Bee community form and function in urban vacant land: Implications for managing pollinator friendly cities

Rare and diverse bee communities have been documented in cities around the world, suggesting that urban areas are potential refuges for declining pollinators. However, successful investment into urban conservation habitat depends on synthesizing urban bee community patterns into actionable guidelines. Thus, we established seven potential conservation greenspace designs across a network of 56 vacant lots in Cleveland, Ohio, in order to investigate how seeded vegetation and landscape context influence bee community structure and foraging. We assessed the distribution of several bee functional traits, diversity, and abundance with pan and malaise traps. Foraging preferences were determined with plant-pollinator networks derived from vacuum collections of bees from flowers. We found that bloom abundance but not bloom identity influenced bee community structure, with increasing bee diversity, richness, abundance, and renter-bee abundance in sites with greater floral resources. Likewise, sites surrounded by larger patches of greenspace were associated with increased bee diversity and smaller sized bees. Plant-pollinator networks were dominated by exotic species, illustrating that weeds have an important role in sustaining urban bees. Together, these results suggest several recommendations for urban conservation habitat’s development and management. Whenever possible, site placement should be optimized so that new sites are in closer proximity to larger greenspace patches. Moreover, as weeds can provide valuable forage, limited management for weeds may improve bee outcomes. While we did not observe our seeded native plants enhancing the bee community, we expect that future establishment of prairie plants will enhance their influence on pollinators.