Pleione 6(1): 5 - 26. 2012. ISSN: 0973-9467 © East Himalayan Society for Spermatophyte Taxonomy A checklist of orchids in Tinsukia District of Assam, India Khyanjeet Gogoi Daisa Bordoloi Nagar, Talap, Tinsukia- 786156, Assam, India E-mail: [email protected] Revised 04.05.2012; Accepted 05.06.2012 Abstract Tinsukia District has a vast stretch of forest cover with varied vegetation; those host many interesting species of orchids. This paper deals with the orchid flora of this district that consists of 95 species covering 48 genera, including terrestrial and epiphytic and concerned with morphological and ecological notes. Key words: Orchid Flora, Tinsukia, Distribution, Enumeration INTRODUCTION The Orchidaceae is one of the most highly specialized and larger families of flowering plants represented by more than 17000 species in nearly 1000 genera in the world and more and more new ones are being added every day (Chowdhery 1998). According to Kumar & Manilal (1994) 1141 species of Orchids in 166 genera are recorded from India, of which a major number of species are endemic. Out of 1141 species of Orchids reported so far from India about 800 species are from North-East India alone (Barua 2001). Assam the second largest state of India, is hosting many interesting Orchids like the other North-Eastern states. But, till date, no comprehensive record of Orchid flora of Assam is available. However according to Rao (1995) the actual enumeration of Orchids of Assam may be around 182 species covering 74 genera. Study area Tinsukia is an extremely important district of Assam in the north-eastern part of India with an area of about 3790 sq km. The district is located at 95022/ E to 95038/ E longitude and 27023/ N to 27028/ N latitude, at a height of 147.83 to 148.30 m AMSL (Map 1). The district is bounded at north by the mighty river Brahmaputra and the state of Arunachal Pradesh, on the west by Dibrugarh district and the on the east and south by Arunachal Pradesh. The area is very rich in terms of biodiversity and is very significant so far wildlife and forests are concerned. There are 35 reserve forests with a total area of 917.31 sq km, one National Park (Dibru- Saikhowa, 340 sq km) and one Wildlife Sanctuary (Borajan Padumoni 7.2 sq km), which covers about 33 % of the geographic area of the district (Mahanta 2002). The Tinsukia district is located in the sub-tropical region which therefore experiences high rainfall and high humidity. The annual rainfall ranges from 2300 mm to 3800 mm most of it is received during June – September with little rains in winters too. The average temperature is 360 C maximum and about 80 C minimum. The ambient high temperature is often checked by frequent showers and thunderstorms. Based on the floristic composition it can be broadly classified into two forest types. The first type is Hollong Nahar forests and this type corresponds to the Assam valley tropical wet 6 Orchids of Tinsukia District of Assam evergreen forest of Champion & Seth’s (1968) revised classification of forest types. The second type is termed as Miscellaneous forests, which is further subdivided in to Mixed deciduous forests and Mixed deciduous forest with evergreen patches. The climatic ambience of different types of vegetation in Tinsukia district suits well for the occurrence of numerous species of orchids. Recorded species of orchids are distributed in almost all zones of the forest according to their temperature and light requirement which varies from species to species, and some terrestrial orchids are found only in grasslands and riverbanks. The present study attempts to provide the information on the orchid flora of Tinsukia district based on recent collections. MATERIALS AND METHODS The present study is the result of several field trips covering all the seasons during 1996 to 2011 in different locations of Tinsukia district. The collected specimens were dissected and examined in laboratory during flowering period. Herbarium specimens were prepared by standard methods (Jain & Rao 1977). Specimens were identified with the help of literature and matched at the herbarium of department of Botany Guwahati University (GUBH) and at ASSAM. Herbarium specimens have been deposited at the GUBH. In the enumeration a generic name is accompa- nied by citation of the number of species in India and in this area and a species with author citation is supported with its flowering and habitat. RESULTS All the species of orchids recorded from the Tinsukia district of Assam during the present taxonomic survey is enumerated below with names of genera alphabetically and, again, species under each genus alphabetically. In the enumeration while a generic name is provided with the author citation only, a species binomial is followed by author citation, protologue reference, flowering period and habitat. ACAMPE Lindley About ten species from tropical Himalayan regions to Indochina, and SE Asia, tropical and subtropical Africa, Madagascar, and the islands of the W Indian Ocean (Chen et al 2009); 6 species in India, 3 species in Assam, 2 in Tinsukia district. Acampe praemorsa (Roxburgh) Blatter & McCann, J. Bomb. Nat. Hist. Soc. 35: 495. 