Present address: The Ohio State University, Evolution, Ecology, and Organismal Biology, 300 Aronoff Laboratory, 318 W 12th Avenue, Columbus, OH 43210, USA.
Environmental sensitivity of sexual size dimorphism: laboratory common garden removes effects of sex and castration on lizard growth
Article first published online: 25 JUL 2006
Volume 20, Issue 5, pages 880–888, October 2006
How to Cite
COX, R. M., ZILBERMAN, V. and JOHN-ALDER, H. B. (2006), Environmental sensitivity of sexual size dimorphism: laboratory common garden removes effects of sex and castration on lizard growth. Functional Ecology, 20: 880–888. doi: 10.1111/j.1365-2435.2006.01177.x
- Issue published online: 25 JUL 2006
- Article first published online: 25 JUL 2006
- Received 1 April 2006; revised 26 June 2006; accepted 27 June 2006Editor: Raoul Van Damme
- Body size;
- growth rate;
- proximate mechanism;
- 1Adult males average 10% larger than females in natural populations of Yarrow's Spiny Lizard (Sceloporus jarrovii). In two previous studies of free-living animals, we found that (1) this sexual size dimorphism (SSD) develops because yearling males grow more quickly than females and (2) the sex steroid testosterone (T) may regulate this sex difference in growth: castrated males (CAST) grow more slowly than either intact control males (CON) or castrated males treated with exogenous T (TEST).
- 2In the present study, we tested the environmental sensitivity of these sex and treatment effects on growth by raising captive males (CAST, CON, TEST) and females under identical ‘common garden’ conditions.
- 3Sex and treatment effects on growth rate were absent in captivity. The development of SSD was suppressed because captive males grew more slowly than free-living males of equal size, while experimental treatments failed to affect male growth because CAST grew more quickly in the laboratory common garden than in the field.
- 4Individual growth rates were strongly related to food consumption, but feeding rate did not differ between sexes or among male treatments.
- 5Our results call attention to the environmental sensitivity of sex-specific endocrine growth regulation and illustrate the importance of combining laboratory and field studies of growth and SSD.