Genetic variation and population structure in Korean populations of eurya japonica (Theaceae)

Abstract

We investigated levels of genetic diversity, population genetic structure, and gene flow in Eurya japonica, a widespread and broad‐leaved evergreen dioecious tree native to Japan, China, Taiwan, and the southern and southwestern coast of the Korean Peninsula. Starch‐gel electrophoresis was conducted on leaves collected from 1,000 plants in 20 Korean populations. All 12 loci examined were polymorphic in at least one population, and the mean number of alleles per locus was 3.79. In addition, mean observed population heterozygosity (Hop = 0.425), expected heterozygosity (Hep = 0.462), and total genetic diversity (HT = 0.496) were substantially higher than average values for species with similar life history traits. Although significant differences in allele frequency were detected between populations at all loci (P < 0.001), <7% of the genetic variation was found among populations (FST = 0.069). There was a significant negative correlation between genetic identity and distance between populations (r = ‐0.341; P < 0.05), but this explained only a small amount of the diversity among populations. Indirect estimates of the number of migrants per generation (Nm) (3.37, calculated from FST; 3.74, calculated from the mean frequency of eight private alleles) indicate that gene flow is extensive among Korean populations of E. japonica. Factors contributing to the high levels of genetic diversity found within populations of E. japonica include large and contiguous populations, obligating outcrossing (dioecious plant), high fecundity, and long generation time. Occasional seed dispersal by humans and pollen movement by domesticated honey bees may further enhance gene flow within the species.