Mechanisms causing variation in sexual size dimorphism in three sympatric, congeneric lizards

Manicom, Carryn, Alford, Ross, Schoener, Thomas W., and Schwarzkopf, Lin (2014) Mechanisms causing variation in sexual size dimorphism in three sympatric, congeneric lizards. Ecology, 95 (6). pp. 1531-1544.

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Sexual differences in adult body size (sexual size dimorphism, or SSD) ultimately can be favored by selection because larger males are more likely to be successful competitors for females, because larger females bear larger clutches, or because intersexual size differences reduce resource competition. Natural selection during juvenile development can influence sexual dimorphism of adults, and selection on adults and juveniles may differ. Studies that address the relative contributions of adult body shape dimorphism and sexually dimorphic patterns of growth and maturity are particularly useful in understanding the evolution of size dimorphism, yet they are rare. We investigated three sympatric, congeneric lizard species with different degrees and directions of adult sexual dimorphism and compared their growth patterns, survival probabilities, and intersexual trophic niche differences. Different mechanisms, even within these closely related, sympatric species, acted on juvenile lizards to produce species differences in adult SSD. Both degree and direction of dimorphism resulted from differences between the sexes in either the duration of growth or the rate of growth, but not from differences in rates of survival or selection on juvenile growth rate. Species- and sex-specific trade-offs in the allocation of energy to growth and reproduction, as well as differential timing of maturation, thus caused the growth patterns of the sexes to diverge, producing SSD. The differences that we observed in the direction of SSD among these species is consistent with their different social systems, suggesting that differential selection on adult body size has been responsible for the observed species-specific differences in juvenile growth rates and maturational timing.

Item ID: 34026
Item Type: Article (Research - C1)
ISSN: 1939-9170
Keywords: body size; Carlia rostralis; Carlia rubrigularis; Carlia storri; growth; head size; lizards; northeastern Australia; prey size; sexual maturity; sexual size dimorphism; survival
Funders: Australian Research Council (ARC), James Cook University, US National Science Foundation (NSF)
Projects and Grants: ARC DP0344219, ARC DP0557170
Date Deposited: 24 Jul 2014 01:02
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060202 Community Ecology (excl Invasive Species Ecology) @ 35%
06 BIOLOGICAL SCIENCES > 0603 Evolutionary Biology > 060303 Biological Adaptation @ 35%
06 BIOLOGICAL SCIENCES > 0603 Evolutionary Biology > 060308 Life Histories @ 30%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%
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