Degenerative expansion of a young supergene

Suppressed recombination ultimately leads to gene loss, as demonstrated by the depauperate Y chromosomes of long-established XY pairs. To understand the shorter term effects, we used high-resolution optical mapping and k-mer distribution analysis on a young non-recombining region of fire ant social chromosomes. Instead of shrinking, the region has increased in length by more than 30%. This demonstrates that degenerative expansion can occur during the early evolution of non-recombining regions.