A supergene affects androgen concentrations during juvenile development in the ruff, a bird with alternative reproductive morphs

Sex steroids play a key role in mediating reproductive strategies within species. Their impact is most striking, and best studied, on mature phenotypes. However, genetic variation underlying endocrine pathways may have mechanistic consequences in early life. Here we examined the effects of supergene variants underlying alternative reproductive morphs in ruffs (Calidris pugnax) on sex steroid concentrations in juveniles and compared the differences with previous results in adults.