Title

Phylogenetic Constraints Do Not Block Food Chemical Discrimination in the Omnivorous Phrynosomatid Lizard Uma Exsul

Document Type

Article

Publication Date

2006

Publication Source

Journal of Herpetology

Volume

40

Issue

3

Inclusive pages

329-335

ISBN/ISSN

00221511

Peer Reviewed

yes

Abstract

In lizards identification of food using chemical cues allows active foragers to locate hidden prey and omnivores and herbivores to identify palatable plant food, but ambush foragers identify food visually rather than chemically. Omnivores and herbivores derived from ambushing ancestors discriminate food chemicals from control substances. The only known exception is the omnivorous phrynosomatid lizard Sceloporus poinsettii, which lacks food chemical discrimination and which might have been constrained from evolving it by scarcity of chemoreceptors. We studied food chemical discrimination by the phrynosomatid Uma exsul, an omnivore whose diet is 25% plant by volume. In 60 s trials in which chemical cues from mealworms, romaine lettuce, cologne, and water were presented on cotton swabs, lizards responded more strongly to plant and animal chemicals than control stimuli. Food chemical discrimination by Uma exsul strengthens evidence that plant chemical discrimination evolves in tandem with plant diet and prey chemical discrimination also appears in omnivores or herbivores derived from ambush foragers. Confirmation of food chemical discrimination in LI. exsul vitiates the evolutionary constraint hypothesis for S. poinsettii. That lizards tongue-flicked and bit infrequently, yet discriminated, is unusual, suggesting that lingually mediated plant chemical discrimination may have evolved recently, few tongue-flicks are needed to evaluate nutritive properties of plant foods, or plant chemical discrimination is an adaptively unimportant epiphenomenon of plant consumption. Because they do not search actively for prey or tongue-flick before attacking, phrynosomatids presumably evolve prey chemical discrimination by genetic correlation with plant chemical discrimination.

Keywords

phylogenetic constraints

Disciplines

Medical Sciences

 
 

Link to Original Published Item

http://www.jstor.org/stable/4093001