The ongoing scienti. c controversy over a putative "global pollination crisis'' underscores the lack of understanding of the response of bees ( the most important taxon of pollinators) to ongoing global land- use changes. We studied the effects of distance to forest, tree management, and. oral resources on bee communities in pastures ( the dominant land- use type) in southern Costa Rica. Over two years, we sampled bees and. oral resources in 21 pastures at three distance classes from a large (similar to 230- ha) forest patch and of three common types: open pasture; pasture with remnant trees; and pasture with live fences. We found no consistent differences in bee diversity or abundance with respect to pasture management or. oral resources. Bee community composition, however, was strikingly different at forest edges as compared to deforested countryside only a few hundred meters from forest. At forest edges, native social stingless bees ( Apidae: Meliponini) comprised similar to 50% of the individuals sampled, while the alien honeybee Apis mellifera made up only similar to 5%. Away from forests, meliponines dropped to similar to 20% of sampled bees, whereas Apis increased to similar to 45%. Meliponine bees were also more speciose at forest edge sites than at a distance from forest, their abundance decreased with continuous distance to the nearest forest patch, and their species richness was correlated with the proportion of forest cover surrounding sample sites at scales from 200 to 1200 m. Meliponines and Apis together comprise the eusocial bee fauna of the study area and are unique in quickly recruiting foragers to high- quality resources. The diverse assemblage of native meliponine bees covers a wide range of body sizes and. ower foraging behavior not found in Apis, and populations of many bee species ( including Apis), are known to. uctuate considerably from year to year. Thus, the forest- related changes in eusocial bee communities we found may have important implications for: ( 1) sustaining a diverse bee fauna in tropical countryside; ( 2) ensuring the effective pollination of a diverse native plant community; and ( 3) the ef. ciency and stability of agricultural pollination, particularly for short- time- scale, mass. owering crops such as coffee.
