Steffan Shawn A, Dharampal Prarthana S, Danforth Bryan N, Gaines-Day Hannah R, Takizawa Yuko, Chikaraishi Yoshito
Am Nat. 2019 Sep;194(3):414-421. doi: 10.1086/704281. Epub 2019 Jul 25.
As pollen and nectar foragers, bees have long been considered strictly herbivorous. Their pollen provisions, however, are host to abundant microbial communities, which feed on the pollen before and/or while it is consumed by bee larvae. In the process, microbes convert pollen into a complex of plant and microbial components. Since microbes are analogous to metazoan consumers within trophic hierarchies, the pollen-eating microbes are, functionally, herbivores. When bee larvae consume a microbe-rich pollen complex, they ingest proteins from plant and microbial sources and thus should register as omnivores on the trophic "ladder." We tested this hypothesis by examining the isotopic compositions of amino acids extracted from native bees collected in North America over multiple years. We measured bee trophic position across the six major bee families. Our findings indicate that bee trophic identity was consistently and significantly higher than that of strict herbivores, providing the first evidence that omnivory is ubiquitous among bee fauna. Such omnivory suggests that pollen-borne microbes represent an important protein source for larval bees, which introduces new questions as to the link between floral fungicide residues and bee development.
作为花粉和花蜜采集者，蜜蜂长期以来一直被视为严格的食草动物。然而，它们储存的花粉中存在丰富的微生物群落，这些微生物在蜜蜂幼虫食用花粉之前和/或食用花粉的过程中以花粉为食。在此过程中，微生物将花粉转化为植物和微生物成分的复合物。由于微生物在营养层级中类似于后生动物消费者，从功能上讲，食用花粉的微生物就是食草动物。当蜜蜂幼虫食用富含微生物的花粉复合物时，它们摄取来自植物和微生物来源的蛋白质，因此在营养“阶梯”上应被归类为杂食动物。我们通过检测多年来在北美采集的野生蜜蜂所提取氨基酸的同位素组成来验证这一假设。我们测量了六个主要蜜蜂科的蜜蜂营养级。我们的研究结果表明，蜜蜂的营养特性始终且显著高于严格食草动物，这首次证明了杂食性在蜜蜂群体中普遍存在。这种杂食性表明，花粉携带的微生物是蜜蜂幼虫重要的蛋白质来源，这就引发了关于花卉杀菌剂残留与蜜蜂发育之间联系的新问题。
