Community composition mediates interannual shifts in pollinators' roles within networks

Plant–pollinator networks are complex structures that describe interactions between plants and pollinators within ecological communities. Understanding how these networks are organized is crucial for the preservation of populations, communities, and ecosystem services, because network structure is linked to the function and resilience of communities. Here, using two‐year data from 18 plant–pollinator communities on Mallorca Island (Spain), we first evaluated whether there were significant interannual variations in the composition of the plant and pollinator assemblages. Second, we examined the relationships between the interannual variation in the abundance and richness of pollinators and plants and the interannual variation in the level of generalization and network role of different pollinator groups, and assessed to what extent these changes were due to variation in the diet of particular pollinator species in response to shifts in their abundance. Our study revealed no significant interannual variation in the abundance or richness of plants, whereas pollinator richness and abundance showed significant interannual changes, with different functional groups responding differently. We also found that interannual variations in pollinator abundance or richness were significantly related to interannual variation in most network metrics. Overall, interannual increases in species' abundance were associated with greater generalization, whereas increases in pollinator richness were related to more specialized interactions. These changes were partly due to changes in the diet of pollinators, as we also detected increases in species' diet breadth with increases in abundance when only species that occurred in both study years were analysed. Our results are compatible with patterns expected under inter‐ and intraspecific competition for flowering resources, as well as niche segregation. Understanding how plant–pollinator interactions reorganize after community changes is necessary to comprehend how future anthropogenic changes may influence pollination communities.