Dragonflies (Odonata) in the Bornean rain forest as indicators of changes in biodiversity resulting from forest modification and destruction

Dragonfly assemblages represent sensitive indicators of environmental conditions including the water environment and forest structure. However, an understanding the ecology of tropical forest odonates remains one of the most significant gaps in our knowledge of the order. We sampled odonates at Sungai Wain Protection Forest, East Kalimantan, Indonesia. Relatively high dragonfly species richness (88 species) was found during 35 survey days divided between two seasons. Seasonal differences in the species diversity were fairly small, in accordance with the fact that the climate in Kalimantan is generally stable. The highest species diversity was observed in intact primary forest: 60% of all recorded species were found there and 32% of all species were exclusive to this habitat. The proportion of biotope specialists decreased along the gradient - intact primary forest, slightly degraded primary forest, secondary forest, heavily degraded forest and non-forest. The ordination obtained from detrended correspondence analysis showed, along the main axis, a gradient in community similarity corresponding to the degree of forest degradation. The evidence indicates that, within the applied spatial scale, any forest degradation results in fewer species, with a pronounced change in the species composition, and an overall reduction in taxonomic diversity.