Spatio-temporal analysis of beetles from the canopy and ground layer in an Italian lowland forest

Canopies of temperate forests are still largely unexplored and the biodiversity they harbor is still poorly known, even for Coleop- tera, the most studied insect group. In a lowland forest in northern Italy, Malaise traps were set in the canopy (n = 7) and ground layer (n = 7) and eleven beetles families (Buprestidae, Eucnemidae, Throscidae, Elateridae, Cantharidae, Dasytidae, Malachiidae, Tenebrionidae, Cerambycidae, Anthribidae, and Scolytidae) were compared for species richness and similarity of assemblages. Additionally it was investigated if species were associated with the forest layers studied and which of the families best qualified as bioindicator taxon. Finally, it was analyzed if similarity between the two layers was affected by season. The beetle assemblages in the two layers were significantly different, but species richness was similar. Eight species were significantly associated with the canopy and 15 species with the ground layer; for 16 of these this association is reported for the first time. Cerambycidae characte- rized the differences between ground and canopy best, as assemblages of this taxon were well separated; and these were signifi- cantly related to the composition of all families considered. Season had a strong influence on the trapping results and the dissimi- larity of beetle assemblages between canopy and ground layer was most pronounced between late May and late July. This study showed that the distribution of beetles in the forest is structured in time and space and that season influences the capacity to dis- tinguish between beetle assemblages sampled in the canopy and at the ground.