Semi-natural grasslands under extensive grazing host a high diversity of plants whose diverse flower traits are crucial for insect pollinators, which are facing a worrying decline. We investigated how grazing regimes in dry calcareous grasslands influence the diversity and composition of flower traits important for pollinators. We measured the taxonomic diversity (TD) of the plant community, as well as the functional diversity (FD) and the community-weighted means (CWM) of seven morphological, phenological, and reflectance flower traits for insect-pollinated species across 116 plots in 22 farms and nearby abandoned areas spanning six regions in Italy and Switzerland. We compared managed and abandoned areas to assess differences in FD and CWM, and fitted two piecewise structural equation models to infer direct and indirect effects of grazing regimes on TD, FD and CWM. Extensive grazing did not alter flower traits’ FD compared to abandonment, but favoured flowers’ characteristics beneficial to pollinators, e.g., increased CWMs of flower size, flowering period length, and UV reflectance. Across different grazing regimes, local grazing pressure emerged as a key driver of TD and, in turn, of the FD and CWM of several flower traits. Plant communities with a more even distribution of dominant and rare species were positively associated with the FD of flower symmetry, flowering initiation and UV reflectance, as well as the representation of zygomorphic and non-yellow flowers. Maintaining extensive grazing is essential to preserve flower characteristics that are important for pollinators. Managing grazing intensity patterns at local spatial scales is crucial to increase the diversity of flower traits, which, in turn, may support a broad range of insect pollinators
