Date of Award

Fall 12-2009

Degree Type


Degree Name

Doctor of Philosophy (PhD)


Biological Sciences

Committee Chair

Brian Kreiser

Committee Chair Department

Biological Sciences

Committee Member 2

Carl Qualls

Committee Member 2 Department

Biological Sciences

Committee Member 3

Jake Schaefer

Committee Member 3 Department

Biological Sciences

Committee Member 4

Michael Davis

Committee Member 4 Department

Biological Sciences


Chelonians (i.e., turtles) are an imperiled group of reptiles with about 66% of the recognized species listed as threatened by the IUCN. Most chelonian species have a unique set of life history traits (i.e., longevity, delayed sexual maturity, and low juvenile survivorship), which makes their populations exceedingly sensitive to increases in adult and juvenile moralities. With numerous anthropogenic effects (e.g., habitat alteration, exploitation, and over harvesting) negatively influencing mortality rates, chelonians have experienced global precipitous declines and extinctions.

This dissertation focuses on species within two chelonian genera, Gopherus and Graptemys. Although these two genera are vastly different ecologically, they are exposed to similar threats and possess similar conservation requirements. Within the genus Graptemys this dissertation focuses on the conservation genetics and systematics of three species (i.e., G. gibbonsi, G. oculifera, and G. flavimaculata) with distributions restricted to the Pearl River of Louisiana and the Pascagoula River of Mississippi. Since the taxonomic status of these species is still unresolved, I used molecular (i.e., mitochondrial) and morphological (only for the G. oculifera and G flavimaculata comparison) data to assess the degree of differentiation and divergence between these species. The last two chapters focus on the conservation genetics of Gopherus polyphemus. In particular, I examined the level of genetic diversity within several western populations experiencing aberrantly low hatching success using microsatellites, and conducted a range-wide phylogeographical study in an attempt to relate patterns of genetic structure with current management units for the species.