Effects of reproductive systems on creation and maintenance of species diversity in Dipterocarpaceae

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Genetic structure and niche divergence of Dipterocarpacea were studied in a tropical rain forest in Sarawak on the Island of Borneo, Malaysia in order to discuss the mechanisms of creation and maintenance of the high species diversity of Dipterocarpaceae. Major results are the followings.1. Novel microsatellite genetic markers were developed in Dryobalanops aromatica, a bee-pollinated emergent free species. Using these markers, genetic structure and reproductive ecology of D.aromatica were studied for a population in a 52-ha long-term ecological plot in Lambir Hills National Park Sarawak Estimated outcrossing rates were high (0.72-1.00), and pollen dispersal distances were fairly long (mean : 179.6-355.7 m). No clear spatial genetic structure was found in the adults of the study population probably due to the high outcrossing rates and log pollen dispersal distances. Shorea curtisii, a beetle-pollinated species, neither showed clear spatial genetic structure in the same forest.2. Neste … More d clade analysis based on difference in chloroplast DNA sequence among 6 species of the genus Dryobalanops revealed a presence of spatial genetic structure at the regional scale in Sarawak and the Malay peninsular Haplotype diversity was highest at the central part of Sarawak, and an ancestral haprotype was found in this region, suggesting that the central Sarawak was the center of the divergence of DryobaLanps. Two sympatric species of the Lambir forest, D.aromatica and D.lanceolata, were gnenetically most apart within the genus.3. The third census of the 52-ha long-term ecological plot of Lambir Hills National Park was completed. All the trees with 1 cm dbh and larger were measured, and a database was established. Using this database, habitat niche analysis was conducted for 788 tree species including species of Dipterocarpaceae. Of the species analyzed, 88% were habitat specialists whose spatial distributions were significantly skewed to species specific habitats. Degree of habitat divergence between species of Dipterocarpaceae was significantly higher than that for all species pairs, suggesting that Dipterocarpaceae was the family that included highly divergent species in terms of habitat. Less