Mating system parameters in a tropical tree species, Shorea leprosula Miq.(Dipterocarpaceae), from Malaysian lowland dipterocarp forest

The mating system in a natural population of Shorea leprosula from Malaysia n lowland dipterocarp forest was quantified by allozyme analysis using the multi-locus mixed-mating model. The population was found to be predominantl y outcrossed (t(m) = 0.837 +/- 0.066). Variation in individual multi-locus outcrossing rates (range = 0.55-1.00) may have reflected variation in indiv idual self-compatibility heterogeneity in the pollen pool, differences in t he mating neighborhood of individuals, or population substructure. Departur e from the mixed-mating model was evident from the differences in pollen an d ovule allele frequencies. Pollen pool heterogeneity and significant level s of biparental mating (t(m) - t(s) = 0.127, P < 0.01) indicated that the p opulation was most probably generically substructured. The inbreeding coeff icient based on Wright's fixation index fur maternal trees (F-a = -0.078) w as lower than that obtained for progenies (F-e = 0.089), suggesting conside rable selection against selfed progenies during growth of seedlings to repr oductive size. Incidence of multiple seedlings was observed in a small prop ortion of seeds, but generic analysis and genotype comparisons shelved that this was not due to apomixis and may have been caused by multiple fertiliz ation.