Species diversity of Odonata in Bega watershed, Agusan del Sur, Philippines

Odonata is dependent upon habitats with standing or flowing water. Its sensitivity to changes in water ecosystems makes it a good biological indicator. This study aimed to determine the species richness of Odonata in Bega Watershed, Prosperidad, Agusan del Sur, Philippines. A survey was conducted in 12 sites on May 8-14, 2014 using sweep netting and hand catching methods. Twenty-seven species consisting of 11 species of dragonflies and 16 species of damselflies under 10 families and 20 genera were recorded. Of the 27 species, 17 are endemic with 62.96% endemism. Bega Watershed had high species diversity with an uneven distribution of species. Among the sampled sites, sites 2 and 4 had the highest species richness (S=14) while highest species diversity (H’=2.47) was recorded in site 4 which is a relatively undisturbed and intact ecosystem. Highest abundance of Odonata was recorded in Site 1, the first level of Bega falls. Rhinocypha colorata, an endemic species, was found to be the most abundant and widespread, being found in seven out of 12 sites. Detrended correspondence analysis showed that Odonata prefers semi-forested riparian areas while Bray-Curtis cluster analysis showed that sites 2 and 4 are the most similar sites. The high level of endemism and moderate to high diversity in most of the sites indicate that Bega watershed is a relatively healthy ecosystem and is of high conservation importance