Odonates of Coimbatore District , Tamil Nadu , India

Odonates were surveyed in Coimbatore District from September 2012 to January 2016. The survey sites covered three major rivers—the Noyyal, Bhavani and Aliyar. Aquatic habitats such as forest streams, riverine sites, irrigational tanks and paddy fields were surveyed in the study. A total of 70 species of odonates were recorded in the survey, which brings the list of odonates in Coimbatore to 87 species. Eighteen species are first time records to the district. In this paper, we catalogue odonates and their distribution from the present survey and pre-existing records.

n e s v fi s fi t h t p : / / t h r e a t e n e d t a x a .o r g / S u bm fi s s fi o n _ G u fi d e l fi n e s .a s p F o r P o l fi c fi e s a g a fi n s t S c fi e n fi fi c M fi s c o n d u c t v fi s fi t h t p : / / t h r e a t e n e d t a x a .o r g / J o T T _ P o l fi c y _ a g a fi n s t _ S c fi e n fi fi c _M fi s c o n d u c t .a s p F o r r e p r fi n t s c o n t a c t < fi n f o@ t h r e a t e n e d t a x a .o r g >

INTRODUCTION
Freshwater ecosystems the world over are under tremendous anthropogenic pressure and there is an urgent need to assess the quality of these freshwater habitats.In biodiversity hotspots such as Western Ghats, which support numerous endemic taxa, freshwater resources are highly exploited.To assess and characterize freshwater habitats, bioindicators are used.Among the bioindicators of freshwater, odonates are known to be highly sensitive indicators of the habitat concerned (Clarke & Samways 1996;Samways & Steytler 1996;Subramanian 2009).Baseline data on the distribution of odonates provide valuable information on habitat specific species and the status and quality of aquatic systems.
Surrounded by the Western Ghats, Coimbatore exhibits varied landscapes, vegetation and aquatic bodies suitable for a rich diversity of odonates.Odonates in this region were first documented by Fraser (1924Fraser ( , 1931Fraser ( , 1933Fraser ( , 1934Fraser ( , 1936) ) enlisting 48 species and by Ayyar & Ayyar (1933) adding six more species.Twentythree species have been documented from the insect collection of Agricultural College and Research Institute, Coimbatore (Abraham 1959), of which two species were additional records after which, studies in the region (1999 onwards) have recorded: 22 species from the paddy fields of Coimbatore (Gunathilagaraj et al. 1999;Chitra et al. 2002;Arulprakash & Gunathilagaraj 2010b); 23 species from tanks (Arulprakash & Gunathilagaraj 1999;Karthika & Krishnaveni 2014); seven species from Bhavani River (Arulprakash & Gunathilagaraj 2010a) and seven species from other opportunistic observations (Arulprakash & Gunathilagaraj 2010b).These checklists provide an addition of 13 species to the district.
Published catalogues of odonates of Coimbatore cover limited habitats and areas of the district.Given the wide geographical extent of the district and its varied habitats, our aim was to catalogue odonates from various aquatic bodies in Coimbatore, covering forest streams, river, irrigational tanks, ponds and paddy fields.We have consolidated the number of species recorded in our survey and from previous existing literature.The distributions of species from various habitats are also provided.

STUDY AREA
Coimbatore District lies in the western part of Tamil Nadu state (10 0 13'4"-11 0 24'5"N and 76 0 39'25"-77 0 18'26"E).Many parts of the district lie in the leeward side of the Western Ghats (Fig. 1).The district is crisscrossed by the Palghat gap (a 30km-wide gap in the otherwise continuous mountain chain) dividing the hills into northern and southern sections.The northern section comprises the Siruvani-Vellingiri Hills; the Anaikatty Hills and Athikadavu Valley which skirts the lower elevations of the Nilgiris.The former hill range contributes to the Noyyal River basin and the latter two to the Bhavani River.The southern section comprises the high rising Anaimalai Hills from which the Aliyar River originates.In between these two sections of mountains lies the Palghat gap, a 30-km stretch of plain which tapers in gradient towards the west.The Aliyar River drains in the gap and adjoins many other tributaries flowing from the Anaimalais and the northern section of the hills to form the Ponnani River.The forested hilly terrains of Coimbatore District are covered by semi-evergreen, wet dry deciduous forest and in most parts by dry deciduous forest.While the plains of Coimbatore and the Palghat gap are predominantly agricultural landscapes.
The south-west monsoon provides copious rainfall (>800mm) to the higher slope of the northern and southern section of the mountains and the Palghat gap (Arun & Vijayan 2004;Rathod & Aruchamy 2010).The rest of the district receives scanty rainfall from the south-west monsoon and this region is supplemented with 600-800 mm rainfall by the north-east monsoon (Rathod & Aruchamy 2010).Rainfall in the higher reaches contributes to the seasonal river Noyyal and the irrigational tanks in the plains during the south-west monsoon.
Our study cover various aquatic habitats such as forest streams; riverine sites; irrigational tanks and ponds and paddy fields across the Noyyal, Bhavani and Aliyar rivers.

