Effects of drought on bumble bee foraging efficiency and community structure

Global climate change is expected to increase the intensity and frequency of both biotic and abiotic plant stress. On the landscape scale, this poses direct risks to insects by altering essential floral cues and resources. Although ~35% of crop production world-wide depends on insect pollinators, such as honeybees (Hymenoptera, Apis mellifera) and bumblebees (Hymenoptera, Bombus spp.), today's agroecosystems are associated with the decline of native bees due to intensive crop production and pest management. Decreased pollinator diversity threatens food security by increasing the ecosystem’s susceptibility to disturbances. Current research has focused on species richness and abundance in response to landscape-scale environmental events (e.g. drought), however, it remains unclear if this type of data provides any strong indication of bumblebee community health. This project thus aims to evaluate how landscape-scale environmental events affect bumblebee community structure by incorporating markers of forager efficiency alongside population dynamics. Specimens were collected from 15 sites around Humboldt, Saskatchewan over the 2018 and 2019 growing seasons, covering a) canola, b) cereal, and c) forage grassland field types along transects originating from i) the field edge and ii) an in-field wetland. The 2018 growing season was significantly drier than 2019, allowing for a natural study on drought effects. To our knowledge, this is the first survey to utilize forager efficiency in evaluating the influence of landscape-scale environmental events on bee community structure, providing vital information for assessing bee community health and potential frameworks for evaluating agricultural and conservation methods.