Relative importance of local- versus landscape-scale habitat for native bee pollinators of highbush blueberry, Vaccinium corymbosum

Within agricultural ecosystems, greater availability of non-agricultural habitat can increase pollinator populations, but the relative importance of habitat availability at the local versus the landscape scale is not well understood. The goal of our study is to measure the relative importance of these two scales for native, wild bee pollinators of commercial highbush blueberry (Vaccinium corymbosum). We worked at 16 blueberry farms in southern New Jersey that varied in the proportion of non-crop vegetation within a 300 m radius (the “local scale”) and within a 1500 m radius (the “landscape scale”). The study was designed so that landscape and local variables were uncorrelated. Each farm was visited on three different days during bloom. On each visit, we observed pollinators visiting blueberry flowers, and net-collected pollinator specimens, during standardized transect surveys. As a measure of pollinator abundance, we pooled observations of bees visiting flowers (n=824) and specimens netted from flowers (n=421). As a measure of diversity, we used the number of bee genera net-collected at a given farm. Multiple regression analysis showed that both bee abundance (t=2.39, p=0.03) and bee diversity (t=4.18, p=0.001) increased significantly with increasing non-crop vegetation at the local scale. In contrast, although both bee abundance (t=1.14, p=0.28) and diversity (t=1.35, p=0.20) increased with increasing non-crop vegetation at the landscape scale, trends were non-significant. These results suggest that the availability of local non-crop vegetation may be of greater importance to maintaining native, wild bee pollinators than is agricultural intensity at the landscape scale.