Pollen load diversity and foraging niche overlap in a pollinator community of the rare Dictamnus albus L.

Bees collect pollen as an important resource for offspring development while acting as pollen vectors for the plants visited. Foragingpreferences of pollinatorstogether with plant species availability shape the web of interactions at the local scale. In this study, we focused on the bee pollinatorcommunity of a population of the rare protected perennial herb Dictamnusalbus, with the aim to characterise the pollen preferences and the foragingniche overlap among species through time. Bees were sampled during four consecutive years in a natural population of D. albus, throughout the blooming period of the plant species. We performed an analysis of insect pollen loads to investigate the interactions with the study species and the co- flowering plantsin the area, and to evaluate the degree of foragingoverlap among pollinators. Over the study years, all bee species showed a high fidelity to D. albus (60–80%), even if some taxa preferentially collected pollen from other flowering species. The foragingniche overlap in the pollinatorcommunity decreased together with an increased diversity of co- flowering plantspecies. The results obtained indicate that bees preferentially forageon D. albus in the studied area, but that co-flowering species contribute to complement their diet and likely reduce competition for foragingresources. It appears therefore important to maintain a high diversity of co- flowering plantsto preserve the diversity in the studied pollinatorcommunity of D. albus.