Sexual size dimorphism among populations of the rose-bellied lizard Sceloporus variabilis (Squamata: Phrynosomatidae) from high and low elevations in Mexico

It is well known that geographic variation in morphological traits occurs among populations of lizard species. In this study, we analysed body size and sexual size dimorphism among four populations of the lizard Sceloporus variabilis from contrasting elevations. Males from all populations were larger than females in snout-vent length, head length, head width, tibia length, and forearm length. These findings are consistent with the hypothesis that sexual selection acts more strongly on males than on females. Females from higher elevations were larger in size than those found at lower elevations, which could be explained by an increased investment in body size to maximise reproductive success. We suggest that environmental (precipitation, temperature) and ecological (food, competition, predation) factors influence the expression of sexual dimorphism and morphological variation in S. variabilis.