Observations on the Phenology and Reproductive Success of the Critically Endangered Nervilia nipponica (Orchidaceae) in Kochi Prefecture, Japan

2006·2.2 MB·English

by  Gale, Stephan

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ISSN I346-7565 Acta Phytotax. Geobot. 57 (1) :g1-93 (2006)
Observationson the Phenology and Reproductive Success of the
CriticallyEndangered Alervilia (Orchidaceae)
nipponica
inKochi Prefecture,Japan

STEPHAN GALE" MAEDA and NOBUHITO KUROIWA
'AYAKO
Kbchi Ptzlflact uirmaklino Botanica lGaiden,Godaisan 4200-6. Kbehi, 78J-8125, Jlrpan
Aiervil nimaponica is critically endangered and poorly known throughout it rsange in Japan ,In order to
i]lumina tdeetai lofsthe species' lif heistor oybs,ervations on the phenology and reproductive success
ef two larg epopulation sin Kochi Prefectur weere made from 20e3-2004 .Pattern sof emergence
were comparable and individuals in both population esxhibited a highl ysynchronous phenoleg yTh.e
average individ ufailowerin gperio dlaste d12.3 and 1 1 .0 days respectively at the two sites, and dehis-
cence of frui ctapsules occurred 25.6 and 25,3 days afier flowerin gO.nly 34.29 ,a6nd 28.49 /o6fplants at
the two sites successfully flowered, but rates of seed set were 38.2% and 52.4% despi ttehe virtual
absence ofa nectar reward and the lack ofpellen vectors, probably indicativ eofselfipollination. Thc
failu roefindividuals marked in 2003 to re-emerge, as wel1 as the appearance ofunrnarked individuals
in 2004, suggests that the species has a capacity for dornianc yandlor rapid propagation via the tuber.
Evidence for th¢ latt eir sprovided by the excavation of 89 tubers from 58 individua lrsep,resenting an
average rate ofincrease of 1 .5 per individu apler year .Recommendations are made for ongoing studies
towards the developmen tof a conservation strategy for the species.
Key words: Conservatio nN,ervili anipponiea, phenology, populatio nre,productivc success
Field observations have been highlight eads the Wells & Cox 1991) .Studies utilizing more intensive
primary means of generati nag demographi cunder- monitoring strategies over shorter time frames (i, e.
,
standing ofthreatened orchid species so as to deter- one to two years )are less frequen tin the litera-
mine both conservation status and the lif ehistory ture, though they have been ttsed to reveal irregular
stages that might be limitin gdistributi opno,pulationpattern sof emergence of plants of (2phT:y ssphe-
growth and persistenc e(Trembla y& Hutchings godes Mill ,over a single growing season (Sang &er
2003), Long-term studies (i, es.ev,eral years to Waite 1998), and changes in the partitioni nofg
decades h)ave been conducted on a select number of biomass among differen ptlan tpart sin regenerating
terrestri asp]ecies, primarily in Europe and North individual osf Dactylorhizafasch i(iDruce M)irmeul.
America, in which individuall ymarked plant ser (Lees oetn aL I99I), In addition to emphasizing
permanent vegetation plots are monitored typically the dynamic nature of terrestri oarlchid populations
on an annual basis to provid einsigh tisnt olif ehis- over short timc frames s,uch approaches are likel tyo
tories andVor populatio ndynamics (Tamm 1991, be usefu1 in establishing annual phenology and
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baselin deata on reproductive biology p,anicularly plants were induced to undergo this sequence
fbr rare species abeut which very litt ilse known, through either artificial selfipollination or through
AJlervi lniijazponica Makino is an inconspicuousmanually shaking the plant (an dthereby possibly
terrestria lorchid that has been reported from a lim- dislodgin tghe pollini aonto the stigma), providing
ite dnumber of sites along the Pacifi sceaboard of anecdota1 evidence fbr the role of selfpoltination for
Japan, firo mTokye to the Ryukyus, and Taiwan seed set in situ (Saw a1979). The population
(Masamun &e Satomi 1972 ,Sawa 1979 ,Hoshi & observed in that study fiowere din MaM with leaves
Katsuyama 1992, Su 2000), In Japan, it soccur- being produced fbllowin gcapsule dehiscenc ein
