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The color of wolves mysteriously changes in America. We finally know why: ScienceAlert

The color of wolves mysteriously changes in America. We finally know why: ScienceAlert

Guessing a gray wolf’s coat color seems like a no-brainer. But canines, whose habitats are spread across North America and Eurasia, are not always gray.

On the North American continent, specifically, the further south you go, the more wolves there are with dark, black fur. The phenomenon went unexplained for a long time, but scientists have now determined that the culprit is one of the main drivers of natural selection: disease.

An international team led by the ecologist Sarah Cubaynes of the University of Montpellier in France has determined that the often fatal canine distemper virus is the trigger that produces a greater number of black-furred wolves (Canis lupus).

“In most parts of the world, black wolves are absent or very rare, but in North America, they are common in some areas and absent in others.” explains biologist Tim Coulson from the University of Oxford.

“Scientists have long wondered why. Now we have an explanation based on wolf surveys in North America and modeling motivated by extraordinary data collected by co-authors working in Yellowstone.”

Evolutionary pressure can lead to some peculiar consequences, especially when it comes to disease. Some individuals may be more likely to survive based on the presence of genes that confer resistance to this disease. Survivors then produce offspring with these genetic variations, and the genetic profile of a population can change over time.

The genetic configurations that confer resistance, however, do not always have a single function. As we recently learnedthe genetic variants that conferred resistance against the Black Death also increase susceptibility to autoimmune disorders such as rheumatoid arthritis, meaning we are still feeling its effects centuries later.

In the case of these wolves, coat color is determined by a gene called CPD103, which historically made their coats gray. However, a CPD103 mutation arose in dogs and crossed with wolves, producing a black coat.

Each wolf has two copies of CPD103, one inherited from each parent. Unlike red hair in humanshowever, only one copy of the black coat gene is needed to produce a black coat.

Scientists suspected that canine distemper virus may play a role in the number of black-coated wolves in North America, as the region of DNA where CPD103 resides is also involved in coding for a protein that protects against lung infections such as canine distemper.

This would mean that if black-coated wolves are more likely to survive the disease, they will reproduce and pass on their CPD103 variant to their pups.

So the team set out to test this hypothesis. Researchers analyzed 12 North American wolf populations for canine distemper antibodies – a sign of having had and survived the virus – was strongly correlated with black-skinned wolves.

They found that wolves with antibodies were, in fact, more likely to have black coats, especially in larger wolves. Black wolves were also more common in areas where outbreaks had occurred.

The team then studied 20 years of wolf population data from Yellowstone National Park, where wolves were reintroduced in the 1990s.

There, the population consists of 55 percent gray wolves and 45 percent black wolves. Of these black wolves, only 5 percent had two copies of the CPD103 black coat variant. This suggests that wolves that choose mates of the opposite color have a better chance of reproductive success and their offspring survive canine distemper.

However, it only works in regions that have experienced canine distemper outbreaks. According to the team’s mathematical model, the competitive advantage of choosing an opposite-colored partner disappears if distemper is not a problem.

The research not only provides a fascinating reason for the increased prevalence of black wolves in some areas, but also provides a tool for studying historical canine distemper outbreaks as well as disease resistance.

The team notes that their results are likely to apply to a wide range of species. In a wide range of insects, mammals, amphibians, reptiles and birds, color variation can be associated with disease resistance; this coloration can act as a signal to help animals choose mates that will give their offspring a survival advantage.

“When coloration is genetically determined and disease resistance is heritable and associated with coloration, preference for a mate of a specific color will improve fitness by maximizing the chances of producing resistant offspring in environments with sufficiently frequent and virulent pathogens “, he added. the researchers write in their paper.

“We may have significantly underestimated the role of pathogens in generating the diversity of morphological and behavioral traits observed in nature.”

Isn’t that an intriguing notion?

The research was published in science.



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