Diversity and Pollen Loads
In total 3352 insects were observed; of those 972 were Apis mellifera (29%), 496 were other bees (15%), and 1884 were non-bee flower visitors (56%) (Supplementary Table 1).
In addition, a total of 604 insects were collected and successfully sequenced (GenBank Accessions OQ622469 – OQ623072). 515 of those were non-bee visitors belonging to 4 orders, 29 families, 53 genera, 62 species (Table 2; Supplementary Table 2). Sequence read lengths ranged from 359 to 658 bp, with an average of 644 bp. For pollen load comparison 89 bee specimens were caught and successfully sequenced, 26 were assigned species level identification representing three families containing 13 species (Table 2). For two genera (Nomada andSphecodes ) DNA barcodes did not provide consistent identifications due to a poorly parameterized reference library on BOLD. Consequently, both were excluded from pollen counts.
When considering only the data from collected specimens, the non-bee families which contributed the most pollen (average pollen count x abundance) were flies of the families Syrphidae, Polleniidae and Anthomyiidae (Figure 1a). Overall, the species that carried the most pollen (in the order of 10,000-70,000 pollen grains on average per individual) were Eristalis tenax > Eristalis similis > Halictus confusus >Lasioglossum pectorale > Ceratina mikmaqi > Neocnemodon coxalis > Callirhytis tumifica > Bombus impatiens (Figure 1b; Table 2). Of the non-bee flower visitors, 30 of the 53 genera caught, had pollen loads that were not significantly different in size from the genus of bee (Halictus ) with the highest pollen count (Table 3).Eristalis was the only genus that carried more pollen thanHalictus (Figure 1b; Table 3). Variation in pollen load size was substantial, even within a species group. For example, Eristalis tenax individual loads ranged from 1,617- 316,300 pollen grains (Table 2).