FLICKR, ARJAN HAVERKAMPMale ruffs (Philomachus pugnux) employ one of three different strategies to mate: defend a territory when they aim to monopolize females, sneak into the territories of the dominant males to steal copulations, or resemble females to evade detection by the dominant males and jump in mid-coitus. Which of these alternative reproductive tactics a male follows is determined by 125 contiguous genes that compose a single supergene stretching some 4.5 million base pairs in length, according to two studies published in Nature Genetics this week (November 16).
Interestingly, the genetic differences between the three male morphs—which vary in their appearance as well as their behavior—is dramatic and quite old. “The sequence difference is larger than the average sequence difference between humans and chimps, so we estimate it occurred at least 4 million years ago,” Leif Andersson, an evolutionary geneticist at Uppsala University in Sweden who coauthored one of the studies, told The Washington Post.
It’s a bit unusual for such a long stretch of DNA to stay together for such a long time, without being broken up by recombination. The sequence data suggest that the supergene originally arose following an inversion event that prevented reshuffling with a sister chromosome. “It’s rather like the emergence of a new sex chromosome,” Terry Burke, an ...
