Directional asymmetry in reptiles (Sauria: Gekkonidae: Ptyodactylus) and its possible evolutionary role, with implications for biometrical methodology



In a study of morphological directional asymmetry (DA) on the population level, four characters were bilaterally examined in geckos (museum specimens, total n Ptyodactylus puiseuxi, P. guttatus and P. hasselquistii, from Israel and Sinai. Significant DA occurred in adults in five or six out of 12 character-taxon-combinations (CTCs): number of supralabilia in P. puiseuxi and guttatus, length of ear aperture in puiseuxi and hasselquistii; number of subdigital lamellae in guttatus; and width of the digital pad in hasselquistii. The average magnitude of DA per CTC ranged from 1.5 to 5% of organ size, without correlation to organ size. Side dominance varied, mostly witin characters between taxa. No sexual differences in DA were significant, although for two CTCs DA was significant only in one sex. Presumably neutral or pleiotropically-adaptive DA is a potential base for the evolution of functional DA. One practical conclusion is that in comparative biometrical studies, bilateral characters should not be examined consistently on only one side.