Table Of Content

Fungal Diversity Fungal succession on fronds of Phoenix hanceana in Hong Kong Yanna, W.H. Ho* and Kevin D. Hyde Centre for Research in Fungal Diversity, Department of Ecology and Biodiversity, The University of Hong Kong, Pokfulam Road, Hong Kong SAR; e-mail: [email protected] Yanna, Ho, W.H. and Hyde, K.D. (2002). Fungal succession on fronds of Phoenix hanceana in Hong Kong. In: Fungal Succession (eds. K.D. Hyde and E.B.G. Jones). Fungal Diversity 10: 185-211. Seventy-three fungal taxa were identified during the decomposition process of frond baits of Phoenix hanceana, comprising leaves, rachis-tips, mid-rachides and rachis-bases. Pioneer, mature and impoverished communities were observed in sequence on the frond baits. Fungal communities on different frond parts reached pioneer, mature and impoverished communities at different rates. Fungal communities on leaves and rachis-tips matured more slowly than other parts, but became impoverished rapidly thereafter, and samples were completely decayed at month 13. On the contrary, fungal communities on mid-rachides and rachis-bases matured earlier at month 1,but became impoverished at month 13.Naturally occurring fronds were also examined at the same time. Only half of the fungi were common to baits and naturally occurring fronds. Thus, examination of both frond baits at different stages of decomposition and naturally occurring fronds isrecommended to obtain abetter estimation of biodiversity. Key words: fungal distribution, fungal ecology, palm, plant decomposition. Introduction Succession has been defined as "the sequential occupation of the same site by thalli (normally mycelia) either of different fungi, or of different associations of fungi" (Rayner and Todd, 1979). There have been numerous studies on substratum succession involving a variety of substrata, for example, cellulose film (Tribe, 1957, 1961), plant litter (Webster, 1956; Tokumasu, 1998) and wool (Ghawana et al., 1997). There have also been several studies of succession of fungi on degrading cellulosic substrates (Kuester, 1979; Gorska, 1982) In succession, biotic communities change over time and the complete sequence of change is called a sere. Seres are made up of recognizable units (seral stages) (Luczkovich and Know1es, 2000). In general, fungal communities go through the following three stages (Dix and Webster, 1985; Gessner et al., 1993): •Corresponding author: W.H. Ho; email: [email protected] 185 Pioneer community This community consists of pioneer species which have low percentages of abundance (Dix and Webster, 1985; Gessner et al., 1993). Pioneer species tend to be fast growing, short-lived, and capable of rapid and wide dispersal (Luczkovich and Knowles, 2000). This community type usually has low species diversity, while a few species have high abundance (Dix and Webster, 1985; Gessner et al., 1993). Mature community The species diversity in mature communities is high and has peaked, while a number of species occur with a low percentages of abundance. However, several species may have a high level of abundance. The dominant species have extremely high levels of abundance. During the later stages of the mature community, the number of dominant species declines, but species diversity is still high (Dix and Webster, 1985; Gessner et al., 1993). The highest species diversity is likely to correspond with the highest rates of decomposition because greater genetic diversity is likely to correspond with greater enzyme diversity. There is also a greater likelihood that mutualistic associations and synergistic interactions can develop that can promote decay (Dix and Webster, 1985). Biirlocher and Kendrick (1974) found that five aquatic hyphomycete species growing together decomposed leaves faster than a single species. Impoverished community The species diversity declines towards an impoverished community. The community is dominated by a few species with extrememly high levels of abundance (Dix and Webster, 1985; Gessner et al., 1993). These dominant species tend to be persistent and longer-lived species (Luczkovich and Knowles, 2000). However, there are still some species with low levels of abundance. The community will be in climax when it is dominated by one or two highly antagonistic species (Dix and Webster, 1985). The present study was initiated to investigate the sequential occurrence of sporulating fungi on frond baits of Phoenix hanceana, and also to address the question, "Where are the undescribed fungi?", with the following objectives: 1. To investigate the fungal communities occurring on palm fronds during different stages of decay on different frond parts until complete decomposition. 