Meeting Abstract
Understanding how selective forces influence patterns of symmetry remains an active area of research in evolutionary biology. One hypothesis, which has received relatively little attention, suggests that the functional importance of morphological characters could influence patterns of symmetry. Specifically, it posits that features with greater functional importance should be more symmetrical. The aim of my research was to examine the patterns of fluctuating asymmetry (FA) present in the limb bones of semiaquatic freshwater turtles from the family Emydidae. Emydid turtles primarily employ a hindlimb-dominant swimming style, suggesting that hindlimbs should display lower levels of FA. However, within the family, some species are more terrestrial. As terrestrial locomotion places more equal importance on fore- and hindlimbs, such behaviors may minimize differences in FA. This dichotomy in propulsive modes provides an excellent test of the biomechanical hypothesis of symmetry. I measured the length of the proximal limb bone of the left and right fore- and hindlimbs (humerus and femur). These data were used to calculate asymmetry (FA) in each set of bones for each species examined. I then used these data to test two predictions. First, I tested whether within emydid turtles, the hindlimbs would display greater symmetry than the forelimbs. Second, I tested whether such patterns differed between highly aquatic species and species with more terrestrial tendencies. Findings indicate that within emydid turtles, symmetry is higher in hindlimbs, thus supporting the morphofunctional hypothesis. Differences consistent with the differing demands of aquatic and terrestrial locomotion were also detected between the subfamilies.
