Honeybee visitation to shared flowers increases Vairimorpha ceranae prevalence in bumblebees

Vairimorpha (=Nosema) ceranae is a widespread pollinator parasite that commonly infects honeybees and wild pollinators, including bumblebees. Honeybees are highly competent V. ceranae hosts and previous work in experimental flight cages suggests V. ceranae can be transmitted during visitation to shared flowers. However, the relationship between floral visitation in the natural environment and the prevalence of V. ceranae among multiple bee species has not been explored. Here, we analyzed the number and duration of pollinator visits to particular components of squash flowers—including the petals, stamen, and nectary—at six farms in southeastern Michigan, USA. We also determined the prevalence of V. ceranae in honeybees and bumblebees at each site. Our results showed that more honeybee flower contacts and longer duration of contacts with pollen and nectar was linked with greater V. ceranae prevalence in bumblebees. Honeybee visitation patterns appear to have a disproportionately large imp..., We collected pollinator visitation data from video recordings of a single flower. We visited 6 winter squash farms two times during the flowering period, and video recorded 8 flowers during each site visit for 30 min. We recorded the number and idenitity of species or morphospecies of all pollinator visitors, and the duration of their contact with each part of the inflorescence (petals, stamen, nectar, or both stamen and nectar simultaneously). Using this data, we calculated the number of visits and duration of visits (seconds) for honeybees, bumblebees, squash bees, and all other pollinator species. From the same sites, we collected honeybees and bumblebees and tested a subset of them for presence or absence of Vairimorpha ceranae., , # Honeybee visitation to shared flowers increases Vairimorpha ceranae prevalence in bumblebees.

Submitted to Ecology and Evolution.

Data collected by: Michelle L. Fearon and Maryellen Zbrozek
Code written by: Michelle L. Fearon and Maryellen Zbrozek
Contact: [e-mail]

The R code files that generate the analysis and figures for the manuscript can be used as follows:
**NosemaDataProcessing.R**: Generates the calculations and data files that are used in the analyses of V. ceranae prevalence and analyses of pollinator visitation behaviors based on pollinator group.
**NosemaAnalysis\_Apr.2023.R**: Generates the statistical analyses and figures for V. ceranae prevalence in honeybees and bumblebees based on different visitation metrics.
**VisitationAnalysis\_Apr.2023.R**: Generates the statistical analyses and figures of differences in visitation patterns among honeybees, bumblebees, and other pollinators.

**Definitions**:
Nosema or Nosema ceranae is the previous name for Vairimor...