External morphology measurements of several species of the plethodontid genus Aneides

While sexual dimorphism has long received special attention from biologists, derived monomorphism, the condition in which both males and females express similar derived features, has been less well studied.  Historically, the appearance of “male-like” features in females has been explained by the genetic correlation between the sexes.  Recent work emphasizes the importance of studying the independent selective forces on both females and males to understand sexual dimorphism.  Sexual dimorphism and derived monomorphism in the genus Aneides are examined in light of predictions of social selection.  Aneides hardii shows the greatest degree of sexual dimorphism in snout-vent length and head width, with the other species of Aneides less sexually dimorphic. This reduced dimorphism, however, is not a return to an ancestral monomorphic state, but rather exemplifies derived monomorphism because females express traits that were limited in expression to males of ancestral species.  Instead of call...