Meeting Abstract
High levels of fluctuating asymmetry, random deviations from perfect symmetry in otherwise symmetric structures, have been shown to negatively impact animal locomotion. Because fluctuating asymmetry is both heritable and affects performance, it is possible for natural selection for enhanced locomotor performance to generate low levels of asymmetry in limbs that perform locomotor roles. Furthermore, it has been hypothesized that asymmetry will vary with the functional importance of structures, suggesting that in animals with two sets of paired limbs, the more functionally important limb set should be more symmetric. Turtles provide an excellent system in which to test this hypothesis because they are obligate limb-based locomotors. The aim of our research was to examine the patterns of fluctuating asymmetry present in the limb bones of emydid turtles (subfamily Deirochelyinae). This group employs a hind-limb dominant swimming style, and is therefore an excellent group in which to test the biomechanical hypothesis of symmetry. We hypothesized that forelimbs would display greater fluctuating asymmetry than hindlimbs, given their lower level of functional importance. We measured the left and right hind- and forelimb bone lengths in six species (one per genus in Deirochelyinae), and used their measurements to calculate asymmetry in each set of bones for each species. A consistent pattern was detected for fluctuating asymmetry (FA). FA was always higher in forelimbs, though not all species showed significant differences. Furthermore, hindlimb FA was less variable then forelimb FA across species. These results begin to generate a clearer picture of the evolutionary pressures exerted by the need for biomechanical efficiency in locomotion.
