DIVERSITY AND HABITAT PREFERENCE OF ODONATE IN CHAKRASHILA WILDLIFE SANCTUARY, WESTERN ASSAM, INDIA

The study was conducted in Chakrashila Wildlife Sanctuary of western Assam to explore diversity and habitat preference of odonata (both dragonflies and damseldly) from April 2018 to March 2019. During study period we recorded total 57 species of odonate from 39 genera and 8 families out of which, dragonfly (Anisoptera) represented by 37 species and damselfly (Zygoptera) represented by 20 species. Suborder Zygoptera were represented by the families Chlorocyphidae, Coenagrionidae, Platycnemididae, Euphaeidae, Calopterygidae and suborder Anisoptera by the Aeshnidae, Gomphidae and Libellulidae. Libellulidae was the Ictinogomphus intermedia, k-Rhyothemis l- m- Ceriagrion

Odonata are charismatic, culturally important species. They plays important functional roles in ecosystems as both predators and prey and have the potential to provide valuable pest-control services to agricultural systems (Corbet 1999). It constitutes a small, well known order of insects that are widely distributed all over the world (Tillyard 1917). Due to their sensitivity to environmental conditions odonate are considered as excellent biological indicators of environmental conditions (Brown 1991;Clark & Samways 1996;Clausnitzer 2003;Smith et al. 2007;Samways, et al. 2010). This group of insects is also used as an ideal model for the investigation of the impact of environmental warming and climate change due to their tropical evolutionary history and adaptations to temperate climates (Nesemann et al. 2011).

Materials And Methods:-
Chakrashila Wildlife Sanctuary (26°15'-26°26'N, 90°15'-90°20'E; 4,500 ha) is located in the districts of Kokrajhar and Dhubri in Assam ( Figure 1). The sanctuary is the only protected area for the golden langur (Trachypithecus geei) in India. The hilly terrain is covered with dense forest which is mostly semi-evergreen and moist deciduous, with patches of grassland and scattered bushes (scrubland). The forest type falls in the category 3C/C.1.a(ii) following Champion and Seth (1968). It is supported by number of streams named as Mauriagaon, Bhalukjhora, Bakuamari and Jornagra. The southern boundary is connected with the Deeplai Beel.  (Sutherland 1996) in all the habitats. Individual specimens were photographed from various angles and cross-checked with field identification guides Subramanian 2009). Those specimens which were difficult to identify in the field, collected in the paper envelopes and identified in the laboratory with the help of taxonomic keys (Fraser 1933(Fraser , 1934(Fraser , 1936.

Results:-
A total of 57 species belonging to 39 genera and 8 families were recorded from the study area. Suborder Anisoptera (64%) was represented by 3 families, 25 genera and 37 species whereas 5 families, 14 genera and 20 species are represented in the suborder Zygoptera (36%). (Table 1 and Table 2 and Figure 4).
Odonate habitat preference among the five different habitats shows diverse result. Highest number of species were recorded from the wetland (n=35, 63%) that was followed by paddy field (n=29, 52%), degraded forest (n=26, 46%), hill stream (n=25, 44%) and dense forest (n=23, 41%). The study shows that total 20 species were recorded as habitat specialist to different habitats while 7 species were recorded as habitat generalist. Figure 3 represents the ratio between the habitat generalist and habitat specialist species in the study area.   Since odonate are amphibian in nature they require both terrestrial and aquatic environment to complete their life cycle. It is well established that odonata occupies almost all types of habitat for perching, breeding, hunting and dispersing (Corbet 1999;Clausnitzer et al. 2009). But mainly found closely associated with wetlands, because wetlands provide them the breeding ground (Corbet 1999and Sarah et al. 2017). In the study area the water body can be further divided into two types-lentic (wetland) and lotic (hill stream). During survey most of the lentic dwelling species recorded in the lotic habitat. But larval stages of odonate were mainly confined to lentic water-bodies than the lotic water-bodies (Painter 1998;Corbet 1999). The fast-flowing lotic water-bodies tend to dry up during the dry season thus the larval survival following oviposition is relatively lower (Samways 1989;Hofmann and Mason 2005). Since the sanctuary possesses many small man made dam for irrigation purpose, those dams along with other standing water-bodies within the study area may be particularly important for dragonfly conservation. Significantly the hill streams alone possess 10 habitat specialist species while no habitat specialist species were recorded from degraded forest ( Table 2). Trithemis aurora, Bradinopyga geminate, Onycothemis testaceae, Onychargia atrocyana, Aristrocypha fenestrella, Aristrocypha quadrimaculata, Coeliccia marginipes, Neurobasis chinensis and Vestalis gracilis were strictly confined in the perennial hill streams. These species mostly prefers fast-flowing water-bodies probably because they require cool temperature with high humidity. From the conservation point of view these species should always get priority since they are habitat specialist. Loss of perennial hill streams may cause their local extinction or migration to other part.
The habitat has been defined as the collection of resources and conditions required by, and accessible to, individuals of a species at a location (Dennis et al. 2003(Dennis et al. , 2007. Because the habitat is necessarily the location where an organism lives out its life-cycle, a suitable habitat must meet the ecological needs of all life-stages. The terrestrial landscape is probably as important as the aquatic habitat (Corbet 1999), as it provides several conditions and resources that are required by the adult phase. 26 species were recorded in degraded forest while family Aeshnidae were recorded in the dense forested only. Many of the species that were recorded in degraded forest were largebodied, sun-loving, cosmopolitan Anisoptera, including many within the Libellulidae family. It is thought that these would have originally been rare in forested areas, and relied on their long-distance dispersal abilities to travel between the few forest gaps available (Orr 2006). The dense forest dwelling species require forest for hunting, and it is known that many Gomphids and females of other families spend much of their time in the forest canopy. Similar observation was also reported in Bornean tropical rain forests (Orr 2006). signata, g-Ictinogomphus distinctus, h-Burmagomphus sp., i-Trithemis festiva. j-Neurothemis intermedia, k-Rhyothemis plutonia, l-Diplacodes trivialis, m-Vestalis gracilis, n-Ceriagrion coromandelianum, o-Ischnura rufostigma, p-Amphiallagma parvum, q-Landscape of Chakrashila Wildlife Sanctuary and r-Man made dam inside the sanctuary).

Conclusion:-
Since the habitat of the studied area is heterogeneous, species shows the complexity and some species are yet to be identified. Since the study area is facing severe anthropogenic disturbance like illegal tree felling, forest fire, grazing by cattle and collection of fire wood odonate also faces the threats of habitat degradation like other taxa as well. Therefore it is necessary that more emphasis should be given on their conservation problems.