2. To compare fungal communities from the succession study and with those of naturally occurring samples. 186 Fungal Diversity Materials and methods Study sites Hong Kong SAR (22°N 114°E) is located at the south-eastern coast of China, east of Guang Dong Province, some 100 km (1° latitude) south of the Tropic of Cancer. The study site was located in Tai Mo Shan (22°25'N 114°05'E) at around 600 m attitude. The climate in Hong Kong SAR is subtropical, tending towards temperate for nearly half of the year (Dudgeon 1994). During April to September, there is a wet and hot season, due to the prevalent south-western monsoon, and during October to the following March, there is a dry and cooler season due to the prevalent north-eastern monsoon (Dudgeon 1994). In general, January and August are the driest and wettest months respectively. The mean daily temperature ranges from 15.8 C in January to 28.8 C in July. It is not uncommon for temperatures to drop below 10 C during January and February (Dudgeon 1994). Sample collection Samples ofsuccession stuay Twelve Phoenix hanceana trees that were higher than 3 m and bearing more than 30 green, mature fronds were selected in a forest at Twisk, Tai Mo Shan, Hong Kong SAR on 16 July 1998. Ten random palm trees were used in this experiment and the remaining two trees were set as backup. Eleven green and mature fronds were cut from each of the ten individual palm trees. One of each of the eleven fronds was randomly collected at day O. The other fronds were tied by nylon string to the host to prevent the fronds being removed. The position and location of the experimental fronds (frond baits) were similar to the adjacent naturally fallen fronds on the ground. At each sampling time, one decaying frond bait was randomly collected from each selected palm tree. It was planned to collect decaying fronds at week 1,months 1,2,4,6, 12, 18,24, 30 and 36. However, at month 13, leaves and rachis-tips were found completely decayed and at month 18, mid-rachides and rachis-bases were completely decayed. Therefore, frond baits were only collected on 16 July 1998 (day 0),23 July 1998 (week 1), 17August 1998 (month 1), 19 September 1998 (month 2), 17November 1998 (month 4),21 January 1999 (month 6) and 8 September 1999 (month 13). Collection of frond baits was more frequent at the early part of this study because fungal communities on palm (Livistona chinensis) were recorded to change rapidly at the earlier stages of decay (Yanna et al., 2001b) and a dramatic increase of activities of saprobic fungi was also observed on newly dead leaves of the monocotyledon, Pisum sp. (Dickinson, 1967). 187 Ten samples were retrieved at each sampling time. Thirty centimeter long tip, middle and basal parts of rachis and a ten pieces of leaves were cut and placed individually in separate snap-locked plastic bags in the forest and brought back to the laboratory. Sterile moist tissue was added in the plastic bags to create a damp chamber within the bags. All samples were examined under a microscope within one month, except for the samples collected at day O.In the latter case, microscopic examination was completed within 2 days in order to prevent growth of fungi that were not sporulating on the living fronds when they were cut. Squash mounts of sporulating fungi were made in water for examination with differential interference contrast microscopy. Fungi were isolated by staff of The University of Hong Kong Culture Collection (HKUCC) and the cultures are cryo-preserved at -140 C in HKUCC. Palm samples were also air-dried in an oven at 35-40 C and deposited in the University