Odonata (Insecta) diversity of Salim Ali Bird Sanctuary and its adjacent areas in Thattekkad, Kerala, India
Aby P. Varghese 1, P.R. Nikesh 2 & Jijo Mathew 3
1 Assistant Professor in Zoology, Mar Athanasius College, Kothamangalam College P.O., Ernakulam, Kerala, 686666, India
2 Padinjattikkudiyil, Chembankuzhy, Neriamangalam P.O., Kerala 686693, India
3 Pappalil House, Malippara P.O., Kothamangalam, Ernakulam, Kerala 686691, India
1 firstname.lastname@example.org (corresponding author), 2 email@example.com, 3 firstname.lastname@example.org
Odonata are valuable indicators of aquatic and terrestrial ecosystems. Out of 5952 species recorded globally, India possesses 474 species and subspecies of Odonata which belong to 142 genera and 18 families (Subramanian 2014). The Western Ghats, one of the hotspots of biodiversity in India, possesses 53 genera and 107 species of Anisoptera (dragonflies) and 29 genera and 67 species of Zygoptera (damselflies) (Subramanian et al. 2011). Out of the 174 odonata identified in Western Ghats, 31 Dragonflies and 25 Damselflies are endemic (Subramanian et al. 2011). Of this, 139 species belonging to 81 genera and 12 families are recorded from Kerala (Emiliyamma et al. 2012).
There are several studies which document the Odonata of Kerala (Fraser 1933–34; Rao & Lahiri 1982; Emiliyamma & Radhakrishnan 2000, 2002; Prasad & Kulkarni 2001; Radhakrishnan & Emiliyamma 2003; Palot & Sonia 2004; Palot et al. 2005; Emiliyamma et al. 2005, 2007, 2012; Emiliyamma 2005, 2008). However, a certain lacuna in the occurrence of the Odonata fauna of Kerala still exists.
The Salim Ali Bird Sanctuary and its adjacent areas in Thattekkad, Kerala, India is well known for its low land forests and avifaunal diversity. It is part of a large contiguous forest belt south of the Palakkad gap on the western slope of the Western Ghats, falling within the latitude 100N and longitude 76–77 0E. The elevation of the area ranges from about 30–523 m. The area is hot and humid being on the western slope of the Western Ghats. Rainfall is received during the southwest and northeast monsoon seasons. The average rainfall recorded is 4000mm. The temperature ranges from 16.1–37 0C. The major forest types occurring in the sanctuary are: tropical evergreen forest (10% of the total area), tropical semi-evergreen forest (10%), tropical moist deciduous forest (60%) and teak, rose wood and mahogany plantations (around 10%). There are patches of grasslands as well as stretches of riparian vegetation (10%) inside the sanctuary.
The sanctuary is bordered by river Periyar on the southwestern side and its tributary Pooyamkutty river on the northern side. A dam was constructed at Bhoothathankettu, 1.5km downstream of Thattekkad, in the Periyar river in 1964. It caused the submergence of all low lying forest and paddy fields. The resultant water bodies have a depth ranging from 5 to 50 feet beyond the river. These water bodies along with the streams and rivers adjacent to the sanctuary were also selected for the study.
Materials and Methods: Studies on odonate diversity were made by visiting various localities in the study area at weekly intervals from 2010 to 2012. Ovumkal and Urulanthanny forest streams and water bodies such as, Koottikkal, Marottichal, Ovumkal and Kolambay were the localities selected inside the protected area (10007Õ48.5ÓN & 76041Õ16.2ÓE). In addition, forest streams and rivers in neighbouring areas such as Pooyamkutty (10009Õ47.1ÓN & 76047Õ09.0ÓE), Pinavurkudy (10006Õ24.4ÓN &76047Õ15.8ÓE), Neriamangalam (10006Õ21.1ÓN & 76047Õ11.1ÓE) and Karimanal (10000Õ59.7ÓN & 76051Õ15.1ÓE) and adjacent water bodies of the Bhoothathankettu reservoir were also selected (Fig. 1). Opportunistic observations were made for documenting the adults of Odonata. Species were photographed in the field. In certain cases, adults were collected and after recording morphological details, measurements and photographs, the individuals were freed. The specimens were identified by following Fraser (1933, 1934, 1936), Subramanian (2008, 2014) and Emiliyamma et al. (2005, 2007).
