Conclusion
Our study found a high diversity of non-bee flower visitors, and the primary non-bee pollinators were flies. Even though bee-mediated pollination is important, our results suggest that non-bee species significantly contribute to total pollination services for strawberry crops in Ontario. On average, syrphids carried more pollen than native bees, contextualizing their role as putative pollinators. The collective contribution of three fly families, Syrphidae, Polleniidae and Anthomyiidae, represented most of the active pollen within the investigated fields. Although these families also tended to be the most generalist foragers, their pollen loads contained large proportions of strawberry pollen. Generalist pollinators are highly valuable in agriculture; they contribute to the diversity of pollinators visiting crop flowers and therefore increase pollination success, and they are more robust in the face of ongoing landscape intensification (Ghazoul 2005, Blüthgen and Klein 2011, Garibaldi et al. 2014). Furthermore, generalists may be more resilient to adverse weather conditions (Heinrich and Mcclain 1986, Inouye et al. 2015). However, further research is needed to understand the quality of pollination services of non-bee pollinators.