Geographic Distribution of Allozyme Variation in Ulmus crassifolia

Abstract

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, = 0.22). Over 94% of the total genetic variation was partitioned within populations (GST = 0.062), even though significant levels of variation at individual loci were detected among populations. Genetic identity between populationrs located in the primary population was high (I = 0.990), while populations located in central Florida were more divergent from each other (I = 0.923) than from populations found within the primary range (I = 0.952). The Florida populations had reduced allelic variation per locus (A = 2.07) in comparison to the primary populations (A = 2.32), even though both sets of populations had equivalent levels of genetic diversity (H, = 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 evolu- tionary history.