Results and Discussion: A total of 82 species belonging to 55 genera and 13 families were recorded during the entire study (Table 1). Out of this, 51 species belong to (39 genera and 4 families) Anisoptera, and 31 species belong to (19 genera and 7 families) Zygoptera. Libullilidae family is represented by 28 genera and 38 species. Gomphidae (9 genera) and Coenagrionidae (5 genera) are represented by nine and 12 species, respectively. Platycnemididae (4 genera) family is represented by seven species. Aeshnidae (2 genera), Platystictidae (2 genera) Calopterygidae (2 genera) and Chlorocyphidae (2 genera) families are represented by three species each. Euphaeidae (2 genera) family is represented by two species. Macromiidae (1 genus) and Lestidae (1 genus) families are represented by a single species each.
Of the total Odonata, 21 species are endemic to the Western Ghats (Table 1). Burmagomphus laidlawi Fraser, 1924, Davidioides martini Fraser, 1924, Gomphidia kodaguensis Fraser, 1923, Megalogomphus hannyngtoni (Fraser, 1923), Merogomphus longistigma (Fraser, 1922), Microgomphus souteri Fraser, 1924, Onychogomphus striatus Fraser, 1924, Idionyx saffronata Fraser, 1924, Macromedia donaldi (Fraser, 1924), Macromia annaimalaiensis Fraser, 1931 and Epithemis mariae (Laidlaw, 1915) were the endemic dragonflies recorded from the area. Agriocnemis keralaensis Peters, 1981, Pseudagrion indicum Fraser,1924, Caconeura risi (Fraser,1931), Esme longistyla Fraser,1931, Esme mudiensis Fraser,1922, Protosticta gravely Laidlaw, 1915, Protosticta sanguinostigma Fraser,1922, Platysticta deccanensis Laidlaw, 1915, Calocypha laidlawi (Fraser, 1924) and Euphaea fraseri (Laidlaw, 1920) are the endemic damselflies identified during the study.
Gomphidae had the most endemic species of all the families. Out of the nine species recorded, seven species are endemic. O. striatus Fraser, 1924 and B. laidlawi Fraser, 1924 were recorded for the first time from the state of Kerala. Several individuals of B. laidlawi Fraser, 1924 were observed along the forest streams of Neriamangalam. One male individual of O. striatus Fraser, 1924 was recorded from the Periyar river in Karimanal. M. souteri Fraser, 1924 had been reported for the first time from Kerala by Emiliyamma et al. (2012) from Aralam Wildlife Sanctuary, but this species was recorded from Neriamangalam during the study. M. hannyngtoni (Fraser, 1923) was included in the nearly threatened (Subramanian et al. 2011). M. longistigma (Fraser, 1922) was found to be a common species along the forest streams. Rare species such as D. martini Fraser, 1924, and G. kodaguensis Fraser, 1923 were also seen along the forest streams of Pooyamkutty and Neriamangalam.
Endemic species such as M. donaldi (Fraser, 1924) and M. annaimalaiensis Fraser, 1931 were recorded only once in Neriamangalam. I. saffronata Fraser, 1924 was recorded from two localities. E. mariae (Laidlaw, 1915) was restricted to a forest swamp near Urulanthanny.
Species such as C. risi (Fraser, 1931), E. longistyla Fraser, 1931, E. mudiensis Fraser, 1931 were the endemic Platycnemididae damselflies recorded. C. risi (Fraser, 1931) was reported previously from Thamaracherry, Calicut district and Kottayam District alone (Emiliyamma 2005). The study recorded this species from three localities such as Pooyamkutty, Urulanthanny and Karimanal. E. longistyla Fraser, 1931 was previously reported from the north of the Palakkad Gap to Dakshina Kannada. But this species was also identified from Pooyamkutty and Neriamangalam. E. mudiensis Fraser, 1931 was recorded from the hill streams of Urulanthanny and Neriamangalam.
