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First published online December 2, 2005
Journal of Experimental Biology 208, 4679-4687 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01948
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Testosterone has opposite effects on male growth in lizards (Sceloporus spp.) with opposite patterns of sexual size dimorphism

Robert M. Cox1,* and Henry B. John-Alder1,2

1 Graduate Program in Ecology and Evolution
2 Department of Animal Sciences, Rutgers University, New Brunswick, NJ 08901, USA



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  		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.

 


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  		Fig. 2. Log10-transformed plasma testosterone (T) concentration vs snout–vent length (SVL) for natural yearling males (open symbols) and females (filled symbols) of (A) Sceloporus virgatus and (B) S. jarrovii, during the mating season. Least-squares regression lines are shown for males of each species: (A) y=8.92x–13.69; (B) y=6.07x–9.44. See text for statistical analyses.

 


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  		Fig. 3. (A,B, left) Growth rate vs initial snout–vent length (SVL) for individual males of (A) Sceloporus virgatus and (B) S. jarrovii, by treatment group. (A,B, right) Growth rate by treatment group, from data in left panels. Lowercase letters denote differences among treatments based on post hoc comparison of growth rates from (A) separate slopes or (B) ANCOVA models with initial SVL as the covariate. Values are means ± 1 S.E.M. (N values are given in bars). Regression equations: (A) CAST, y=–0.002x+0.235; CON, y=–0.013x+0.702; TEST, y=–0.004x+0.251; (B) CAST, y=–0.001x+ 0.113; CON, y=–0.008x+0.591; TEST, y=–0.005x+0.406. See text for statistical analyses.

 




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