Management Effects on Biodiversity and Pollination Services in a Suburban Landscape

Previous research has indicated that urban and suburban areas may provide quality habitat for bees and support pollination services. However, the mechanisms determining the suitability of urban environments as bee habitat are still largely unknown. I conducted a series of field studies in the Chicago area to determine the effects of the suburban environment on bee biodiversity and pollination services. Sampling was done in residential backyards and gardens as well as in powerline corridors (the strips of land under high-voltage powerlines and towers). I conducted visual surveys of floral resources and sampled the bee community using both timed visual observations and pan trapping. I also conducted two sentinel plant assays (using cucumber, Cucumis sativus, and a native annual, Bidens aristosa) to monitor pollination services in my study sites. I found that beta diversity for both floral resources and bees was higher in residential neighborhoods than in powerline corridors, most likely due to the resource and management heterogeneity of neighborhoods managed by many small-scale decision makers. I also found that cucumber seed set increased with increasing bee community functional evenness, suggesting that sites with more even representation of many bee functional trait values have higher pollination activity than sites dominated by a few trait values. Finally, I utilized a structural equation model to illustrate the direct and indirect relationships between pollination, bees, floral resources, and management in my sites. I found that floral functional divergence directly affected both bees and pollination. The combined results of this dissertation indicate that powerline corridors and suburban residential neighborhoods provide opportunities for biodiversity conservation and support a vital ecosystem function, but that these opportunities are heavily dependent on site management type. Future research should focus on determining causal relationships between suburban site characteristics and both the bee community and pollination services.