(iv) Comparative single-visit effectiveness of
honey bees and native bees
During single-visit effectiveness trials, we observed 96 visits from 5
different pollinator taxa to previously unvisited flowers (Table S5).
Taxa differed in their single-visit effectiveness as pollinators and
honey bees were among the least effective (Fig. 2). Specifically,Bombus spp. and Osmia spp. were both significantly more
effective than honey bees and unvisited controls (Table S5). “Small
dark bees”, which mostly comprised Lasioglossum andAndrena, were marginally more effective than honey bees, but were
as effective as controls and when compared to other pollinator groups.
Pollinators also varied in how often they contacted stigmas and other
aspects of visit behavior (Table S1). 76.7% of native bees contacted
stigmas during single-visit trials compared to only 14.6% of honey
bees. Honey bees almost exclusively collected nectar, sometimes
“robbing” plants by visiting from behind petals (Fig. S4), whereas
native bees did not rob nectar and often collected pollen.