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Distribution of mangroves in Andaman and Nicobar Islands

Distribution of mangroves in Andaman and Nicobar Islands
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  B IO D IV E R S IT A S ISSN:1412-033XVolume 15, Number1, April 2014E-ISSN:2085-4722Pages:12-23 Distribution of mangrove species reported as rare in Andaman andNicobar islands with their taxonomical notes PANDISAMY RAGAVAN 1, ♥ , K. RAVICHANDRAN 2 ,R.S.C. JAYARAJ 1 , P.M. MOHAN 3 , ALOK SAXENA 4 ,S. SARAVANAN 1 , A. VIJAYARAGHAVAN 1 1 Institute of Forest Genetics and Tree Breeding, R.S.Puram, P.B. No 1061, Coimbatore 641002,Tamil Nadu, India.Tel. +91-422-2484100,Fax. +91-422-2430549,   email : 2 Department of Environment and Forest, Andaman and Nicobar Administration,Port Blair,A & N Islands, India 3 Department of Ocean studies and marine Biology, Pondicherry University, Brookshabad Campus, Port Blair,A & N Islands, India 4 Indira Gandhi Forest Training Academy, Dehradun,Uttarakhand, IndiaManuscript received:7 February 2014. Revision accepted:20 March 2014. ABSTRACT  Ragavan P, RavichandranK,JayarajRSC, Mohan PM, Saxena A, Saravanan S,VijayaraghavanA.2014.Distribution of mangrovespecies reported as rare in Andaman and Nicobar islands with their taxonomical notes.Biodiversitas 15:12-23. During the recent fieldsurvey it was found that among 15 rare mangroves in Andaman and Nicobar Islands, ten rare species i.e.  Acanthus ebracteatus, Acrostichum speciosum, Bruguiera cylindrica, Cynometra iripa, Cynometra ramiflora, Lumnitzera racemosa, Rhizophora hybrids  ,Sonneratia alba, Sonneratia griffithii and  Xylocarpus mekongensis are present in Andaman and Nicobar islands. In addition to  Acanthusvolubilis, Brownlowia tersa and Sonneratia ovata are recorded after their first report. Key words: Andaman and Nicobar islands,mangroves,rare species INTRODUCTION Rarity in natural systems is common and ismost oftendefined by two attributes: a species' distribution and itsabundance. Species are considered rare if their area of occupancy or their numbers are small when compared tothe other species that are taxonomically or ecologicallycomparable(Flather and Sieg2007).Mangrove forests areunique plant communities of the critical interface betweenterrestrial, estuarine, and near-shore marineecosystems intropical and subtropical regions (Polidoro et al. 2010).Despite its ecological and economical values, globallymangrove areas are disappearing at the rate of approximately 1% per year (FAO 2003, 2007). However,little is known about the effects of either widespread orlocalized mangrove area loss on individual mangrovespecies or populations due to the lack of speciesinformation. The mangroves of Andaman and Nicobarislands (ANI) are gregarious, dense and diverse in natureand found along the tidal creeks, bays and lagoons.However, the mangrove plant diversity in many areas of ANIhas not drawn much attention. Only few references areavailable regarding the mangrove diversity in ANI (Sahni1957; Blasco 1977; Mall et al. 1987; Dagar et al. 1991;Singh and Garge 1993; Debnath 2004; Mandal and Naskar2008; Kathiresan 2008). Among them Dagar et al. (1991)critically surveyed the mangroves of ANI and listed out 34true mangrove species.After thatKathiresan (2008)reportedthe occurrence of36 mangrove species in ANI;of which 15 species were rare i.e  Acanthus ebracteatus, Acrostichum speciosum, Aegialitis rotundifolia, Bruguieracylindrica, Bruguiera sexangula Ceriops decandra,Cynometra iripa, Cynometra ramiflora, Kandelia candel, Lumnitzera racemosa, Rhizophora lamarckii, Sonneratiaalba, Sonneratia apetala, Sonneratia griffithii and  Xylocarpus mekongensis. After that no such detailed surveyhas been taken place in ANI andthe occurrenceofcertainmangroves species viz .  