ROBSON, Michael A.; None: Morphology and locomotor performance co-variation in a demographically known population of the banded rock lizard, Petrosaurus mearnsi

A population of the banded rock lizard (Petrosaurus mearnsi) was the focus of a five-year longitudinal study. Data on growth and survivorship were obtained for each of the five years. Two performance variables, sprint speed and endurance, were measured for each individual as well as seven skeletal features presumed to effect locomotion using x-rays. The patterns of co-variation among morphological traits, different age classes and years were calculated. In addition, the performance gradient, which describes the covariance between morphology and locomotor performance, was estimated. The longitudinal study provided an opportunity to ascertain whether the performance gradient differed among years or among age classes. Significant differences in the size-adjusted locomotor performance measures were observed among-age classes, among-years and in the interaction of the two. Likewise, size-adjusted morphological characters differed significantly in age classes, years and their interaction. The observed variation in maximum sprint speed among age classes was a consequence of size: no differences in size-adjusted sprint speed were observed among age classes despite significant differences among individuals. However, maximum endurance capacity increased significantly with age. Principal components analysis on the size-free morphological characters revealed the largest proportion of variance was explained by relatively longer distal limb elements, coupled with a narrower and longer pelvis. Significant differences between age classes were evident in tarsus length, fourth toe length and pelvis width. Elements of the pelvic girdle were significant predictors of locomotor performance. However, the performance gradient exhibited significant temporal heterogeneity.