Fig. 1. (A,B, left) Plasma testosterone (T) concentration vs sampling date for natural yearling males and females of (A) Sceloporus virgatus and (B) S. jarrovii. Lowercase letters denote monthly differences within males (ANOVA with REGWQ post hoc test). Shaded areas indicate the approximate duration of T manipulation experiments. (A,B, right) Plasma T concentration for treatment groups at the conclusion of our experiments. Lowercase letters denote differences among treatments (ANOVA with REGWQ post hoc test). Values are means ± 1 S.E.M. (N values are given beside symbols and in bars). See text for statistical analyses.