Disentangling biodiversity and temperature effects on bees and pollination services in mountain agroecosystems

Pollinating insects are declining globally due to habitat loss, agricultural intensification, and climate change. Wild bee loss threatens the delivery of pollination services essential for agriculture and ecosystem stability. Our study examined how multidiversity, reflecting the richness of four functional groups and indirectly indicating land-use intensity, together with temperature as a climatic proxy, shapes wild bee diversity and pollination services in mountainous agroecosystems. We selected 24 farmland sites in South Tyrol (NE Italy) spanning independent gradients of multidiversity and temperature. We used pan traps to quantify wild bee species richness and abundance of wild and managed bees. Additionally, we performed a phytometer experiment using radish and strawberry model plants to assess wild bee visitation and the resulting seed and fruit production. Our results showed that wild bee diversity and visitation rates increased with multidiversity, reflecting the strong influence of land-use intensity. In contrast, temperature had limited direct effect on wild bee diversity, partly because floral resources were not a limiting factor. Visitation rates varied with multidiversity: honeybee visitation rates dominated in low-diversity landscapes, while wild bee visitations peaked in more diversified landscapes. The pollinator exclusion experiment on strawberries revealed that higher temperatures reduced fruit weight more in the absence of insect pollination, suggesting an interaction between climate and pollination provision. Overall, our results findings highlight the complex interplay betweenbiotic and abiotic factors shaping wild bee communities and pollination. They also suggest that preserving biodiversity in agricultural landscapes could help buffer climate change impacts and support more resilient agroecosystems.