Diversity and distribution of odonates in Rani Reserve Forest, Assam, India

Odonata are the bioindicators of freshwater ecosystem health and is recognised as an excellent ‘flagship’ group among insects.  Baseline knowledge on the diversity and distribution of odonates over spatiotemporal scale is the key to biodiversity conservation. Rani Reserve Forest of Assam is a mosaic of all the habitat types suitable for odonates.  The present work aims at studying the diversity and distribution of Odonates in Rani Reserve Forest.  The study was carried out from December 2014 to November 2017 by categorising the study area into three major habitat types: 1. lentic system, 2. lotic system and 3. terrestrial woodland.  A total of 67 species belonging to 44 genera, representing 11 families were recorded.  First published records of three species, Onychothemis testacea (Libellulidae), Philoganga montana (Philogangidae) and Indocnemis orang (Platycnemididae) from the state are also provided herewith.  Species richness was the highest in lentic system whereas recorded the lowest in running waters of larger forested streams.  Shannon diversity index also indicated that the lentic system is relatively diverse (2.95) and smaller streams of the lotic system showed the highest species evenness (0.87).  Libellulidae (43%) was found to be the most dominant family belonging to suborder Anisoptera followed by Coenagrionidae (22%) of suborder Zygoptera.  Philogangidae (1%) recorded the lowest number of species.  Taxonomically related species showed distinct ecological segregation within these different habitat types occupying different microhabitats therein.