Table Of ContentBLUMEA 41 (1996) 223-230
Capparis buwaldae Jacobs (Capparaceae).
A new Myrmecophyte from Borneo
U. Maschwitz K. Dumpert J. Moog J.V. LaFrankie & I.Hj. Azarae
Summary
Capparisbuwaldae,aclimber ofprimary forestsendemic toBorneo,is amyrmecophytewith stem
domatia.Thestemsbecome hollow by pith degenerationanddevelopovalopeningsallowingants to
enter.Theseopeningsarelocalized atastrictly defined areaabovethe insertion ofthe leaves and a
pairofnodal thornystipules. Theygraduallysplit openfrom theoutside.Theopeningsmay develop
intoelevatedchimney-like structures orcloseagain bygrowthifnotkept openby ants.
Theplant may beinhabited byvariousopportunistically nestingarborealants includingCremato-
gaster,Monomorium,andCamponotusspecies. Specializedmyrmecophytic antscould notbefound.
Neither nectaries,norfoodbodies,nor trophobioticendophytichomopteranscould beobserved. In the
Rijksherbarium, Leiden 65 otherCapparisspecies and subspecies from the Indo-Australian region
were examined forant-plantcharacters.Noneofthese speciesshowed anymyrmecophytic character.
Introduction
Inlatteryearsin SoutheastAsia anincreasing numberofdomatia-forming non-epi-
phyticant-plants havebeen discoveredinvarious families.Highly evolvedsystems
came to light withspecific partner ant species biting entrances into their domatia
(Maschwitz et al., 1989, 1991;Moog & Maschwitz, 1994,and unpublished results),
as well asmore generalistic ant-plants whose domatiaare opened by theplant itself
through growthprocesses, giving access toa varietyofopportunistically nesting ar-
boricolousants (Maschwitz etal., 1992, 1994a,1994b,unpublished results). In the
lastfive years atleast 19plantspecies from 10generain 8 angiosperm familiesprov-
edto benew ant-plants. Therefore, thenumberofknown Asiannon-epiphytic ant-
plant generais nearly as large as thatoftheNeotropics (32 versus 39) whichuntil
nowwas thought to beby farthelargest oftheworld (Davidson & McKey, 1993).
During an excursion through Sarawak (East Malaysia) we came upon a further
new ant-plant which belongs to the second association type. For thefirst timewe
becameattentiveto its myrmecophytic characterbecausethestemoftheplant speci-
men was severely damagedby arodentina characteristicway whichcan frequently
beobserved inspecific Asianant-plants likeMacaranga andNeonauclea(unpublished
data).Recognizable by thetracesofitsteeththisanimal(possibly a tree rat orsquir-
rel) hadtorn upthehollowplantstemrepeatedly inasectionofhalfametre. Similar
tracesofdestructioncouldbeobserved in5otherplant specimens.
1) Zoologisches Institutder J.W.Goethe-Universitat,Siesmayerstrasse70, D-60054Frankfurt am
Main,Germany.
2) Center forTropicalForestScience,InstituteofEducation,Singapore.
3) University ofMalaya,DepartmentofZoology,KualaLumpur,Malaysia.
224 BLUMEA —Vol. 41, No. 1, 1996
Fig. 1.Capparisbuwaldae Jacobs,habitofthe upperpartoftheplant.
Maschwitz,Dumpert,Moog,LaFrankie & Azarae: A newmyrmecophytefromBorneo 225
MATERIALSANDMETHODS
Eightspecimens ofCapparis buwaldaewerefoundinLambirHills NationalPark, an
undisturbedmixeddipterocarp lowlandforestnearMiriabout100mabove sealevel.
They grewon aridge in adenseand dark undergrowth ofshrubs, tree saplings, and
palms. IntheRijksherbarium (Leiden) specimens ofC.buwaldaeas well as other
Capparis species fromtheIndo-Australianregion wereexaminedforpossible ant-
plant characters. Driedspecimens ofC. buwaldaehavebeen deposited in theper-
sonalcollectionofJ. Moog; later, they willbehandedover totheRijksherbarium at
Leiden.
