Hindlimb asymmetry reduces escape performance in the lizard Psammodromus algirus.

Locomotor performance of lizards and its relationship to the ecology and morphology of the forms concerned has been well studied recently. Asymmetry of limbs might make the body unstable and make performance less effective. However, their effects on terrestrial locomotion remain almost unexplored. In this article, the escape performance of the lizard Psammodromus algirus running at high speed was related to hindlimb morphology and fluctuating asymmetry levels. Femur length was significantly shorter than crus length. However, absolute fluctuating asymmetry in femur length was significantly larger than in crus length. Asymmetry was not related to body or limb size, thus larger individuals or those with longer limbs did not have significantly greater fluctuating asymmetry. Neither body size nor the length of the limbs (femur or crus) were significantly related to any of the variables describing escape performance. However, escape performance was affected by femur-length fluctuating asymmetry, which resulted in significantly reduced overall escape speeds. In contrast, asymmetry in crus length did not affect escape performance. We discuss the possible basis of these alterations of locomotion, the relevance of reduced performance for the ecology of this species, and how individuals may compensate for the costs of asymmetry.