Multi-scale environmental drivers of pollinator community composition, richness, and abundance across multiple taxa

Pollination is a crucial ecosystem service sustaining plant reproduction, biodiversity, and ecosystem functioning. Understanding how pollinator communities respond to environmental factors is therefore essential for supporting pollinator services, particularly in agricultural landscapes. We surveyed three pollinator taxa, wild bees, hoverflies and butterflies, across 26 semi-arid grassland sites in Vojvodina (Serbia) during three seasons in 2022. We assessed how landscape-scale (agricultural, forest, and grassland cover) and local habitat variables (total flower cover and vegetation height) structure species composition, and how these variables, together with short-term weather conditions, influence species richness and abundance. Redundancy analysis (RDA) was used to assess drivers of community composition, while generalized additive models (GAMs) were applied to model richness and abundance patterns. Because observed richness was correlated with total abundance, we additionally conducted sensitivity analyses using Fisher's alpha for wild bees and butterflies and Shannon diversity for hoverflies. Species composition in all three taxa was primarily structured by landscape-scale variables. Wild bee, hoverfly, and butterfly assemblages differed in their responses to landscape gradients, likely reflecting variation in life-history traits, dispersal, and larval ecology. In contrast, richness and abundance reflected additional fine-scale and short-term processes. Observed wild-bee richness was influenced by grassland cover and weather (temperature and wind speed), whereas Fisher's alpha indicated a stronger role of vegetation height. Hoverfly richness was associated with local floral resources and weather, but these relationships were not retained in Shannon diversity models, suggesting that they partly reflected variation in abundance, activity, or detectability. Butterfly richness was associated with cloud cover, a pattern also supported by Fisher's alpha. Weather variables affected observed richness despite surveys being conducted under standardized meteorological thresholds, demonstrating that biologically meaningful variation in pollinator activity and detectability can persist within accepted monitoring protocols. Pollinator responses were taxon-specific and differed between landscape and local environmental drivers, with landscape context shaping community composition and local habitat or weather conditions influencing richness, abundance, and activity-related patterns. Sensitivity analyses highlighted the importance of distinguishing observed richness from abundance-independent diversity, particularly for wild bees and hoverflies. Effective monitoring and conservation strategies should therefore integrate landscape context, local habitat quality, and weather covariates, while interpreting observed richness cautiously when abundance and detectability vary among sites.