RESULTS
Capparis buwaldae(Capparaceac) is a climber2-15 m long (Jacobs, 1960,1976).
Thefirstspecimen foundby us, whichwill be described inmore detail, was a deep-
rooted, erect, woody, green-stemmed plant 1.5 m high,whichwas originally broken
offata height of0.65 m(lower part)andhadformeda newshoot0.86m high,with
21 leaves inthe upperpart and 3 small sidebranches. The leathery, short-stalked,
lanceolateleaves(length = 18.2± 2.2cm,width=3.7±0.5cm) withawater drain-
ing tip(Fig. 1)were growing inawhorl. Theleaves were sittingbetweentwo small
thorny stipules which wereslightly pointing downward.Insteadofaleafsometimes
apeculiar thread-likegreenappendage was found,0.2-1 cm long (Fig. 3a). About
3mmabovetheinsertionofleavessidebrancheshad developed.
Ant-plant characters
The stem did not form any distinct internodaldomatiaswellings but was hollow
as awhole. However, itsupperregion was rather wide.The cavity was developing
by degeneration ofthestempithintheupperparts, i.e., thepithbecamefragmented
intothin,lamellous, translucent, whitishdiscs(Fig. 2). Thelowestandoldestparts
ofthestem,5-6.5mmindiameter, were solid.With increasing height and diameter
Fig.2.Pith degenerationinayoungshootofCapparisbuwaldae Jacobs. Scale bar= 1mm.
226 BLUMEA Vol. 41, No. 1, 1996
Fig. 3.Stagesofstomadevelopmentin Capparisbuwaldae Jacobs (fromatof).a. Stomaless node
ofa shoot;instead ofaleaf afathom-like green structure has developedbetween a pairofthorny
stipules; b. still closed young stoma; c& d.developingstoma;e. elder stomaopening, kept open
by antinhabitants;f.unused stoma, closedagainbycallus growth.
ofthestemthecavity was developing, measuring from4mm(stem diameter11mm)
to6.5 mmin width(stem diameter 10-11 mm in theupper stemregion). In most
hollowsections ofthe stem,wall openings (stomata) occurred. Theirdevelopment
couldbe observedbest inthe upperstem part(Fig. 3). The openings were located
about2-3mmabove themiddleoftheconnectionlineofthetwo thorny stipules,
i.e., atthe same position wherealso the small side branchesoriginated. In some
casesneitheranopening nor abranch haddeveloped. Theyoungeststillclosed open-
ings consistedofsmall greenring-shaped bulges onthegreenstemwith awhitish
centre (Fig. 3b). Inthis centre,beginning fromtheouter surfaceatiny, oblong, slit-
likegroove(at firstonly visiblewith ahand lens) developed successively. Finally,
theslitbrokethrough into theinteriorandformedasmall opening (Fig. 3c), which
successively became larger(Fig. 3d). One such open oval stoma(1 mmlong,0.3
mm wide) couldbeobservedin theupperleafy partofthe new shoot. Inthelower
leafy partbothstillclosedstomata and3 fullyopenholescouldbeobserved, theup-
peronewas 1.2by 0.85mmin diameter,themiddlestoma hadatinybutrecogniz-
Maschwitz,Dumpert,Moog,LaFrankie & Azarae: A new myrmecophytefrom Borneo 227
ableholeandtheloweronewas 0.6by 0.35 mmindiameter.As faras not destroyed
by the predator very obvious stomata couldbefoundalso in the loweroldpart of
theplant. They consistedofchimney-like elevationswiththick crater-likebulges and
a centralhole(Fig. 3e). The largest elevationmeasured 10mmin length, 9mm in
width,and3 mm inheight. Its holemeasured2 by 1 mm. Aslightly smaller second
stomawas openas well,whilethreeothershadclosedagain byplant growth(Fig. 3f).
Possibly, theants which hadinhabitedthestem priortoits partial destruction(and
ofwhich only nest remnants andunidentifiableparts were left) hadkept open both
holes.
