Jumping gene gave fish a freshwater start

Fish diversification depended on multiple copies of a metabolic gene When organisms evolve to occupy new environments, what adaptations are necessary for the transitions, and how predictable are these solutions when the transitions occur repeatedly? On page 886 of this issue, Ishikawa et al. ( 1 ) describe a refreshingly precise and thorough example of how a single adaptive genetic innovation has repeatedly allowed marine fish to colonize and diversify in freshwater. Whereas previous studies on evolutionary transitions and subsequent radiations to new ecological niches have largely focused on morphology ( 2 , 3 ), the new study neatly links ecology, physiology, and genetics through a dietary adaptation.