Pollination biology of Gelsemium sempervirensL. (Ait.) (Gelsemiaceae): do male and female Habropoda laboriosa F. (Hymenoptera, Apidae) differ in pollination efficiency?

SummaryIn the outer coastal plain of Georgia, USA, Gelsemium sempervirens (Gelsemiaceae) is heavily visited (69–100% of all flower visits) by male and female blueberry bees, Habropoda laboriosa (Hymenoptera-Apidae). Fruit set is, however, consistently low (8–36% range). The pollination efficiency of male and female blueberry bees was studied using: 1. comparison of pollen loads on foraging male and female bees; 2. calculation of pollen loads on fresh stigmas of flowers exposed to a single visit by a female bee; and 3. an experimental test of fruit and seed set following exposure to one to eight visits by both male and female bees. Females had larger pollen loads in four of five body regions, but male bees consistently carried pollen in quantities sufficient for fertilization. A single visit from a female bee resulted in mixed pollen deposition of 76 pollen grains, 20 of which were from Gelsemium and 56 from Vaccinium. There was no significant relationship of either fruit or seed set with number of visits ...