Organic management, reduced tillage, and increased vegetation cover promote ant abundance and diversity in Mediterranean Vineyards

Background: Vineyards are regarded as one of the most intensively managed crops worldwide. Organic management is increasingly promoted as an ecologically friendly alternative to conventional farming and organic vineyards are expected to promote the abundance and diversity of arthropods and the associated ecosystem services. However, the effects of organic vineyards on arthropods show great variability depending on the local climate, landscape composition, and the considered taxon. Among arthropods, ants are one of the most dominant terrestrial organisms worldwide, with a multifaceted role in agriculture. Ant responses to organic management in vineyards have rarely been studied. Methods: We conducted this study in Italy, across 16 pairs of organic and conventional vineyards belonging to very different ecological and biogeographical settings, from Sicily to the southern Alps. We explored how ant communities were affected by organic management, inter-row vegetation cover, pesticide use, tillage intensity, mean annual temperature, and semi-natural habitats surrounding the vineyard. Moreover, we investigated whether ant communities showed geographic differentiation across Italy. Results: Our results highlight a significant positive effect of organic farming on both ant abundance and species richness. Moreover, ant species richness and abundance increased in vineyards with reduced tillage and a high vegetation cover in the inter-rows. The effects were consistent across different climates and landscapes, despite ant communities being highly different across Italy and showing a strong geographic characterization. Conclusions: Our study supports the positive role of organic agriculture, reduced tillage intensity, and spontaneous vegetation cover in protecting insect biodiversity. Among the diverse species pools that we identified, several species are known to play ecological roles and may provide services and disservices to winegrowers, encouraging further investigation to characterize ant role across different management systems and geographic areas. Implications for insect conservation: Organic farming proved to have a positive role promoting both the species richness and the abundance of ants as compared to conventional management. The preservation of spontaneous vegetation and reduction of tillage were identified as key biodiversity-friendly practices. The ant fauna of vineyards was found to be very different across the geographic gradient that we explored, suggesting that the characteristics of the local fauna should be taken into consideration for management and conservation actions.