The relationship between managed bees and the prevalence of parasites in bumblebees.

Peter Graystock,William O H Hughes,Dave Goulson

doi:10.7717/peerj.522

Abstract

Honey bees and, more recently, bumblebees have been domesticated and are now managed commercially primarily for crop pollination, mixing with wild pollinators during foraging on shared flower resources. There is mounting evidence that managed honey bees or commercially produced bumblebees may affect the health of wild pollinators such as bumblebees by increasing competition for resources and the prevalence of parasites in wild bees. Here we screened 764 bumblebees from around five greenhouses that either used commercially produced bumblebees or did not, as well as bumblebees from 10 colonies placed at two sites either close to or far from a honey bee apiary, for the parasites Apicystis bombi, Crithidia bombi, Nosema bombi, N. ceranae, N. apis and deformed wing virus. We found that A. bombi and C. bombi were more prevalent around greenhouses using commercially produced bumblebees, while C. bombi was 18% more prevalent in bumblebees at the site near to the honey bee apiary than those at the site far from the apiary. Whilst these results are from only a limited number of sites, they support previous reports of parasite spillover from commercially produced bumblebees to wild bumblebees, and suggest that the impact of stress from competing with managed bees or the vectoring of parasites by them on parasite prevalence in wild bees needs further investigation. It appears increasingly likely that the use of managed bees comes at a cost of increased parasites in wild bumblebees, which is not only a concern for bumblebee conservation, but which may impact other pollinators as well.

Highlights

In recent years several bumblebee species as well as other pollinators have suffered range declines in parts of Europe, the Americas and Asia (Biesmeijer et al, 2006; Cameron et al, 2011; Goulson, Lye & Darvill, 2008; Potts et al, 2010)
The study involved only a very limited number of sites and must be interpreted with caution, the results suggest that the prevalence of parasites in bumblebees may be affected by the presence of managed bees
The prevalence of A. bombi and C. bombi was respectively 12% and 15% higher in bumblebees near greenhouses at the three sites using commercially produced bumblebees compared to the two sites not using these bees, and the prevalence of Apicystis bombi was much higher 0.5 km from the greenhouses compared with 5 km away from them

Summary

Introduction

In recent years several bumblebee species as well as other pollinators have suffered range declines in parts of Europe, the Americas and Asia (Biesmeijer et al, 2006; Cameron et al, 2011; Goulson, Lye & Darvill, 2008; Potts et al, 2010). Changes in anthropogenic land-use is a major contributing factor to these declines, with agricultural intensification reducing floral diversity and nesting habitats from many pollinators (Goulson et al, 2005; Ricketts et al, 2008; Vanbergen et al, 2013) This has left some bumblebee species fragmented, in small populations with low genetic diversity, something which may make bees more vulnerable. In areas utilising commercially produced bumblebees, higher parasite prevalence may be expected to be the result, due to either the spillover of parasites from the commercially produced bumblebees, parasite spillback from wild bumblebees, or stress related to the high pollinator density (Kelly et al, 2009; Power & Mitchell, 2004; Schmid-Hempel, 2011)

Methods

Results

Conclusion