ISSN: 2087-3948E-ISSN: 2087-3956DOI: 10.13057/nusbiosci/n040203Vol. 4, No. 2, Pp. 57-61July 2012Adult mangrove stand does not reflect the dispersal potential ofmangrove propagules: Case study of small islets in Lampung, SumatraAGUNG SEDAYU , NOVITA FARAH ISYADINYATI, DIANA VIVANTI SIGITDepartment of Biology, Faculty of Mathematics and Natural Sciences, State University of Jakarta. Jl. Pemuda 11 Rawamangun, Jakarta Timur 13220.Tel. 62-21-4894909. Fax. 62-21-4894909. email: [email protected] received: 26 December 2010. Revision accepted: 19 February 2011.Abstract. Sedayu A, Isyadinyati NF, Sigit DV. 2011. Adult mangrove stand does not reflect the dispersal potential of mangrovepropagules: Case study of small islets in Lampung, Sumatra. Nusantara Bioscience 4: 57-61. Most mangrove species are dispersed bywater current with distance being a major constraint. We tried to demonstrate that distance is indeed the dispersal limiting factor inmangrove, and perhaps other marine plant species. Secondly, we also tried to clarify whether landmass is a real blockade for mangrovedispersal. Lastly, we argued that in order to study plant dispersal potential, one should not study the later stage of plant population, asnormally plant ecologist would do, rather at their early life stage. Cluster analyses were used to test those hypotheses and confirmed ourresearch hypotheses.Key words: biogeography, dispersal, mangrove, propagules.Abstrak. Sedayu A, Isyadinyati NF, Sigit DV. 2011. Tegakan mangrove dewasa tidak mencerminkan potensi penyebaran propagulmangrove: Studi kasus pulau-pulau kecil di Lampung, Sumatera. Nusantara Bioscience 4: 57-61. Sebagian besar jenis mangrovetersebar oleh arus air dengan jarak sebagai kendala utamanya. Penelitian ini mencoba untuk menunjukkan bahwa jarak menjadi faktorpembatas dalam penyebaran mangrove, dan jenis tumbuhan pantai lainnya. Kedua, penulis juga mencoba untuk mengklarifikasi apakahdaratan adalah secara nyata membatasi penyebaran mangrove. Terakhir, penulis memperdebatkan bahwa untuk mempelajari potensidispersal tumbuhan, seseorang tidak harus mempelajari tahap akhir dari populasi tanaman, sebagaimana banyak dilakukan para ahliekologi tumbuhan, namun dapat pula pada tahap awal kehidupannya. Analisis klaster digunakan untuk menguji hipotesis tersebut dandikonfirmasi dengan penelitian ini.Kata kunci: biogeografi, penyebaran, mangrove, propagul.INTRODUCTIONCoconut tree, most probably originally from PolynesiaMelanesian, is naturally distributed pantropically on mostbeach areas, with the help of its floatable fruits. However,being an ethnobotanically ancient important crop, itslimited distribution range in some places like SouthAmerica, especially Panama, is mostly caused by preindustrial human migration (Ward and Brookfield 1992).On the other hand, mangrove, with similar dispersalcapability, had no economic importance to prehistorichuman, hence their almost identical worldwide distributionto coconut tree is solely attributed to their own capability tocolonize adjacent areaMany of mangrove species are known to spread byfloatable propagules. Some propagules, such as inRhizophora, are dispersed by viviparous seed/embryo,;while others with their floatable non-viviparousfruits/seeds. The survival, including dispersal, recruitmentand growth of the propagules depends on many inherent(genetic traits) and external (environmental) factors.Initial propagule characters such as weight, shape,orientation, time of shoot emergence, and buoyancy, andearly growth, such as (time?) and numbers of plants withinitiated roots and shoots are important traits determiningthe dispersal and recruitment of mangrove species alongtidal area (Rabinowitz 1978a, b). These traits interact withexternal/environmental factors, such as salinity, waterturbulence, water depth, temperature, tidal amplitude, watercurrent and light exposure, disturbance, predatory andcompetition (McMillan 1971; Smith and Duke. 1987;Osborne and Smith 1990; Jimenez and Sauter 1991; Sousaet al. 2007). The interaction of such factors has resulted in theexisting mangrove population stands along the pantropic.For tidal species, water current and distance frommother tree (genetic source or original population) areparticularly important in propagule dispersal. For landplants, water bodies such as seas, lakes, oceans or rivers actas physical barriers of natural distribution. On the contrary,for mangroves, landmasses virtually act as physical barriersof their distribution.Using the natural mangrove stands at differing lifestages at Teluk Lampung, Sumatra, we aimed to (i)understand the dispersal potential of mangrove species interms of predicting the long distance travel of propagulesfrom bigger island to smaller satellite islets and
