The pollination mechanism of three sympatric Prescottia (Orchidaceae : Prescottinae) species in southeastern Brazil

The pollination biology of three Prescottia (Orchidaceae: Prescottinae) species was studied in Picinguaba, Sao Paulo State, south-eastern Brazil. Plants are self-compatible but pollinator-dependent and offer nectar as the only reward for pollinators. Prescottia plantaginea Lindl. and Prescottia stackyodes (Swartz) Lindl. are pollinated by pyralid moths (Lepidoptera: Pyralidae). Moth-pollination is reported for the first time in the genus Prescottia and the subtribe Prescottinae. Pollination by halictid bees (Halictidae) is confirmed for Prescottia den, flora Lindl. The pollination mechanism is the same regardless of pollinator-type: pollinaria are fixed on the ventral surface of the insect's proboscis through the pad-like viscidium and are removed when the insect leaves the flower. A pollinarium-carrying insect visiting another flower will brush the stigmatic surface and leave clumps of pollen. thus effecting pollination. Prescottia stachyodes is protandrous. a feature that increases the chances of cross-pollination. As far as we know, this is the first report of protandry in the genus Prescottia and also the subtribe Prescottinae. (C) 2001 Annals of Botany Company.886999100