Carrion crows and hooded crows are virtually indistinguishable genetically, and hybrid offspring are fertile. Ludwig-Maximilians-Universitaet (LMU) in Munich biologists now present that the two varieties have remained distinct mainly owing to the dominant function of plumage coloration in mate alternative.
Crows have divided Europe between them. Western Europe is the area of the soot-black carrion crow, whereas the eastern half of the continent is dwelling to the hooded crow with its grayish black plumage. The boundary between the two populations — or extra exactly, the hybrid zone the place the two meet — is just 20-50 km huge, and in Germany, it follows the course of the River Elbe. That is the one stretch of territory by which each of those species is discovered and successfully mate with one another. The plumage of the fertile offspring of those pairings is intermediate in the shade between these of their mother and father.
The sharp boundary between the two populations, nonetheless, clearly signifies that gene circulates throughout the hybrid zone is restricted, which suggests that hybrids are at a selective drawback. Europe’s crows as soon as shaped a single inhabitant. That is thought to have been damaged up repeatedly over the last glacial maxima in the previous tens to thousands of thousand years in the past, throughout which the crows retreated from Central Europe to milder refuges in Spain and the Balkans.
On the finish of the last Ice Age, they returned to their old haunts. However, they’d modified through the interval of their isolation. “Most probably, a mutation had arisen within the easterly inhabitants, which endowed its carriers with a lighter colored, grey plumage,” says Wolf. Then carrion and hooded crows got here into contact as soon as once more and shaped a narrow hybrid zone. Nonetheless, the genetic mechanisms liable for sustaining the excellence between the two populations have remained unclear.