Variability of beetle assemblages in Mediterranean cork oak woodlands: does the higher taxa approach reliably characterize a specific response to grazing?

Studying macroarthropod community responses to different land uses is particularly interesting in agroforestry for the conservation of Mediterranean landscapes, which need to be managed in terms of ecological and functional sustainability. Because of the sensitivity of many taxa to human impacts, we assessed the response of beetle assemblages at low taxonomic resolution (i.e. family level) to grazing in Mediterranean cork oak woodlands in northern Sardinia (Italy). Scarab assemblages were also analysed at the species level because of their ecological role in grazed areas. Cork oak woodland descriptors were also recorded in order to relate beetle assemblages to the forest structure. Over the entire sampling period, 4550 beetles belonging to 47 families were captured using pitfall traps. Multivariate analyses performed on ground-dwelling beetle data showed a distinct separation in terms of assemblages between grazed and ungrazed sites. The average diameter of cork oak trees and the degree of shrub cover were significantly linked to the beetle family assemblages. Constrained multivariate analyses indicated the significance of grazing, by both large and small domestic herbivores, and altitude, as variables determining the pattern of scarab beetle assemblages. Mantel test showed a significant correlation between the beetle and scarab dissimilarity matrices indicating a similar pattern for the two levels of identification. Our results show the predictive power of beetles at the family taxonomic level, as well as scarab beetles at the species level. These turned out to be valuable indicators in biomonitoring programmes in Mediterranean cork oak woodlands in order to increase the resilience of cork oak agroforestry systems under future global change scenarios.