Local landscapes and microhabitat characteristics are important determinants of urban–suburban forest bee communities

Despite their diversity and abundance, the importance of native, forest bee communities to pollination services and inherent biological diversity conservation is often overlooked. We studied forest bee communities in Delaware and Pennsylvania, USA, to better understand how forest bee community structure varies with changing land use and microhabitat quality among small, urban and suburban forest fragments in the mid-Atlantic United States. Our hypotheses were that (1) microhabitat quality would affect relative abundance of bee taxa, (2) surrounding landscape composition would drive local patch colonization-extinction dynamics, and (3) forest patch size would not affect community structure and composition. We found a lack of spatial autocorrelation among forest patches, indicating the importance of individual fragments in the autonomous generation and/or maintenance of bee communities. Community analyses revealed the importance of both landscape context and microhabitat quality in defining forest bee communities. By partitioning beta diversity into its constituent components, we also found that landscape composition drove changes in the relative abundance of taxa, while both landscape and microhabitat characteristics significantly influenced species turnover. Neither landscape composition nor quality of the microhabitat influenced initial site occupancy or colonization-extinction dynamics. Bisected by highways, suburban neighborhoods, agricultural lands, and urban development, many urban and suburban forest patches in the eastern United States are similar in composition to our study sites. As many native forest bees have limited capacity for long-range movement between forest patches, these remaining forest fragments are critical to the conservation of unique and speciose forest bee communities.