Similarlargestomata whichwerealso partly closedby growth were foundinthe
lowerpart ofasecond plant(0.95 mlong). In itsupperpart thedevelopment ofnew
stomatacouldbeobserved as describedabove.
The third plant, 1.3 mlong,also hadbeenpartly destroyed atleastthreetimes.
Here,too,large holescouldbe observed, partly atthenormalsitesabovethethorns
andpartly atother sites, which apparently had beenproduced by gnawing ofthe
predator andkept openby ants duringsubsequent regeneration ofthestem. Judging
fromnest remainsin thestem interiorthis plant had been occupied by ants, which
hadkept open theholes but laterhad disappeared. A youngsideshoot was thinner
thanthemainstem (11 mmmaximum)buthollowas well (5.5-7mm outerdiameter
withhollowwidth2.5-5 mm).Betweenthecavitiesofthemainoldandyoungshoot
therewas ashortsolidstemsection. Thisshoothadneverbeeninhabitedby ants.
We couldobserve neithernectariesnor foodbodieson thesurfaces ofleavesor
stems.
Fivefurtherplants withatypical lianashape couldbefoundduringasecondand
thirdvisit atthesame site. Theplants all showedthesametypical ant-plant charac-
ters. They were climbing on trees orgrowing along the ground and were 6,5, 3.5,
3, or 1.6 m long. All showed hollow internodesandthe stemsoffourplants were
partially tornopen, presumably by arodent,intheway describedabove.
Ant inhabitants
Inthefirstplant, which appeared tohave been initially inhabitedby acolony of
dolichoderineants (Tapinoma sp.?), smallMonomoriumworkers were found. The
secondplant was colonizedby a groupofbroodlessworkers ofalargeCrematogas-
ter species, whosemainnestwithqueenandbroodprobably was locatedelsewhere.
Inthethirdplant only antcolony remnantsbut noliving antswere found. As already
mentioned,theformerantinhabitantsappeared tohavebeenpreyedupon bythepred-
ator(possibly arodent). Though antless, thisplanthadproduced new entrances atits
young shoots. Thefourthplant, 1.6mlong, was inhabitedby aCrematogaster spe-
cies as well. Thenest entrances witha diameter>3mmdifferedfromtheotheropen-
ings by being protected witha 'carton' cover builtby theants.These'carton' covers
showedsmall roundholes (diameter 1.5 mm), big enough to allowtheantsto enter.
The hollowstem interiorwas separatedintoseveral compartmentsby 'carton' walls.
All internodesofa youngsidebranch, 1.2mlong and withstill unopened stomata,
were hollowbutnot colonizedby theants.
Ofall fourplants withdamaged stemsonehadbeen abandonedcompletely by its
ants whiletheintactstem sectionsoftheremaining threewere inhabitedby ants. One
228 BLUMEA —Vol. 41, No. 1, 1996
was occupied by acolonyofpolymorphic Crematogasterandtwoby coloniesoftwo
Camponotus species, oneofthembelonging to thesaundersigroup,whoseworkers
burstwhengripped withthefingers.
All eightstudy plantslackedtrophobiotic homopterainthesteminterior.Noneof
theplant specimens showedany signs ofcolonizationby aspecific ant.
Herbariummaterial
IntheRijksherbarium atLeidenwecouldcompareourplant samples with10Cap-
parisbuwaldaespecimens collected inBorneo.Inallaspects oftheirouter vegetative
morphology, i.e.,ofstem, thorny stipules, andleafstructures,no differencestoour
plantscouldbe detected.Allotherspecies oftheregion differclearly fromCapparis
buwaldaeinvegetative characters.
Only 4ofthese 10specimens oftheLeidenherbariumwere largeenough indiam-
eterto allowa meaningful investigation forant-plant characters. Oneofthesefour
plants showedstem structures which weresimilar tosecondarily closedstomata,in-
dicating apossible myrmecophytic characterofthisplant. However,itsstem, aswell
asthestemsofthreeotherplants, were solidatthecutting site.
