General and species-specific impacts of a neonicotinoid insecticide on the ovary development and feeding of wild bumblebee queens

Gemma L Baron,Nigel E Raine,Mark J F Brown

doi:10.1098/rspb.2017.0123

Abstract

Bumblebees are essential pollinators of crops and wild plants, but are in decline across the globe. Neonicotinoid pesticides have been implicated as a potential driver of these declines, but most of our evidence base comes from studies of a single species. There is an urgent need to understand whether such results can be generalized across a range of species. Here, we present results of a laboratory experiment testing the impacts of field-relevant doses (1.87–5.32 ppb) of the neonicotinoid thiamethoxam on spring-caught wild queens of four bumblebee species: Bombus terrestris, B. lucorum, B. pratorum and B. pascuorum. Two weeks of exposure to the higher concentration of thiamethoxam caused a reduction in feeding in two out of four species, suggesting species-specific anti-feedant, repellency or toxicity effects. The higher level of thiamethoxam exposure resulted in a reduction in the average length of terminal oocytes in queens of all four species. In addition to providing the first evidence for general effects of neonicotinoids on ovary development in multiple species of wild bumblebee queens, the discovery of species-specific effects on feeding has significant implications for current practices and policy for pesticide risk assessment and use.

Highlights

Pollination by wild insects, such as bees, is important for a vast array of crop systems and wild plants [1 –4]
As wild bumblebees are unlikely to be exposed to lethal doses, here we investigate variation in sublethal impacts of the neonicotinoid insecticide thiamethoxam on four common bumblebee species, all of which are known to forage in agricultural areas
Wild bumblebee queens are likely to be exposed to pesticides while foraging or nesting in agricultural areas

Summary

Introduction

Pollination by wild insects, such as bees, is important for a vast array of crop systems and wild plants [1 –4]. There is evidence for declines in wild bee populations since the 1900s on a global scale [5,6,7,8,9,10,11,12]. There is considerable variation among bumblebee species in life-history traits, foraging behaviour and phenology, which may cause differences in their exposure and sensitivity to pesticides. Given these differences, extrapolating the effects of pesticides from one species to others is not always appropriate [29,30,31,32,33,34].

Methods

Results

Conclusion