All the three species identified from the family Platystictidae are endemic. Vulnerable species such as P. deccanensis Laidlaw, 1915 and P. sanguinostigma Fraser, 1922 (Subramanian et al. 2011) were found to be locality specific. Of these, P. deccanensis Laidlaw, 1915 had been previously reported from a few locations in Kodagu, Thrissur, Ernakulam and Thiruvananthapuram districts only (Subramanian et al. 2011). But this species was sighted in a hill stream in Pinavurkudy. P. sanguinostigma Fraser, 1922 has been reported from a few localities in southern Western Ghats (Subramanian et al. 2011) but a good number of individuals of this species were located in the Neriamangalam stream. P. gravelyi Laidlaw, 1915 another endemic species of the family was identified from six localities in the study area along the forest streams.
C. laidlawi (Fraser, 1924) had been previously reported from Myristica swamps of Nilgiri-Wyanad-Kodagu region, north of the Palakkad Gap, and Kollam District only (Subramanian et al. 2011). This species was sighted at Mlavana in the Pooyamkutty River. A. keralaensis Peters, 1981 had been reported so far from Thiruvananthapuram, Kottayam and Kuttanad (Emiliyamma 2005, Raju 2007) but this was identified as a common species along the marshy areas. P. indicum Fraser, 1924 was a common species across the water bodies of Thattekkad. E. fraseri (Laidlaw, 1920) was recorded from the forest streams of Urulanthanny, Pooyamkutty and Neriamangalam.
The family Libullilidae is the most species-rich and widely distributed family. Out of the 38 species, 30 species were found across the water bodies selected for the study. However, families like Gomphidae, and Macromiidae were confined to the forest streams and rivers. Dragonflies such as Neurothemis tullia (Drury, 1773), Orthetrum sabina (Drury, 1770), Pantala flavescens (Fabricius, 1798), Trithemis aurora (Burmeister, 1839) and Diplacodes trivialis (Rambur, 1842) were the wide spread and common species. Tetrathemis platyptera Selys, 1878 and Hylaeothemis indica Fraser, 1946 were restricted to one or two habitats inside the forest. Ictinogomphus rapax (Rambur, 1842) was the commonest Gomphid species found across forest streams and water bodies.
Damselflies of the family Coenagrionidae were widely distributed in all the localities selected. The Platystictidae family was found only in streams running through the forest. Calopterygidae, Euphaeidae and Chlorocyphidae families were recorded from the rivers. Pseudagrion microcephalum (Rambur, 1842), P. indicum Fraser, 1924 and Copera vittata Selys, 1863 were recorded as the abundant species across the localities selected.
Species diversity varied across the localities selected for the study. High species diversity was observed in the water bodies of the Bhoothathankettu dam. But most of the endemic species observed were found only in streams and rivers running through the forests. The streams and rivers outside the forest area had low species diversity and endemism.
It was observed that the water bodies were drained out during June to November which created a number of problems for the aquatic habitat of the area. The study clearly indicated that the water bodies support the aquatic flora and fauna only for a period of six months from December to May. An abundance of Odonata were also observed during these months in the water bodies. More studies and management efforts are required to maintain a stable population of Odonata in Salim Ali Bird Sanctuary, Thattekkad, Kerala.
Conclusion: The study results in the identification of 82 species of Odonata out of which 51 species belong to dragonflies and 31 belong to damselflies. Twenty-one species are endemic to the Western Ghats (Images 1–21). The occurrence of IUCN categorized near threatened species like M. hannyngtoni (Fraser, 1923) and vulnerable species like P. deccanensis Laidlaw, 1915 and P. sanguinostigma Fraser, 1922 were remarkable. The area was found to be rich in odonate diversity. More studies are needed to understand the population dynamics and seasonal patterns of Odonata in this particular geographical area.
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