Native bees provide a valuable ecosystem service by pollinating both flowering crops and native plants, supporting agricultural production, and terrestrial plant diversity and productivity. Recent evidence suggests native bees are in decline due to the cumulative effects of multiple stressors. These potential declines have raised interest in monitoring and management strategies for native bees. However, the lack of foundational information on bee communities, including species composition, abundance and response to disturbance, is a barrier to characterizing impacts to these species and the services they deliver. In this study, we surveyed native bee communities in 68 sites that fell in either cultivated cropland or rangeland systems over two years and across three eco-regions in the Canadian prairies covering a broad environmental gradient. Bees were sampled using a combination of pan trapping and targeted netting. We evaluated differences in bee abundance, richness, diversity, and community composition between these two land uses and across eco-regions.
Results/Conclusions
There were significant patterns in both the abundance, richness, and composition of native bees across regions and land use types. Regional patterns in abundance and richness showed opposing trends depending on the method of bee capture, with the highest abundance of pan-trapped bees in the southern driest region, and the highest abundance of netted bees in the northern wettest region. Bee abundance and richness responded inconsistently to land use across years, method, and regions with no strong discernible impact of cultivation. However, bee community composition between the two land uses was consistently different across methods and years, indicating that different species of bees tend to use these two different types of habitat. Indicator species analysis identified several species of cavity-nesting bees that are strongly associated with rangeland habitat, and several species of ground-nesting bees that are associated with cultivated fields. These results suggest that nesting biology may be an important factor to consider when assessing response to land disturbance. This study represents one of the first detailed inventories of the bee community at such a large spatial scale in the prairies and captures a valuable baseline condition for future comparisons.