Dogs flash back to their wild ancestry when they howl inexplicably at the full moon or pace a circle before lying down. These behaviors may be vestiges of the dogs’ early days as wolves. But new research shows that some wild wolves probably inherited a trait from their domesticated cousins. Black wolves received a gene for coat color from domesticated dogs through interspecies breeding, suggests research in the Feb. 6 Science.“This may be the first time a domestic trait has gone into the wild and been beneficial,” says coauthor Tovi Anderson of Stanford University.
A specific mutation in a stretch of DNA called the K locus is to blame for giving some domesticated dogs black hair, shows a 2007 report. In fact, most black labs, poodles and shepherds have this mutation. To see whether the same DNA mutation caused dark fur in wolves, researchers collected DNA samples from wolves in Yellowstone National Park, where both black- and gray-colored wolves live. Despite their name, North American gray wolves display a range of coat colors from light gray to midnight black. Darker wolves are more prevalent in heavily wooded areas, whereas lighter-colored wolves are more common in the snowy tundra.
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The researchers found that 102 of 104 black-colored wolves carry the same mutation in their DNA as black dogs, whereas none of 120 lighter gray-colored wolves had the mutation. The K locus mutation segregated with coat color, suggesting the change also does the fur-darkening job in wolves. “Once we saw the mutation was the exact same one in wolves, we wondered how old it was,” Anderson says. The mutation could have happened before dogs were domesticated from the gray wolves between, it is estimated, 15,000 and 40,000 years ago. In that case, the mutation would have been lost in wolves but kept in dogs. Alternatively, the mutation could have happened in dogs after the species split, and then been transferred into wolf populations through interbreeding. Mutation patterns in large stretches of DNA can act as time stamps of how old, ancestrally, a section of DNA is. Around the K locus, these time stamps showed that the second scenario was more likely because the mutation had been in dogs much longer than in wolves. Moreover, not only was the mutation was being passed on to wolf generations, it also appears to be beneficial, the team reports. “The present study is the first convincing evidence I’ve seen showing that introgression of domestic genes into the wild may, under some circumstances, have positive side effects,” says conservation biologist Frank Hailer of the Smithsonian National Zoological Park in Washington, D.C. Although the benefit for wolves is unclear, Anderson says dark wolves may have better camouflage while hunting in the forest. Another possible benefit may come from the protein that the K locus encodes, a protein known to play a role in the immune system’s defense against infections. The researchers conclude in their report that genes from domesticated animals may “enrich the genetic legacy of natural populations.” Interbreeding between wild and domestic species is usually thought of as a negative event. “Many wild species are threatened by hybridization with their domesticated relatives,” says Hailer. He points to North American red wolves, salmon and quails, all of which have been threatened by genes from domesticated relatives. “From a conservation perspective, such hybridization is really a double-edged sword.”