title: Asteraceae Pollen Provisions Protect Osmia Mason Bees (Hymenoptera: Megachilidae) from Brood Parasitism.
abstract: 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.
authors.forename: Dakota M
authors.initials: DM
authors.lastname: Spear
authors.forename: Sarah
authors.initials: S
authors.lastname: Silverman
authors.forename: Jessica R K
authors.initials: JR
authors.lastname: Forrest
mesh_terms: D000818:Animals; D019659:Asteraceae; D001516:Bees / Q000469:parasitology*; D004032:Diet; D007887:Fabaceae; D007814:Larva / Q000254:growth & development; D011058:Pollen; D014863:Wasps / Q000254:growth & development*
keywords: Sapygidae; cleptoparasites; oligolecty; specialization; tritrophic interactions