rence is changeable and sporadic with populations June. Elsewhere o,bservations of a small population
typicall ybeing isolat eadnd prone to sudden local on Oshima, Tokyo, were seen to flewe rin mid-
extinctions (fb erxample in Kanagawa Prefectur eT,. May and to have produced leave sby mid-June
Katsuyama pers, comm. and in Miyazaki Prefecturc,(Ogaw a1969) ;the timing ofthe same phenological
T. Minamitani pers .comm.). In addition, most events was similar fbr a populatio nin Kanagawa
reports fbr the species refer to populatio snizes of Prefectur e(Hosh i& Katsuyama 1992),
tens of individua lats most (Suzu k1i955, Ogawa Though these studies provid ea platfbrm fbr
1969 ,Hoshi & Katsuyarna 1992), The small total furthe rresearch, none involve dregular observa-
number ofindividuals and extant sites confirrned for tions of individual lrnyarked plant sto gauge the
the species in Japan have led to N nimponica being relative abundance of individual spassin gthrough
rated as Critical Elnydangere d(CR ;IUCN 2001) at successive phenological stages, the lengt hof key
both the Prefectura (lMakin oMemorial Foundation phenological events, or the fat eofindividuals with-
of Kochi Prefectur e2000, Red Data Book Com- in and between growing seasons. A demographic
mittee of Miyazaki Prefectu r2e000, Kagoshima understanding of the species' phenology and repro-
Prefectu Dreepartrne nftbr Environmenta1 Protection ductive biology might facilita tien the short temn
2003) and national leve l(Environme nAgteanlcy intervenie mneatsures such as establishment ef ex
of Japan 2000), situ collections, supplementary hand pollinations,
Like all members of the genus, Nlervil niiap- seed collection or (fb prarticularl vyulnerable pop-
ponica consists efa subterranean tuber tha tsequen- ulations) relocations, as well as promote more tar-
tially produce sa single fiowerin sgcape and then, at geted research (e. gp,o,pulation genetics ,in vitro
or after seed set, a single cordate lea fwithin a single propagation ,etc,) towards an integrat credcovery
growing season, a growth habit known as hyster- programme in the long term. Moreovcr, whereas
anthy; all above-ground parts (i. , teh.e leaf and peti- most long-ter rstnudies of other terrestri aorlchids
ole) die back over the winter, ln common with othcr have relied on a single annual census, matters are
Linervia(Schlech1t9e1r1), forNervilia by itshyster-
members of section complicated nipponica
the scape bear sjus otne flowe rand elongates during anthous growth habit ,such that rcproductivc and
imctificatien. photosynthet piocpulatio ncsannot be censured on
In the most detaile sdtudy of the species to the same site visit. It therefbre remains necessary to
date, Sawa (1979 re)ports that the flowers of most establish the best strategy fbr long-term monitoring
fiowering individual sat a site in Kochi Prefecture of the species.
did not open widely and that pollinati ownas marked The objectives ofthe present study were there-
by the erect or horizont afllower becoming first fbre :to (i p)rovid edetaile dinfbrmation on the phe-
pendulou sb,efbr eresuming an erect positio dnuring nology and background fluctuatio inn numbers ef
scape elongation. A small number of cultivated Nervilia nim)onica throughout a single growing
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season; and to (i ipr)ovid ebasel] ndeat aon modes of Despite difference sin species composition,
reproduction including flowerin gand frui trate, the habitat sat the two sites are similar in the fo1-
seed productio annd capacity for vegetative propa- lowing respects: (i t)he presence of a thick Ieaf litter
gatio nvia synthesis of new tubers ,a prominent and soils with a high rcd clay content (apparent
featur oef the reproductive biolog yofAfrican mem- from a depth of c. 6 cm), which together generate
bers of the genus (Petter s1s9o9n1) ,The data is high, stable moisture Ievel sin the upper soil hori-
intende das preliminar tyo long-ter mpopulation zons in which tubers of Aiervil iniapponica are
studies and is discusse idn terms of it srelevance to fbund; and (i ia) fores tfieor cast in shade by a
