Aquilaria spp. (Thymelaeaceae) are the principal source of Gaharu, a valuable resin, yet information about their reproductive ecology is almost entirely lacking. Individuals of six species (A. beccariana, A. crasna, A. filaria, A. hirta, A. malaccensis and A. microcarpa) in cultivation in Indonesia were investigated to assess reproductive phenology, pollination, seed production and germination. Seed production and seedling dispersion were also assessed in natural populations of A. beccariana, A. malaccensis and A. microcarpa in Kalimantan.
Most of the selected trees flowered during the dry season, fruits requiring between 36 and 72 days to develop, depending on the species. Twenty different species of insect were recorded visiting flowering trees. The probability of flowers developing into fruit varied between species from 0.04 to 0.43, although flowers from which pollinators were excluded never produced fruit. Seed production of A. malaccensis and A. microcarpa peaked at a dbh of approximately 40 and 50 cm, respectively, individual trees producing up to 19,000 seeds in a single season. Germination under nursery conditions was initiated 7-15 days after sowing; seeds of A. crasna had the highest probability of germination success (92) whereas those of A. filaria had the lowest (53). In natural forest, most seedlings (>65) occurred within 5 m of an adult tree, suggesting limited dispersal. These results indicate that Aquilaria spp. have high reproductive potential, but suggest that seed dispersal might be limited in natural forests. The implications of these results for the management of Aquilaria spp. are discussed.
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