26th Annual Meeting and Symposium of the
Desert Tortoise Council, March 16-18, 2001
Abstracts

STUDENT PAPER

Genetic Variability Among and Within Sonoran Populations of the Desert Tortoise: Attempts to Identify Informative Microsatellite DNA Markers

Taylor Edwards¹, Don E. Swann², and Cecil R. Schwalbe^3
1Wildlife and Fisheries Science, University of Arizona, 125 Biological Sciences East, Tucson, AZ 85721
²National Park Service, Saguaro National Park
³USGS, Sonoran Desert Field Station, Room 125 Bio Sciences East, University of Arizona, Tucson, Arizona 85721

In this study we are attempting to gather information on the population genetics of the desert tortoise (Gopherus agassizii) in southern Arizona to assess potential long-term effects of habitat fragmentation due to valley-bottom development, such as roads, canals, and agriculture. Using microsatellite markers, we will estimate gene flow and compare genetic distance with geographic distance between desert tortoises in different mountain ranges to determine extent of relatedness and degree of genetic isolation. In addition, we will examine genetic relatedness of individuals within a seeming continuous population in Saguaro National Park while simultaneously gathering movement data with radiotelemetry. We will relate genetic distances among these individuals to geographic distances between them to determine if behavior or habitat features influence gene flow within the population. A goal is to recommend management strategies such as reserve design coupled with translocation for maintaining genetic integrity of desert tortoises in the Sonoran population in Arizona. During summer 2000 we collected blood samples from 117 tortoises in 11 sites around the Tucson Basin. We are currently constructing a microsatellite-enhanced genomic library using biotin-labeled repeat oligos and streptavidin beads. Inserts containing tandem repeat arrays will be sequenced, and flanking primers will be designed for amplification of microsatellites. Identification of informative microsatellite markers in the desert tortoise genome may have application in other Gopherus species in the United States and Mexico. Project completion is scheduled for 2002. This project is funded by the Arizona Game and Fish Department Heritage Grant Program.