Mating system of Ophiopogon xylorrhizus (Liliaceae), an endangered species in southwest China

The mating system of Ophiopogon xylorrhizus Wang et Dai was studied in three natural populations with allozyme electrophoresis. The outcrossing rate was estimated by assaying eight enzyme loci. A mixed mating system model was used, and outcrossing rates were estimated for populations and families. The multilocus outcrossing rates in three populations were 0.467, 0.323, and 0.091. The extent of outcrossing in populations depended on the plant density (r = 0.9998; P < 0.02; df = 1). The frequency distribution of family outcrossing rates was slightly bimodal. A mixed mating system with considerable complete selfing and complete outcrossing was found in this species. Positive correlations were observed between family outcrossing rate and maternal heterozygosity (r = 0.70-0.98) and between family outcrossing rate and fecundity (r = 0.971; P < 0.0005; df = 7). Inbreeding depression was examined in populations P3 and P4, both of which had high outcrossing rates. Inbreeding depression was expressed mainly in seed production. Mating system pattern contributed to the high genetic variation in this species. Because of high inbreeding depression and habitat destruction, this species is threatened with extinction. Conservation in situ by protecting the habitat is the best way to conserve this species.