Digest: Chromosomal architecture of behavioral isolation in marine isopods.

How do reproductive barriers persist when diverging species come back into contact? Ribardière et al. (2026) investigated this question in 2 marine isopods, Jaera albifrons and Jaera praehirsuta, whose males court females using divergent specialized setae. By combining population genomics and controlled crosses, the authors show that genomic regions resisting interspecific gene flow are concentrated on sex chromosomes and rearranged chromosomes-regions of low recombination that harbor the genetic bases of divergent male courtship traits.