The Reproductive Ecology of an Emergent Dipterocarp in a Lowland Rain Forest in Sarawak

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Abstract
This paper reports the first direct observation of reproductive processes of an emergent tree, Dryobalanops lanceolata (Dipterocarpaceae), and its interactions with pollinators and seed predators, using a canopy observation system built in Sarawak, Malaysia. D. lanceolata flowers were mostly pollinated by medium‐sized stingless bees (Trigona spp., Apidae), and stigmas of all unbagged flowers received pollen grains. Ovaries did not develop without pollination. Abortion rate in the early stage of fruit development was 93% in fruits fertilized by natural pollinators. All the experimentally selfed ovaries were aborted at this stage. Despite the heavy abortion rate, the dry weight loss at this stage was only 17% of the total reproductive effort, because abortion occurred before active investment in fruits. Among the remaining fruits, 40% were lost to the primary seed predator, Mecysolobus crassus (Curculionidae). Such attacked fruits were also selectively aborted at the middle stage of fruit maturation. Final germinating fruits, which were 3.6% of the total number of flowers, got 47% of the total reproductive effort.