MILLER, G.*; ANGIELCZYK, K.D.; California Academy of Sciences; California Academy of Sciences: Geometric Morphometric Analysis of Shell Kinesis in Emydine Turtles

To provide context for an ongoing study of plastron (lower shell) shape variation in the emydine turtle Emys marmorata, we examined plastron shape in six other emydine species (E. blandingii, E. orbicularis, Clemmys guttata, Glyptemys insculpta, G. muhlenbergii, Terrapene ornata) using geometric morphometrics. We digitized 19 landmarks on photographs of over 1000 specimens, and all landmarks but two were junctions between or extremal points on the sulci separating the plastral scutes. Multivariate regression showed that plastron shape is highly correlated with size in the seven species, although differences exist in how each species� shape is affected by size. Pairwise comparisons using MANOVA and canonical variates analyses showed that the seven species have significantly different plastron shapes that can be differentiated with great certainty. Principal components analysis shows that a major component of shape variation among the specimens is related to the presence or absence of a kinetic plastron. Terrapene ornata clearly occupies a different region of morphospace than the included taxa with akinetic plastra. However, the kinetic taxa E. blandingii and E. orbicularis are intermediate in shape between the T. ornata specimens and the other taxa. Emys blandingii and E. orbicularis are more closely related to one of the akinetic taxa (E. marmorata) than they are to T. ornata, and share the former species� semi-aquatic to aquatic lifestyle. Therefore, our results suggest that phylogeny and/or habitat also are important determinants of plastron shape. Additional insight into the relationships between phylogeny, habitat, kinesis, and plastron shape may be gained by the future inclusion of additional Terrapene species, which all possess kinetic plastra, but display lifestyles ranging from aquatic to terrestrial.