Drive, suppression and escape from suppression of a selfish chromosome

Meiotic drivers are selfish genetic elements that are predicted to spark rapid intra-genomic arms races with their suppressors. However, the long-term persistence of unsuppressed selfish chromosomes in natural populations violates these theoretical expectations. The Drosophila pseudoobscura Sex-Ratio (SR) chromosome exemplifies this problem, sometimes referred to as the ‘ancient gene drive paradox’. Here, we analyse the evolutionary history of this SR chromosome and show that its genetic architecture and complexity have likely been shaped by a history of drive, suppression and escape from suppression. Our results suggest that the current lack of resistance to the SR chromosome may represent a transient condition awaiting the emergence of new suppressors.