Comparing the Seasonal Diets of Buff-tailed Bumble Bees and Honey Bees (Hymenoptera: Apidae) 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 (Apis mellifera L.) 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 buff-tailed bumblebees (Bombus terrestris L.) using metabarcoding techniques with three primers (ITS2, TrnLgh, and TrnLch) in Avensan, France. Primers detected different species pools, indicating a high diversity of plants visited by both species - including some false positives results inherent to metabarcoding methods. 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 or with bumblebees, regardless of the primer. The metabarcoding technique was found to be accurate in separating pollinator food niches, despite some biases of this technique: this result is not comparable with previous literature studying the diets of these two species, as traditional field studies are needed to complement it and overcome these biases. To conclude, this study provides a fast and inexpensive approach to study pollinators' floral resources sharing in the same geographical area and time scale, and provide insights to improve metabarcoding effectiveness in order to better describe diet niches.