As long-time readers of this blog know, I consider dogs to be a form of gray wolf. I do not consider Canis familiaris to be a valid taxon, because of cladistics and because of the gene flow between domestic dogs and wolves.
The extent of this gene flow was largely denied in much of the literature on wolves. But last year, it was discovered that the majority of Eurasian wolves have recent dog ancestry. This gene flow has been going on for a while, and although people do get a bit worked up about domestic animal genes filtering into a wild species, it has been shown that the melanism in wolves that is conferred by a dominant allele originated in a Native American dog that was living in the Yukon or the Northwest Terrtories thousands of years before Columbus. Further, this melanistic allele is associated with higher immune responses, and there is evidence for natural selection favoring black individuals following a distemper outbreak.
In a paper released this week in the European Journal of Wildlife Research found extensive crossbreeding between dogs and wolves in agricultural landscapes in Central Italy. The authors estimate that about half of all wolves in this region have recent dog ancestry, and they think it is because humans have disturbed wolf habitat to have agriculture.
Of course, humans, wolves, and dogs have been living in Italy alongside agriculture for thousands of years. Dogs and wolves have been mating ever since there was a population of somewhat domesticated wolves.
Further, European wolves are much better adapted than North American wolves to living in agricultural areas. It may simply be that North Americans are much more likely to kill wolves that appear in agricultural areas and that this is what has created this asymmetry. But North American wolves tend to be in remote areas, where they rarely encounter dogs. Thus, there is not as much gene flow between dogs and North American wolves as there is between dogs and Eurasian wolves.
There is a lot of gene flow between dogs and coyotes in North America, and this finding does make sense. Coyotes do live in agricultural and urban areas much more easily than large wolves do.
I don’t think it worth becoming alarmed that dogs and wolves are mating in the wild. Dogs have lots of interesting mutations that could be of great use to wolves as they adapt to more and more human-dominated planet. If the dog alleles are deleterious, nature will select against them, but if they are advantageous, they will help wolves thrive into the future.
So it is quite short-sighted to think of wolves as being a some sort of pure entity that must be kept free of “foreign” alleles. If it were more widely accepted that dogs were just a domestic form of gray wolf, we would have a much easier time accepting a more holistic understanding to how these populations can continue exchange genes and adapt to new challenges.