Genetic Delineation of Management Units for the Desert Tortoise, Gopherus agassizii, in Northeastern Mojave Desert

Abstract

Blood samples from 236 desert tortoises, Gopherus agassizii, representing 15 sites in northeastern Mojave Desert (Nevada, Utah), were assayed for variation in allozymes and mitochondrial DNA restriction sites. Morphometric measurements from 257 tortoises from the same locations were subjected to sheared principal component analysis. The 15 localities were partitioned into five management units. Geographic concordance between the five management units delineated in this study and proposed Desert Wildlife Management Areas (DWMAs), delineated ecologically, was assessed. Suggestions for improving placement and boundaries of DWMAs are discussed. THE desert tortoise, Gopherus agassizii, is one of four extant species of testudinid tortoises found in desert and semitropical regions of North America. Its range includes the Mojave Desert of southern Nevada, California, and Utah and the Sonoran Desert of western Arizona, western Sonora, Mexico, and northern Sinaloa, Mexico (Lamb et al., 1989). Beginning in the early 1970s, declines of from 3-59% in desert tortoise populations were noted over much of its range in the United States (USFWS Recovery Plan, 1994, unpubl.). De