Aegialitis rotundifolia ,  Aglaiacucullata ,  Rhizophora x lamarckii , Sonneratia griffithii ,  Xylocarpus mekongensis and  Acanthus volubilis weredoubted by earlier studies (Mall et al 1987;Dagar et al1991;Debnath 2004).Further, the mangroves of rareoccurrence are poorly understood for their ecology andbiology (Kathiresan 2008). So it became necessary to findout the truth behind the existence and distribution of theserare species, because species composition of mangroves isa basic and important prerequisite to understanding all theaspects of their structure and function, as well as theirbiogeographical affinities for their conservation andmanagement (Jayatissa et al. 2002; Wang et al. 2003). MATERIALS AND METHODS Random survey was carried out in major creeks/ mangroves areas in 8 forest division of Andaman andNicobar islands (ANI), Bengali bay, India (Figure 1; Table1). The totalof30 sites were visited anditwas achievedusing a combination of road plus small boat transportationto gain access to the extensive range ofmangrove area.  RAGAVA Further searching was donealong the edge of themangrove forest and insidethe mangrove area bywalking. Even in some smallislands such as Havelock andNeil, the exploration was doneby walkingaround thebeaches and by boat aroundthe island. Targetedspecieswas counted in each observedsite. The status of each specieswas assessed based on thefrequency of occurrence insampling sites (Kathiresan2008). As we adapted randomsurvey to cover extensiverange of area, each site wasconsidered as single sampleunit and species status wasassessed based on percentagefrequency of each species(Table 2). All sites have beenvisited at least once at thetime of flowering of thedifferent species to cross-check identification withflower-based diagnosticfeatures. As many as 2-5specimens for each speciesweresampled, each samplewas supposed to have flowersand hypocotyls/ fruits, andgrouped according to themorphological characters . The collected plants werepacked separately inpolythene bagsand brought tolab for analyzingtaxonomically with priorassessments (Duke and Bunt(1979), Tomlinson (1986),Duke and Jackes (1987),Banerjee et al. (1989), Duke(1991, 2006a), Kathiresan(2002), Kathiresan (2000),Debnath (2004), Dagar et al.(1991), and Giesen et al.(2006).Herbarium wasprepared for each observedspecies and deposited atBotanical Survey of India(BSI), Regional Centre at PortBlair. Figure Burma 7.Man 13.Y Karma 22.Par 27.Ki et al.  –   Mangrove of Andaman and Nicobar islands     1. Sampling site inAndaman and Nicobar islands ( nallah,2.Chediyatapu,3.Sippighat,4.Shaolbay creek,5.glutan,8.Wandoor,9.Middle strait,10.Wrafter creek,11. rrata creek,14.Shayamkund creek,15.Dhaninallah c tang creek,18.Tugapur creek,19.Austin creek,20.Chain angara creek,23.Kishorinagar creek,24.Kalighat creek, ous bay,28.Radhanagar,29.Govindnagar,30.Neil island A & IIslands   13  ANI), Bengali bay, India.1. Wrightmyocreek,6.Jirkatang, Baludera,12.Kadamtala creek, reek,16.Pachwati creek,17. pur creek,21.Mohanpur creek, 5.V.K.pur creek,26.Hut bay,   B IO D IV E R S IT A S 15 (1):12-23, April 2014 14 Table 1. Distribution of rare mangrove species in ANI DivisionSiteSpecies recorded ( values within bracket indicate number of individual trees recorded) South AndamanBurmanallah Sonneratia ovata (7)  , Cynometra irripa (4)  Lumnitzera racemosa (5)  , Bruguiera cylindrica (13)  , Sonneratia alba (13)Chediyatapu Sonneratia alba (31)  , Sonneratia ovata (15)  , Rhizophora hybrids (2)  , Bruguiera cylindrica (8)  ,Cynometra ramiflora (1)Sippighat  Bruguiera cylindrica (16)  , Sonneratia alba (7)  , Acanthus ebracteatus (small patches)Shaolbay creek  Sonneratia ovata (17)  , Rhizophora hybrids (1)  , Bruguiera cylindrica (18)  , Acanthus volubilis (small patches)  , Acrostichum