Divergent scute asymmetry among pure and crossed individuals of Testudo hermanni (Gmelin, 1789)

Abstract

Fluctuating asymmetry (FA) refers to subtle differences between left and right sides in bilaterally symmetrical organisms or their parts. Both genetic and environmental changes can increase FA, reflecting deterioration in developmental homeostasis of adult morphology due to a loss of developmental stability. In this study, we used geometric morphometric techniques to examine plastral scute asymmetries in a sample of 31 pure and crossed Testudo species (T. hermanni hermanni n = 23 and crosses with T. hermanni boettgeri n = 8) only females by means of 19 anatomical landmarks. Procrustes ANOVA indicated that FA in crossed individuals was significantly higher than that in pure individuals. Crossed individuals also showed a greater degree of phenotypic plasticity than T. hermanni hermanni. We conclude that crosses among T. hermanni hermanni and T. hermanni boettgeri can increase homozygosity and are responsible for greater developmental instabilities. Nonetheless, more information on crossed phenotypes could be of great interest to raise pure Hermann’s tortoises for reintroduction programmes. Key words: Carapace, Geometric morphometrics, Hybridization, Plastron, Testudines