Diversity of Dragonflies (Insecta: Odonata) in a Deciduous Forest of Thoothukudi District, Tamil Nadu, South India

Abstract

The study of Odonata communities along deciduous forest requires the basic understanding of the abundance, distribution and number of species present. As habitat conditions change, they also exhibit changes in their diversity and distribution. The present study was carried out in Kuthiraimozhi theri deciduous forest located in Thoothukudi District, Tamil Nadu, South India during July 2009 to June 2010 to assess the diversity of odonates. The forest is open, sandy, low tree lands with predominance of thorny, usually hard wood species. Observations were carried out twice in a month during morning, and evening times. A total of 958 dragonflies belonging to 20 species (2 species unidentified) belonging to 16 genera and 4 families were recorded. The family Libellulidae (15 species) was found to be dominant in the study region, followed by families Aeshnidae, Chlorogomphidae and Gomphidae, which were represented by a single species. The data was analyzed for Species richness, Shannon's diversity index and Simpson's index. Maximum number (237) of dragonflies was collected during December 2009 and the highest Species richness (2.35) and Shannon's diversity index (2.08) was recorded during June 2010. This study has shown that, Odonata diversities along the Kuthiraimozhi theri deciduous forest vary hence these populations can be monitored, related and used as indicators of the physical structure of the deciduous forest and its surrounding ecotones. This inventory has served as the baseline for Odonata communities in the deciduous forest hence can be a measure of monitoring in the near future. Finally, there must be an increase in education on the importance of using local insect species as first level indicators of environmental health which when improved upon can save the nation a lot of money otherwise used in the chemical evaluation and monitoring of environment.