Thrips Cross‐Pollination ofPopowia pisocarpa(Annonaceae) in a Lowland Dipterocarp Forest in Sarawak1

This paper reports thrips (Thysanoptera) cross‐pollination in the primitive angiosperm,Popowia pisocarpa(Annonaceae), in lowland rain forest of Sarawak, Malaysia. Flowers ofP. pisocarpahave a tiny pollination chamber (3–4 mm in depth) with the entrance almost closed by the disk‐shaped stigmatic heads, allowing only small insects to enter. Experiments showed that thrips were effective pollinators and flowers ofP. pisocarpawere self‐incompatible. Seed set was limited by pollen. Clumped adult trees had higher seed‐set than more distant individuals (>5 m from nearest flowering neighbor), indicating limited inter‐tree movement by thrips.