Ground beetles in Mediterranean olive agroecosystems: Their significance and functional role as bioindicators (Coleoptera, Carabidae)

The impact of agricultural practices and soil management on the communities of arthropods living in the agricultural landscape is acknowledged as a critical issue by the literature, and it needs to be better investigated to improve the ecological sustainability of agriculture. In the present study, we aimed to study how soil management affect carabid species distribution in one of the most typical agroecosystem of the Mediterranean region, i.e. the olive grove. In South Italy olive plantations feature different types of soil management, from tillage to half- or full-cover cropping. Species distribution has been examined for a total of 10,189 individuals and 62 species collected from 17 sites. Notably from our analysis we have observed that three factors (climax vegetation, soil features and soil management) explained half of the data variability. The composition of species groupings mirrors both bioclimatic conditions (climax vegetation) and soil features, especially watering, while soil management affects the species distribution, with different intensity from site to site. Eleven species have been recognized as the most abundant in the different facets of the studied olive groves and consequently designated as characteristics of the olive agroecosystem. The species traits of the sampled species have been weighted for a compelling evaluation of the effects of agricultural management on biodiversity, showing uniform traits distribution when coping with the ecological factors that characterize the different plantation facets. We have found that carabid beetles can be used as model organisms for studying the effects of agricultural practices. Our study suggests that the interaction of man-induced trasformation with the natural background of the olive agroecosystem may be difficult to disentangle, so that such complexity must be taken into account when carabid beetles are expected to provide an ecosystem service for good agricultural practices.