Black wolf is the first genetically modified predator

Way through the trees or through the snow, wolves have come to legend with white, gray or even black legs in North America. According to researchers at Stanford, the last group of wolves owed an unexpected debt to their cousin cousins. In an unusual evolutionary transformation event, dogs that mate with wolves thousands of years ago passed on a genetic mutation that codes for black fur for ancestors of wolves. As a result, gray wolves, also known as Canis lupus, are no longer gray-colored.

The impact of this phenomenon is not simply as a cosmetic but rather the formation of black wolves, almost becoming a feature of North America. The event also offers a selective advantage over brighter colored wolves in areas with dense forests. This is a rare example of farm animals, in this case perhaps the dogs of the first Native Americans, contributed to the genetic diversity of wild relatives and relatives. in a way that affects the appearance as well as the existence of an individual receiving mutations.

Genetic Professor Greg Barsh said: 'We often consider domestication as a process that benefits people. So we were surprised to find that domesticated animals acted as genetic reservoirs that could benefit populations in the wild that they originated from. It is also interesting to think of the first part of the body of the first indigenous American dogs, now extinct, living in the wolf's body. ' Canine geneticists also agreed that the Native American dogs today are descendants of European dogs.

Barsh and graduate student Tovi Anderson and other scientists at the University of California - Los Angeles, University of Calgary, National Park at Yellowstone National Park and the National Human Genome Research Institute conducted the study. Scientists from Sweden and Italy also participate.

Anderson and his colleagues collected DNA from 41 gray, white and black wolves in the Canadian Arctic and 224 black and black wolves in Yellowstone National Park to compare with DNA of domestic dogs, gray grass coyotes. and black. Their goal is to build a Barsh lab value study to identify dog ​​pigmentation control mechanisms that are different from most other mammals.

"We used to think this was just a group research project to confirm that wolves and domestic dogs share a genetic pathway that determines black hair color," Anderson said . But the story became much more interesting when we expanded our research and began to question the mutant origin of wolves'.

Black-haired wolves are quite common in dense areas of Canada's Arctic compared to the number of black-haired wolves in icy tundra (62% and 7% of the total population). Biologists have long thought that having black hair seems to give a special advantage to the wolves living in the forest, but they are not sure. Because black wolves will turn gray when they are old, the root cause seems much deeper.

Barsh's lab has spent many years studying genes that affect hair color as well as other biological pathways in mammals. In 2007, they discovered that the gene responsible for producing black hair in dogs named beta-defensin belonged to a family of genes previously thought to be involved in fighting infection. A variant of the gene causes dogs or wolves to have yellow fur or bright coat color; a mutation that loses 3 nucleotides makes the animals black.

Black wolves dominate the pack in North American forests, while white wolves are more numerous in bare tundra. (Photo: Marco Musiani, University of Calgary)

Barsh said: 'Wildlife wildlife biologists do not think that wolves are largely based on their ability to camouflage to protect themselves or to increase successful hunting rates. There may be a certain phenomenon going on. For example, the protein regulates the difference in hair color associated with inflammation or infection, so it gives black-haired animals a distinct advantage over its pigmented effect. ' .

Although the question of why this selection advantage is still a mystery, its way is gradually becoming clear. Anderson's research has confirmed that the gene for black hair bears evidence of positive selection in the forest wolf species. She also showed that this gene is dominant, which means that even an animal's copy of the gene has black hair. Of the 14 children of the mating pair between black and gray wolves, 10 small wolves carry dominant and black haired genes.

She and her colleagues have used many genetic tests to determine that mutations are likely to be introduced into dogs by wolves about 10,000 to 15,000 years ago, which is equivalent to the time when the first Americans migrated. pop through Bering nose. These people may have brought dogs along, some of them with black fur mutations that appeared 50,000 years ago. The rest of the story, as people say, is history.

Anderson said: 'It is simpler for dogs to be exposed to wolves in North America than in Europe. At that time, the density of wolves was higher than that of domestic dogs, like humans, and migrated. '

Unfortunately, so far it is not known whether any black wolf exists before the purebred dog period. It is possible that mutations occurred in the wolf population before domestic dogs were domesticated about 15,000 to 40,000 years ago and then the black wolves died. Or the mutant gene first appeared in domestic dogs and did not enter the wild population until Native Americans migrated from Europe. In any case, the beneficial aspect of mutation along with its origin also inspired scientists.

Anderson said: 'This is a mutation that has been cultivated by humans in the form of domestic dogs for thousands of years. We now see that it has not only infiltrated the wild population but also benefited them. ' Researchers believe that the loss of the wolf's tundra habitat will probably encourage the spread of the black-haired gene. They are very interested in finding the exact path that mutants benefit the jungle wolves.

The study emphasizes the view that evolution may include phenomena in which traits are passed down in unexpected ways. Barsh said: 'We now know that domestic dogs become genetic heritage objects that could benefit wolves. This makes us expand our thinking to the path of application to other animals and plants. '

With the tundra environment expected to narrow in the coming years due to the expansion of northern forests related to global warming, the researchers stress that black coat colors can help adapt the gray wolf. with environmental change.

Marco Musiani, an international expert on wolves and professor at the University of Calgary's School of Environmental Design, said: 'It's a bit ironic that a human-made trait is now beneficial for wolves when they are faced with their changes are also created by humans on their environment. '

Barsh and Anderson's colleagues include Hua Tang (Ph.D. and assistant professor of genetics) and Sophie Candille (Ph.D. at Tang Laboratory). The research was funded by the National Institutes of Health, the National Science Foundation and the Swedish Research Council.

Refer:
Molecular and evolutionary history of melanism in North American gray wolves.Science, Feb 5, 2009