Monitoring of environmental disturbance using abundance and distribution of red-vein and dark-vein species of genus Trithemis (Odonata: Libellulidae)

Abstract

Environmental changes as a result of human disturbance in Akure Forest Reserve were investigated for a period of twelve months using abundance and diversity of Red-vein and Dark-vein Trithemis species as an assessment tool. Four study sites (AGO, ALA, APO, and ROD), based on type of water bodies and landscapes, were identified and selected for this study. Diversity indices and Dragonfly Biotic Index (DBI) were used to compare the assemblages of the odonate species in the study-sites. A total of 199 specimens were collected out of which 121and 78 were Red-vein and Dark-vein species respectively. Members of this genus differ in their dispersal capacities and coloration. Based on Dragonfly Biotic Index (DBI) used and the pattern of distribution of Trithemis (Red-vein and Dark-vein species), in the forest ROD and APO were the least disturbed site with the highest DBI value of 9. AGO with DBI value of 2 was the most disturbed site. The pattern of distribution of this species revealed that Akure Forest Reserve is degenerating, a situation that could lead to loss of biodiversity if urgent conservative measures were not put in place.

Keywords: Odonata; Trithemis spp; Akure Forest Reserve; diversity indices; Dragonfly; Biotic Index (DBD)