Native bees in Wisconsin cranberry across a landscape gradient

Native bees have been shown to provide a majority of pollination services in some agricultural systems as well as increasing yield. As severe declines in managed honey bees make it difficult and expensive for growers to acquire hives, native bees will become more important in agricultural systems. However, native bee populations may also be in decline due to habitat loss and fragmentation, land-use changes, and agricultural intensification. The purpose of this study was to document the native bee assemblages in Wisconsin cranberries and relate their community structure to surrounding land cover. To address this we pan trapped bees in 15 commercial cranberry bogs in central Wisconsin. Bogs were chosen such that the landscape within one kilometer varied from 20-83% woodland and 0-39% agriculture. Overall, we collected 1282 specimens representing 108 species of native bees. Native bee species composition changed as a function of surrounding woodland and agriculture. Species richness was positively correlated with wooded habitat and marginally negatively correlated with agriculture in the surrounding kilometer. Bee abundance was positively correlated with species richness but was not significantly correlated with any landscape variables. This study found that native bees are abundant and diverse in Wisconsin cranberries, suggesting that their contribution to cranberry pollination could be significant. As the causes of honey bee die-offs remain uncertain, growers will need to seek alternative pollination methods. Habitat management and landscape planning may be one way for growers and communities to enhance native bee populations and thus pollination services on their farms.