CAN NECTAR BE A DISADVANTAGE? CONTRASTING POLLINATION NATURAL HISTORIES OF TWO WOODY VIOLACEAE FROM THE NEOTROPICS

We present the first pollination data on Neotropical species of Violaceae with actinomorphic flowers. Floral biology of Paypayrola blanchetiana and Amphirrhox longifolia were studied in Brazilian Atlantic rainforest. Petals of both species form a corolla tube, restricting access to floral rewards to visitors with long mouth parts. Flowers lack a spur, common in zygomorphic Violaceae, to store nectar. Both species' flowers open in the evening and continue flowering during daytime. They emit a sweet scent dominated by benzenoid and monoterpenoid compounds. While A. longifolia flowers are nectarless, flowers of P. blanchetiana produce nectar throughout anthesis. A wide range of night- and day-active visitors, including moths, bees, and butterflies, were observed at P. blanchetiana; 68% of all nocturnal visits took place at dawn. Fruit set of P. blanchetiana was extraordinarily low. Nectar production and pollen presentation occur in close proximity, and pollen dissolves in accumulating nectar. After contact with nectar, experimental pollen germination rates were near 0. Amphirrhox longifolia flowers received few visits by diurnal and nocturnal bees and pollen-collecting Heliconius butterflies. Fruit set was still low (11%) but was ten times higher than that in P. blanchetiana (1%). Low fruit set seems to result from diminished pollen viability through nectar contact in P. blanchetiana and pollinator limitation in A. longifolia.