Neonicotinoid pesticide limits improvement in buzz pollination by bumblebees

Abstract

Neonicotinoid pesticides have been linked to global declines of benefcial insects such as bumblebees. Exposure to trace levels of these chemicals causes sub-lethal efects, such as reduced learning and foraging efciency. Complex behaviours may be particularly vulnerable to the neurotoxic efects of neonicotinoids. Such behaviours may include buzz pollination (sonication), in which pollinators, usually bees, use innate and learned behaviours to generate high-frequency vibrations to release pollen from fowers with specialised anther morphologies. This study assesses the efect of feld-realistic, chronic exposure to the widely-used neonicotinoid thiamethoxam on the development of sonication buzz characteristics over time, as well as the collection of pollen from buzz-pollinated fowers. We found that the pollen collection of exposed bees improved less with increasing experience than that of unexposed bees, with exposed bees collecting between 47% and 56% less pollen by the end of 10 trials. We also found evidence of two distinct strategies for maximising pollen collection: (1) extensions to the duration of individual buzzes and (2) extensions of the overall time spent buzzing. We fnd new complexities in buzz pollination, and conclude that the impacts of feld-realistic exposure to a neonicotinoid pesticide may seriously compromise this important ecosystem service.