Garland 9723758 The proposed research will test hypotheses concerning the morphological and physiological determinants of interspecific variation in locomotor performance of lizards. This will constitute one of the first integrative, multilevel studies of locomotor abilities in any group of animals. It will provide unique information concerning the mechanisms underlying the origin of biological diversity in performance abilities. It may also provide important clues as to how adaptation can overcome potential morphological and physiological constraints. Because the lizards to be studied are fairly generalized in their locomotor modes, the results will also provide an important baseline for future investigations of other tetrapod groups. Members of the North American family Phrynosomatidae will be emphasized because this group is readily accessible and exhibits a remarkable diversity of ecology, behavior, locomotor abilities, and morphology. Endurance running capacity will be measured on a motorized treadmill. Maximal sprint running speed will be measured both on a photocell-timed racetrack, an established method, and on a high speed treadmill. A range of traits that probably affect speed, endurance, or both will be studied for approximately 19 species of Phrynosomatidae and 11 outgroup species, including body size, fimb and tail proportions, body temperature, and muscle fiber type composition.
