Meeting Abstract
Horned lizards of the genus Phrynosoma are well known for their iconic horns, a unique trait among North American lizards. Horned lizards share similar body form and dietary specializations but display disparity in size, tail length, and most notably in horn and head morphology. Morphological traits in Phrynosoma such as head size and limb length have been shown to be correlated with environmental factors like precipitation and temperature. Evolutionary reduction in horn size has been suggested to co-occur with shifts in life history traits like viviparity and viviparous species tend to occur at cooler, higher elevations. The relationship between environment and head ornamentation in horned lizards is not fully understood. We used micro-computed tomography (micro-CT) scanning to generate volumetric models of skulls across the full range of Phrynosoma from 127 specimens across 13 species. Variation in horn and head shape was examined using 3D geometric morphometric techniques. We partitioned this variation into its multiple explanatory components including environmental characteristics, phylogenetic relatedness, and life history traits. Here, we describe preliminary morphometric variation in Phrynosoma skulls and compare this to the patterns reported using traditional 2D morphometric methods. Our results improve understanding of how species morphology and specialized defense traits respond to environmental gradients and provide hints on future evolutionary and ecological trajectories under impending climate change.