speciosum (small patches)  , Cynometra iripa (5)  , Sonneratia alba (31)  , Acanthus ebracteatus (small patches)Wrightmyo creek   Bruguiera cylindrica (13)  , Acrostichum speciosum, Sonneratia alba (19)  , Cynometra iripa (3)Jirkatang  Acanthus volubilis (Small patches)  , Acrostichum speciosum (small patches)  , Bruguieracylindrica (17)  , Cynometra iripa (4)  , Sonneratia alba (12)Manglutan Sonneratia ovata (4)  , Bruguiera cylindrica (11)  , Sonneratia alba (7)Wandoor Sonneratia ovata (2)  , Bruguiera cylindrica (7)  , Sonneratia alba (7)BaratangMiddle strait  Bruguiera cylindrica (57)  , Sonneratia alba (29)  , Cynometra iripa (8)Wrafter creek   Xylocarpus mekongensis (6)  , Bruguiera cylindrica (87)  , Sonneratia alba (32)  , Cynometra iripa (6)Baludera  Xylocarpus mekongensis (1)  , Bruguiera cylindrica (5)Middle AndamanKadamtala creek   Rhizophora hybrids(13)  , Sonneratia ovata (1)  , Sonneratia alba (16)  , Cynometra iripa (11)  , Bruguiera cylindrica (16)Yerrata creek   Rhizophora hybrids(5)  , Lumnitzera racemosa (34)  , Xylocarpus mekongensis (41)  , Bruguieracylindrica (24)  , Sonneratia alba (14)  , Cynometra iripa (12)Shayamkund creek   Brownlowia tersa (small patches)  , Bruguiera cylindrica (21)  , Xylocarpus mekongensis (3)  ,Sonneratia alba (15)  , Cynometra iripa (16)Dhaninallah creek  Sonneratia griffithii (34)  , Xylocarpus mekongensis (7)  , Lumnitzera racemosa (4)  , Bruguieracylindrica (7)  , Sonneratia alba (21)  , Cynometra iripa (9)Pachwati creek  Sonneratia griffithii (7)  , Sonneratia alba (3)  , Cynometra iripa (7)MayabunderKarmatang creek   Bruguiera cylindrica (17)  , Lumnitzera racemosa (29)  , Xylocarpus mekongensis (5)  , Cynometrairipa (7)Tugapur creek   Xylocarpus mekongensis (3)  , Bruguiera cylindrica (16)  , Cynometra iripa (4)  , Sonneratia alba (5)Austin creek   Rhizophora hybrids(16)  , Cynometra iripa (7)  , Bruguiera cylindrica (14)  , Sonneratia alba (7)Chainpur creek   Xylocarpus mekongensis (4)  , Cynometra iripa (9)  , Bruguiera cylindrica (17)  , Mohanpur creek   Xylocarpus mekongensis (7)  , Cynometra iripa (13)  , Bruguiera cylindrica (18)  , Sonneratia alba (14)  , Sonneratia griffithii (1)DiglipurParangara creek   Xylocarpus mekongensis (13)  , Cynometra iripa (5)  , Bruguiera cylindrica (14)  , Sonneratiagriffithii (13)  , Kishorinagar creek  Cynometra iripa (9)  , Bruguiera cylindrica (11)  , Sonneratia alba (7)Kalighat creek  Sonneratia griffithii (8)  , Cynometra iripa (4)  , Bruguiera cylindrica (11)  , Sonneratia alba (9)Little AndamanV.K.Pur creek  Sonneratia alba (11)  , Sonneratia caseolaris (17)  , Cynometra iripa (16)  , Bruguiera cylindrica (14)Hut bay Sonneratia griffithii (1)  , CarnicobarKimous bay  Rhizophora hybrids(4)  , Lumnitzera racemosa (5)HavelockRadha nagar Sonneratia ovata (7)  , Bruguiera cylindrica (4)Govindnagar  Bruguiera cylindrica (13)  , Sonneratia alba (18)  , Rhizophora hybrids (11)Neil island  Rhizophora hybrids(6) Table 2. Species status based on percentage frequency SpeciesNumber individualsrecordedNumber of sites in whichspecies occurredTotal number of sitesPercentage of frequencyStatus  Acanthus volubilis Small patches2306.67Rare  Acanthus ebracteatus Small patches2306.67Rare  Acrostichum speciosum Small patches33010Rare  Bruguiera cylindrica 469263086.7Abundant Cynometra iripa 159203066.7Frequent Cynomtera ramiflora 11303.33Rare  Lumnitzera racemosa 7753016.7Rare  Rhizophora hybrids5883026.7Rare Sonneratia alba 328223073.3Frequent Sonneratia griffithii 6463020Rare Sonneratia ovata 5373023.3Rare  Xylocrpus mekongensis 90103033.3Common  Brownlowia tersa Small patches1303.33Rare Sonneratia caseolaris 171303.33RareNote: Abundant (a):if the species is present in 81-100% of sampling points; Frequent (f):if the species is present in 61-80% of samplingpoints; Common (c ):if the species is present in 31-60% of sampling points; Rare (r ):if the species is present in 1-30% of samplingpoints  RAGAVAN et al.  –   Mangrove of Andaman and Nicobar islands 15 RESULTS AND DISCUSSION Theresultsofpresent study confirm the occurrence of 10 out of the 15 rare mangroves reported earlier.Remaining five species namely  Aegialitis rotundifolia, Bruguiera sexangula, Ceriops decandra, Kandelia candel and Sonneratia apetala were not recorded in this study.Contrary to earlier reports in this study  Avicennia alba wasnot recorded and Sonneratia caseolaris was recorded inonly one site; both species are reported as frequent in ANIby Kathiresan (2008).  Acanthus volubilis,BrownlowiatersaandSonneratia ovata are reported after their firstreport,i.e.Parkinson (1923)and DamRoy et al. (2009).Inthe discussion below,we highlighted the diagnosticfeatures of each mangrove species and their distribution inANI.  Acanthus volubilis the only climber known tooccur in mangroves and considered as true mangrovespecies (Duke 2006;Polidoroet al.2010).  A.volubilis wasfirst reported from ANI by Parkinson (1923) after that itwas included in the mangrove species list by severalauthors (Thothatri 1962; Mall et al. 1987; Dagar et al.1991;Debnath 2004; Mandel and Naskar 2008). But,Mall et al . (1987) mentioned that he included this species basedonParkinson (1923) report and he has not encountered in anysites.Once  A. volubilis was consideredasanextinctspecies in India,but recently it has been recorded againwith its very limited population from Sunderbans(Mandeland Naskar 2008). Kathiresan (2008)didnot included thisspecies in his report. Dam Roy et al. (2009) reported thisspecies from ANI,butdescription and photographs givenfor  A. volubilis reveal that the only character of theobserved specimen used to identify the species is spinelessleaves and stem; however, this can be a feature of   A.ilicifolius as well (Jayatissa et al. 2002). Moreoverherbarium deposited byThothathri(1962) in BSI, Regionalcentre at Port Blair also resembles the same.Thus  A.volubilis reported here after its first report(i.e. Parkinson1923). In thisstudy  A. volubilis was reported attwo sitesi.e. Shoalbaycreekand Jirkatang inSouthAndaman. Inbothsites,itwas observed in small patches along with  Acrostichumaureum and  Acrostichumspeciosum on thelandward edge.  A. volubilis waseasilyidentified by itssmooth (without stem axial spines)and twining with delicatesprawlingstems, spineless leaves,terminal inflorescencesand white flowers without bracteoles (Figure 2.A-2.D).In India  Acanthus ebracteatus known to occurin Andaman and NicobarIslandsand Kerala(Kathiresan2008). But the details abouttheir status and distribution areinadequate, because the taxonomicaldiscriminationbetween the  A. ebracteatus and  A. ilicifolius arestill notclear (Kathiresan 2010). For instances,Remadevi andBinojkumar (2000) argued that many specimen identifiedand indexed as  A. ilicifolius in Indian herbarium areactually  A. ebracteatus . In contrast,Anupama andSivadasan (2004) questioned the identification made byRemadevi and Binojkumar (2000). In this study  A.ebracteatus wasrecordedat two sites i.e Shaolbaycreek and Sippighatin South Andaman. Generally  A. ebracteatus is identified by its whitecoloredflowers,but someecological variants of   A. ilicifolius exhibit whitecoloredflowers with unarmed leaves and stems(Jayatissa et al.2002). Hence,identification basedonflowers may causemisidentification in the field. During the present study,itwas found that position ofinflorescences and direction of stem axial spines at nodeshelpsthe rapid differentiation of   A. ilicifolius from  A. ebracteatus apartfrom flowercolorand presence of bracteoles.  