Field sampling & floral community characterization
From May to August 2019 we characterized interactions between insect pollinators and plants at six natural and six urban sites in the Bay Area of California, USA (Figure S1). Urban sites were sites embedded within city limits, and contained either remnant or restored natural habitat (Table 1). Sites were designated as urban or natural using data available at https://www.bayarealands.org/maps-data along with imagery from Google Earth. Between the two points furthest from one another along the perimeter, urban sites spanned less than 4 km, and natural areas spanned at least 60 km (see Figure S1). Between 10 am and 4 pm we used areal netting to haphazardly catch an average of 41.1 foraging insects per site (range 15-49). We targeted non-Lepidopteran insects, and obtained 493 insects on 47 plant species in total. For each plant on which a pollinator was caught, we recorded the species and sampled three anthers from one flower. At each site we also counted and recorded the species of all flowers within 15 cm of a 90 m transect, and we sampled anthers from the other flowering plants.