Native plants are the bee’s knees: local and landscape predictors of bee richness and abundance in backyard gardens

Abstract

Urban gardens may support bees by providing resources in otherwise resource-poor environments. However, it is unclear whether urban, backyard gardens with native plants will support more bees than gardens without native plants. We examined backyard gardens in northwestern Ohio to ask: 1) Does bee diversity, abundance, and community composition differ in backyard gardens with and without native plants? 2) What characteristics of backyard gardens and land cover in the surrounding landscape correlate with changes in the bee community? 3) Do bees in backyard gardens respond more strongly to local or landscape factors? We sampled bees with pan trapping, netting, and direct observation. We examined vegetation characteristics and land cover in 500 m, 1 km, and 2 km buffers surrounding each garden. Abundance of all bees, native bees, and cavity-nesting bees (but not ground-nesting bees) was greater in native plant gardens but only richness of cavity-nesting bees differed in gardens with and without native plants. Bee community composition differed in gardens with and without native plants. Overall, bee richness and abundance were positively correlated with local characteristics of backyard gardens, such as increased floral abundance, taller vegetation, more cover by woody plants, less cover by grass, and larger vegetable gardens. Differences in the amount of forest, open space, and wetlands surrounding gardens influenced abundance of cavity- and ground-nesting bees, but at different spatial scales. Thus, presence of native plants, and local and landscape characteristics might play important roles in maintaining bee diversity within urban areas.