Bird-pollination of three Durio species (Bombacaceae) in a tropical rainforest in Sarawak, Malaysia

Pollination ecology of three Durio species, D. grandiflorus, D. oblongus, a nd D. kutejensis (Bombacaceae), was studied in a lowland dipterocarp, fores t in Sarawak, Malaysia, during a peak flowering period when at least 305 sp ecies of plants bloomed in 1996. Durio has been reported to be pollinated b y hats in Peninsular Malaysia. However, my observations of flower visitors and pollination experiments indicated that two species, D. grandiflorus and D, oblongus, were pollinated by spiderhunters (Nectariniidae) and that the other species, D. kutejensis, was pollinated by giant honey bees and bats as well as birds. Hand-pollination experiments showed that all three specie s were obligate outbreeders. A resource limitation in fruit production was suggested. The former two species were visited only by spiderhunters, and t he bagged flowers that were opened for animal visitors only at night bore n o fruit, while those that were opened only during the day bore fruits, at c omparable fruiting ratios to open pollination. Durio kutejensis was observe d to be visited by gi;mt honey bees. birds, and bats at different times of day, and three series of bagged experiments that exposed the flowers to ani mal visitors at different times of day bore fruits at a comparable ratio to open-pollination.