Publication Date


Degree Program

Department of Biology

Degree Type

Master of Science


Most modern reptiles are carnivorous or insectivorous, whereas less than 2% of the >7,800 currently recognized species are considered to be herbivorous. Of these, herbivory is confined entirely to lizards; less than 3% of known lizard species eat significant amounts of plants. Most, if not all, herbivorous animals utilize a population of symbiotic microorganisms which can break down plant structural polymers. This study analyzes the bacterial populations from fecal/uric acid deposits of wild and captive samples of the endangered, herbivorous San Esteban chuckwalla (Sauromalus varius: Iguanidae). Substrate and diet samples were also analyzed. Most studies of digestive symbionts use indirect microbiological methods, which are unable to detect and identify many species. 16S rDNA polymerase chain reaction-based denaturing gradient gel electrophoresis (DGGE), which overcomes many limitations of indirect microbiological methods, was used in this study. The banding patterns produced suggest that the wild and captive-bred lizards have different bacterial populations being excreted in their feces. Diet and substrate samples do not appear to be contributing to these differences. All four statistical methods used produced dendograms with two distinct clades for wild and captive-bred lizard fecal/uric acid deposit samples. The data from this study suggest that the fecal bacterial composition of captive-bred lizards are not a subset of the original wild population, but are a distinctive group with as much diversity as the wild population. Differences in diet between these two populations may have impacted the differences presented here. A herbivore must have the digestive microbial symbionts required to digest their native diet and this is especially important for S. varius, which has a native diet that consists of toxic substances and scarcely available food.


Medical Sciences