Impacts of multiple stressors on bumblebee queens and their colonies

Bumblebees have an annual colony cycle, several stages of which may be particularly vulnerable to environmental stress. Founding queens represent such a stage; they must forage, nest search and initiate a colony alone, often under challenging environmental conditions. Loss of the queen at this stage, or even sublethal impacts on her behaviour or ability to lay eggs could lead to failure of the colony. A range of stressors, such as parasites, pesticides, adverse weather and difficult foraging conditions could all have negative impacts on queens during this critical phase in their lifecycle. While much is known about the impacts of natural parasites and hibernation duration on queen success, almost nothing is known about the impacts of pesticides at this stage of the colony cycle. The large size of queens may buffer them from the impacts of low level of pesticide exposure, but when faced with additional potentially stressful events, such as diapause, parasitism, or reduced food availability, these stressors may interact to negatively impact the health and fitness of queens. Here we present data on the survival, egg-laying and colony founding ability of Bombus terrestris queens when challenged with multiple stressors, and discuss its implications for wild bee populations.