Brosi Berry J, Daily Gretchen C, Ehrlich Paul R
Center for Conservation Biology, Department of Biological Sciences, Stanford University, California 94305, USA.
Ecol Appl. 2007 Mar;17(2):418-30. doi: 10.1890/06-0029.
The ongoing scientific 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 floral resources on bee communities in pastures (the dominant land-use type) in southern Costa Rica. Over two years, we sampled bees and floral resources in 21 pastures at three distance classes from a large (approximately 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 floral 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 approximately 50% of the individuals sampled, while the alien honeybee Apis mellifera made up only approximately 5%. Away from forests, meliponines dropped to approximately 20% of sampled bees, whereas Apis increased to approximately 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 flower foraging behavior not found in Apis, and populations of many bee species (including Apis), are known to fluctuate 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 efficiency and stability of agricultural pollination, particularly for short-time-scale, mass-flowering crops such as coffee.
关于假定的“全球传粉危机”的持续科学争议凸显了人们对蜜蜂（传粉者中最重要的分类群）对当前全球土地利用变化的反应缺乏了解。我们研究了距森林的距离、树木管理和花卉资源对哥斯达黎加南部牧场（主要土地利用类型）中蜜蜂群落的影响。在两年时间里，我们在距离一个大型（约230公顷）森林斑块三个距离等级的21个牧场中对蜜蜂和花卉资源进行了采样，这些牧场有三种常见类型：开阔牧场；有残留树木的牧场；以及有活篱笆的牧场。我们发现，在蜜蜂多样性或丰度方面，牧场管理或花卉资源没有一致的差异。然而，与距离森林仅几百米的森林砍伐后的乡村相比，森林边缘的蜜蜂群落组成明显不同。在森林边缘，本地社会性无刺蜂（蜜蜂科：无刺蜂属）约占采样个体的50%，而异国蜜蜂西方蜜蜂仅占约5%。远离森林时，无刺蜂降至采样蜜蜂的约20%，而西方蜜蜂则增至约45%。无刺蜂在森林边缘的地点也比远离森林的地方种类更多，它们的丰度随着到最近森林斑块的距离增加而减少，并且它们的物种丰富度与200至1200米尺度上样本地点周围的森林覆盖率相关。无刺蜂和西方蜜蜂共同构成了研究区域的群居蜜蜂动物区系，并且在迅速招募觅食者到优质资源方面很独特。本地无刺蜂的多样组合涵盖了西方蜜蜂中未发现的广泛体型和花朵觅食行为，并且许多蜜蜂物种（包括西方蜜蜂）的种群数量已知每年会有很大波动。因此，我们发现的与森林相关的群居蜜蜂群落变化可能对以下方面具有重要意义：（1）在热带乡村维持多样的蜜蜂动物区系；（2）确保对多样的本地植物群落进行有效授粉；（3）农业授粉的效率和稳定性，特别是对于咖啡等短时间尺度、大量开花的作物。
