The Role of Nectar and Oil in the Pollination of Drymonia serrulata (Gesneriaceae) by Epicharis Bees (Anthophoridae) in Panama

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Abstract
The pollination biology of Drymonia serrulata was studied in central Panama. D. serrulata produces a small number of flowers daily for several months. Flowers are dichogamous with a one day male phase followed by a one day female phase. The average volume of nectar produced by a Drymonia flower over the two-day period was 264.4 .mu.l (SD = 9.98, N = 4), a value much higher than has been reported for other bee-pollinated flowers. D. serrulata is completely self-compatible. Fruit set for between and within plant pollinations in greenhouse grown plants was 67 percent. Autogamy is precluded by the temporal separation of anther dehisscence and stigma receptivity. Glandular trichomes inside the corolla secrete an oil which is deposited on the anthers and transferred to the thorax of visiting bees. This oil facilitates pollen adhesion. Only Trigona pallens (Apidae) actively collects this oil, but it is ineffective as a pollinator. The main pollinators of Drymonia serrulata in Panama are Epicharis monozona and Epicharis rustica (Anthophoridae). Visitors that remove nectar, but are ineffective pollinators include seven Euglossa spp. and three species of matinal butterflies (Hesperiidae).