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The decline of pollinators may alter the complex system of interactions that they establish with flowering plants, with potential negative consequences on both partners. Within this context, network analysis may be a useful tool to study ecological properties of plant-pollinator interactions and to evaluate the outcomes of conservation actions. Three conservation measures were implemented within the European LIFE + PP-ICON project to support the local pollinator community of a population of the rare plant Dictamnus albus in a protected area near Bologna, Italy. Artificial nesting sites were installed to support solitary bees, populations of native plants were reinforced to increase foraging resources for pollinators, and colonies of bumblebees reared from wild queens were released in the study area. In this work we evaluate the effects of these conservation actions on plant-pollinator networks over a period of four years, comparing a pre- (2011–2012) and a post-conservation (2013–2014) action period. The overall network generalisation increased after the implementation of conservation measures and interactions were more evenly distributed. Module composition significantly changed between the two periods, showing a marked rewiring of interactions. D. albus was a module hub both before and after conservation actions, thus emerging as an important node within its own module. In addition, some plant and pollinator species directly targeted by conservation measures became module connectors, highlighting their increased importance in linking different modules. Finally, the reinforcement of plant and pollinator populations led to increased flower visitation. These results indicate that conservation actions affected species both directly and indirectly and that the network of interactions has potentially increased its robustness and resilience towards possible species loss. This study highlights ways in which network analysis can be used to measure changes in plant-pollinator interactions in response to conservation actions.

Bees collect pollen as an important resource for offspring development while acting as pollen vectors for the plants visited. Foraging preferences of pollinators together with plant species availability shape the web of interactions at the local scale. In this study, we focused on the bee pollinator community of a population of the rare protected perennial herb Dictamnus albus, with the aim to characterise the pollen preferences and the foraging niche 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 plants in the area, and to evaluate the degree of foraging overlap 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 foraging niche overlap in the pollinator community decreased together with an increased diversity of co-flowering plant species. The results obtained indicate that bees preferentially forage on D. albus in the studied area, but that co-flowering species contribute to complement their diet and likely reduce competition for foraging resources. It appears therefore important to maintain a high diversity of co-flowering plants to preserve the diversity in the studied pollinator community of D. albus.