Mating System Parameters in a Tropical Tree Species, Shorea leprosula Miq. (Dipterocarpaceae), from Malaysian Lowland Dipterocarp Forest

• Published in: Biotropica 2000-12, Vol.32 (4a), p.693-702
• Main Authors: Lee, S. L., Wickneswari, R., Mahani, M. C., Zakri, A. H.
• Format: Article
• Language: English
• Subjects: Apomixis; Forest trees; Inbreeding; Inbreeding coefficient; Mating systems; Plants; Pollen; Population genetics; Trees; Tropical rain forests
• ISSN: 0006-3606; 1744-7429
• DOI: 10.1111/j.1744-7429.2000.tb00517.x

The mating system in a natural population of Shorea leprosula from Malaysian lowland dipterocarp forest was quantified by allozyme analysis using the multi-locus mixed-mating model. The population was found to be predominantly outcrossed (tm= 0.837 ± 0.066). Variation in individual multi-locus outcrossing rates (range = 0.55-1.00) may have reflected variation in individual self-compatibility, heterogeneity in the pollen pool, differences in the mating neighborhood of individuals, or population substructure. Departure from the mixed-mating model was evident from the differences in pollen and ovule allele frequencies. Pollen pool heterogeneity and significant levels of biparental mating (tm- ts= 0.127, P < 0.01) indicated that the population was most probably genetically substructured. The inbreeding coefficient based on Wright's fixation index for maternal trees (Fa= -0.078) was lower than that obtained for progenies (Fe= 0.089), suggesting considerable selection against selfed progenies during growth of seedlings to reproductive size. Incidence of multiple seedlings was observed in a small proportion of seeds, but genetic analysis and genotype comparisons showed that this was not due to apomixis and may have been caused by multiple fertilization.