Fifty shades of gray wolf how a virus and sexual selection changed the color of a predator

(ORDO NEWS) — The authors of a new article for Science have learned the genetic causes of differences in the coloration of gray wolves (Canis lupus) inhabiting North America.

It turned out that the distribution of the black and gray color of this predator is determined by resistance to the CDV canine distemper virus, as well as the choice of a sexual partner.

The coloration of animals is an important feature that determines their adaptability to the environment. It is known that the level of pigmentation is associated with different environmental conditions (such as the availability of resources and the presence of predators, parasites and competitors) and even geographic latitude – the latter describes the so-called Gloger’s rule.

However, the significance of color in the life of an animal does not end there. Color also affects the choice of a sexual partner, since it allows you to assess the level of adaptability of the animal, including its immunity.

The authors of a new article in the journal Science figured out the genetic aspects of this issue using the example of the famous predator – the gray wolf Canis lupus.

In fact, the color of the skin of a predator, say, in North America forms a smoothly changing spectrum: the proportion of black skins increases in the direction of the southwest. Most dark-colored wolves live around the Rocky Mountains, regardless of latitude.

The coat color of C. lupus is determined by the CDB203 gene , located at a gene locus called K. This makes gray wolves generally gray, but one mutation (namely, a deletion ) in CDB203 makes them black.

This is a dominant mutation that was heavily culled over the last few thousand years of wolf evolution until a new evolutionary factor came into play.

In this case, it was not the color of black wolves that was subjected to selection, but other traits determined by the same CDB203 gene (which, on the basis of this, belongs to pleiotropic , causing a number of different effects).

The fact is that a gene with a mutation gives wolves greater resistance to distemper (or distemper) of dogs, a dangerous respiratory infection caused by the CDV (Canine Distemper Virus) virus.

Fifty shades of gray wolf how a virus and sexual selection changed the color of a predator 2
Black and gray wolf puppies

To uncover the link between coat color and susceptibility to the virus, an international team of scientists collected a lot of data. They characterize 12 wolf populations that live in different parts of North America.

The authors tested their blood samples for antibodies to CDV – that is, they found out whether the animals had distemper or not. Along the way, they noted the color of the wolf ‘s coat – and found out that black wolves were more likely to become infected with CDV.

Next, they studied a specific population of wolves – those that live in Yellowstone National Park. To do this, they had to describe in detail the local predators, including collecting their “biography” for more than 20 years. It turned out that 55% of the wolves had a gray color, 45% – black.

However, only 5% of black wolves were homozygous, that is, having both mutant copies of the gene. The rest were heterozygous, having one “normal” and one mutant copy of CBD203 . This, along with earlier results, indicated a greater viability of this genotype.

Next, the authors built a model that linked mutations, color, and many other characteristics of animals: distribution, mortality, and so on. As a result, there was no doubt: black wolves are indeed more viable under certain conditions, and this determines precisely their resistance to the plague.

Such a curious evolutionary picture has another important aspect – sexual selection. It turned out that the “immunity” of black wolves compensates, among other things, for the reduced fertility of females with this trait.

In addition, it turns out to be “profitable” for wolves to mate with animals of a different color: black with gray, and gray with black.

This breeding strategy is called disassortative, and it is this strategy that ensures the maximum fitness of wolf offspring in conditions of repeated CDV epidemics .

Summing up their work, the researchers emphasized that this result is not only applicable to the gray wolf Canis lupus . Coloration is known to be associated with resistance to infection in insects, amphibians, reptiles, and a number of mammals.

The effect is based on fundamental genetic mechanisms – including changes in the major histocompatibility complex (MHC) and the so-called supergenes, which alone are able to determine the complex adaptations of living beings.


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