Managed honey bees aggravate pollination challenges for pollen‐limited species in alpine meadows

Abstract Managed honey bees ( Apis mellifera L.) are increasingly used worldwide to meet the growing demand for agricultural pollination services and honey production. The spillover of managed honey bees into natural habitats can strongly transform wild plant‐pollinator communities, resulting in mixed consequences for plant reproduction. To effectively predict and cope with the impacts of managed honey bees and conserve the biodiversity of natural communities, we need a deeper understanding of the factors that determine the type and magnitude of the response of different species within‐plant communities. Here, we examined pollinator visitation, stigma pollen deposition and seed set of eight common wild plant species (for two of which honey bee visitation has not been observed) with various degrees of pollinator dependency and pollen limitation (PL) under high (within 50 m from hives) and low ( c . 700 m from hives) managed honey bee density in three alpine meadows on the eastern Tibetan Plateau. Near managed hives, honey bees visited flowering plants more often at the expense of wild pollinators, both at the community and species levels. The displacement of wild pollinators by honey bees generally increased heterospecific pollen deposition, while the responses of seed set were modest and mixed. The two species not visited by honey bees also suffered lower visitation rates or a more heterospecific pollen load in meadows near the hives, indicating indirect effects of managed honey bees through pollination networks. Overall, plant species with a higher degree of pollinator dependency and PL were more strongly affected by managed honey bees, experiencing a greater extent of decrease in the visitation of wild pollinators and an increase in heterospecific pollen deposition with adjacency to managed hives. Synthesis and applications . Managed honey bees reduced pollination and reproductive success of wild plants, especially those suffering PL. Our findings help identify priority plants and their pollinators for conservation in alpine meadows of the Tibetan Plateau, and we call for more attention to the indirect impacts of managed honey bees and more cautious management of introduced honey bees to protect this sensitive ecosystem.