Comparison of two Odonata communities from a natural and a modified rainforest in Papua New Guinea

Abstract

The Odonata fauna of Papua New Guinea is species-rich, but human population growth and resulting modification of primary rainforests may lead to a loss of valuable habitat and species diversity. In this study, I compared the odonate assemblages of a natural tropical rainforest and a modified forest in order to assess the loss that could result from human forest alteration. I collected odonates and recorded habitat use at both study sites for several weeks. The assemblages were compared with similarity indices, and total species richness was estimated using a jackknife procedure. The natural forest community, with 61 species, had both a higher diversity and evenness than the village community, with 38 species. Altogether I found 78 species of 13 families, of which 21 were shared between the two areas. Among the families with more than one species, Megapodagrionidae and Libellulidae had the highest similarity between the two sites, whereas Coenagrionidae and Platycnemididae had fairly dissimilar community composition. Three families occurred only in the natural forest. The most important habitats in the village were open sunny areas, artificial ditches, and small permanent creeks, compared to most running waters and the forest interior in the natural forest. Based on habitat preferences in the natural forest, species inhabiting temporary water sources under closed canopy rainforests are most vulnerable to forest modification. They comprised a third of the forest community, and I estimate that approximately 25% of natural rainforest species will disappear following human-induced forest alteration.

Keywords: Odonata, dragonfly, species assemblage, forest modification, tropical rainforest, species richness, conservation, Rapua New Guinea

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