Trophic Level Effects on Species Diversity in Arthropod Communities of Forest Canopies 1

Species diversity for arthropod communities inhabiting white pine and coppice canopies was measured using the Shannon Wiener information theory index, H(s), the Margalef index, D, and the Pielou evenness index, J'. The 2 insect orders Coleoptera and Hymenoptera were investigated. The general index H(s) was significantly higher for the more diverse coppice stand than for the white pine monoculture, and was significantly higher for Hymenoptera than for Coleoptera. The other 2 indices demonstrated that differences in diversity between watersheds were due to greater species richness in the coppice, while differences between insect orders were due to greater evenness of individuals in the Hymenoptera. Since the Coleoptera were principally herbivores and the Hymenoptera predator-parasites, results can be interpreted in a trophic level context. It is suggested that, in a plant monoculture, low diversity is not propagated along food chains but rather is recovered at higher trophic levels.