584 (2): 57-61, July 2012confirming whether the landmass are actual dispersalbarriers for mangroves; (ii) test which life stages ofmangroves (seedling, sapling and tree) are best to detectthe mangrove dispersal potential.MATERIALS AND METHODSSix stations on the western coast of Lampung had beenchosen for this study. Two of which, Suamalu (05.724o S,105.207o E) and Kalangan (05.645o S, 105.207o E) aresituated on the coast of main Island, Sumatra, while theother four are on two small islets just across the formertwo. Two stations are situated at Puhawang islet with onestation (Puhawang Barat; 05.674o S, 105.207o E) is facingdirectly toward Sumatra and the other one (PuhawangTimur; 05.672o S, 105.235o E) facing Sunda Strait. The lasttwo stations are situated at Kelagian islet, with one station(Kelagian 05.630o S, 105.213o E) is facing Sumatra and theother one (Goreng; 05.617o S, 105.222o E) facing SundaStrait (Figure 1.). At each station, a line transect was setfrom the sea, landward, starting from where the outermostmangrove stands was located. The length of transectsdepended on how thick the mangrove stand was, about 60 mto 100 m each.Figure 1. The study sites in Teluk Lampung; the symbols on each site depict their relative similarity as depicted in Figure 2.
SEDAYU et al. – Mangrove of small islets in LampungAt each transect, three nested quadrats were laid, thesmallest one, 1 x 1 m, was designated for seedlings, the 5 x5 m quadrat for saplings and the 10 x 10 m for trees. Wecounted for each quadrat the number of species, frequencyand basal area in order to calculate the importance value ofeach species (Cox 1972). For identification, specimens ofunknown individuals were taken and once identified werekept at the herbarium of UNJ (JUNJ). Data from eachtransects were treated as one to portray each station as oneentity, therefore there were six figures of importance valuesof all species surveyed representing six stations, thusassembling a matrix of 6 x number of all species (Table 2).The matrix was analyzed for its similarity index, usingprogram PRIMER (Plymouth Routines in MultivariateEcological Research) version 5.1.2., and the results weredrawn as dendrograms.59The sapling data plotted on figure 2B shows a distinctcluster between Kelagian at Pulau Kelagian and PuhawangBarat at Pulau Puhawang. Kelagian which is located on theclosest end of Pulau Kelagian to Sumatra which has adistinct similarity with Puhawang Barat, which is alsolocated at the closest end of Pulau Puhawang to Sumatra.Other study sites are clumped together in an above cluster,consisting of four sites, however with unclear informationwith regards to its geographical position.The seedling data on Figure 2C showed two bigclusters, each forming an interesting grouping where siteson small islets adjoining the bigger main island (Sumatra)have the greatest similarity index, as well as those distal toSumatra. The sites on Sumatra are not joined, interestingly,to each other, but clusters to sites facing the main island orafar from the main island.Table 1. Composition of species in combined study areas.RESULTS AND DISCUSSIONThree dendrograms were produced representing threelife stages of mangrove, seedling, sapling and tree. Figure2A shows that the tree similarity indexes between sites isalmost incongruous in the biogeographical point of view,since each site does not reflect its close affinity based ongeographical distances. The mangrove on t h e furthestsouth site on Suamalu, which is located in Sumatra is theclosest according its importance value similarity index toour northernmost site at Goreng on Pulau Kelagian. In thesense of biogeography, the closer the areas, the moresimilar their species component. Trees tend to form randomstands, without a distinct pattern between ophoraceaeSonneratiaceaeSpeciesCamptostemon schultziiExcoecaria agallochaXylocarpus granatumBruguiera cylindricaBruguiera gymnorrhizaCeriops tagalRhizophora apiculataR. x lamarckiiR. mucronataSonneratia 77.72.65100Figure 2. The dendrogram of similarity between sites; (A) Tree; (B) Sapling; (C) Seedling. For information about symbols and names ofplaces see Figure 1.
