Urbanization is increasing worldwide, relatively few studies have investigated patterns of urban biodiversity outside of city parks and reserves, in urban neighborhoods where people live and work. We evaluated models including local and landscape factors that might influence the bee and butterfly richness of community gardens located within densely populated neighborhoods of the Bronx and East Harlem in New York City (>10,000 people/km2). The gardens were surrounded by buildings and amounts of green space (3,600–17,400 building units and 10–32% green space within a 500 m radius). Contrary to our initial prediction that landscape green space might be especially influential in this heavily urbanized setting, the most highly supported models for both bee and butterfly richness (based on Akaike Information Criterion) included just the local, within-garden variables of garden floral area and sunlight availability. There was marginal support for models of bee richness including the number of building units surrounding gardens within a 500 m radius (which exhibited a negative association with bee richness). In addition, perhaps because bees are central place foragers that may nest within. Or near gardens, supported models of bee species richness also included total garden area, canopy cover, and the presence of wild/unmanaged area in the garden. Generally, our findings indicate that sunlight and floral abundance are the major factors limiting local pollinator diversity in this setting. This suggests that rooftop and other “open” urban habitats might be managed to increase local pollinator diversity, even if seemingly “isolated” within heavily developed neighborhoods.
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We describe the richness, abundance, and ecological characteristics of bees in community gardens located in heavily developed neighborhoods of the Bronx and East Harlem, NY. In total, 1,145 individual bees, representing 54 species (13% of the recorded New York State bee ) were collected over 4 yr. The nesting habits of these species include bees that nest in cavities (33% of species), hives (11% of species), pith (1.9% of species), wood (1.9% of species), or soft/rotting wood (7.4% of species) substrates. Soil-nesting individuals were relatively rare (25% of individuals), perhaps due to a lack of proper soils for nesting sites. Parasitic species were scarce (5.6% of species, 2.6% of individuals), most likely because of an absence or rarity of host species. Overall, exotic species were abundant and constituted 27% of the total individuals collected and 19% of the identi?ed species. We compare these results to several bee faunal surveys inNewJersey andNewYork State, including newly reported species lists for Central Park and Prospect Park in New York City. Relative to other studies, bee richness of the urban gardens is reduced and composition is biased toward exotic and cavitynesting species. Nevertheless, despite their small size and location within highly urbanized areas, urban community gardens harbor a diverse assemblage of bees that may provide pollination services and opportunities for ecological exposure and education.