Genetic diversity in island and mainland populations of Aster spathulifolius (Asteraceae)

Using starch gel and polyacrylamide gel electrophoresis, we examined allozyme diversity in six island and seven mainland populations of Aster spathulifolius Maxim., a plant species occurring in the coastal regions of Korea and Japan. We estimated four parameters of genetic variability: percentage of polymorphic loci (P), mean number of alleles per locus (A), mean expected frequency of heterozygotes (h(e)), and mean observed frequency of heterozygotes (h(o)). Genetic diversity within island populations (P = 35.6, A = 1.36, h(e) = 0.103, and h(o) = 0.097) was not significantly less than within mainland populations (P = 37.1, A = 1.37, h(e) = 0.102, and h(o) = 0.092). The proportion of total genetic diversity found among the island populations (G(ST)), among the mainland populations, and the total sample were 0.480, 0.427, and 0.491, respectively, indicating the number of migrants per generation (Nm) were 0.270, 0.335, and 0.259, respectively. This indicates that gene flow among the populations was highly restricted. Genetic diversity at the species level is fairly high for a species with a narrow distribution range. Genotypic frequencies did not deviate significantly from Hardy-Weinberg equilibria in most loci we examined, indicating that random mating occurs in the species.