Comparing the Seasonal Diets of Buff-tailed Bumblebees and Honey Bees in a Forest Landscape: A Metabarcoding Approach

The declining diversity of pollinating insects is a major threat to ecosystem conservation, pollination services, and global food security. Honeybees dominate managed pollination, but their dominance can affect other pollinators. Competition for resources can lead to decreased foraging success and survival rates for wild bees, especially bumblebees. This study explores the dietary composition of honeybees and bumblebees using molecular metabarcoding techniques with three primers (ITS2, TrnLgh, and TrnLch) in an agricultural and forest land, Avensan, France. It aims to characterize pollen diversity within their diets, allowing for the inference of floral diversity in the study site. The primers detected pools of different species, indicating a high diversity of floral species in the plants visited by both species. The “primer” effect was more important than the “pollinator” effect in segregating plants found. The Schoener index revealed a slight diet overlap in plant species used by honeybees and bumblebees, depending on the primer. Correspondence analyses showed a high segregation between species associated with honeybees and species associated with bumblebees, regardless of the primer. However, the metabarcoding technique was found to be accurate in separating different pollinator food niches, and did not find a significant overlap in the diet of these two insects. The study provides a good approach to study their floral resources sharing in the same geographical area and time scale, but it is not powerful enough to infer floral diversity.