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.

Direct benefits and indirect costs of warm temperatures for high‐elevation populations of a solitary bee

“…However, because O. iridis are typically semivoltine in our study area (i.e., taking 2 yr to complete a Fig. 1c), which oviposits through recently completed nest partitions of several cavitynesting Osmia species (Spear et al 2016). Only the most recently completed nest cell-the one nearest the nest entrance-is vulnerable to this parasite.…”

“…1a). 1c), which oviposits through recently completed nest partitions of several cavitynesting Osmia species (Spear et al 2016). Nests consist of a linear series of brood cells, each provisioned with a mass of pollen and nectar and containing a single egg.…”

Bumble bee parasite prevalence but not genetic diversity impacted by the invasive plantImpatiens glandulifera

“…) but also in some solitary bee species (Spear et al. ). Understanding how plant species affect parasite prevalence is important for the selection of plant species for mitigating strategy (e.g., composition of floral strips to support pollinators and optimize pollinator health) (Vaudo et al.…”

“…In addition, among floral traits, the chemical composition of floral resources and especially secondary compounds has been shown to impact interactions between pollinators and their parasites by reducing parasite transmission (Richardson et al 2015) and parasite load (Manson et al 2010, Spear et al 2016, Giacomini et al 2018, LoCascio et al 2019. Such potential for floral resources to provide natural resistance to pathogens has been partly studied in bumble bees (Manson et al 2010, Giacomini et al 2018, LoCascio et al 2019 and honey bees (Giacomini et al 2018) but also in some solitary bee species (Spear et al 2016). Understanding how plant species affect parasite prevalence is important for the selection of plant species for mitigating strategy (e.g., composition of floral strips to support pollinators and optimize pollinator health) (Vaudo et al 2015).…”

A dual role for farmlands: food security and pollinator conservation

“…Although generalist plant species can provide floral resources for numerous pollinators, these plant species may also play key roles in pathogen transmission. Conversely, some plant species offer nectar or pollen resources that may have 'medicinal' or protective value for some pollinators (Manson, Otterstatter & Thomson 2010;Richardson et al 2015;Spear et al 2016). Understanding the roles of certain flower types in the transmission of pathogens, protection from parasites and selfmedication will help avoid unintended management consequences, limit exposure to pathogens and assist pollinators in fighting pathogen infections.…”