subsequent conservation efTbrts fbr the species. mature, prcdominantly evergreen canopy but
cxposed to a regime of temporally and spatially
Materials Methods
and complex sunfiecks due to the absence of a shrub
laye ror undergrowth direct laybove N nioponica
Stucly
sites patches.
Ofthc handfu 1of sites known in Kochi Prefecture,
two populatio nofs Nervili nainponica were select- Marking and observations
ed fbr study because oftheir accessibility and large All plant sat populatio KnL (n = 524) were marked
size, featur ewhsich facilita rtegeudlar fiel vdisit asnd on 25-27 September 2003 by inserti na gnumbered
permitte tdhe collection ofunusually large data sets stainless steel tag into the ground within 3 cm of
fbr the species. The two populations occur on the each leaf Similarl ayl,l plant sat populatio KnU (n
same southeast-facing slope of a low mountain (2 1 2 - 170) were labeled on 11-12 Octobcr 2003.
m altimde at summit) situated 5 km from the Pacific Irregula rsite visits thereafter in 2003 confirrned
coast of Kochi City .Populatio nKL, the large orf the that both population swere in declin weith all above
two population soc,curs between c. 40-50 m a,s,1. ground part shaving undergone complete senes-
and covers an area of approximately 35 m × 40 m. cence by 6 December 2003. The timing of the
The site here consists ef secondary woodland com- appearance of new buds in spring 2004 was pre-
posed of a mixture of broadleaved eyergreen empted by making dail yobservations of a small
(euerc ugslattca Thunb, ex Murray, Ligustrum number of 2Vervi lnmipaonica plant scultivated in the
J'crponicum Thunb., Camellia juponic aL. and Makino Botanicai Garden. New growth in these
Lithoca}pu gslabra (Thun bex, Murray) Nakai) and plant swas fir sobtserved on 9 Apri1 2004, somewhat
deciduous (Pninus,iamas Saikeub .vexa Koidz. and earlier than plant sin situ at population KL and
Rhus succeclana L.) tree sto 20 m ht ,many ofwhich populati oKnU. In order to avoid trampling in dense-
have resprouted from stools cut back about 50 years ly populate dareas and to allow some plants to be
ago. The second population ,populatio KnU, is sit- used in other associated studies (of flora lbiology,
uated between c.75-80 m a,s,1, and covers an area of seed sct ete.), not all plant swere include idn the phe-
approximately 28 m × 24 m. The site at KU con- nological study: 4 1 6 plant swere monitored at pop-
sists of an abandoned softwood plantatio nof ulation KL, and 86 plant swere monitored at popu-
Cilyptomeri aJ'aponica (L ,fi1. >D. Don and latio nKU.
C7iamaec){pa robitussa (Si eetb Zucc. )Endl. ,which Regular (± weekly) fiet dobservations of
has attained about 17 m ht .Other woody species marked plants commenced on 15 April 2004 and
including Ligustrum j'aponicum Thunb. and continued throughout one complete growing season
Cinnamomum.faponicu mSieb ,ex Nakai have seed- until no plant remained above ground .On each site
ed in. visit, each plan twas observed in turn and assigned
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TABLE1. Phenologica lstages and deseriptio nussed to score plant sin the study.
StagePhase Description
1234 ScapeSeapeFlewerSFclapeewe brud visibl eabove ground, to c.20mm tall.
Flower bud visible beyond (an dfre eofi upper cataphyll. 20-50mm tall.
Flower erect. pedicel visible, sepals partin gslightly te rcveal white petals >.30rnm tall.
Bract visible, flower ± horizonta ls,epals open, petal snot at all, very weakly <t oreveal lip o)r weakly
spreading {t oreveal celumn). 45-] 1Omm tall.
56 FlowerFruit Flower dreopin agt pedice sle,pals and petal vsery weakly spreading or closed, 45-11Ornm tall,
Flower parts closed, ovary s]ightly swollen and scape internode s(partieu ulppaerrmolsty) and pedicel
extending. 50-160mm ta11.
7 Fruit Ovary swellen and hel d±horizont oar lvertically upwards by pedicel ,Yellowish fissur eline saleng
Iength ofcapsule. 80-20emm tall.
8910111F2rultImmature Capsul eburs treleasing many dust-li skeeeds. 80-ZOOmm ta11.
leaf Tap¢ring ligh tgreen leafbud visible above ground, to c. 25mm tall.