604 (2): 57-61, July 2012Table 2. Importance values of each mangrove species matrix.KelagianPuhawang Barat Puhawang TimurTr SaSeTr SaSeTrSa SeBruguiera cylindrica27.1 32.08 45000000Bruguiera gymnorrhiza 40.8 45.8 84.4 32.23 023.01 000Camptostemon schultzii 16.44 00000000Ceriops tagal034.7 28043.17 17.35 000Excoecaria agallocha000000000Rhizophora apiculata162.8 75.5 129,75 160.1 184.4 211 49.9 300 261.2Rhizophora mucronata 027.34 0107.6 72.42 47.91 000Rhizophora x lamarckii 23.4 71.14 12.88 000250.1 038.8Sonneratia alba2900000000Xylocarpus granatum012.96 0000000Note: Numbers are in percentage (%); Sa: Sapling; Se: Seedling; Tr: Tree.SpeciesAll species within our study area are species withfloatable propagules. Rhizophoraceae (Rhizophora andBruguiera) are species with highest important values, andthe most common in all sites (Table 1 and 2), are equippedwith viviparous propagules. Other species seed types arenot viviparous, but buoyant. Sonneratia has edible arillatefruits known being eaten by bats and macaques, but thedispersal mode of this species is solely by floating, sincethe fruit has outer floatable tissue and too big to be swollenin whole. Excoecaria agallocha and Xylocarpus granatumhave exploding capsules and fruits, and the shooting seedswhich also have buoyancy potential. Camptostemonschultzii has floatable a capsule which, when splits,releases the seeds, having potential to disperse by water aswell as wind (Noor et al.1999). We did not test whether theviviparous species thrives more successfully compared tothe non-viviparous species, but this character seems to be acrucial feature in determining why species ofRhizophoraceae (all with viviparous fruits in our study site)were much more common in all three life stages surveyed.Other investigators such as Smith and Sneadaker (2000)confirmed that the vivipary of Rhizophoraceae has asignificant effect on its distribution along tropical andsubtropical coastal areas. This explains why viviparousspecies is much more common than non- viviparousspecies, although they have similar means of distribution,water floatable propagules. Traits related to establishmentwere stronger predictors of distribution than thoseassociated with dispersal (Clarke et al. 2001).The distance between sites is the best explanation of thepattern shown in Figure 2.C., where the location adjacent togenetic source (i.e. bigger landmass, like Sumatra) has thelargest similarity to that landmass, where the propagulespresumably originated. Clarke (1993) observed thatpropagules of Avicennia marina was best transplantedwithin only 500 m afar from its point of release (mothertree), and the success slightly decreased at a distance of 1km and was the least at 10 km, resulting restricted genevariation between populations and very slow recoverywhen mass mortality occurred. That explains why the sitesdistal to Sumatra landmass had much different importancevalues from those proximal to Sumatra. The immigration ofmangrove propagules to sites secluded by land (i.e.opposing the small islets), from the genetic source isSuamaluTr Sa027.8000002100164.4 177.961.5 43.60062.3 29.711.3 0Se00078.650221.30000GorengTr Sa000000000050.85 14800180 120.668.31 31.400KalanganSe Tr SaSe0 0 000 65 17.71 00 0 000 0 19.33 1580 0 24.9 049 0 238 1420 0 00251 235 000 0 000 0 00inevitably much lower, as the landmass acts as physicalbarrier for the water transported propagules (Duke et al.1988).In both tree and sapling dendrograms (Figure 2 A, B),the pattern of dispersal potential of mangrove by watercurrent is not obvious. In fact, the dendrograms producedin Fig. 2 A is almost illogical. In the Figure 2 B, at least thelocations distal to Sumatra (Kelagian, 3 and PuhawangBarat, 5) are grouped in one cluster, showing that seedlingsin those areas have higher similarity in species importancevalues, however the rest of clustering give no informationin terms of biogeographical distribution of mangrovespecies. Both irrelevant dendrograms most likely reflect thelater development of each mangrove population. Saplingsand especially trees suffer from longer period of bothinherent, genetic and environment pressures. Pinzon etal.(2003) demonstrated that natural mortality, humaninduced mortality, diseases and natural predations producegaps in natural population. (Osborne and Smith 2003).This research study implies that biogeographicalstudies focused on plant dispersal potential should focus atthe plant’s early stages, when stands of juveniles are lesslikely affected by environment, competition, predation orhabitat modification, leading to individual mortality.Analysis for such purposes with later stages of plantdevelopment as sapling and tree may introduce bias in theanalysis, as those stages are exposed to many factorsleading to mortality for a longer period of time, henceafflicting the distribution of plants in a certain site.CONCLUSIONSMost mangrove species are dispersed by water currentwith distance as a major constraint. We tried todemonstrate that distance is indeed the dispersal limitingfactor in mangrove, and perhaps other marine plant species.Secondly, we also tried to clarify whether landmass is areal blockade for mangrove dispersal. Lastly we arguedthat in order to study plant dispersal potential, one shouldnot study the latter stage of plant population, as normallyplant ecologist would do, rather at their early life stage.Cluster analyses were used to test those hypotheses andconfirmed our research hypotheses.
