A TEST FOR ISOLATION-BY-DISTANCE IN CENTRAL ROCKY-MOUNTAIN AND GREAT-BASIN POPULATIONS OF EDITH CHECKERSPOT BUTTERFLY (EUPHYDRYAS-EDITHA)

A total of 18 Edith's checkerspot butterfly (Euphydryas editha) populations, seven from the central Rocky Mountains and II from the Great Basin, were assayed for genetic variability at 14-28 isozyme loci. Of the surveyed loci, 13 were polymorphic in at least one of the sampled populations. Slatkin's method for detecting isolation-by-distance using a regression of pairwise estimates of interpopulation dispersal [log(Nm)] against pairwise linear distance between populations [log(D)] was applied to these data. Central Rocky Mountain populations exhibited isolation-by-distance while the Great Basin populations did not. These differences in population structure are probably due to the weak dispersal abilities of this species and to the insular nature of its habitat in the Great Basin.