Comparisons of allozyme diversity among rare and widespread Rhus species

Genetic diversity in three species of Rhus was investigated using starch gel electrophoresis. Rhus michauxii is a rare species endemic to North Carolina, whereas R. glabra and R. copallina are widespread. All three species are clonal, typically dioecious, woody shrubs. Forty-seven percent of the loci examined for R. michauxii were polymorphic, compared to 88% of the loci examined for both R. glabra and R. copallina. Mean genetic diversity (H(e)) within populations of R. michauxii (0.05) was lower than the genetic diversity within populations of R. glabra and R. copallina (0.15 for both species). Mean number of multilocus genotypes per population was lower for R. michauxii, 4.1, versus the other two species, R. glabra, 27.5 and R. copallina, 26.6. Genotypic diversity indices (D(c)) were 0.41, 0.95 and 0.95 for R. michauxii, R. glabra and R. copallina, respectively. The proportion of genetic diversity among populations (G(ST)) was higher in R. michauxii (0.335) and R. copallina (0.301) than in R. glabra (0.198). Genetic identity values among the species ranged from 0.52-0.96, and grouped R. michauxii closely with R. glabra. Rhus glabra and R. copallina have levels of genetic diversity similar to wide ranging plant species with the same suite of life history characteristics. The lower level of genetic diversity in R. michauxii is characteristic of species with limited geographic distributions. The relatively high levels of genetic diversity seen among populations indicates that clonal reproduction may play an important role in the genetic structuring of these species