METHODS
Our study was conducted from September 2012 to January 2016 across different aquatic bodies in Coimbatore District (Images 1-10).Adult dragonflies were surveyed between 09:00-16.00hrs by direct search technique (Sutherland 1996).Opportunistic observations have also been included to the current list.The species were photographed using Lumix FZ 200 and identified with the help of standard field guides: Subramanian (2009), Nair (2011) andFraser's Fauna of British India (1933-36).A total of 36 locations were surveyed (Table 1).We seasonally surveyed 24 sites with a frequency of 12 visits.The other sites were visited with a minimum frequency of one to a maximum of four visits.Previous records of odonates from this region are also included in the checklist (Table 2).

RESULTS AND DISCUSSION
We have recorded 70 species of odonates in our study, of which 18 species are first time records to the Coimbatore District making the list with 87 species, belonging to 58 genera and 12 families (Table 2).From the enlisted 87 species, there are 20 endemics (14 species and 6 subspecies level) of which 14 are endemic to the Western Ghats (10 species and 5 sub-species level) (Babu et al. 2013).Of the 70 species from the present survey, we recorded 14 endemics, eight of which are endemic to the Western Ghats.Recorded distribution of odonates shows that the highest number of species was recorded from forest streams (70), followed by river (52), tanks (37) and paddy fields ( 23) respectively (Fig 2).The most speciose family is Libellulidae (39), followed by Coenagrionidae ( 14) and Gomphidae (10) (Table 2).
In the present study, 18 species were recorded for the first time from Coimbatore District; however, most of these species have been recorded from various adjoining regions of Coimbatore-the Nilgiris, the Anaimalai and Palani hills (Fraser 1923(Fraser , 1924(Fraser , 1931,   1933, 1934, 1936;Rao & Lahiri 1972;Verghese et al. 2014;Adarsh et al. 2015).Of the first time records, we were unable to authenticate the record of one species, belonging to the genus Gomphidia, which was sighted twice in the Bhavani river near Mettupalayam.The damselfly, Euphaea dispar, known for its high elevational distribution (900-1,500 m) (Kakkasery 2011) was recorded in the fast flowing cascade in Siruvani forest, Coimbatore (550m).Fraser (1924) attributes the presence of E. dispar at lower elevations due to its competition with E. fraseri, the latter driving the former to higher elevations.In the absence of E. fraseri, the species is known to occur in lower elevations.Indothemis carnatica, a Near Threatened IUCN Red list species (Dow 2009) was recorded in streams and tanks in the Siruvani and Anaikatty forests of Coimbatore.The IUCN cites that this species could be under recorded and   Image 63. Prodasineura verticalis Image 62. Copera vittata its population size uncertain (Dow 2009).
Species like Vestalis apicalis and V. gracilis which are known only from forest and riverine areas in our survey have been observed far inland in the Tamil Nadu Agricultural University Campus (Arulprakash & Gunathilagaraj 2010b); the authors suggest that these stream dependent species spread far inland when aestivating.
Similarly, Trithemis aurora a species predominantly found in streams and rivers are occasionally observed in paddy fields (Arulparakash & Gunathilagaraj 2010b).
Of the 69 species previously recorded from the region, 16 species were not observed during the study period (Fraser 1931(Fraser , 1933(Fraser , 1934(Fraser , 1936;;Ayyar & Ayyar 1933;Gunathilagaraj et al. 1999;Arulprakash & Gunathilagaraj 2010b).Some of the species, which Fraser had observed in the 1930s but were not observed in the present survey include Asiogomphus nilgiricus, Heliogomphus promelus, Megalogomphus superbus, Microgomphus souteri, Macromia cingulata, Macrodiplax cora, Protosticta sanguinostigma, Caconeura t-coerulea (Fraser 1931(Fraser , 1933(Fraser , 1934(Fraser , 1936)).The species Megalogomphus superbus recorded in the Coimbatore forest and Caconeura t-coerulea in the Mettupalayam ghats and Nilgiris remain to be the only record of these species (Fraser 1933).Macrodiplax cora a species recorded mostly in coastal areas and occasionally inland was found nearly in every bush in Coimbatore District by Fraser (1936).However this species was not recorded in over three years of our study.
