Taxon-specific associations of tallgrass prairie flower visitors with site-scale forb communities and landscape composition and configuration

Pollinators are integral to global plant biodiversity and agroecosystems, yet our understanding of the multi-scale drivers of pollinator community structure remains underdeveloped. In this study, we used a dataset comprising almost 7000 highly taxonomically resolved records of tallgrass prairie forbs and flower visiting insects to evaluate potential roles of site-scale forb communities as well as the composition and configuration of the surrounding landscapes, in structuring flower visitor communities. We examined the whole flower visitor community and three focal subgroups-bees (the principal pollinators worldwide), butterflies (often less efficient pollinators, but potentially useful as indicator taxa) and syrphid/bombyliid flies (which, as non-bee taxa, are often overlooked). At the site-scale, the composition of the entire flower visitor community was significantly associated with forb composition, but only bees were significantly, positively associated with forb α-diversity. Bee, butterfly, and fly diversity exhibited taxon-specific relationships with landscape composition and configuration. Butterfly richness was positively correlated with the combined extent of warm-season grasslands and woodlands, whereas bees were associated with the extent of warm-season grasslands, only. Bee and fly diversity was higher in landscapes with greater grassland edge density, indicating that habitat heterogeneity may be beneficial for these taxa. Our work adds to the growing body of research indicating that pollinators' responses to floral resources and land use in highly modified landscapes are often complex, taxon-specific and scale dependent, and our results highlight the importance of distinguishing among different types of natural and semi-natural lands when formulating pollinator conservation and restoration plans.