A biomechanical analysis of intra- and interspecific scaling of jumping and morphology in Caribbean Anolis lizards.

Scaling models predict how functional variables change as animals grow or increase in size evolutionarily. However, few experimental studies have found support for the predictions of these models. Here, we use a force plate to investigate the scaling of functional variables associated with jumping within (for three species) and across adults of 12 species of Anolis lizards. Both ontogenetically (with the exception of Anolis carolinensis) and across the 12 species examined, limb dimensions increased geometrically, making Anolis lizards an ideal study system to test the predictions of geometric scaling models. However, both the ontogenetic and interspecific scaling of functional variables deviated in several aspects from model predictions. Unexpectedly, the scaling of functional variables such as acceleration differed for different species. Whereas acceleration capacity increases with hindlimb length for A. carolinensis, no relationship was detected for the other two species. Interspecifically, the inclusion of two large species in our analysis appears to drive the absence of a correlation between acceleration capacity and hindlimb length across species. These data suggest that selection for enhanced jumping performance is relaxed in larger anoles and support the notion that no scaling model seems to be able to comprehensively predict changes in function with size across species; rather, natural selection seems to drive changes in the scaling relationships of some key variables such as force output or acceleration capacity.