28th Annual Meeting and Symposium of the
Desert Tortoise Council, February 21-23, 2003
Abstracts

Defining the Desert Tortoises(s): Our First Priority for a Coherent Conservation Strategy

Robert W. Murphy¹, David J. Morafka², and Kristin H. Berry^3
1Centre for Biodiversity and Conservation Biology, Royal Ontario Museum, 200 Queen's Park, Toronto, Ontario M5S 2C6 Canada
²Department of Herpetology, California Academy of Sciences, Golden Gate Park, San Francisco, California 94118
³U. S. Geological Survey, Western Ecological Research Center, 22835 Calle San Juan de Las Lagos, Moreno Valley, CA 92553

Many populations of desert tortoises within the Gopherus agassizii - G. berlandieri complex could be designated as species, subspecies, Distinct Population Segments (DPSs), Evolutionarily Significant Units (ESUs), or Management Units (MUs). However, the appropriate designations for populations remain incompletely resolved. Ambiguities regarding the phylogenetic relationship and taxonomic status of desert tortoises impede precise and efficient legal protection, and compromise extrapolations from the studies of one population to another. Herein, we (1) identify the impediments to constructing a phylogenetic taxonomy and both genetic and ecological determinations of conservation units, (2) examine the consequences of delaying such resolution, (3) summarize the current data base available for systematic studies, (4) compare taxonomic solutions in other terrestrial chelonians, and (5) suggest remedies. A standardized program of sampling that includes all major populations across the entire range of both G. agassizii and G. berlandieri is proposed to complete the identification of populations and their assignments to mtDNA-based ESU and MU categories. Populations in potential contact zones should be sampled more extensively to determine the absence or extent of gene flow among different ESUs to resolve the identity of species. Finally, morphological, ecological, behavioral, and physiological distinctions among populations would establish a complete and broadly based array of DPSs. These efforts would promote more effective protection of desert tortoises and their diversity and would focus future ecological and behavioral studies more precisely. (From Chelonian Conservation and Biology 2002 4(2).