SEDAYU et al. – Mangrove of small islets in LampungACKNOWLEDGEMENTSWe gratefully acknowledge the Research Center forOceanology, Indonesian Institute of Science (P3O LIPI),Jakarta for their cooperation in collecting field data. Wethank our field assistants during the data collections inLampung, and The State University of Jakarta’s staffs fortheir valuable discussions and supports.REFERENCESClarke PJ. 1993. Dispersal of grey mangrove (Avicennia marina)propagules in southeastern Australia. Aquat Bot 45: 195-204.Clarke PJ, Kerrigan RA, Westphal CJ. 2001. Dispersal potential and earlygrowth in 14 tropical mangroves: Do early life history traits correlatewith patterns of adult distribution? J Ecol 89 (4): 648-659.Cox GW. 1972. Laboratory manual of general ecology. W.M.C. BrownCompany Publishers, Iowa.Duke NC, Ball MC, Ellison JC. 1998. Factors influencing biodiversity anddistributional gradients in mangroves. Global Ecol Biogeograph Lett7 (1): 27-47.Jimenez JA, Sauter K. 1991. Structure and dynamics of mangrove forestsalong a flooding gradient. Estuaries 14 (1): 49-56.61McMillan C. 1971. Environmental factors affecting seedlingestablishment of the black mangrove on the Central Texas Coast.Ecology 52 (5): 927-930.Noor YR, Khazali M, Suryadiputra INN. 1999. Panduan PengenalanMangrove di Indonesia. Ditjen PKA, Dephut, Wetland InternationalIndonesia Programme, Bogor.Osborne K, Smith III TJ. 1990. Differential predation on mangrovepropagules in open and closed canopy forest habitats. Vegetatio 89(1): 1-6.Pinzón ZS, Ewel KC, Putz FE. 2003. Gap formation and forestregeneration in a Micronesian mangrove forest. J Trop Ecol 19 (2):143-153.Rabinowitz D. 1978a. Dispersal properties of mangrove diaspores.Biotropica 10, 47-57.Rabinowitz D. 1978b. Early growth of mangrove seedlings in Panama andan hypothesis concerning the relationship of dispersal and zonation. JBiogeograph 5: 113-133.Smith III TJ, Duke NC. 1987. Physical determinants of inter-estuaryvariation in mangrove species richness around the tropical coastlineof Australia. J Biogeograph 14 (1): 9-19.Smith SM, Snedaker SC. 2000. Hypocotyl function in seedlingdevelopment of the red mangrove, Rhizophora mangle L. Biotropica32 (4a): 677-685.Sousa WP, Kennedy PG, Mitchell BJ, Ordóñez L. 2007. Supply-sideecology in mangroves: Do propagule dispersal and seedlingestablishment explain forest structure? Ecol Monograph 77 (1): 53-76Ward RG, Brookfield M. 1992. The dispersal of the coconut: Did it floator was it carried to Panama? J Biogeograph 19 (5): 467-480.
Tegakan mangrove dewasa tidak mencerminkan potensi penyebaran propagul mangrove: Studi kasus pulau-pulau kecil di Lampung, Sumatera. Nusantara Bioscience 4: 57-61. Sebagian besar jenis mangrove tersebar oleh arus air dengan jarak sebagai kendala utamanya. Penelitian