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取食的食物看似"低质量"。不良饮食带来的补偿益处，或可使其免受天敌侵扰。多个蜂类支系特化取食菊科（Asteraceae）植物的花粉，而菊科花粉被公认属于低质量食物。本研究针对"菊科花粉特化可使蜂类免受寄生"这一假说开展验证。我们于多年间、多野外位点中，对比了塞蜂属（Sapyga）胡蜂对菊科专食性、野豌豆族（Fabeae）专食性及其他壁蜂属（Osmia）蜂类的子代寄生率，结果发现菊科专食性蜂类的寄生频率显著低于其他类群。随后，我们通过将塞蜂属胡蜂幼虫饲养于三种花粉混合物（菊科花粉混合物、野豌豆族花粉混合物，以及以非菊科花粉为主的泛食性混合物）中，验证了菊科花粉对寄生蜂的作用效果。在菊科花粉饲喂组中，寄生蜂幼虫的存活率显著降低。本研究结果表明，专食低质量花粉的习性之所以能够演化，或正是因为该习性可帮助蜂类抵御天敌。