Gene regulation of aggression and courtship in ruffs (Calidris pugnax)

Androgens are highly pleiotropic modifiers of gene expression playing pivotal roles in the formation and variation of three alternative sexual phenotypes in ruffs (Calidris pugnax). We show that, in ruffs, differences in circulating androgens between male morphs are linked to 17-beta hydroxysteroid dehydrogenase 2 (HSD17B2) expression, which is part of an autosomal inversion that genetically determines the morphs. A combination of regulatory and evolutionary changes in this single steroid-related gene introduces endocrine variation that ultimately results in the diversification of reproductive phenotypes.