American ginseng, Panax quinquefolius L., is a herbaceous species of highly fragmented forest habitat in eastern North America that is harvested from small wild populations for export, primarily to Asian markets. In general, small populations (< 500 individuals) of species exhibit lower genetic diversity than larger ones (1000 to 10,000 individuals), which may reduce their evolutionary capability to adapt to environmental change. We tested the hypothesis that genetic variation is positively correlated with population size. Neutral genetic diversity was assessed using electrophoretic allozyme variation in individuals selected from seven Illinois populations of American ginseng that vary in size from fewer than 10 to several hundred individuals. Allozymes are codominant markers inherited in Mendelian fashion that are frequently used to detect population differentiation. A large body of literature exists for comparison that describes allozyme variation in numerous species characterized by a variety of reproductive modes and threat status. We used cellulose acetate gel membrane electrophoresis to separate and visualize allozyme variants. During preliminary analyses, ten individuals from each of the seven populations were analyzed for eight enzyme systems. As a high proportion of those individuals were homozygous for the same allele, most populations analyzed so far are monomorphic. Two possible reasons explain these results: (1) these markers are not sufficiently sensitive to reveal differences among populations, or (2) significant loss of genetic diversity has already occurred due to small size and isolation of populations and long history of harvest pressure. In order to determine the more likely explanation we will continue our screening for additional loci and determine genotypes for up to thirty individuals per population. In addition, we will expand our genetic analysis to include more variable molecular markers, such as RAPDs.

Key words: allozymes, extinction risk, genetic diversity, Panax quinquefolius, population size, wild-harvested species