Irnmature leaf Leaf involut eor only slightly unfurled, blade and pet{el eindistinc 2t0,-45mm tall.
Immature leaf Petiel eand leafblad edistinc tth,e latt einrcornpletc luynfurled, margin sinuate, 20-60mm tall,
Mature leaf Leafblade fu11y open, usually herizonta lg,reen to deep green ,5 {rare l7y) primary veins, 15-55mm
wide, 15-50mrn long. Petiol eerect, to 80mm long.
1314 Senescence Merc than 1I3 of the leaf area yellow ,secondary reticulate veins visible, petioL ewilting.
Senescence Leaf entirely yellow and no lenger phetosyntheti cp,etiol ecollapsed.
to one ofa sequence ofdiscrete stages according to part of the phenelogical study, they were marked
it sphenological state. Each stage was delineated and counted in August 2004 ip an assessment of
throug hongoing fiel odbservation, complemented by demographi cchange from 2003-2004 at the two
frequent in
more monitoring ofplants cultivation at study sites.
the Makino Botanical Garden, Notes were also Tb gain a bette urnderstanding of the develop-
made on plant asffected by herbivory or other stress, ment ofbelow-ground parts over one growing sea-
as well as those that withered prio rto completing a son, 4 plant snot involve din the phenological study
particul pahrenologjcal stage. Whenevcr possible,were excavated from the soil every fourt hsite visit
observations at both sites were made on the same (17 June, 15 July, 12 August, 21 September and 2
daM though due to practica l]imitatio snosme site November) at KL. In addition, unavoidable con-
visits ( 11 ofa tota lof 30 per population) were car- struction work at KL facilita ttheed excavation of
ried out over two consecutive days. indiyidu apllants at twe microsites (constituting
Notes on the presencelabse nofciensect visitors two patches of Nervili anipponica) on 15-21
were made in the course of site visits during the November 2004. The number of tubers recovered
flowerin sgeason, The production ofnectar by flow- per marked individua lwas recorded at both
ers oflVeivitia nipponica was checked by dissectingmicrosites in an assessment of the species' potential
5 flowers under a binocular mjcroscope, The num- fbr clonal reproduction,
ber in fi;uit
ofseeds contained a single was estimated
by dissectin g5 ripe pods under low power magni- Results
ficatio annd counting the contents against a squared
paperbackground, A total of 14 stages were recognised to score plants
During the monitoring period, leaves which on each site visit (Ihb l1e; Figs. 1, 2 & 3). These
had been in2003 describ6e (scape,
not marked appeared above successive phenotogica] phases
ground at both populatio KnL and populatio KnU, flower f,rui ti,mmature leag mature leaf and senes-
Though these plant swere not observed regularly as cence) covering the complete above-ground phe-
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FIG.l . Phenelogy ofNervilla n4zponlcalscape and flower .(a )Stage 1. (b)Sta g2.e (c )Stage 3.(d) & (e)Sta 4g,e(D Stage 5,
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FIG. 2. Phenology ofNervilia nmponica: fnit .(a )Stage 6. Cb )Stage 7. (c )& (e )Stage 8.
nology oflVervilia nijzponica. 3-5) commenced two weeks latc ron 6 May and
continucd unti1 1 June, a perio dof 27 days. The size
Phenology of the fiowerin pgopulation peaked on 15 May at
Fig. 4 shows the composite number of individualspopulation KL (n = 79) and on 16 May at popula-
fa11i nignt oeach of these phases at populatio KnL tion KU (n = 16) .Fructificat (iosntag 6e-s8) com-
and populatio KnU throughout the monitoring peri- menced on 25 May at both sites, and all fruiting
od. Buds ofnew fiowering scapes (sta g1) ewere first individual shad gone to seed by 17 June at popula-
observed at both sites on 22 opri F1l.oweimg (stagestio nKL and by 25 Jtme at populatio nKU, [[hu simit
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FIG. 3. Phenology o and senescence. (a )Stag e9. fo S)tage10 (.c S)tage 11.(d) & (e )Stage12. (D Stage 13.
(g )Stage 14.fNlervilianijzponica:leaf
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Z50
-Scapesu
Flower

