While developmental plasticity has been shown to contribute to sexual size dimorphism (SSD) in laboratory studies, its role in shaping SSD variation in wild vertebrate populations is unclear. Here we use a field study and a laboratory experiment to show that resource availability influences the degree of SSD among insular populations of Anolis sagrei lizards in the Bahamas. Total amounts of food biomass explained variation in male, but not female, body size on six Bahamian islands, giving rise to significant differences in SSD. Laboratory experiments on a captive colony of A. sagrei confirmed that variation in SSD was mediated by the effects of prey biomass on developmental plasticity in males, but not females. Indeed, males grew faster and attained larger sizes as adults under high food treatments than under restricted diets, whereas adult females retained similar body sizes under both conditions. Our results indicate that the amount of food available can influence inter-sexual variation in body size within a vertebrate species. Sex-specific developmental plasticity may be favored if it allows individuals to take advantage of varying levels of food opportunities offered by different habitats, by reducing competition between the sexes. As such, plasticity in response to food availability may have played a role in the invasion success of A. sagrei. This study adds to our growing understanding of the effect of resource availability in shaping SSD in reptiles and lends further support to the condition-dependence hypothesis, according to which the larger sex should display greater plasticity in growth in response to environmental conditions. This article is protected by copyright. All rights reserved.
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