1932. Epidendrum praemorsum Roxburgh, Pl. Coromandel. 1: 34. 1795. Acampe papillosa (Lindley) Lindley, Fol. Orchid 2, 1853. Saccolabium papillosum Lindley, Edwards’s Bot. Reg. 18: t. 1552. 1833. Epiphyte; flowers 1 cm across, yellow, slightly fragrant; sepals and petals yellow with reddish brown transverse stripes; lip white, slightly spotted with purple-red. Flowering: November – December. Exsiccatae: Gogoi 0031 Habitat: Epiphyte on tree trunk. Acampe rigida (Buchanon-Humilton ex J.E. Smith) P.F. Hunt in Kew Bull. 24: 98. 1970; Chowdhery, Orch. Fl. Arunachal Prad. 41, 1998. Aerides rigida Buchanon-Humilton ex J.E. Smith in A. Rees, Cycl. 39: 12. 1818. Epiphyte; flowers yellow with purplish brown transverse stripes; lip white, with purplish brown longitudinal stripes above. Flowering: June – July. Exsiccatae: Gogoi 0020 Habitat: Epiphyte on tree trunks or large branches. Khyanjeet Gogoi 7 Map 1. Location map of Tinsukia district of Assam ACANTHEPHIPPIUM Blume Fifteen species from S and NE India and Bangladesh, throughout SE Asia, to S Japan, New Guinea, and the SW Pacific islands (Chen et al 2009); 3 species in India, 2 in Assam and 1 species in Tinsukia district. Acanthephippium striatum Lindley, in Edwards’s Bot. Reg. 24(Misc.): 41. 1838; Hooker f., Fl. Brit. India 5: 816. 1890. [Fig. 1] Terrestrial; flowers creamy white with parallel red venation, tubular, 3.5 – 4.5 cm across. Flowering: June – July. Exsiccatae: Gogoi 0233 Habitat: Growing in shaded and humid places in dense forests, banks of streams. AERIDES Loureiro About 20 species in Sri Lanka, India, Nepal, Bhutan, Myanmar, China, Thailand, Indochina, and Malaysia to the Philippines and Indonesia (Chen et al 2009); 10 species in India, 5 species in NE India and 3 species in Tinsukia district. Aerides multiflora Roxburgh, Pl. Corom. 3: 68, t. 271. 1820. [Fig. 2] Epiphyte; flowers reddish or pinkish purple with darker spots, 2 – 2.5 cm across. Flowering: May – July. Exsiccatae: Gogoi 0034 Habitat: Shaded and humid places in dense forests, banks of streams. 8 Orchids of Tinsukia District of Assam PLATE - I: Photographs of some orchids of Tinsukia District. Fig. 1. Acanthephippium striatum; Fig. 2. Aerides multiflora; Fig. 3. Bulbophyllum andersonii; Fig. 4. Cleisocentron pallens; Fig. 5. Coelogyne fimbriata; Fig. 6. Dendrobium densiflorum; Fig. 7. Dendrobium nobile; Fig. 8. Dendrobium sulcatum; Fig. 9. Pinalia acervata; Fig. 10. Eulophia dabia; Fig. 11. Habenaria stenopetala; Fig. 12. Nervilia juliana; Fig. 13. Phalaenopsis mannii; Fig. 14. Phalaenopsis parishii; Fig. 15. Rhynchostylis retusa; Fig. 16. Vanda tessellata. Aerides odorata Loureiro, Fl. Cochinch. 2: 525. 1790; Hooker f. Fl. Brit. India 6: 47. 1890. Epiphyte; flowers white with purple blotches at the extremeties, 2.2-2.5 cm across, fragrant. Flowering: May – June. Exsiccatae: Gogoi 0040 Habitat: Epiphyte in lowland forest. Aerides rosea Loddiges ex Lindley & Paxton, Fl. Gard. 2: 109. 1852; Chowdhery, Orch. Fl. Arunachal Prad. 49. 1998. Epiphyte; flowers fragrant, purplish-pink suffused with white, dark pink spotted, opening widely, about 2 cm across. Khyanjeet Gogoi 9 Flowering: May. Exsiccatae: Gogoi 0013 Habitat: Epiphyte in mixed deciduous forest and humid evergreen forest. AGROSTOPHYLLUM Blume About 60 species in Old World tropics from the Seychelles and tropical Asia east to the Pacific islands, with the center of distribution in New Guinea (Chen et al 2009); 4 species in India, 1 in Assam and in Tinsukia district. Agrostophyllum planicaule (Wallich ex Lindley) Reichenbach f. in W.G.Walpers, Ann. Bot. Syst. 6: 909. 1864. Eria planicaulis Wallich ex Lindley, Edwards’s Bot. Reg. 26(Misc.): 8. 1840. Agrostophyllum khasianum Griffith in Calcutta J. Nat. Hist. 4: 378, t. 19. 1844. Epiphyte; flowers white, 6 – 8 mm across. Flowering: August – October. Exsiccatae: Gogoi 0132 Habitat: Epiphyte in mixed deciduous forest and humid evergreen forest. BRYOBIUM Lindley About 20 species from Sri Lanka and SE Asia to New Guinea, NE Australia, and the SW Pacific islands (Chen et al 2009), 1 species in Tinsukia district. Bryobium pudicum (Ridley) Y.P. Ng & P. J. Cribb, Orchid Rev. 113: 272. 2005. Eria pudica Ridley in J. Linn. Soc. 32: 294. 1896. Epiphytic; flowers pinkish white, pubescent, buff with darker Strips. Flowering: April – August. Exsiccatae: Gogoi 0495 Habitat: Epiphyte in deciduous forest and evergreen forest. BULBOPHYLLUM du Petit-Thouars About 1,900 species largely in tropical areas of both Old and New Worlds (Chen et al 2009); 100 species in India and Assam represent 24 species, 7 species in Tinsukia district. Bulbophyllum affine Lindley, Gen. Sp. Orchid. 48. 1830; Hooker f., Fl. Brit. India 5: 756. 1890. Epiphyte; flowers white with pink lined, about 3 cm long, solitary. Flowering: June – August. Exsiccatae: Gogoi 0098 Habitat: Epiphyte in mixed deciduous forest and humid evergreen forest.