Adaptative directional asymmetric shape in Testudo hermanni hermanni Gmelin, 1789 (Reptilia: Testudines: Testudinidae)

Pere M. Parés-Casanova

Abstract


Asymmetries consist of deviations from perfect symmetry. If the variation is normally distributed around a mean of zero, fluctuating asymmetry is present; when the variation is normally distributed around a mean that is significantly different from zero, it is called directional asymmetry (DA). We analysed DA comparing plastron shape from 42 captive individuals of Testudo hermanni hermanni (24 males and 18 females) on which ventral digital pictures were obtained. Nineteen landmarks were digitized on the plastron, excluding exterior marginal scutes (12 pairs of opposing landmarks and 7 unpaired landmarks on the body mid-line). We then based the asymmetry analysis on the DA scores from Procrustes ANOVA; all effects of the model were statistically significant, being DA clearly higher. Asymmetric component was different between sexes being larger in males. DA is considered by authors to be as an adaptative trait related to active control on the up-righting.

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