Ground-dwelling arthropods as biodiversity indicators in maize agroecosystems of Northern Italy

Reliable monitoring of arthropod diversity in a given agroecosystem is essential for the conservation of the related ecosystem services, such as biological control. The often daunting complexity of arthropod collection and identification, however, highlights the need for surrogate taxa that can be easily sampled and be representative of a number of other taxa in term of diversity, general community features and specific composition. In this study, we used pitfall traps to sample three ground-dwelling arthropod taxa important as biocontrol agents (ground beetles, rove beetles and spiders) in 9 conventionally managed maize agroecosystems of Northern Italy over the course of two years, with the goal of characterizing their assemblages and evaluating their reciprocal potential as indicators of activity density, species richness, community turnover and species co-occurrence. Although dominated by few generalist species, sampled arthropod communities were relatively species-rich, and included the first Italian record of the spider Zelotes metellus (Roewer) (Araneae: Gnaphosidae). Ground beetles as a group were confirmed as promising indicators for the species richness and community composition turnover of rove beetles and spiders. Additionally, several abundant arthropod species acted as indicators of the species richness of their respective groups, and the ground beetle Pterostichus macer (Marsham) also worked as an indicator of overall rove beetle activity density. While the co-occurrence of individual arthropod species was limited for the studied taxa, a few species such as the ground beetle Parophonus maculicornis (Duftschmid) did show promise as species-specific bioindicators. Our results could be useful in improving the monitoring and management of these important natural enemies in maize-growing regions.