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Area of Expertise:Conservation Biology, Conservation Genetics, Population Genetics, Herpetology
Advisor(s):Dr. Melanie Culver
At the root of conservation genetics is the resolution molecular data can contribute to defining taxonomy. As a PhD student in the School of Natural Resources under Dr. Melanie Culver, I am interested in the biogeographic evolution of one of the Sonoran Desert’s most charismatic reptiles, the Desert Tortoise, Gopherus agassizii. I am using a genomic approach to better understand what evolutionary processes were responsible for shaping what the Desert Tortoise is today.
Over the last decade, I have used molecular approaches to describe gene flow among and within Desert Tortoise populations, to examine multiple paternity, to contribute to the genetic assessment of ESA Recovery Units, and to identify hybrids in captive and wild populations (e.g. Edwards et al. 2004, Murphy et al. 2007 and Edwards et al. 2010). During this time, and with the help of many collaborators, I have built up an extensive collection of desert tortoise DNA samples from the United States and Mexico.
Critical to this effort has been my participation in a multinational, cooperative research effort focusing on crucial aspects of desert tortoise health, genetics, general biology and ecology in Mexico. This has allowed me to obtain tortoise samples from south of the Arizona border, including Sonora and Sinaloa, Mexico. My preliminary data suggest that what we are currently calling Gopherus agassizii is likely three separate lineages (Mojave, Sonoran, and Sinaloan) that have diverged over the last 5-6 million years. The next step is to sort out this phylogeny relative to its geographic distribution, particularly in Mexico.
Phylogenetic clarification is of upmost importance for the continued management of this species. My effort to resolve the taxonomy of the Desert Tortoise in the context of its geographic distribution will help us better direct conservation measures and resources where they are needed most and will ensure that we are able to fully preserve the genetic diversity across the range of this species.
At the UA, I am an Assistant Staff Scientist with the University of Arizona Genetics Core (UAGC) where I oversee genealogical DNA testing services, including the public testing for National Geographic's Genographic Project. I also am an instructor (along with Dr. Hans-Werner Herrmann and Dr. Tom Wilson) for the Desert Ecology and Conservation Biology in Namibia program (RNR 495A/595A) offered through the UA Office of Study Abroad and Student Exchange. In addition to my work at the UA, I work with National Geographic and Lindblad Expeditions as a “National Geographic Expert” and have accompanied programs to Costa Rica, Panama, Peru, and the Galapagos Islands.
Edwards, T., A. Lathrop, K. Choffe, A. Ngo and R. W. Murphy. 2011. STR/microsatellite primers for the Desert Tortoise, Gopherus agassizii, and its congeners. Conservation Genetic Resources 3:365-368.
Edwards, T., C. J. Jarchow, K. E. Bonine and C. A. Jones. 2010. Tracing Genetic Lineages of Captive Desert Tortoises in Arizona. Journal of Wildlife Management, 7(4):801-807.
Murphy, R.W., K.H. Berry, T. Edwards, and A.M. McLuckie. 2007. A Genetic Assessment of the Recovery Units for the Mojave Population of Desert Tortoises, Gopherus agassizii. Chelonian Conservation and Biology 6(2):229-251.
Engstrom, T.N., T. Edwards, M.F. Osentoski, and E.M. Myers. 2007. A compendium of PCR Primers for mtDNA, Microsatellite, and Other Nuclear Loci for Freshwater Turtles and Tortoises in Defining Turtle Diversity: Proceedings of a workshop on Genetics, Ethics, and Taxonomy of Freshwater Turtles and Tortoises. Eds. H.B. Shafer, N.N. FitzSimmons, A. Georges, and A.G.H. Rhodin. Chelonian Research Monographs 4:124-141.
Edwards, T., C.R. Schwalbe, and D.E. Swann, and C.S. Goldberg. 2004. Implications of Anthropogenic Landscape Change on Inter-population Movements of the Desert Tortoise (Gopherus agassizii). Conservation Genetics 5:485-499.
Edwards, T. C.S. Goldberg, M.E. Kaplan, C.R. Schwalbe, and D.E. Swann. 2003. PCR primers for microsatellite loci in the desert tortoise (Gopherus agassizii, Testudinidae). Molecular Ecology Notes, 3:589-591.
Goldberg, C.S., T. Edwards, M.E. Kaplan, and M. Goode. 2003. PCR primers for microsatellite loci in the tiger rattlesnake (Crotalus tigris, Viperidae). Molecular Ecology Notes, 3:539-541.