of Hong Kong Herbarium [HKU(M)]. Details of the fungi (specimens and cultures) are stored in the databases of HKUCC and HKU(M). Naturally occurring samples During the experimental period, naturally occurring fronds of Phoenix hanceana were collected on 17 August 1998, 21 January 1999 and 8 September 1999 for comparison with the frond baits. At each sampling time, a frond which had been decaying for a long time (later stages of decay) and a frond which was recently dead (the early stages of decay) were collected from each palm tree selected for the successional study. Samples were examined and stored as described for the frond baits. Statistical analysis and simple calculation A 3-dimensional correspondence analysis was performed to examine the differences in fungal communities at different times of decay. The fungi recorded on the palm frond parts were also compared with those from naturally occurring samples by correspondence analysis (Booth and Kenkel, 1986; Anonymous, 1995). The fungi found in this study are presented in terms of percentage abundance. Fungal taxa with a percentage abundance equal to or higher than ten are regarded as dominant species. These fungal taxa are plotted to illustrate changes in the dominant species throughout the experimental period. Shannon indices (H') are used to express species diversity of a community (Shannon and Weaver, 1949), whereas species area curves are used to determine the adequacy of the sampling size. Percentage abundance = occurrence of taxon A x 100% of taxon A occurrence of all taxa 188 Fungal Diversity Shannon index (H') = -L Pilog2Pi where Pi is the probability of finding each taxon in a collection Results Determination of adequacy of sampling size The species area curves for each frond part almost reached asymptote because the slopes of the curves were declining with the increase number of sample and at about 10samples the slopes were near zero (Figs. 1-7). Although the curve did not completely level off, the number of samples was large enough to obtain highly representative results. Colonisation patterns on different frond parts Correspondence analyses of fungal communities at different times throughout the decay process are presented in Figs. 8-15. Shannon indices for different frond parts are plotted in Fig. 16 to illustrate changes of fungal diversity throughout the study period. Dominant species at different stages of decay are given in Figs. 17-20. The percentages of abundance for each species are listed in Table 1. The values of Shannon index increased from 1.4-2 at the beginning of the study and reached peaks of about 3.7-4.1 at 120-200 days (Fig. 16). Fungal communities on leaves peaked first (at about 120 days) and were followed by rachis-tips (at about 150 days), and mid-rachides and rachis-bases (at about 200 days). Fungal diversity subsequently gradually declined. The changes of fungal communities on different frond parts were as follows. Leaves There were 44 fungal taxa found on the palm leaves over the experimental period, while three-dimensional correspondence analysis of fungal communities showed that there were at least three distinct communities (day 0, week I-month 1, months 2-6) (Figs. 8, 9). The fungal community composition was distinct at each stage of succession, while dominant species at each sampling time were distinct (Fig. 17, Table 1). Actinopelte sp., Asterina clasterosporium, Everhartia phoenicis, Graphiola sp., and an unidentified discomycete were recorded on green leaves at day O. Everhartia phoenicis was associated with yellow spots on leaves (Yanna et al., 2000), while Graphiola sp. was associated with brown spots. Fruiting bodies of Actinopelte sp., Asterina clasterosporium, and the unidentified discomycete, were formed on thin mycelial mats on the leaf 189 Table 1.Percentage of abundance of fungi found on samples of Phoenix hanceana during succession process in Hong Kong SAR (10 sub samples per sampling time). III I Spe93m6r535m331mmm628811111ct3120251i3rrrrres4r231r2r9rr11bbbbb302755 826rr81rr32411r1ttttt914 49634m51wmmm8r31m1m3t210eooooroennnnnk2811trtttthhhhbh29414612764514 23 d33a33y344027 4433 3333366661133332813 753 5100 3336 3 5 615 47 5 3 ActinopeACltsehKtae.erBBDCsitpelnor.e.lyaptnHprsBnatiyoocneCndllpraiatieiahrfCas.ait)oahenrslorbiPhetaonuaeosgxnempkuiartoiabodfnFrrlinaleicirygucgl.alemaaannwPsaICaieccsSenrlhSCD.aazin.vn.HPaGaeaoHpicuortetsaoughyuzghlla.Hohe&rsseoi&psal1o.f*-urJsaeicfohbrmruinsneBisSopAheoendraatiijrpneorKd&.