Flowering Solidago canadensis restructures pollinator patch use and assemblage composition at an intermediate stage of invasion in urbanizing landscapes

Mass-flowering invasive plants can generate strong floral resource pulses, but their effects on pollinator communities are unlikely to be uniform across taxa. We investigated how flowering stands of invasive Canadian goldenrod ( Solidago canadensis ) shape pollinator assemblages at an intermediate stage of invasion in a Central European suburban landscape, by comparing paired goldenrod-dominated and non- Solidago plots with diverse co-flowering vegetation located within the same suburban landscapes where S. canadensis was already present. During two flowering seasons, we sampled wild bees, butterflies, hoverflies, and honey bees, and tested how plot type, urbanization intensity (impervious surface area, ISA), and site-level goldenrod cover were associated with pollinator abundance, richness, diversity, and community composition. Pollinator community composition differed significantly between goldenrod-dominated and control plots. Goldenrod-dominated plots supported higher honey bee and hoverfly abundance, but lower wild bee abundance and lower butterfly abundance and species richness. By contrast, wild bee richness and alpha diversity, as well as hoverfly richness, did not differ significantly between plot types, indicating assemblage reorganization rather than consistent taxon loss. Associations between honey bee abundance and wild bee metrics also reversed between plot types, suggesting that flowering S. canadensis can alter local patterns of pollinator co-occurrence around concentrated floral resources. Overall, our results show that, during the flowering peak, a mass-flowering invader can restructure pollinator use of floral patches by disproportionately attracting managed and generalist visitors, while other guilds are less strongly represented in goldenrod-dominated vegetation. These findings indicate that, at an intermediate stage of invasion, the ecological effects of mass-flowering invasive plants may involve taxon-specific redistribution of pollinator activity among floral patches rather than uniform changes in pollinator diversity.