Checklist and trait dataset of ground-dwelling arthropods across urban habitats in four major Italian cities.

Urbanization is one of the most extensive forms of land-use change globally and a major driver of biodiversity loss. Ground-dwelling arthropods are sensitive indicators of environmental change and play crucial roles in ecosystem functioning, yet trait-based data on urban arthropods remain limited. We present here an expert-curated checklist and dataset of ground-dwelling arthropods sampled across four major Italian cities-Turin, Milan, Florence and Rome-following a standardized sampling protocol. The dataset includes 297 species from six major taxonomic groups (Coleoptera Carabidae, Coleoptera Tenebrionidae, Isopoda Oniscidea, Chilopoda, Araneae, and Pseudoscorpiones), for which we report presence and activity density across cities and provide taxonomic, biogeographical, ecological, functional, morphological and genetic information. Ecological and functional traits datasets were compiled from literature, expert knowledge, and direct measurements, covering feeding habits, autoecology, habitat preference, dispersal ability, circadian activity, and body size. To our knowledge, this is the first multi-taxon, trait-based dataset of urban ground-dwelling arthropods for the Italian peninsula, providing a valuable baseline for exploring taxonomic and functional diversity across urban environments and for advancing research on how urbanization shapes ecological and evolutionary processes in ground-dwelling arthropod communities.