Limited fruit production in Hancornia speciosa (Apocynaceae) and pollination by nocturnal and diurnal insects

"Frequency and efficiency of pollinator visits strongly influence the reproductive success of self-incompatible plants. We investigated the breeding and pollination systems of Hancornia speciosa, a small tree that produces fleshy berries used in the Brazilian fruit industry. Observation and experiments were carried out in Northeastern Brazil. Thirty-three species of the visitor were recorded. Hawkmoths (Sphingidae), bees (Euglossini and Centridini), and butterflies (Nymphalidae and Hesperiidae) with long mouth parts were effective pollinators of H. speciosa. Access to nectar, the only reward for flower visitors, is determined by corolla tube length. Nylon threads of various diameters and dried mouth parts from a number of flower visitors were used in experiments to simulate flower visits. The number of pollen grains removed during such simulated visits showed no significant difference. Although xenogamic, H. speciosa presented a low pollen/ovule ratio (77). This might be related to the high efficiency of its pollination mechanism. Flowers of H. speciosa had 76 ovules on average. Seed set varied from 1 to 25, indicating that individual flowers received different amounts of outcross-pollen. Fruit production of hand cross-pollinated flowers increased by 90 percent when compared to natural pollination, suggesting pollinator limitation of H. speciosa."