Evidence that minor directional asymmetry is functional in lizard hindlimbs



I examined directional asymmetry (DA) in the number of subdigital lamellae under the fourth toe (MDA) and in injury frequency (IDA) on the hindlimbs of eight Agamidae. In no species were MDA and IDA statistically significant, neither was there significant sexual dimorphism in MDA. But a strong, positive relationship exists between MDA and IDA, contrasting with the weak positive correlation between the side of injury and the morphologically dominant side in individual lizards. Therefore the relationship between MDA and IDA results from an evolutionary process, probably involving higher survival after injury of the morphologically dominant side. This process suggests functional importance of DA in the frame of evolution caused by unsuccessful predation.