Authors: Cappellari, Andree; Bonaldi, Giovanna;Mei, Maurizio;Paniccia, Dino;Cerretti, Pierfilippo;Marini, Lorenzo;

Managed and wild pollinators often cohabit in both managed and natural ecosystems. The western honeybee, Apis mellifera, is the most widespread managed pollinator species. Due to its density and behaviour, it can potentially influence the foraging activity of wild pollinators, but this effect is often context-dependent. We observed plant–pollinator interactions in 51 grasslands and we explored whether the resource overlap between wild pollinators and honeybees was affected by honeybee abundance, plant functional diversity, and trait similarity between wild pollinators and the honeybee. Resource overlap decreased with increasing honeybee abundance only in areas with high functional diversity of plant communities, suggesting a potential diet shift of wild pollinators in areas with a high variability of flower morphologies. Moreover, resource overlap increased with increasing trait similarity between wild pollinators and the honeybee. In particular, central-place foragers with proboscis length similar to the honeybee exhibited the highest resource overlap. Our results underline the importance of promoting functional diversity of plant communities to support wild pollinators in areas with a high density of honeybee hives. Moreover, greater attention should be paid to areas where pollinators possess functional traits similar to the honeybee, as they are expected to be more prone to potential competition.