MCBRAYER, L.D.; Stephen F. Austin State University: Head shape and foraging mode in lizards: What is�or is there�a relationship?

This study explores the potential relationship(s) between skull morphology, foraging mode, and phylogeny in lizards. For many vertebrates, there is close correspondence between skull morphology, diet, and foraging behavior, but comparatively little is known about these relationships in lizards. An association among phylogeny, tongue morphology, chemosensory ability, and foraging behavior is well established in lizards, however, we have little understanding of how these traits might be related to overall variation in skull form. Substantial variation in skull shape exists across the Iguanian, Scleroglossan, and Autarchoglossan clades, and thus it is possible that some skeletal variables may change in tandem with the above traits. To explore this possibility, 8 measurements of the skull were collected in 22 lizard species (13 ambushing species, 9 actively foraging). Two questions were addressed: can skull morphology reliably predict foraging mode? and which variable(s) are most important in separating foraging mode and phylogeny? Of the 248 observations, 80% were correctly classified as ambush foragers and 89% of the active foragers were correctly classified by discriminant functions analysis. A cluster analysis revealed 2 assemblages of species that generally followed taxonomic groupings. However, a cluster of 5 autarchoglossan species were nested within the group of 6 iguanian species. Several hypotheses were explored, using PCA and MANOVA, to explain this pattern. Apparently, active foragers (i.e., Autarchoglossans) elongate the tooth row length while ambush foragers (Iguanians) tend to elongate the insertion site for the jaw adducting musculature. These findings support and refine earlier correlations of skull length and skull width with foraging mode in lizards.