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Introduced honey bees increase host plant abundance but decrease native bumble bee species richness and abundance

Citation

Mu, Junpeng (2022), Introduced honey bees increase host plant abundance but decrease native bumble bee species richness and abundance , Dryad, Dataset, https://doi.org/10.5061/dryad.sn02v6x5f

Abstract

Long-term variation in the population density of introduced honey bees (Apis mellifera) has been shown to be associated with variations in floral traits in alpine lotus (Saussurea nigrescens). However, it remains to be determined whether a high density of honey bees affects the abundance of nectariferous plants and the species richness and abundance of native bumble bees. We predicted that a high density of introduced honey bees lasting three decades would decrease the species richness and abundance of native bumble bees but increase the abundance of honeybee host plant species. Here, the field experiments were conducted to examine the diversity of nectariferous plants and native bumble bees along the typical gradients of honey bee density (high density of honey bee at close apiary and low density of honey bee at distant of apiary). We investigated nectariferous plant abundance, floral and seed traits, bumble bee species richness and abundance at sites with either a high or low honey bee density in an alpine meadow. Our results demonstrated that an increased population of introduced honey bees was associated with increased host plant abundance and flower/capitula number per plant but decreased nectar volume per flower, seed mass, species richness and abundance of native bumble bees. The bumble bee visitation rate was positively correlated with nectar volume per flower at sites close to and far from apiaries. The honey bee visitation rate was positively correlated with flower/capitula number per plant at sites close to apiaries and nectar volume per flower at sites far from apiaries. Seed mass was negatively correlated with nectariferous plant abundance. Our findings showed that introduced honey bees decreased the species richness and abundance of native bumble bees, attributed to evolutionary decrease nectar resources among honey bee host plant species, but increased the abundance of nectariferous plants, attributed to the production of many small seeds by plants. This suggests that long-term high-density beekeeping affects the biodiversity of honey bee host plants and native bumble bees. Our results provide new insights into the mechanisms of maintaining the biodiversity of nectariferous plants and native bumble bees.