Elevation gradients and lizard assemblage structure in the Bonneville Basin, western USA

We analyzed lizard assemblage structure as a function of elevation in the Bonneville Basin region of the Great Basin Desert using data from visual surveys performed between 2000 and 2003. A total of 1221 lizard observations were recorded, representing eight of the nine species known to occur in the Bonneville Basin. Individual species response curves showed Gaussian and truncated Gaussian distributions for most taxa, and most species demonstrated a nonrandom dispersion of occurrences along the elevation gradient. Nonmetric multidimensional scaling (NMS) revealed hierarchical structuring of lizard species, and strong correlation of NMS axes with elevation provided evidence of uniform lizard community assembly with respect to elevation throughout the study region. Species richness averaged between 2 and 3 across surveys and specific species pairs were frequently associated with each other. Collectively our analyses provide insight into the possible roles of history and habitat heterogeneity in the structuring of a depauperate lizard fauna at the mesoscale.