Document: REB-3-39-16

Evaluation of extinction risk factors in American ginseng (Panax quinquefolium).

ANDERSON, M.R.* and S.S.LOEW

Illinois State University, Normal, IL 61790-4120 USA ¹

Abstract:
American ginseng, Panax quinquefolium, is a commercially valuable forest herb and, due to widespread commercial harvesting, it is vulnerable, imperiled or critically imperiled in 19 of 36 states and provinces of its range. Life history traits, such as long juvenile periods, gravity dispersed seeds and absence of vegetative reproduction, increase risk of local extinction through slow population growth in fragmented populations. In 1999, we visited seven American ginseng populations with 5 to 150 plants to evaluate the effects of population size and life history traits on maternal reproduction. We recorded plant size and numbers of leaves, leaflets, flowers, fruits and seeds for > 300 individuals. All measurements were transformed to improve normality of residuals in the data analysis. Based on linear regression analysis, mean flowers, fruits and seeds per reproductive plant were a function of number of reproductive plants in the population (F = 20.516, p <0.001; F = 22.24, p < 0.001; F = 27.6, p < 0.001 for flowers, fruits and seeds, respectively). Per capita fruit production ranged from < 1 to 4.75 and was mainly affected by presence of large four-leaf plants. On average an individual two-leaf plant produced 0.8 seeds, three-leaf plants produced 5.86 seeds, and four-leaf plants produced 32.8 seeds. We performed path analysis using number of flowers per plant, number of leaflets per plant and plant height as predictor variables and number of seeds per plant as the criterion variable. Number of flowers strongly affected the number of seeds per plant (p = 0.74, model r² = 0.97, p < 0.0001). We further analyzed the predictor variables plant height, number of leaflets and area of longest leaflet on the criterion variable number of flowers. Plant height was the strongest predictor of number of flowers (p = 0.35, model r² = 0.52, p < 0.0001). We will monitor plants across several seasons in order to allow modeling of growth rates and survival of our populations.

Keywords: American ginseng, population size, population viability, maternal reproduction, fruit, seed

This abstract is being presented at: 3:30 PM in session:
CONSERVATION ECOLOGY