A. ebracteatus is distinguishedfrom other  Acanthus spp by its highly serrated leaves,whitecoloredflowers, absence of bracteoles, stem withauxiliary spines facing downwards and terminalinflorescences (Figure 2.E-2.J).Butin  A.Ilicifolius ’  leavesand stemsare either armed or unarmed, flowercoloris blueor white (rarely white), inflorescences arebothaxial andterminal and stem with auxiliary spines facing upwards(Figure 2.K-2.N)Species of   Acrostichum are usually called mangroveferns. In ANI  Acrostichum aureum L . is a common species,in contrast,  Acrostichum speciosum Willd . is rare. In thepresent survey  A. speciosum was recorded atthreesitesi.eShoalbay creek, Wrightmyo creek, and Jirkatang. In all thesites,  A. speciosum was observed at the mangroveunderstory, and just at the margins of high intertidal zones.These areas are frequently inundated by tides and areusuallyshady. Itwasalso observed on the landward edgesalong with  A. aureum in Shoalbay creek. In fields,  A.aureum and  A. speciosum are easily distinguished based onfrond shape and texture. The frond of   A. speciosum narrows gradually to a pointed tipand papery(Figure 2.O,2.Q), while that of   A. aureum has a broadly roundedendandthickly coriaceousfronds(Figure 2.R).Recently DamRoy et al. (2009) reported this species in WandoorandBurmanallah,but description and photographs given for  A.speciosum reveal that the only character of the observedspecimen used to identify the specieswaspointed leaf tip;however, this can be a feature of  Stenochlaena palustris aswell(Giesenet al.2006). S. palustris differfrom  A.speciosum by its serrated leaflet margin and parallelvenation(Figure 2.S).  Bruguiera cylindrica (L.) Bl.was mentioned as a rarespeciesby Dagar et al. (1991) and Kathiresan (2008). Butin the present studyit wasobserved in 26 sites and total469 individual were recorded.So it is noteworthy that  B.cylindrica is now abundantin AndamanIslands.It is smalltreegenerally found inside the mangroves and occasionallyforms pure stands that appear similar in appearance tothose of   B. parviflora .  B. cylindrica is distinguished fromother  Bruguiera species by its small flowers,threeflowered inflorescences and calyx with fully reflexed calyxlobes (Figure2.T-2.V). In field it is easily distinguishedfrom  B. parviflora by itsdark green leaves, folded whenmatureand reflexed calyx lobes,whereas  B. parviflora possess small yellowish green leaves,long ribbed calyx withsmall adpressed lobesand thin propagule(Figure 2.W-2.Y).  Brownlowia tersa (L.) Kosterm. is generally found onthe soft mud of intertidal estuarine banks and can berecognized in the field by its greyish brown branches,lanceolate leaves with dull silvery under surface,yellowishpinkcolorflowers (Figure 3.A-3.C) and pear-shapedwoody fruits with two valved carpels (Kathiresan 2010). It  B IO D IV E R S IT A S 15 (1):12-23, April 2014 16 Figure 2. (A) Terminal inflorescences (B) white flower with bract (C) smooth leaves and (D) fruits of   Acanthus volubilis (E) terminalinflorescences (F) highly serrated leaves (G) fruits (H) mature bud without bracteoles (I) white flower and (J) downward facing stemaxial spinesof   Acanthus ebracteatus (K) terminal and (L) axillary inflorescences with purple flowers (M) bud with bract and bracteolesand (N) upward facing stem axial spines of   Acanthus ilicifolius (O) habitat (P) sterile leaves with narrowly pointed leaflets and (Q)pointed tip of   Acrostichum speciosum (R) blunt leaf tip of   Acrostichum aureum (S)serrated margin of leaflet of  Stenochlaena palustris (T) dark green leaves (U) flowersand propagule of   Bruguiera cylindrica with reflexed calyx lobes (W) yellowish green leaves (X)flowers and (Y) propagule of   Bruguiera parviflora with long calyx tube. EFGABCDJMNIHKLSRQPOVUTYXW
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