Guessing the color of a gray wolf’s coat seems foolhardy. But dogs whose habitats are common in 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 coats. This phenomenon was long unexplained, but now scientists have identified the culprit as one of the greatest drivers of natural selection: disease.
It is often fatal, an international team led by France’s University of Montpellier ecologist Sarah Coubains has found. canine distemper virus is a trigger that spawns more black cloaked monsters (Canis lupus).
“Black wolves are absent or very rare in most parts of the world, but in North America they are common in some areas and not in others” explains biologist Tim Coulson of Oxford University.
“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 at Yellowstone.”
Evolutionary pressure can have some special consequences, especially when it comes to disease. Some individuals may have a higher chance of survival based on the presence of genes that confer resistance to the disease. Survivors then produce offspring with these genetic variations, and the genetic profile of a population can change over time.
Genetic configurations conferring resistance do not always have only one function. As we recently learnedGenetic variants that confer resistance to the Black Plague also increase susceptibility to autoimmune diseases such as rheumatoid arthritis, meaning we still feel 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 appeared in dogs and was passed on to wolves, causing the black coat.
Each wolf has two copies of CPD103 inherited from each parent. Different red hair in humansalthough only one copy of the black coat gene is needed to produce a black coat.
Scientists suspected that dogs were dogs virus It may play a role in the number of black-coated wolves in North America, because the DNA region where CPD103 is located is also involved in coding for a protein that protects against lung infections such as distemper.
This means that if black-coated wolves are more likely to survive the disease, they will reproduce and pass on the CPD103 variant to their offspring.
So the team set out to test this hypothesis. Researchers analyzed 12 wolf populations in North America to find out if the disease was present in dogs antibodies – a sign of having the virus and surviving – was strongly associated with black-cloaked wolves.
They found that wolves with antibodies, especially older wolves, were more likely to have black coats. Black wolves were also more common in areas of outbreaks.
Next, the team studied 20 years of wolf population data from Yellowstone National Park, where wolves were reintroduced in the 1990s.
There, 55 percent of the population are gray wolves, and 45 percent are black wolves. Only 5 percent of those black wolves had two copies of the black coat variant CPD103. This suggests that wolves of the opposite color have a higher chance of reproductive success and their offspring survive canine distemper.
However, it only works in areas where distemper occurs. According to the team’s mathematical modeling, if dogs’ stupidity is not a problem, the competitive advantage of choosing a mate of the opposite color disappears.
The study not only reveals a surprising reason why black wolves are more common in some areas, but also offers a tool to study historical outbreaks of dogs as well as their resistance to disease.
The team notes that their results can be applied to a wide range of species. Color variation can be associated with disease resistance in a wide range of insects, mammals, amphibians, reptiles and birds; 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 inherited and associated with coloration, preference for a mate of a particular color will increase fitness, maximizing the chance of producing resistant offspring in environments with frequent and sufficiently virulent pathogens.” researchers write in their paper.
“Perhaps, we have significantly underestimated the role of pathogens in generating the diversity of morphological and behavioral traits observed in nature.”
Isn’t that an interesting idea?
The study was published Science.
