Pollination biology of Gelsemium sempervirens L. (Ait.) (Gelsemiaceae): do male and female Habropoda laboriosa F. (Hymenoptera, Apidae) differ in pollination efficiency?
John B Pascarella
In 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 from either males or females. Whilst both male and female bees are effective as pollen delivery agents of G. sempervirens, much of the pollen they deliver may be from the same floral morph, leading to rejection in this self-incompatible distylous species. Low fruit set may also be related to other factors such as resource limitation and / or herbivory.
Habropoda, male bee, pollination efficiency, Gelsemium, Vaccinium