Modeling wild bee functional trait responses to landscape structure in agricultural landscapes

Wild bees contribute important crop pollination in many parts of the world. Despite their importance, agricultural fields often offer poor floral and nesting resources to bees. To persist in agricultural landscapes, many wild bees rely on semi-natural habitat within the landscape, and the proportion and distribution of this habitat have consequences for wild bee populations. The addition of habitat enhancements, such as wildflower strips and hedgerows, can provide additional resources for wild bees in agricultural landscapes. However, there is a limited understanding of how the configuration and amount of existing semi-natural habitat affect bee populations. We used a spatially explicit landscape model to explore how different archetypal bees, representing combinations of functional traits such as body size, nesting biology, and specialization, responded to the composition and configuration of semi-natural habitat within artificial landscapes. We also modeled how the addition of habitat enhancements may support wild bee populations and identified which bee archetypes benefited most. We generated landscapes varying the proportion and aggregation of semi-natural habitat, grain size, and the amount and size of habitat enhancements. We then simulated archetypal bee populations within these landscapes over multiple generations. We expect that small-bodied specialist bees will be most sensitive to sparse semi-natural habitat and benefit most from habitat enhancements, due to their limited foraging range and reliance on floral resources in natural habitats. On the other hand, large-bodied generalists will be less impacted by limited semi-natural habitat due to their ability to gather floral resources from cropland and extended foraging range.