Comparison of the pollination efficiency of Apis cerana with wild bees in oil-seed camellia fields

Camellia oleifera Abel is an economically-important, cross-pollinated oil tree grown commercially in China. Fruit set is greatly enhanced when animal pollinators are available in this system. Prior studies have shown that bees are the primary pollinators of Camellia oleifera, but we do not know which are the most effective. This study was conducted in Xinyu, Jiangxi province, China. Through tracking observation, we measured visit duration and the tendency of bees to visit new plants, critical for the self-incompatible C. oleifera. Further, we assessed pollen loads, pollen removal rates and pollen deposition per single visit to C. oleifera, as measures of pollination efficiency for comparing the managed honey bee (A. cerana) with wild bees (C. gigas and four Andrena species). Determining the pollination efficiency of bees is important for increasing fruit set and crop yield.The managed hongeybee Apis cerana has the longest single-visit time (92.40±8.31s) with a higher visit frequency to flowers on the same tree. The difference in duration was not significant between Apis cerana and three wild bee species (A. camellia, A. hunanensis and A. striata). Conversely, the pollen deposition of A. cerana was the lowest, significantly lower than that of four species of Andrena. Further, there were significant differences in the pollen load of six species: the amount of pollens on hind legs and body surface of A. cerana was much lower than in the wild bees. Compared with the four species of Andrena, Colletes gigas moved between plants more frequently. Given its large size, it also had the highest pollen load size, pollen removal and higher deposition rates, meaning it can essentially deposit more pollen across more flowers per unit time. The efficiency of Andrena striata Wu was relatively low compared to its congeners, which were similar.