Quantifying pollination efficiency of flower-visiting insects and its application in estimating pollination services for common buckwheat

Pollination services provided by managed honey bee and wild pollinators are essential for a range of crops. Pollination services can be measured as species-related services, which can be quantified by the combination of each species’ pollination efficiency and their abundance, as well as harvest-related services, which can be quantified by the pollinator exclusion method. Species-related pollination services are poorly documented and have never been directly compared to harvest-related services. Here, we aimed to quantify the pollination efficiency for common flower-visiting species of common buckwheat (Fagopyrum esculentum) and to scale it up to estimate pollination services. We assessed pollination efficiency by single-visit pollen deposition and visitation rate for common flower-visiting insect species. We monitored the abundance of these species during the entire flowering period across seven sites, where pollinator exclusion treatments were undertaken by caging. In total, we observed 27 flower-visiting species and calculated the pollination efficiency of 17 species. We found that flower-visiting species had different capabilities in transferring compatible pollen grains for two flower morphs and different visitation rates. The estimated pollination efficiency was highest for two honey bee species (Apis mellifera and A. cerana), followed by the hoverfly species (Eristalis tenax), and wasp species (Tiphia vernalis). Species-related pollination services estimated by pollination efficiency and abundance showed a strong positive relationship with harvest-related services, which were estimated by the pollinator exclusion method. Our results suggest that to achieve substantial pollination services for common buckwheat, it is important to maintain sufficient managed honey bees, particularly in areas lacking highly efficient wild pollinators species. Our study also suggests that it is possible to estimate pollination services by scaling up the pollination efficiency of common flower-visiting insects. We provide recommendations for the application of this technique.