Recent studies have indicated that frequent anthropogenic disturbances in tropical developing countries are primary drivers of reduction in community diversity and local extinction of many arthropods, including dragonflies. We assessed the impact of anthropogenic disturbances on odonate assemblages across three different land use types, in a biodiverse nature reserve in Ghana. A total of 37 transects (100 x 10 m) were used to survey odonate species over two seasons and three rivers which pass through agricultural, matured forest and forest margin habitats. A total of 6940 individuals, belonging to 53 species (23 Zygoptera and 30 Anisoptera) in eight families, were recorded. Sapho ciliata (15% relative abundance) was the most abundant zygopteran, whereas Orthetrum julia (4.8% Relative abundance) was the dominant anisopteran. Rarer species like Umma cincta, Chlorocnemis sp. and Elattoneura sp. were represented by < 50 individuals. The effective number of species was affected by the surrounding terrestrial habitat type and this most strongly reflected the difference between agricultural habitats (8.09 ± s.e. 0.41) and matured forests (5.0 ± s.e. 0.24). A canonical correspondence analysis revealed that turbidity, surface water temperature, canopy cover and channel width were the key factors that influenced odonate assemblages. Degraded habitats were dominated by generalist and heliophilic dragonflies, while matured forest habitat included more stenotopic damselflies and dragonflies. These findings improve our understanding of the drivers of odonata distributions and diversity and will help river managers use odonates to monitor riverine health, as part of conservation activities.
Bibliographical noteThe authors are grateful to Worldwide Dragonfly Association (WDA) for providing fund for this study. Special thanks to Tropical Biology Association (www.tropical-biology.org) for their advice and mentoring. My heartfelt appreciation to Viola Clausnitzer and Klaas-Douwe B. Dijkstra for providing us with the identification hand books and for their immense contribution, mentoring, advice and guidance for the species identifications and towards the successful completion of the study. We are greatly indebted to Robb Fitt for his assistance throughout the data analysis
at University of Aberdeen. Finally, to Daniel Acquah-Lamptey, George Ashiagbor, Paul Tehoda, Sulemana Bawa and Emmanuel Amoah, for their role in field data gathering.
- agricultural habitat
- matured forest
- forest margin
- effective number of species
- canonical correspondence analysis
- ecosystem health