waFruitwa

200 ImmatureIeaf

MMature leaf

ifSenescence

150
e:.syptigodZ
1OO
50
o
1OO
se
oM
J J A S N D
Menth(2e04)o
FiG. 4. Above-ground phenology of two population sofNepvilia nmponica in Kochi Prefecture, Japan.
maturation and dehiscen coeccurred over a period ef observations also permitte cdalculation of the aver-
24 days at population KL and 32 days at population age lengt hoftime a single plant spends in any one
KU. Ncw leaf buds (sta 9g) ewcre fir sotbscrved on key phenologic aplhase (Tab 2l)e.
6 May at populatio KnL and on 25 May at popula- The numbers ofmarked plant tsha tre-emerged
tio nKU, and most plant sat both sites had developed in 2003 at either site as fiowers ,leaves or both are
into mature leave s(sta g1e2) by 8 July .Leafing given in [Iltb 3l. eIn addition to the plants marked in
populatio npseaked on 22 July at both population 2003,atota lof353 and211 `new' plants appeared
KL (n = 207) and populatio nKU (n = 65); both respectively at populati oKnL and populati oKnU in
populations were in decline after this date. 2004.
Senesccncc was apparcnt at both populatio nKL
and populatio KnU from 2 October ,and all leayes Repioductivesuccess
had died and disappeare adt populatio nKL by 3 Of the total marked populatjo nobserved above
December and by 6 December at pepulation KU. ground at population KL andpopulation KU, only
Since all plant swcre individua lllaybele dth,e repeat 89 (34.2 a%nd) 21 (28.4 %p)lant rsespectively actu-
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TABLE 2. Average length sofkey phenologica plhases at the two rates (fb trhe wholc population )of 16.99 /an6d 8.1%
sonttuody ssuibtseesq ,uOennlty tshtoasgee pwelraent istnhactl wuerde eid sn etenhe tcoa lccounlnaitniuoen respectively. During the course of the present study
(numbe rofs plant sused to calculate average given in no insec tpollinator swere observed on flowcrs of
parentheses). IVervil iniapponica at either site, and only minute
Length in days ±SD (n) amounts ofnectar were fbund in dissect efdiower (sri
nz KU = 5) harvcst ferdom plants nQt inyolve din the phe-
Scape (sta g1 e- 2) 8.6±1.9 92 ±3.4 nological study (da tnoat shown). Thirty-fou prlants
(47)12.3 (11)11.0
Flowcring (sta g3 e- 5) (3 ±93).196.9 (1±31).168.5patr poodpuucleadt iseoend -KbIea.r ianngd 1 1c appslualnest sa tw hpicohpu ldaethiio sKncUed,

Fructificati (onsta g6 e- 8) ±3.7 ±4.5 reprcscnting fruiti nrgates of 38.29 ,a6nd 52.49,6
(34)25,6 (ll)25.3 Five but
respectively. ripe non-dehisced capsules
E(nsdt oaf fg5l ee-we r8i)ng to dehiscence (2 ±66),233.3 (1 1±)5.203.0 were found to contain approximately 1540, 1780,
Immatureleaf(stag9e- 11) 10,6 9.1 1950, 2100, and 2180 seeds respectively. These
± ±
(67)90.4 (28)96.3 figure sare underestimates becaus esomc ofthe dust
Mature leaf(stag e12) ±21,6 ±23.4 seeds were unavoidably los twhen opening and
(78) (33)
moving thc capsules.
Segmentcd runners which extended ± hori-
ally fi(rwer e(dstag 3e tso 5). The maximum number zonta11y from the subterranean stem above the tuber
ofplants observed in fu1 1anthesis (sta 4g) eon any began to develo pon all leafi nigndividu aelxasmined
one site visit was 44 at populatio nKL and 6 at (n = 4) in mid-June. Between 2-4 runners were
populatio nKU, constituting fiowerin gsynchrony observcd per plan texcavated in mid-July (Fi g5,(a)).
a
'ge
{ 1･ .･ ･
li

