Black Wolves the Result of Interbreeding With Dogs
- 11:37 am |
The black fur of some North American wolves is the result of long-ago dalliances with domestic dogs, probably the companions of the earliest
And a black coat seems to provide an advantage to forest-dwelling wolves, meaning dogs passed on some useful genetic diversity to their wild cousins.
“This is pretty unique,” said biologist Tovi Anderson of
Anderson and her team compared the genes of wolves from
Arctic to those of domestic dogs and coyotes. They found that, in each species, the black individuals have the same mutation, which first arose about 45,000 years ago. And molecular-clock analysis showed the mutation was oldest in dogs, suggesting it originated with them and then spread to wolves and coyotes through interbreeding.
This all happened in
12,000-15,000 years ago, when people first crossed the Bering Land Bridge from Asia.
“We don’t see any evidence of recent interbreeding between dogs and North American wolves,”
The team also found genetic evidence that the black-fur mutation established itself very quickly in forest-dwelling wolves, meaning it must provide them with some significant advantage. Improved camouflage in the dark woods is one possible explanation.
“I think there’s more going on,” said Paul Paquet, a biologist at the
A better immune system may be the answer. The black-fur mutation belongs to a family of genes that, in humans, is involved in fighting off infections.
“The advantage we see in wolves could be a result of this immune system function,”
This hypothesis is complicated by the fact that, while black wolves are common in North American forests, they’re rare on the open tundras. Wildlife biologists noticed this pattern long ago, and the new study further confirms it. If a black coat confers a better immune system, why not be black on the tundra, too?
“Perhaps there’s some sort of parasite that’s more prevalent in forested areas,”
“This is a beautifully conceived and executed study,” Paquet said. “I have considered many of these things previously, and this article made me think about them again.”
Paquet said the study also raises interesting questions. Why, for example, haven’t other dog colors worked their way into the wolf wardrobe? And if black wolves do well in woodlands, why are there so few of them in the forests of British Columbia, among the continent’s thickest?
The authors suggest that the black-coat mutation may become increasingly important to North American wolves, as much tundra may shift to woodland in a warming world. And the study shows genetic diversity can be found in surprising places.
"Adaptation really depends on genetic diversity, especially with the environment changing so rapidly," Paquet said.
"Domestic dogs might be a reservoir for resiliency."
Citation: "Molecular and Evolutionary History of Melanism in North American Gray Wolves." By Tovi M. Anderson,
Bridgett M. vonHoldt, Sophie I. Candille, Marco Musiani, Claudia Greco,
Daniel R. Stahler, Douglas W. Smith, Badri Padhukasahasram, Ettore
Randi, Jennifer A. Leonard, Carlos D. Bustamante, Elaine A. Ostrander,
Hua Tang, Robert K. Wayne, Gregory S. Barsh. Science Vol. 323, 5
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Image: Daniel Stahler/NPS.