EFFECTS OF SERIAL INBREEDING ON FITNESS COMPONENTS IN IMPATIENS-CAPENSIS

Studies of inbreeding depression in wild plants customarily compare th e fitness of outcrossed progeny to progeny derived from one generation of self-pollination. We compare levels of inbreeding depression in a greenhouse in two populations of jewelweed using progeny derived from random outcrosses, one generation of self-pollination, and three gener ations of selfing. The progeny have expected inbreeding coefficients o f, respectively, 0, 0.5, and 0.875. Seedling survivorship declined lin early with the level of inbreeding in both populations. Inbreeding als o increased the variability of emergence date. Maternal family members hip affected early seedling performance and often interacted significa ntly with the level of inbreeding. In contrast, path analyses reveal t hat inbreeding had both negative linear and positive quadratic direct effects on seed and final plant weight, causing the highly inbred prog eny to outperform progeny derived from one generation of selfing. Thes e results suggest either the rapid purging of deleterious alleles or d iminishing epistasis among the loci affecting these characters. It is not clear why the loci affecting survival responded differently.