Semi-natural habitat cover but not late season mass-flowering crops affect pollinator-plant networks in non-crop habitats

Plant-pollinator networks in agricultural landscapes are subject to high flower resources fluctuations due to mass-flowering crops cultivation. Mass-flowering crops can attract pollinators and alter community compositions in non-crop habitats, yet their impacts on plant-pollinator networks in non-crop habitats remain understudied. In this study, we investigated the effects of late-season mass-flowering red clover crops in 120 plant-pollinator networks in non-crop habitats during and after the clover bloom period in southern Sweden. Our findings show that late-season mass-flowering red clover crops did not impact the structure of plant-pollinator networks in non-crop habitats. On the other hand, plant-pollinator network structure in agricultural landscapes was predominantly affected by local flower richness and semi-natural habitat cover in the landscape. Semi-natural habitat (SNH) cover positively impacted network specialisation after clover bloom. Greater flower availability with increasing semi-natural habitat cover might increase the possibilities of pollinator species to focus on different resources to optimise foraging and avoid competition at time when flower resources are scarce in temperate landscapes (e.g. after clover bloom, late August). In line with this, both Bombus terrestris became more specialised in landscapes with high SNH cover after clover bloom. Specialisation may help reduce inter-individual and inter-specific exploitative competition for floral resources and thus favour coexistence in pollinator assemblages, especially in a context of agroecosystems, where flower resources are generally limited and fluctuating due to mass-flowering crop cultivation. In conclusion, our study underscores the robustness of plant-pollinator networks in non-crop habitats to shifts caused by mass-flowering crop cultivation and emphasises the critical role of semi-natural habitat preservation and flower richness in shaping plant-pollinator network structure in agricultural ecosystems.