Beetle pollination of Shorea parvifolia (section Mutica, Dipterocarpaceae)in a general flowering period in Sarawak, Malaysia

Pollination ecology of an emergent tree species, Shorea (section Mutica) pa rvifolia (Dipterocarpaceae), was studied using the canopy observation syste m in a lowland dipterocarp forest in Sarawak, Malaysia, during a general fl owering period in 1996. Although the species has been reported to be pollin ated by thrips in Peninsular Malaysia, our observations of Bower visitors a nd pollination experiments indicated that beetles (Chrysomelidae and Curcul ionidae, Coleoptera) contributed to pollination of S. parvifolia in Sarawak . Beetles accounted for 74% of the Bower visitors collected by net-sweeping , and 30% of the beetles carried pollen, while thrips accounted for 16% of the visitors, and 12% of the thrips carried pollen. The apical parts of the petals and pollen served as a reward for the beetles. Thrips stayed inside the flower almost continuously after arrival, and movements among flowers were rare. Fruit set was significantly increased by introduction of beetles to bagged flowers, but not by introduction of thrips. Hand-pollination exp eriments and comparison of fruit set in untreated, bagged, and open flowers suggested that S. parvifolia was mainly outbreeding.