Body-Size Variation across Environmental Gradients in an Ectothermic Organism: An Intraspecific Approach to Ecogeographic Patterns

Bergmann's rule states that endothermic species from cool areas tend to have larger body sizes than those from warm areas. Allen's rule maintains that endothermic species from cool environments should have shorter extremities than their counterparts from warm areas. Although a number of studies have supported both rules, the validity of these trends remains controversial, especially for ectothermic organisms. Here, we studied intraspecific morphological variation in Four-Eyed Frogs (Pleurodema thaul) to determine if these rules are valid in an ecogeographic context. Specifically, we analyzed how morphology varies across nine traits in males of P. thaul collected from nine localities in Chile. A discriminant analysis of all measured traits indicated differentiation between localities, and the first two canonical variables explained ∼80% of the total variation in morphometric features. Additionally, these two canonical variables were correlated with precipitation and monthly minimum temperature. To...