A preliminary study of biodiversity and biomonitoring potential of Odonates of Benin-Owena River Basin catchment, Igbara-Oke, Ondo State, Nigeria

Ecologically, dragonflies and damselflies (Odonata) are good indicators of aquatic and terrestrial ecosystem. They are abundant and important members of the vicinity of inland waters. This study was carried out at Benin – Owena Basin catchment, Igbara-Oke, Nigeria. Sampling was carried out at three water bodies within the catchment of Rivers Aro, Elemo and Owena Dam. The water bodies were selected based on types of water body and prevailing anthropogenic activities around their vicinity. Sampling of specimens was randomly carried out once a month from 9am-2 pm between June, 2017 and July, 2018. Odonata naiads were collected using Kick net. Species composition, distribution and richness of the study sites were calculated using diversity indices (Shannon–wiener, Simpson, Margalef, Evenness and Equitability). Monthly collections of odonates revealed that January 2018 had the highest number of species while the least was in April 2018. Two anisopterans, Neodythemis klingi and Orthetrum julia both with 30 individuals, were the dominant odonate species. Pseudagrion kersteni (19 individuals) was the dominant zygopteran while Africallagma subtle (2 individuals) was the least represented odonate in this study. From the diversity indices analyses, Owena Dam was the richest (Shannon (H`) = 3.12, Simpson = 0.9521, Margalef = 4.42). The site was also the best in terms of distribution and spread of odonate species (Equitability = 0.9693). Similarity in odonate community structure among the 3 study sites was determined using Jaccard Coefficient (Coefficient of Community: CC), The CC analysis showed Elemo Stream and Owena Dam as the sites with similar community structure; and the diversity indices revealed Owena Dam as the richest site with the best species distribution.