Floral biology of Schismatoglottis baangongensis (Araceae) in West Sarawak, Borneo

The flowering mechanism, visiting insect activities, reproductive system, and floral scent composition of Schismatoglottis baangongensis a Northwest Bornean locally endemic limestone-restricted protogynous mesophyte were investigated. Anthesis started at dawn and lasted ca 29 h. Fruit set for open pollination (93 %) and restricted access pollination (88 %) were high. Colocasiomyia (Diptera, Drosophilidae) and Cycreon (Coleoptera, Hydrophilidae) were the main pollinators. Colocasiomyia flies present in much higher numbers than Cycreon beetles individually carried significantly less pollen load. Chaloenus (Chrysomelidae, Galerucinae) was inadvertent pollinators, and Atheta (Coleoptera, Staphylinidae) passive visitors. Pollen transferal between dissimilar insect genera (Colocasiomyia and Chaloenus) is reported for the first time. Low pollen/ovule ratio of S. baangongensis indicated an efficient pollination mechanism. Ester compound class floral odours, especially the dominant compounds 3-butenoic acid, 3-methyl-, methyl ester, were decisive in attracting pollinators. The spadix appendix of S. baangongensis was the main olfactory body although the spathe was detected to release an additional N-containing compound, an indole. An increase in the total amount of floral scent from the pistillate flower zone during pistillate phase of anthesis from Period I (06:00—08:00 h) to Period II (08:00—10:00 h) was postulated to detain insects in the lower chamber of the inflorescence.