Allozyme variation in American ginseng (Panax quinquefolius L.): Variation, breeding system, and implications for current conservation practice

Abstract

Sustained harvest of wild North Americanginseng (Panax quinquefolius L.) for overtwo centuries has led to heightenedconservation concern and a recent interest inthe population genetics of this species. Thisstudy examined allozyme variation from 32 wildand 12 cultivated populations of Americanginseng to: (1) document the amount anddistribution of genetic variation over a wideportion of the species' natural range, (2)examine genetic differences between wild andcultivated populations, and (3) provideindirect estimates of its breeding system. Strong genetic differences between wild andcultivated populations were found in the amountof variation within populations and thedistribution of variation among populations. Wild populations were significantly lower inall within-population diversity measures, butcontained significantly higher levels ofvariation partitioned among populations. Similarities between wild and cultivatedpopulations were also found. As a whole,cultivated and wild groups shared nearly allalleles, and populations of both groups showedstrong homozygote excess compared toexpectations under random mating. Thehomozygote excess is best explained by highlevels of selfing. In wild populations,significant correlations were found betweengenetic diversity and estimated populationsize, and between interpopulation geneticdistance and geographic distance. Overall, theresults for wild populations suggest that theyare influenced by high levels of genetic driftand low migration among populations. Conservation implications for American ginsengare discussed with particular emphases on: (1)the current debate surrounding the existence ofwild populations, (2) the ongoing practice ofintroducing cultivated seed into wildpopulations, and (3) the collection of geneticmaterial for the establishment of breedingprograms.