Out on a limb:: the differential effect of substrate diameter on acceleration capacity in Anolis lizards

We investigated how substrate diameter affects acceleration performance in three Anolis lizard species (A. sagrei, A. carolinensis and A. valencienni), representing three different ecomorphs (trunk-ground, trunk-crown, and twig, respectively). We did so by measuring maximal acceleration capacity of the three species on a broad and narrow dowel. In addition to acceleration capacity, we quantified maximal sprint speed on both dowels. Both acceleration capacity and sprint speed are affected by substrate diameter, but the way in which they are, differs among species. Acceleration capacity in the trunk-ground anole, A. sagrei, was least affected by dowel diameter, whereas it was greatly reduced on the narrow dowel in the twig anole, A. valencienni. Sprint speed on the narrow dowel, however, was reduced to the greatest extent in the fastest running species, A. sagrei, whereas sprint speed was hardly affected by dowel diameter in the slow A. valencienni. The differential effect of dowel diameter on maximal acceleration capacity cannot be explained by differences in the timing of reaching maximal acceleration, but may be due to interspecific differences in the relative positioning of the limbs on the different dowels. The differential effect of dowel diameter on sprint speed, on the other hand, may be based on interspecific differences in the relative contribution of subsequent acceleratory bouts to maximal sprint speed on the broad and narrow dowel.