| In this dissertation I examined the role of variation in limb and body morphology among western fence lizards (Sceloporous occidentalis) from within the same population. I asked three major questions: (1) do lizards within populations exhibit variation as a function of habitat occupancy, (2) does variation in morphology affect locomotor performance, and (3) is the variation genetically based or the result of phenotypic plasticity.;In addressing the first question, I captured lizards in rock and tree habitats within two Southern California populations and measured the length of their limb segments, mass, and torso. After adjusting for variation in body size, I used Multivariate statistical techniques to determine if morphology varied as a function of habitat. At the Botanic Gardens, lizards from the trees had longer limbs and bodies than lizards from the rocks. At the Motte Reserve, the pattern was reversed; lizards from the rocks had longer limbs than lizards from the trees.;To address the second question, I quantified the locomotor capabilities of lizards from tree and rock habitats at both sites to determine if trade-offs exist among lizards exhibiting different morphologies as predicted from biomechanical models. I videotaped and then timed lizards as they ran along a flat racetrack and along a series of artificial tree branches of different diameters. I quantified jumping by coaxing lizards to leap from a stationary platform and measuring the horizontal distance traveled. There were no differences among the Motte Reserve lizards. At the Botanic Gardens, the longer limbed tree lizards ran faster on the flat racetrack and jumped farther than the shorter limbed rock lizards. The rock lizards ran slightly faster on the medium diameter branch than did the tree lizards.;To address the last question, I raised hatchling male lizards to adult size in a common garden experiment. At hatching, lizards differed morphologically as a function of population and habitat of origin, but these differences did not persist as the individuals aged. I also compared the in-situ growth-rates of lizards from different habitats at each site. At the Botanic Gardens in 1995, lizards from the rocks grew faster than lizards from the trees, but their limbs grew at the same rate. In 1996, the pattern was reversed, lizards from both habitats grew at the same rate, but the forelimbs of the lizards from the trees grew faster than the forelimbs of the rock lizards. Taking into account both the lab and field data, it appears that the environment lizards experience during ontogeny may be instrumental in shaping their adult morphology. |
