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.