Abstract Pollinator biodiversity may benefit crop pollination. Yet benefits in agro-ecosystems may be context-dependent and offset by agronomic or other limiting orchard-specific or tree-specific factors that obscure biodiversity-ecosystem service relationships. To test if crop pollination benefitted from pollinator biodiversity, we sampled local wild bee communities in five organic and five Integrated Pest Management (IPM) apple orchards in Germany and experimentally measured the pollination success of apple flowers, quantified as the number of pollen tubes reaching the base of styles. Using standard statistical modelling approaches for over-dispersed count data, we found little or no effect of wild bee biodiversity on pollination success, irrespectively of farm management (organic versus IPM). There was, however, a positive relationship between the number of pollen tubes in insect-pollinated and pollen-supplemented flowers across trees and orchards, suggesting confounding effects of local tree- or orchard-specific factors limiting pollination success. Using a statistical two-part hurdle model which allowed us to separate (i) the probability of pollination and (ii) the quantity of pollination, we were able to demonstrate that the collective effects of local tree/orchard factors acted as a primary limiting threshold for pollination success. Once the threshold was crossed, the hurdle model demonstrated that increasing wild bee abundance enhanced pollination success of apple trees. We advocate the use of statistical two-part models as a more powerful approach to identifying limiting factors of, and the role of biodiversity in, crop pollination and potentially other ecosystem services in agro-ecosystems.

中文翻译：

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一种由两部分组成的建模方法揭示了传粉媒介生物多样性在促进苹果花授粉方面的积极作用

摘要 传粉媒介生物多样性可能有益于作物授粉。然而，农业生态系统的收益可能取决于环境，并被农艺或其他限制性的果园特定或树木特定的因素所抵消，这些因素模糊了生物多样性-生态系统服务关系。为了测试作物授粉是否受益于传粉者的生物多样性，我们在德国的五个有机和五个综合害虫管理 (IPM) 苹果园中对当地野生蜜蜂群落进行了采样，并通过实验测量了苹果花的授粉成功率，量化为到达植物群的花粉管数量。风格的基础。对过度分散的计数数据使用标准统计建模方法，我们发现野生蜜蜂生物多样性对授粉成功几乎没有影响，无论农场管理如何（有机与 IPM）。然而，有 树木和果园中昆虫授粉和补充花粉的花中的花粉管数量之间存在正相关关系，表明当地树木或果园特定因素的混杂效应限制了授粉成功。使用统计两部分障碍模型，该模型使我们能够将 (i) 授粉概率和 (ii) 授粉数量分开，我们能够证明当地树木/果园因素的集体效应充当主要限制阈值为授粉成功。一旦越过阈值，障碍模型表明，增加野生蜜蜂丰度会提高苹果树的授粉成功率。我们提倡使用统计两部分模型作为一种更有效的方法来确定生物多样性的限制因素和作用，