Conservation of genetic diversity in wild American ginseng (Panax quinquefolius L.)
Cruse-Sanders, Jennifer Michelle
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Conservation of harvested species requires information about the impact of extraction on population processes and genetic diversity. Allozyme diversity was examined at 16 loci in 21 wild populations of the medicinal plant American ginseng, Panax quinquefolius, harvested from North America for over 250 years. We found significantly more genetic diversity within protected populations (He = 0.076 + 0.028) compared to unprotected ones (He = 0.070 + 0.045). Genetic structure was greater among unprotected populations (GST = 0.491) than among protected populations (GST = 0.167) suggesting significant evolutionary implications of harvest for this species. Based on analyses of the spatial autocorrelation of genotypes within populations, we conclude that the spatial structure of ginseng results from the establishment and persistence of plants in favorable microhabitats coupled with limited seed dispersal around maternal individuals. We found no differences in the pattern of fine-scale genetic structure between protected and unprotected populations. Simulated harvest was used to study the impact of varying harvest strategies on genetic diversity in ginseng. Relative to initial levels, average genetic diversity was significantly lower when plants were culled randomly at the legal limit (Mann-Whitney U = 430, P < 0.001) or when adults only were culled (Mann-Whitney U = 394, P < 0.01). Within-population genetic diversity was significantly higher with legal limit adult harvest (He = 0.068) than when plants were culled randomly at the legal limit (He = 0.064; U = 202, P < 0.01). The information gathered from ginseng hunters and dealers was organized under a list of themes which included: types of harvesters, potency of plants, knowledge of habitat among ginseng harvesters, post harvest methods, scarcity of plants, natural history of ginseng and ginseng harvesters, and methods for planting seeds. Because of the high degree of genetic structure, conservation recommendations include protecting populations throughout the range of P. quinquefolius. Based on simulated harvest, we recommend that harvesting less than the proportion of adult plants could reduce the negative genetic impacts of harvest on ginseng populations. Ultimately management strategies must account for the biology of the plant, genetic diversity as well as harvester practices to ensure long-term sustainability.