Scale-dependent effects of landscape context on urban bee diversity

As urbanization continues throughout much of the world, there is great interest in better understanding the value of urban and residential environments to pollinators. We explored how landscape context affects the abundance and diversity of bees on 50 residential properties in northern Georgia, USA, primarily in and around Athens, GA. Over 2 years of pan trap sampling we collected 4938 bees representing 111 species, from 28 genera in five families, constituting 20% of the species reported for the state. Development correlated positively with bee diversity at small (< 2.5 square km) scales, and positively with six of eight individual bee species' abundances. Agriculture often correlated positively with bee diversity at larger spatial scales (> 2.5 square km), and negatively at smaller spatial scales. Forest cover correlated negatively with bee diversity at small spatial scales, but positively at larger scales. This trend was also largely true for individual bee species abundances. Bee communities differed between sites by predominant land cover types (agriculture, forest and development). Simper and indicator species analysis revealed which species contributed heavily to the observed patterns and helped to determine group distinctions. Implications for insect conservation Our results show that residential landscapes can support high bee diversity and that this diversity is sensitive to landscape context at different scales. Although development appears to have a negative effect on bee diversity overall, some bee species are favored by the open conditions characteristic of developed areas. Moreover, forest remnants appear to be valuable habitats for many species and are thus important to regional bee diversity. Urban planning that prioritizes and incorporates forest remnant conservation will promote bee abundance and diversity.