Selfish X chromosomes in Drosophila

Selfish genetic elements violate the rules of Mendelian inheritance in order to increase their transmission, often at the expense of the organism. They are pervasive and important players in organismal ecology and evolution, but have traditionally been difficult to study because they are often cryptic. Amongthe most striking examples of selfish genetic elements are selfish X chromosomes that interfere with meiosis; these have been documents so far in insects, plants, and rodents. In insects, males that carry a selfish 'distorting' X chromosome produce a gene product that destroys Y-bearing sperm, so that they produce only (or mostly) daughters. A major outstanding question is to understand the ecological and evolutionary consequences of this extreme sex ratio distortion. What prevents a selfish X chromosome from driving its host to extinction? How does the rest of the genome respond to distortion? We have discovered a selfish X chromosome in a common woodland fly, Drosophila testacea, and I will present our recent work aiming to understand its ecology, genetics, and evolution.​