&iDumR.KJe.H.LiCDta.ysa.rmdmeeHacpayoedsepMo&raiutsEmu.MsBh..a.GJ.n.tWeJnoinnnagetfsu.mAHstarorksnp.haeriella nypae K.D. Hyde CCCCC*Ciyyyyo11rlllld3ciii=innnniinnddddlaoerrrretoooaoravccccilllcelaaaahsidddd;nuiiiitmuuueretlmmmrlma=peradqsbaleciurcmaloahieinpsicgsqiaRoal-uritlnaeiiaeupmsnsmsseb;eJCpe.tErlamMol(.itBuuroTsmar=tag.&yaml&noird,-rachides; rb = rachis-bases. Tab934332m335638ml1e9rr1239363r186r9113b9cb590onIrr1Ittt7inu223mmrmm13mmwmr6rr1et6tt8t5deoorroooe.nnnnnkrm1rtttttbhhb4hhhr12461Ir1Ib9 5I 8 d77ay101 5 613 8 393 3104 9 2 3 33 25 25 DiaporHthuDegihcpetysDhooiFSccehritnnEoyaicohcneWYlsildtas.paoai.ornBm&,rPn.mieauaEKlteKami..ncn&DekicnsK.eopdtrneo.HrDti.rr)u&yo.amdisHdeBHeReorhysi.lpaFad.-htl.eJVeoHeCe.coGnGhali.s..c-otJiahRcef,ociaehload.)aKrt.D.mHryrdbe I EDniYcdtaoynconacalhy,axeKtac.Din.csitHmuysp&dlePeDGxKeor&t.camD(hpSGi.hn.oiHgHohoyluaedglelhase-psli.k&e species DDDEEDDFGvxiiiaiil1ncdpsiesso3ctereylcyocohrmmioltcamaaiasooctrdpiyssctlsipopiaccpuaorhveiomuiatrauremipeaumrhmvsioapapes.seetniotlfilrecovcaagaeirnskamrlaiainitimussY(mi(MacCM(noM.onNBlharaaa.da,stgaskEAWualRsplrih.tasHr.j)o)&.o&RHtS,..eo.J. 20 Species Tab44m434555mmmm573388338385111l0419errrrr646rrr18rr311bbbbb41co3Irr3rrIrI4nIIttttttin9mm6rmwmm1mut0eeoorooodennnnn.krttttthhbhhh14261I day 03 3 19 8 7 339 33 44 '74 52 53 222 11 GuignaSruPdObihraxBaoymrmHdHomo.aoeatamlrhpnksieoosnp)tke.rwpsiScsPaaihalear'ienviacauz.gilgalKmKoobm.a.M(DDoScys.roy.caondeHHtts.ra)yRiyKgcddCPhnne.ePDeau.oteld&.ras.Sitp(HauBEeltsyPs.eot&tBdohrrtekino.o(oGMP.mmpe.a&saaniutJtszooob.srsnlut.pp&esoasrlSmaJa.aEcPrc.bau.ep)TmruaklyeaSll(soeCtpeyrooy,iSoraaykeSrdeat).eSsceh&.poeePdm.oPanSkhiyoeodirmd.ea&s sCpP..rEe.usBsabe. LMLMPNPPaihehe1eonsracolno3iiatemocorcnoodiadaaosnirippgcipphalrtcooyuaahndstpeaamirhaemiippitanuoiaunumpnttutrhsdseemiesaundoinpsamibntiaeorSailsommp(mSSeoiCcg(ayaiWdoo.mdeelr.aduaslaeP(lPlr.Gs(.aS)Sto.ay)hHedeG.u&.))grihfef.s Species Tabm795m42543398mm3653333521l1errrr51r157rrr31bbbb91co3nIrr627Ir4Ir5I3ttttt4in466wmu36mmmmmr22r633222331tt125e51erooooodennnnn.krm21tttttbhhhhh53r12146I2r35b5 7I 3 day 0 9 6 93 310 448 5 63 44 212 2 33 PTuhMboam.Bkaih.atyoESTaspsplhlEoIpoooisl.srrzlpiaeidestCreemslolsmalapeRi.eale(lVofaCfeuor&srtPaSPhidcehdyoRiarBaoelle)ylalmi.notHbCuProosemeY.o.pmpMntoeo.shSMygri.p.ucesmh.eftKto.vasoJaRiralnruararak,c.stvmehh&Jamreie.rcciDra.itahGniir.luliic.omiTmTR(arSe.urioPtd.amrAge(itauEeat.prrmh.sr(lAroSjtMeaara&nscercbhtroie.ceHc)rlarulyu)dil,shaoiBnitud.mcCo.rofokSeuVtt.oGn. RSSPSVTSeptprohoi1Sliooluolecb3aurrsmnheritisodteodlooollsedepaelrpssaeylsmmolriasamriiR&euluablimmplaloavMurmansheitopamnuy(clerPuldu.aazd)teircianuaarvrVssneinu.sc)uarpSuulm(BoeelSEmarin.faClattelucaRi.resm(tiS.MfSa&aueactc(ctEPo.)vneGceaMkrrh)v..B)ie. Species Leaf <> Rachis-tip o Mid-rachis l> Rachis-base x 4.5 - ~ 4- a ~ ..8D ~ - •• --- ;j >r<o3.53 -.- B--,go -.-- .a._..--~-------a----~- - ----""'(r - -'LT- - '0 o ;::, -'_- - - -;::. _ a) ro 2.5 .~ _- 0:,.-::"' _ - ;> bJ) , ~ - .~ ~ 2- • •tfJ 9-- •....•<> <> <> <> f~ ",.. .....• 0.8 ;j 4-c 1.5 - ,' ",.. 8 0 1~ , /' ;j , U 0.5" ~'/ O~--- 2 4 6 8 10 1. Day 0 Number of samples U•;;..>.j•D..•.4.-•...•.~c....... .:aa8•;r.x.))8;o.j~:.j4-brr0;oo~Jcj)8 -1142602--'-- --- ---------- ............ - o [J [J r .~.-1:i -• -.r--~------- ..-~- - O .__ ~ __' . ' - - -- - - --A - - - -=_-.:6-- ----~-----' .- 2.Week1 __ "-<>2 4xA -_.--- 6 -8 --T--~~ 10 Number of samples 25 - •.. 15 20 - 8 ~ ;j ro ~ :: 15 a) ro _ •••_• ~. rr ;> b~J) :;io'"--- u ...... ~ ;j 10 ~ n ••••••4-c "" -.0 lJ. ;j4-c ~,.(. _.._.i'-'--"-.•,".--."--.•-.-.-"-.' -" § 0 5 -r ~ '" ,..-."""" U •,,'"..I,t- .".'""!( - - ••.- -'"" - -",. - -- - --"- - - o 2 4 6 8 10 3. Month 1 Number of samples Figs. 1-3. Species area curves for fungi collected on Phoenix hanceana frond baits at different stages of succession. 194