Abstract
Urban green spaces can provide quality habitat for insect pollinators. However, few studies have investigated the quality of pollination services provided by urban insect pollinator communities or compared pollination services between different types of urban green spaces. We evaluated both the taxonomic and functional trait diversity of flowering plant and bee communities in two common types of suburban green space: residential backyards and electric powerline corridors. We also quantified seed set from sentinel cucumber plants as a measure of pollination services. We analyzed the response of the flowering plant community to site type and impervious surface cover, as well as the response of the bee community to flowering plant taxonomic and functional diversity and impervious surface cover. Seed set was analyzed in response to bee abundance, species diversity, and the community-weighted mean of bee body size. Site type affected floral resource diversity. Bee abundance was negatively affected by both impervious surface cover and floral resource functional evenness, and pollination services were negatively affected by bee total abundance. Our findings suggest that certain suburban management practices and site characteristics can lead to bee communities with highly abundant but mostly ineffective pollinators. Ultimately, these results also reinforce the need for more urban ecology studies that directly measure ecosystem functions and attempt to trace the mechanistic relationships between those functions and the organisms facilitating them.