Foraging dynamics and pollination efficiency of Apis mellifera and Xylocopa olivacea on Luffa aegyptiaca Mill (Cucurbitaceae) in southern Ghana

As a result of different levels of pollination efficiency of pollinators, knowledge on appropriate pollinators of a plant has become important, especially in the management and conservation of both the pollinators and the plants. In this study, the pollination efficiency of Apis mellifera and Xylocopa olivacea, important pollinators of Luffa aegyptiaca, were assessed in the southern coastal part of Ghana from June 2009 to September 2010. Pollination efficiency of A. mellifera and X. olivacea was estimated in terms of fruit set and fruit size. Further, data on daily and seasonal nectar dynamics of Luffa aegyptiaca were collected. In the early mornings (0600-0700), X. olivacea was the most frequent visitor (0.47 min-1) on the female flowers compared to A. mellifera (0.13 min-1). The mean nectar (sugar) concentration in the dry season was 36.58 ± 0.55 %, which was higher than the 34.03 ± 0.38 % obtained for the rainy season (F = 14.986; df = 2; P < 0.0001). Total amount of sugar in the early mornings was 1.88 ± 0.37 mg which was higher than 0.28 ± 0.04 mg in the mid mornings (χ2 = 14.33, df = 1, P < 0.0001). Fruits that developed from flowers that had received a single visit from X. olivacea had a mean weight of 428.7g and were 1.5 times heavier than fruits from flowers visited by A. mellifera (286.76 g). X. olivacea was more efficient than A. mellifera in terms of number of fruit set per single visit. This study has provided some knowledge on pollination ecology of L. aegyptiaca, which can be exploited to improve fruit production in commercially grown vine crops.