In the present study, we have attempted to cover a wide range of aquatic habitats in the district.Our survey however, did not cover the Anaimalai hills which lies in the southern part of the district.Though earlier records are available (Fraser 1931), we were not able to demarcate species distribution records between the wide range of the Anaimalai and Mudi Hills, hence they are not presented here.Moreover, the Anaimalai ranges as a whole have a rich odonate entity, which at present requires a rigorous assessment.Similarly, an extensive list of odonates has been recorded from the Kallar and Buraliyar rivers (tributaries of Bhavani, Nilgiri District).Some of the species recorded here include, Idionyx buraliyaarensis, Idionyx nilgiriensis (Fraser, 1926), Euphaea fraseri (Fraser, 1931;Abraham, 1959), Onychogomphus striatus, Hylaeothemis indica (Fraser, 1931).
The Palghat gap in our study area is known to be a geographic barrier for many taxa, in the mountains either side of the gap (Daniels 1992;Robin et al. 2010;Klaus et al. 2014).The same status was established in high altitude odonate assemblage study by Fraser (1923), who indicated that the gap distinctly divides the odonate faunal group into northern and southern groups.Fraser (1931) also reported that the direction of flow of rivers in this region could influence the segregation of odonates into eastern and western groups.Considering this, studies can be intensified in the rivers flowing east and west of Coimbatore District and also in the high altitudes to establish the above observations.The consolidated list of 87 species, indicate the rich odonate diversity in Coimbatore.More species can be expected from this region; given the fact that the region supports varied landscapes and drainages.This region along with core areas of Siruvani hills may hold additional species, which needs to be revisited.Along with the knowledge in the distributional range of species, an understanding of species and their suitable habitats will help in the conservation implication of fresh water sources.
T h e J o u r n a l o f T h r e a t e n e d T a x a fi s d e d fi c a t e d t o b u fi l d fi n g e v fi d e n c e f o r c o n s e r v a fi o n g l o b a l l y b y p u b l fi s h fi n g p e e r -r e v fi ew e d a r fi c l e s o n l fi n e e v e r y m o n t h a t a r e a s o n a b l y r a p fi d r a t e a t www .t h r e a t e n e d t a x a .o r g.A l l a r fi c l e s p u b l fi s h e d fi n J o T T a r e r e g fi s t e r e d u n d e r C r e a fi v e C omm o n s A t r fi b u fi o n 4 .0 I n t e r n a fi o n a l L fi c e n s e u n l e s s o t h e rw fi s e m e n fi o n e d .J o T T a l l ow s u n r e s t r fi c t e d u s e o f a r fi c l e s fi n a n y m e d fi um , r e p r o d u c fi o n , a n d d fi s t r fi b u fi o n b y p r o v fi d fi n g a d e q u a t e c r e d fi t t o t h e a u t h o r s a n d t h e s o u r c e o f p u b l fi c a fi o n .O P E N A C C E S S P a r t n e r www .t h r e a t e n e d t a x a .o r g I S S N 0 9 7 4 -7 9 0 7 ( O n l fi n e ) | I S S N 0 9 7 4 -7 8 9 3 ( P r fi n t ) B u fi l d fi n g e v fi d e n c e f o r c o n s e r v a fi o n g l o b a l l y J o u r n a l o f T h r e a t e n e d T a x a P u b l fi s h e r / H o s t F o r F o c u s , S c o p e , A fim s , P o l fi c fi e s a n d G u fi d e l fi n e s v fi s fi t h t p : / / t h r e a t e n e d t a x a .o r g / A b o u t _ J o T T .a s p F o r A r fi c l e S u bm fi s s fi o n G u fi d e l fi

Figure 1 .
Figure 1.Study locations from the present survey.

Figure 2 .
Figure 2. Odonate species richness in different aquatic habitats of Coimbatore

Odonates of Coimbatore District Muhil & Pramod Table 1. List of locations surveyed in the present study
FS -Forest Streams; R -Rivers; T -Tanks and PondsOdonates