Pollination effectiveness of exotic Apis mellifera compared to native bees and flies

Growing evidence shows that the exotic honeybee, Apis mellifera, disrupts plant-pollinator networks by outcompeting native pollinators for nectar and pollen. Moreover, honeybees are not always the most effective pollinators for all plant species. Therefore, assessing the relative pollination efficiency of A. mellifera and native species is crucial when selecting apiary sites in agro-ecosystems. The current study was conducted to assess the relative pollination potential of A. mellifera compared to native bees, including solitary bees, native honeybees, and true flies, on Brassica napus (canola) and Sesamum indicum (sesame) crops. Results showed that in canola, A. dorsata and A. mellifera collected the highest number of pollen grains; however, neither species transferred as much pollen to the stigma as Halictus sp., which resulted in the highest seed count per pod during a single visit. In sesame, Andrena sp. and A. dorsata collected and deposited the highest number of pollen grains, leading to the greatest number of seeds per capsule and the highest seed weight in a single visit. A. mellifera exhibited an intermediate level of pollination potential, along with a few other native pollinators, in both crops. Overall, our findings suggest that solitary bees (Halictus sp. and Andrena sp.) and the native honeybee (A. dorsata) are more effective pollinators of canola and sesame than A. mellifera in Southern Punjab, Pakistan. This study provides valuable insights that can inform decisions on hive placement in canola and sesame fields. Future research should extend this comparison to other cross-pollinated crops.