Intraspecific variation in a lizard from the Central Mexican Plateau: Intersexual differences in size and shape explored

Morphological adaptations of individuals are directly (or indirectly) determined by the environment. Depending on sex, these adaptations may vary in different ways, given that different selective forces may be operating on organisms. Here, we evaluate intraspecific morphological variation (size and shape) in two populations of Sceloporus grammicus that occur in different structural habitats (trees and rocks). No difference in overall body size was found between the two populations. However, strong differences were found in body shape; the tree population was characterized by having shorter hindlimb proportions than the rock population, which agrees with the theory of biomechanical models. Furthermore, our results show that this species is dimorphic in size and shape, both in sex and population effects. A review of the literature suggests that the large overall body size and relatively longer distal segments of males could be an advantage for defending their territory, and the observation that females had relatively longer head length may be related to trophic niche divergence; however, this remains to be tested. Detailed quantification of behaviour, performance and reproductive characteristics must be performed to shed light on the evolution of sexual dimorphism in this widely distributed species in Mexico.