GEOGRAPHIC-DISTRIBUTION OF ALLOZYME VARIATION IN ULMUS-CRASSIFOLIA

We investigated the distribution of genetic variation in cedar elm, Ulmus crassifolia. This species has an unusual geographic distribution with a primary range in the south central United States (central Texas east to Mississippi) and a few isolated populations located in central Florida. Cedar elm was polymorphic at 86% of the 15 loci examined and maintained high levels of genetic diversity within populations (H(e) = 0.22). Over 94% of the total genetic variation was partitioned within populations (G(ST) = 0.062), even though significant levels of variation at individual loci were detected among populations. Genetic identity between populations located in the primary population was high (IBAR = 0.990), while populations located in central Florida were more divergent from each other (IBAR = 0.923) than from populations found within the primary range (IBAR = 0.952). The Florida populations had reduced allelic variation per locus (ABAR = 2.07) in comparison to the primary populations (ABAR = 2.32), even though both sets of populations had equivalent levels of genetic diversity (H(e) = 0.20 and 0.19, respectively). This reduction in alleles suggests that the Florida populations of U. crassifolia may have experienced a mild genetic bottleneck during their evolutionary history.