PATTERNS OF CAUDAL-AUTOTOMY EVOLUTION IN LIZARDS

Using comparative techniques to account for phylogenetic effects, I ex amined patterns of evolution of caudal autotomy and foraging in 39 liz ard species to test the hypothesis that caudal autotomy has co-evolved with morphology, locomotor performance, and foraging behaviour. There were significant positive associations between evolution of the point on the tail (distance from cloaca) at which tail loss occurs (an indi rect measure of caudal autotomy) and evolution of each of the followin g: tail length, caudifemoralis longus (CFL) muscle length, and jump di stance. The correlation with the evolution of sprint speed approached significance. These relationships primarily were due to the influence of tail-length evolution on autotomy-point evolution. With the effect of tail-length evolution removed, autotomy-point evolution was negativ ely correlated with the evolution of tail-loss frequency. The CFL rest ricts tail loss to portions of the tail posterior to the most distal p oint of its insertion in the tail. In addition, with the effect of tai l-length evolution removed, CFL length coevolved with sprint speed. Th ese results indicate that tail morphology has co-evolved with caudal a utotomy such that the evolution of the CFL has reduced caudal autotomy in certain groups of lizards. Ambush foraging, the ability to lose th e tail, intermediate CFL length, and low locomotor performance (i.e. s low sprint speed and short jump distance) are hypothesized to be the a ncestral conditions in lizards using outgroup rooting. The diversifica tion of lizard taxa has resulted in some lineages moving away from anc estral character states (i.e. family Teiidae, superfamily Varanoidea), while others are very similar or identical to their ancestors (i.e. s uperfamily Iguania).