ALLOZYME DIFFERENTIATION AMONG GOPHER TORTOISES (GOPHERUS) - CONSERVATION GENETICS AND PHYLOGENETIC AND TAXONOMIC IMPLICATIONS

The genetic diversity among 18 loci within and among four species of g opher tortoises was investigated using horizontal starch gel electroph oresis. Within species variation ranged from 2 to 4% by direct count a nd from 2 to 8% by Hardy-Weinberg expectation. Of the loci resolved, 1 1-22% expressed variation. The northern and southern populations of Go pherus flavomarginatus could not be distinguished. No fixed difference s were observed between G. agassizii and G. berlandieri, as reflected in a Nei genetic distance of 0.008. These latter species may be little more than allopatric populations of G. agassizii. Differentiation bet ween the two remaining species was not extensive; G. polyphemus was on ly slightly distinct from G. flavomarginatus, being separated by a Nei genetic distance of only 0.006. The two pairs of species were separat ed by an average genetic distance of 0.200. The evolutionary rates of divergence were observed to be unequal, especially between G. polyphem us and G. flavomarginatus. The overall genetic similarity suggests a r elatively recent age of origin.