Electronic Theses and Dissertations

Date of Award


Document Type


Degree Name

Ph.D. in Biological Science



First Advisor

Brice P. Noonan

Second Advisor

Burton K. Lim

Third Advisor

Louis G. Zachos

Relational Format



The neotropics are characterized as the most species rich region in the world. Unfortunately, the region's unparalleled biodiversity has not protected it from ongoing threats such as agriculture, mining, logging, oil extraction, and climate change. I studied the biodiversity and evolution of the herpetofauna of South America in order to investigate the influence of historical geological and climatological events in shaping extant neotropical diversity, particularly the Guiana shield. For my research, I set out to explore the processes involved in shaping the remarkable extant diversity using anuran amphibians as models. With my dissertation, I provide a comprehensive review of the evolutionary history of Guiana shield biota, synthesizing relevant biogeographic and phylogeographic investigations to summarize what is presently known, and more importantly, to prioritize necessary future research. Through rigorous fieldwork, I explored the herpetofaunal assemblage present in and around an isolated mountain system in central Guyana, filling in a large sampling gap while simultaneously expanding the list of known herpetofauna for the country. Using molecular methods, I conducted the most comprehensive geographic analysis to date exploring the evolutionary patterns and cryptic diversity within the widespread Rhinella margaritifera species complex, and reveal the presence of many additional lineages awaiting description within this group throughout its entire distribution. Lastly, I modeled patterns of anuran biodiversity within the Guiana shield under past, present, and future climatic scenarios to understand which regions have been most important for supporting high species diversity and endemism. I recover core areas throughout the Guiana shield which have been most important amphibians and warrant conservation efforts to safeguard them for the future. Broadly, this work shows that species richness of neotropical amphibians still remains underestimated and identifies core areas within the Guiana shield that are likely to harbor additional uncovered diversity. Through the combination of fieldwork, molecular techniques, and predictive modeling, the factors responsible for the generation of extant diversity and the locations of regional endemism become clearer.

Included in

Biology Commons



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