The Potential Influence of Bumble Bee Visitation on Foraging Behaviors and Assemblages of Honey Bees on Squash Flowers in Highland Agricultural Ecosystems.

Zhenghua Xie,Dongdong Pan,Jiandong An,Jonathan Teichroew,Zhong-Jian Liu

doi:10.1371/journal.pone.0144590

Abstract

Bee species interactions can benefit plant pollination through synergistic effects and complementary effects, or can be of detriment to plant pollination through competition effects by reducing visitation by effective pollinators. Since specific bee interactions influence the foraging performance of bees on flowers, they also act as drivers to regulate the assemblage of flower visitors. We selected squash (Cucurbita pepo L.) and its pollinators as a model system to study the foraging response of honey bees to the occurrence of bumble bees at two types of sites surrounded by a high amount of natural habitats (≥ 58% of land cover) and a low amount of natural habitats (≤ 12% of land cover) in a highland agricultural ecosystem in China. At the individual level, we measured the elapsed time from the departure of prior pollinator(s) to the arrival of another pollinator, the selection of honey bees for flowers occupied by bumble bees, and the length of time used by honey bees to explore floral resources at the two types of sites. At the community level, we explored the effect of bumble bee visitation on the distribution patterns of honey bees on squash flowers. Conclusively, bumble bee visitation caused an increase in elapsed time before flowers were visited again by a honey bee, a behavioral avoidance by a newly-arriving honey bee to select flowers occupied by bumble bees, and a shortened length of time the honey bee takes to examine and collect floral resources. The number of overall bumble bees on squash flowers was the most important factor explaining the difference in the distribution patterns of honey bees at the community level. Furthermore, decline in the number of overall bumble bees on the squash flowers resulted in an increase in the number of overall honey bees. Therefore, our study suggests that bee interactions provide an opportunity to enhance the resilience of ecosystem pollination services against the decline in pollinator diversity.

Highlights

Wild bees and managed honey bees are declining at both local and global scales [1,2,3]
In the fields within the HN habitats, the pistillate flowers previously visited by a bumble bee experienced a significantly longer elapsed time before being revisited again by a new visitor than the flowers previously visited by a honey bee, no matter if the new visitor was a honey bee (Fig 2A left: t = 3.16, df = 70.56, p = 0.002) or a bumble bee (Fig 2A right: t = 2.07, df = 55.65, p = 0.04)
The staminate flowers previously visited by a bumble bee experienced a significantly longer elapsed time before being revisited by a newly-arrived honey bee than the flowers previously visited by a honey bee (Fig 2B left: t = 3.95, df = 34.51, p < 0.001)

Summary

Introduction

Wild bees and managed honey bees are declining at both local and global scales [1,2,3]. Habitat loss is one of the key factors driving the decline of wild bees. The responses of wild bees and managed honey bees to habitat loss are often quite different due to their diverse life history [4], and are affected differently according to the intensity of environmental disturbances [5]. Inter- and intra-specific bee species interactions act as important factors regulating the foraging activities of bees on flowers and the services they provide to plants. Bee interactions are recognized as drivers to repel effective pollinators [11,12], showing negative effects on plant pollination. Since bee interactions show diverse effects on pollinator performance [12,16], they can influence the flower visitors and result in different pollination services to plants [17]. Bee interactions may act as drivers regulating pollinator assemblages and pollination services of ecosystems

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Conclusion