Data from: Asteraceae pollen provisions protect Osmia mason bees (Hymenoptera: Megachilidae) from brood parasitism

Many specialist herbivores eat foods that are apparently low quality. The compensatory benefits of a poor diet may include protection from natural enemies. Several bee lineages specialize on pollen of the plant family Asteraceae, which is known to be a poor-quality food. Here we tested the hypothesis that specialization on Asteraceae pollen protects bees from parasitism. We compared rates of brood parasitism by Sapyga wasps on Asteraceae-specialist, Fabeae-specialist, and other species of Osmia bees in the field over several years and sites and found that Asteraceae-specialist species were parasitized significantly less frequently than other species. We then tested the effect of Asteraceae pollen on parasites by raising Sapyga larvae on three pollen mixtures: Asteraceae, Fabeae, and generalist (a mix of primarily non-Asteraceae pollens). Survival of parasite larvae was significantly reduced on Asteraceae provisions. Our results suggest that specialization on low-quality pollen may evolve because it helps protect bees from natural enemies.

诸多专食性植食昆虫的取食对象看似品质低下。劣质饮食所带来的补偿性益处，或可帮助宿主抵御天敌。多个蜜蜂演化支特化取食菊科（Asteraceae）植物的花粉，而菊科花粉素来被视作品质低下的食物。本研究针对“特化取食菊科花粉可保护蜜蜂免受寄生”这一假说展开验证。我们在多年间、多野外站点中，对比了塞氏蜂属寄生蜂（Sapyga wasps）对特化取食菊科花粉、特化取食野豌豆族（Fabeae）花粉以及其他壁蜂属（Osmia）蜂类的巢内寄生率，结果发现特化取食菊科花粉的蜂类，其被寄生频率显著低于其他蜂类。随后，我们通过将塞氏蜂幼虫分别饲养于三种花粉混合饲料——菊科花粉组、野豌豆族花粉组以及广谱混合饲料（主要由非菊科花粉构成）——来探究菊科花粉对寄生蜂的影响。实验结果显示，在菊科花粉饲料组中，寄生蜂幼虫的存活率显著降低。本研究结果表明，特化取食低品质花粉的习性之所以能够演化，或许是因为该习性可帮助蜜蜂抵御天敌。