Abstract

Examining the genetic diversity of rare and threatened plant species can give insight into how environmental factors and human forces influence plant populations. Environmental and human activities have been correlated with reduction in population size and extirpation. American ginseng (Panax quinquefolius) is an understory herb that has been threatened by overharvesting pressures. This species has been exploited due to its medicinal uses and has been viewed as a panacea. In this study, genetic diversity was analyzed from seventeen different populations in western North Carolina, two populations from Virginia, and a commercial seed. DNA was extracted from leaflets, and PCR was performed for seven microsatellite loci. Overall populations exhibited little genetic variation, with pairwise FST values ranging from 0.0 to 0.05. However, pairwise comparisons ranged from low to moderate differentiation with few comparisons of 0.15 to 0.25 indicating great genetic differentiation. Allelic and genotypic diversity values were moderate and varied among populations. Mantel tests of geographic and genetic distance indicated that populations that are physically closer to one another and are more related due to metapopulation dynamics. Mantel tests of chemical and genetic distance indicate that there is a relationship between chemotype and genotype but only accounting for 10% of the variability explained by epigenetics and environmental factors. Low genetic diversity and population similarity is influenced by a variety of factors such as poaching, gene flow and fragmentation of historically larger populations. Allelic and genotypic diversity could be explained by overharvesting and habitat fragmentation of populations. Insight into the dynamics of genetic diversity of these populations will allow additional valuable information in the conservation and restoration efforts of for this ecological and medicinally important plant.

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