Plant chemical discriminations by an herbivorous iguanid lizard, Sauromalus ater

Abstract

AbstractWe experimentally studied the ability of the iguanid lizard Sauromalus ater to discriminate between plant and animal foods and control stimuli using only chemical cues. When chemicals were presented on cotton swabs, the lizards exhibited stronger responses, as indicated by tongue-flicking and biting, to chemical stimuli from romaine lettuce than from crickets and control substances. Responses to plant and animal food did not differ significantly in S. ater, which eats animal prey only occasionally in natural populations. Although there were no significant differences between responses to cricket chemicals and other stimuli for the entire data set, those individuals that ate or attacked crickets tongue-flicked at high rates in response to cricket chemicals. Based on the presence of herbivory and plant chemical discrimination in three iguanid genera, it is likely that plant chemical discrimination is ubiquitous in iguanids. Given the uncertainty of iguanian phylogeny, the evolution of herbivory and response to plant chemicals cannot be traced with confidence. However, it appears very likely that lingually mediated plant chemical discriminations evolved in the common ancestor of Iguanidae or earlier in iguanian history in response to a shift to an herbivorous diet.