Single-visit effectiveness and controlled honey bee visit
experiments
To assess the relative quality of honey bee visits and their direct
contribution to C. quamash pollination, we performed two
field experiments. In 2019, we conducted a controlled multiple-visit
experiment to isolate the direct relationship between increasing honey
bee visits and C. quamash pollination in one of the meadows where
hives were introduced. In 2020, we returned to a different meadow, where
honey bee abundance was more moderate, and assessed the single-visit
pollination effectiveness of honey bees and other insect visitors. In
both years, we bagged a selection of plants to prevent visitation and
conducted observations from 7:00 until 16:00 across several days. For
controlled honey bee visit experiments, we allowed a randomly assigned
number of honey bee visits (between zero and twenty) to freshly opened
flowers and all other visitors were excluded. For single-visit
effectiveness experiments, we allowed a single visit from different
visitors, noting the pollinator identity and aspects of its visit
behavior (described in Table S1). Because we did not want to impact an
insect’s visit by capturing it, our identifications were done in the
field. We grouped visitors into several broad categories: Andrenaspp., Apis mellifera , Bombus spp., Halictus spp.Osmia spp., “Small dark bees”, and Syrphid flies. For both
field experiments, we re-bagged plants to prevent further visitation
after experimental visits had concluded, collected fruits two weeks
later, and counted fertilized ovules.