? They've both historically grown very rapidly, but does one maintain higher mean fitness than the other? Are there more animals in the Custer herd that fail to reproduce?"
Interesting stuff. RTWT
2 comments:
It's very strange that most people think plant hybrids are very good (except maybe for genetically altered and trademarked plants) and most modern young people seem to think "cross-bred" people are a good thing, but they demand that wild animals remain "pure." Buffs must be kept segregated to keep them from fooling around with cows, but at the same time, it is demanded that the buffs can go out where the cows are in spite of the threat of transmitting brucellosis to a cash crop.
Inconsistent thinking.
Prairie Mary
I wouldn't be suprised if the hybridization itself is a good thing, even if the cattle aren't laden with wild-adapted genes. Hybrid vigor is a very real phenomenon.
If "punctuated equilibrium" is an accurate model of speciation, I wonder how many events of puntuation are catylized by hybridizing populations.
-R. Arthur Wilderson
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