Larger bees facilitate the deposition of oilseed rape pollen (Brassica napus L.)

Abstract

Oilseed rape is the third-largest source of vegetable oil and the second-largest source of protein meal in the world. Pollinators are vital in the production of oilseed rape. However, pollination efficiency could be influenced by the morphology and foraging behaviors of pollinators. To evaluate the effect of pollinator size and foraging behavior on pollination efficiency, the intertegular distances (ITDs) of five bumble bees (Bombus pyrosoma, B. lantschouensis, B. melanurus, B. sichelii and B. sibiricus) and two honey bees (Apis mellifera and A. cerana) were evaluated. Their foraging activities and single visit depositions (SVDs) on oilseed rape were observed and counted. The ITDs of bumble bees were significantly larger than honey bees (P < 0.05). The single-visit duration of A. mellifera (2.43 ± 0.06 s) was significantly longer than other bees (P < 0.05). The interval time of the A. cerana was longer than other bees (P < 0.05). Larger bees tended to deposit more pollen on stigmas at each visit than smaller bees. The interspecific ITD of bees had a positive effect on SVD (P < 0.001). There was no correlation between ITD and SVD among individuals of the same species. In conclusion, the size of bees had a positive impact on pollination efficiency. Bees with a greater ITD deposited substantially more pollen and had a significantly shorter interval between flowers. Understanding the foraging behavior and pollination efficiency of these bee species and developing habitats to support them should enable growers to achieve resilient production.