Meeting Abstract

94.4  Monday, Jan. 6 14:15  Testosterone pleiotropically regulates sexual dimorphism in multiple traits COX, C. L.*; HANNINEN, A. F.; REEDY, A. M.; COX, R. M.; The University of Virginia; The University of Virginia; The University of Virginia; The University of Virginia clcox@virginia.edu

Sexual dimorphism is predicted to evolve slowly as genetic correlations are gradually eroded. However, this theoretical expectation is at odds with the observation that closely related species often differ in the direction and magnitude of sexual dimorphism, as well as in the trait combinations that exhibit dimorphism. This phylogenetic lability may be facilitated by the evolutionary coupling and decoupling of pleiotropic modifiers, such as sex steroids, to conserved developmental pathways that are shared between the sexes. To begin to assess this possibility, we tested for pleiotropic effects of testosterone on a suite of physiological and morphological traits in the sexually dimorphic brown anole lizard (Anolis sagrei). In two separate experiments on captive animals, we administered either testosterone or placebo implants to (1) intact males and females at approximately the age (6-7 mo) when sexual dimorphism first becomes pronounced, and (2) intact females and castrated males at an age (10-11 mo) when developmental trajectories are highly divergent between the sexes. In both sexes and at both ages, testosterone stimulated (1) growth in length and mass, (2) growth and coloration of the dewlap, (3) resting metabolic rate, (4) utilization of fat bodies, and (5) size of the gonads. These results confirm that testosterone regulates many sexually dimorphic traits and suggest that males and females share the same physiological and genetic potential to respond to this pleiotropic developmental modifier.