ivge
....di---"kts

A'tde' ptg''s/si"
,,,.p,',V'
:.iiY}nti.ll,pVniFpTHaimsgpt!nlvmglli.fttliTnltt'ivfitlwhieqf}llF}"illSIFaiiftliTttl'
.itifi'
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- .
FIG. 5. Subterranea npart sin JVbrvil iniapponica, (a )Four rLmners extending lateral lfyroi nthe subterranean stem (1 5July 2O04), (b)
tcrminal intemodes ofrunners enlargmg to form daughte truber s(arro wl2s A;ug. 2004) ,(c )Daughter tuber with bud Carrow)
at apex opposite attachment to severed runner (2 1Nov. 2004), Fine increment sin (a )(,b )and (c )= 1 mm.
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TABLE 3. Number ef plant msarked in 2003 tliat falled te re- firs otf the two microsite s4,9 tubcrs wcre rccovereq
esntiuedryge ,pe eriineordg eidn 2 0ase 4f, iNouwmebres r,lsea yien s p,oaTr ehnotthh edsuer sidnegn tehtee representing an average rate ofincrease of1.5 per
percentage osf the tota1 monitored populati (otnet a= l41s6 individu aAlt. the second microsit e4,0 tubers were
plant sat populatio nKL, 86 plant sat populatie nKU). rccovered, als orepresenting a rate of increas oef1.5
PopulationKL per individn aTlhe.se observed rates of clonal regen-
Leaf+
eration fa1 1short ofthose predicted from the abovc
156(37.5%) 162(38,9%) observations of runner production.
Flowcr
37(8,9%) 61(14.7%) HerbivoT: aynd stress
+ The nunibers ofplants eliminated from either pop-
ulatio dnue to herbivor oyr other stress at successive
inFig.6.At
phenological stages are given popula-
PopulationKU tion KL, 49 plant sthat produccd scape buds (o af
Lcaf+
tota lof 98, 50%) were prevente dfrom potentially
12(14%) 4S(52,3%) setting seed dne to herbivor Ay. funhe r1 5 withered.
Flower Similarl y1,8 of the 29 plants (62.1 %t)hat pro-
s(5.8%) 24(27.9%) duced scape buds at populatio nKU were lost
+ through hcrbivor pyrio rto seed set. All plant snot
afTected by herbivory at populatio nKU success-
fu11y set seed, i.e. ,none withered prio rto dehis-
By mid-August, the runners had attained length sof cence. Larvae of the moth Ercheia niveostrigata
2-15 cm, and daughte rtubers had begun to fbrrn at (Lepidopt Neorcat:uidae )were found feedin gon
their tips threugh radial enlargement of the apical- the scapes of 1 1 plant sat populatio KnL and popu-
most 1-3 internod ewisth reduced latcr aexltcnsion latio KnU
,
(Fi g5.(b)) .Thc ncw tubers continued to enlarge Only 82 ofthe 223 plant ast populati oKnL and
in September ,and had attained diameter sof <2- 34 plants of the 69 at population KU that produced
5.5 mm by early November. A single conical bud leaf buds (sta 9g)e were seen to complete the grow-
had develope dat the apex (i, eop,po,site the attach- ing season through senescence (sta g1e3 sand 14).
rnent to the runner) on some tubers by late One hundred and sixteen leave s(52.0 a%t )popula-
November (Fi g5(.c)) .It is inferre tdhat the stem tion KL and 26 (37.7 %at) populatio nKU were
develop sfrom this bud the fbllowin ygear .As plants prevented from doing so through herbivor yT.he
began to senesce from Octobcr, the runners also remainder were eliminated through stress eithcr in
degraded ,leavin gthe new tubers as independent long dry spells (nota ibnl Jyuly-August o)r, by one
units. These observations suggest tha ta single plant ofseveral severe typhoons (i nSeptember-October).
might produce up to 4 new tubers over a single The main herbivor oens leave swere unidentified
growmg season. moth instars.
in mid-Novembeg 32 and 26 plant osf IVervilia
nipponica were excavated respectively at the two Discussion
microsites at populatio nKL. As most plants had
already senesced by this time, pctiole asnd runners Plant sat both sites underwent a predictab sleequence
were mostly absent and individua tlubers were ofphenological developmen twith the two popula-
fbund in the F, H and Ai strata of the soil. At the tions showing a highl ycomparable trend in the
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