Data from: Species richness of wild bees, but not the use of managed honey bees, increases fruit set of a pollinator-dependent crop

1. Native, wild bees are important pollinators for both crop and wild plants. With concerns over the availability and cost of managed honey bees, attention has turned to native, wild bees as crop pollinators. However, the ability of native, wild bees to provide sufficient pollination may depend on their populations at local scales. 2. Therefore, at the farm scale, we examined the pollination contribution of both native, wild bees and managed honey bees to apples, and assessed the relative importance of bee abundance versus species richness. Over three growing seasons, apple fruit set, bee abundance, and bee species richness were measured at orchards in Wisconsin, half of which used managed honey bees, thus allowing us to independently examine the contribution of native, wild bees to fruit set. We additionally conducted observations of honey bees and wild bees foraging on apple blossoms in order to examine functional complementarity. 3. We found that apples are highly dependent on animal pollinators. However, fruit set was not significantly higher at orchards with managed honey bees, nor did it increase with the number of honey bees per orchard. Instead, fruit set significantly increased with the species richness of native, wild bees during bloom. 4. Honey bees and wild bees showed different foraging preferences: honey bees more frequently visited apple flowers on densely blooming trees, while wild bees showed no preference for floral density, thereby evenly visiting trees throughout the orchard. 5. Synthesis and applications. Our results show that native, wild bees play a significant and unique role in apple pollination within our region, and cannot therefore be replaced by managed bees. Moreover, our findings suggest that bee conservation efforts should focus specifically on maintaining or increasing bee species richness in order to improve pollination and crop yields.1. 野生本土蜂（native wild bees）是作物与野生植物的重要传粉者。鉴于人们对商业饲养蜜蜂（managed honey bees）的供应情况与成本的担忧，研究焦点已转向将野生本土蜂用作作物传粉者。不过，野生本土蜂能否提供充足的传粉服务，可能取决于其局域种群规模。 2. 因此，本研究在农田尺度下，探究了野生本土蜂与商业饲养蜜蜂对苹果的传粉贡献，并评估了蜂类多度与物种丰富度的相对重要性。在三个生长季中，我们对威斯康星州各苹果园的苹果坐果率、蜂类多度及蜂类物种丰富度进行了测定，其中半数果园使用了商业饲养蜜蜂，这使得我们可以独立评估野生本土蜂对坐果率的贡献。此外，我们还对在苹果花上觅食的蜜蜂与野生蜂进行了观察，以探究二者的功能互补性。 3. 研究发现，苹果高度依赖动物传粉者。然而，使用商业饲养蜜蜂的果园坐果率并未显著更高，坐果率也未随单果园饲养蜜蜂数量的增加而提升。相反，在开花期，苹果坐果率随野生本土蜂的物种丰富度显著升高。 4. 商业饲养蜜蜂与野生蜂展现出不同的觅食偏好：商业饲养蜜蜂更频繁地访问开花密集的果树上的苹果花，而野生蜂对花的密度并无偏好，因此会均匀地造访果园内的所有果树。 5. 总结与应用：本研究结果表明，在本区域内，野生本土蜂在苹果传粉中发挥着不可替代的独特重要作用，无法被商业饲养蜜蜂所取代。此外，我们的研究结果显示，蜂类保护工作应针对性地聚焦于维持或提升果园内的蜂类物种丰富度，以优化传粉服务并提高作物产量。