Contrasting bee foraging in response to resource scale and local habitat management

It is hypothesized that two main factors drive the foraging patterns of native and exotic species: food resource availability and habitat composition. These factors are particularly relevant for native bees and exotic honeybees, essential crop pollinators that are sensitive to floral resources and habitat management, and that have recently exhibited alarming population declines. Mechanisms driving native and exotic bee foraging patterns may critically depend on floral resource availability and habitat composition, yet the impacts of these factors on bee foraging have never been simultaneously analyzed. In a coffee producing region in southern Mexico, we investigated the influence of coffee floral resource levels and habitat management on native and exotic bee foraging. We measured the amount of flowering coffee available at multiple spatial scales within two distinct agroforestry habitat types (high-shade and low-shade coffee) and recorded visits to coffee flowers, documenting bee species, visit duration and visit frequency. We observed a significantly greater number of visits in high-shade coffee habitats than in low-shade coffee habitats for both native and exotic bees. In high-shade coffee habitats, native solitary bee and native social bee visitation decreased significantly in response to increasing floral resource availability, exhibiting a 'dilution effect' at the smallest spatial scale. In contrast, in low-shade coffee habitats, Africanized honeybees exhibited a 'concentration effect', increasing visitation significantly in response to increasing floral resource availability at the largest spatial scale. This study is the first to show that foraging patterns of native bees and exotic honeybees contrast in response to floral resource level and scale and that this response is mediated by the vegetation management of the local habitat.