Collaborators:

• This project involves over 40 collaborators from the US and Mexico.

This project is a multi-faceted, multinational, and cooperative effort to focus on crucial aspects of desert tortoise health, genetics, general biology and ecology in Sonora, Mexico. The project will draw on the expertise of scientists and field biologists in Canada, the United States, and Mexico and will provide information critical for managing and conserving the desert tortoise throughout its range, but especially in Mexico, where tortoises occur in habitats different from those in the United States, and much relevant information needs to be collected. Taylor Edwards is a principal investigator for the genetics portion of this ambitious project.

Approximately 40-45% of the desert tortoise's geographic range is in Mexico (Patterson, 1982), but the distribution and ecological requirements in Mexico are poorly understood. In general, populations of desert tortoises in Mexico have been sorely neglected compared to the ambitious research efforts in the United States. Over the past three decades some work has been done, but much more is needed to determine the status of the species in the southern portions of its range. In the initial phase of the project, studies will focus on behavior of desert tortoises in the dry tropical forest in Alamos, Sonora. The initial proposed study site occurs in the northern most extent of the geographic range of the dry tropical forest habitat in Mexico. Dogs, trained to locate desert tortoises in U.S. habitats, will be used to help gather data on the tortoises in the dry tropical forest where earlier survey efforts were hindered by the low tortoise visibility in the dense understory vegetation. Focal studies of individual tortoises using radiotelemetry will be used to compare movements and behavior of tortoises in dry tropical forests to focal studies of tortoises in other habitats. This project was initiated in November 2004 where a team was assembled to locate tortoises, attach telemetry equipment, and draw blood samples for genetic and disease studies. Fifty samples were collected and are currently being analyzed at the UofA.

Recent data from nuclear DNA indicate fixed differences between Mojave and Sonoran individuals suggesting that these populations are on separate evolutionary trajectories and should potentially be defined and managed independently. Indications suggest that tortoises in Mexico may be equally as differentiated as the Sonoran and Mojave populations in the U.S. and defining these distinctions are necessary for effective conservation of tortoises outside the U.S. In our current efforts to better define the populations, subspecies, and species distinctions of desert tortoises, these samples are critical to our overall understanding of the Gopherus agassizii population structure. Our goal is to assist in the designation of management units for the entire range of the desert tortoise, including Mexico, so that conservation efforts can be applied with specificity to each area. We will use genetic data to determine the extent to which sampled populations have experienced population declines and therefore which populations are most vulnerable from the combined effects of barriers to gene flow and loss of genetic variability. In addition to autosomal microsatellites, we will use mitochondrial DNA sequence data to assess phylogenetic relationships among sampled regions and clarify the currently unresolved taxonomy of the G. agassizii and G. berlandieri complex.