A comparison of ground-dwelling insect communities in gaps and closed canopy forest in the elfin forest of Monteverde, Costa Rica

Elizabeth Green

Abstract

This experiment compared communities of ground-dwelling insects in gaps and closed canopy forest in the elfin forest of the Estación Biológica Monteverde in Puntarenas, Costa Rica. Insects were trapped with pitfall traps in six gaps and adjacent forest areas in October and November 2000. Shannon-Weiner Diversity indices, Margalef species richness indices, evenness (H’ /(In S)), mean abundance per site, and Morisita Similarity indices were compared. Diversity differed only for Coleopterans, which were more diverse in gaps (H’ = 1.201) than in forest (H’ = 0.8387; modified t-test t= 1.979, p < 0.001). The Margalef index of species richness did not vary between paired gap and forest sites for total insects captured, but was significantly higher for Coleopterans in the gaps than in the forest (sign test, a level 0.05). Coleopterans also had greater evenness in gaps than in forest (sign test, a level 0.05). Mean abundances in gap (8.04 +/- 7.669 mean number of insects/trap) and forest (5.09 +/- 3.191 insects/trap) sites were not different. The Morisita Similarity index was 0.4846, with 47.05% of ground-dwelling insect morphospecies shared between gaps and closed forest. Perhaps conditions in gaps and closed canopy areas in this forest are sufficiently different to allow specialization by ground-dwelling insects to one or the other habitat type.