Body size variation across climatic gradients and sexual size dimorphism in Tropidurinae lizards

摘要

In certain lineages of tetrapods, latitude and climate relate to body size in agreement with Bergmann's rule. Trends for squamates are ambiguous, even between genders within a species. Therefore, additional studies are required before generalizations can be made, and attention is needed to the possibility that male and female experience distinct selective pressures and display different patterns. We examine body size in male and female Tropidurinae lizard species and test both Bergmann's and Rensch's rule, using phylogenetic comparative methods. We also analyze whether trends are better explained by latitude or climatic conditions. In Tropidurinae lizards, body size does not vary in accordance with Bergmann's rule within the range of latitudes studied. Therefore, within this range, tropidurines seem not to experience thermal constraints limiting activity time, and therefore growth and body size. Yet, female body size relates to rain patterns, expectedly linked to productivity, suggesting that this gender experiences a stronger tradeoff between energy allocated to growth and to reproduction. In Tropidurinae, males tend to be larger than females and sexual dimorphism is male biased, with an isometric relationship between both sexes that does not support Rensch's rule.