Engaging the public to unveil urban biodiversity: a decade of ant monitoring in Italy

Abstract Citizen science (CS) has become an increasingly effective approach in biodiversity research, helping to overcome data gaps that are difficult to address through conventional methods. In entomology, CS initiatives have grown significantly, yet ants (Hymenoptera: Formicidae) remain underrepresented, partly due to challenges in species identification. The Italian “School of Ants” (SoA) project aimed to fill this gap by engaging over 6,000 participants from diverse backgrounds between 2012 and 2023 to monitor urban ant diversity across the country. Participants used a standardised sampling protocol, while expert researchers ensured taxonomic accuracy. Data were collected from 136 municipalities across three-quarters of Italian regions, resulting in the identification of 62 species, both native and non-native. Diversity indices were calculated for each city and analysed along with demographic, geographic, and climatic variables to identify the environmental drivers of urban ant diversity. The results revealed that dominant species diversity was higher in less populated cities with higher edge density and higher green-to-impervious ratios, suggesting that fragmented urban green spaces promote habitat heterogeneity, whereas high human population density negatively affects ant communities. Additionally, hotter cities harbour a taxonomically less diverse ant fauna, suggesting that cities may filter for certain taxonomic groups with higher thermal tolerance. On the other hand, no effects of the considered environmental variables were found on species richness. Spatial trends highlighted a diversity hotspot in north-western Italy, overlapping with major European urban corridors. By combining inclusive recruitment strategies with rigorous scientific validation, SoA demonstrates the potential of CS for large-scale urban biodiversity monitoring and for guiding conservation and sustainable urban planning.