Ground-Dwelling Ant Diversity in Olive Orchards Under Conventional and Green-Infrastructure-Enhanced Organic Management

Ant diversity and community structure in Greek olive orchards are under-researched, with only one study conducted to date, despite the extensive area occupied by olive orchards and their agronomic, ecological, and socioeconomic importance. In this study, we provide the first data on both ant assemblages and functional groups in Greek olive orchards. The study was designed to capture variation in ant diversity associated with management systems (MS) and agroecological zones (AZ). Ants were collected monthly for two consecutive years, using pitfall traps from 16 olive orchards, eight of which implemented Green Infrastructure (GI). A total of 32 ant species belonging to 12 genera and seven functional groups were recorded. Opportunists (OPP) and Generalised Myrmicinae (GM) were the dominant functional groups. Organic green-infrastructure-enhanced orchards had statistically significantly higher exponential Shannon diversity than conventional orchards, whereas ant worker captures, species richness, sample-based γ-diversity, species composition, and the proportions of major functional groups did not differ between management systems. Agroecological zone significantly affected ant worker captures and species composition, with higher captures recorded in hilly than in plain olive orchards. In contrast, sample-based γ-diversity, species richness and effective Shannon diversity did not differ between zones. Strong interannual variation was observed, with both ant worker captures and species richness being significantly higher in the second sampling year, while effective Shannon diversity remained stable between years. Overall, olive orchards support diverse and functionally complex ant communities, including both widespread and endemic species. These findings highlight the dual role of olive orchards as productive agricultural systems and reservoirs of biodiversity. The adoption of Green Infrastructure, together with low-intensity management and the maintenance of habitat heterogeneity, could further enhance the role of olive orchards in supporting biodiversity and ecological processes across the landscape.