Levels of Sex Steroids in Plethodontid Salamanders: A Comparative Study Within the Genus Aneides

ABSTRACT Derived monomorphism is a condition in which males and females are phenotypically similar, but the similarity is derived. Derived monomorphism typically evolves from sexual dimorphism or from a different monomorphic state. We examined the hormonal basis of derived monomorphism in the salamander genus Aneides (Plethodontidae). We reject our hypothesis that circulating levels of androgens explain the derived traits, such as enlarged jaw musculature, in females (some would call them “male‐like traits”). There was no clear pattern of differences in androgen levels or degree of dimorphism in androgen levels, between the sexually dimorphic Aneides hardii and the other, derived monomorphic, species studied. Concentrations of testosterone and dihydrotestosterone were higher in males than in females in all species examined. The degree of sexual dimorphism in androgen level was also consistent among the species studied. Levels of androgens in female plethodontids have not been previously reported. Species in the salamander genus Aneides (family Plethodontidae) show interesting patterns of sexual dimorphism. Levels of androgens in males and females do not explain the variation observed between species in the degree of dimorphism and monomorphism.