In theLeidenherbarium65otherCapparis species andsubspecies fromtheIndo-
Australianregion wereexaminedforpossible ant-plant characters. Twelve ofthese
species wererepresented by 18or more specimens each, anumberwhich may be
regarded sufficienttodecideifa myrmecophytic characterwas present.Noneofthe
species checked showedany sign ofant-relatedstructures such as domatiaorpre-
formedentrance holes: C. callophylla Blume(18 specimens), C. cantoniensisLour.
(45), C. floribundaWight (24), C. lanceolarisDC. (41), C. lucida(Banks exDC.)
Benth.(19), C. micracanthaDC. (121), C. pubiflora DC.(71), C. pyrifolia Lam.
(44), C. quinifloraDC.(35), C. sepiaria L. (55), C. zeylanica L. (62), Ci . zippeliana
Miq. (29).
DISCUSSION
Capparis buwaldaeisthe firstmyrmecophyte foundintheCapparaceae. Theants gain
access to thecavitiesinthestemthrough spontaneously formedshortslit-likeopen-
ings whichbecomeovalwhenenlarging. The smallsize andthecompact designof
theopenings apparently does not compromise thestability ofthestem. They soon
close again when not used or strengthen theirstability by growth whenkept open
by ants.Generally, stemstability appearsan importantfactorindomatiaevolution.
Neglected till now, ithas tobetakenintoaccount infutureinvestigations andreflec-
tions.
Theexaminationofherbariummaterialindicatesthat theformationofstomata is
restrictedto C.buwaldae,all theother65species checkedare devoidofsuch struc-
tures(although for somespecies, including C.buwaldae, the sample sizes were
small).
In SoutheastAsiasimilar spontaneously formedstomata areknown tooccur in
speciesofvariousplantfamilies:Myrmeconauclea strigosa (Rubiaceae), severalZanth-
oxylum species (Rutaceae), Ficusobscura var. borneensis(Moraceae) andCleroden-
Maschwitz,Dumpert,Moog,LaFrankie& Azarae: A new myrmecophyle fromBorneo 229
drumfistulosum (Verbenaceae) (Maschwitz et al., 1989, 1992, 1994a, 1994b). All
theseplantsare colonizedby avarietyofnon-specific ants.Hostspecificity is not ex-
pected tobestrongly developed since manydifferentantsareableto colonizethestem
ifan entrance holeisprovided by thehost-plant. In contrast,ant-plantswith (moreor
less) specialized ant tenants,forinstanceAmericanCecropia, Triplaris,AfricanLeo-
nardoxa andAsianMacaranga, form atmostweak spots in thestem wallsthrough
whichthecolony-founding queenspenetrateintotheplantcavities. Only few ant spe-
cies are ableto tunnel entrances into living plant tissueand thus donot depend on
herbivorousstem boring insects toestablishprotected permanentnest sites in living
plantparts. Such traitsin colony-founding antqueens, whichlead tohost specificity,
cannot develop or will be lostifpreformed stomata permit thecolonizationofthe
host-plant by opportunistically nesting non-specific ant species. In C. buwaldaewe
expectto findspecies offurtherantgeneraas regularinhabitantsofthehollowstems.
Theant species foundin C.buwaldaedidnot cultivate homopteran trophobionts
insidethestems. Otherfoodsources fortheantslikenectariesandfoodbodiescould
notbeobserved.The absenceofanyobviousfoodrewardsuggests thattheants have
toleavetheirCapparis hosttoforage. Davidson &McKey (1993) discussedinMyr-
meconaucleathepossibility ofnutrientaugmentation by theants.Thestorageofre-
fuse andfaecesin thedomatiaby theants couldconcentrate nutrientswhich, ifthey
couldberesorbed, wouldenhance hostfitnessin nutrient-poorenvironments. At
present, evidencefor suchapositive effectto Myrmeconauclea orCapparis by their
inhabitantsis lacking.
InSouthAmericathesubtropical shrubCapparis retusa possesses nectariesandis
oftenvisitedby nectarivorousants.Forexample, oneofthesenectary visitors, Cam-
ponotus blandus,whilenot nesting inthis Capparis species, nonethelesslowersthe
level ofleafdamageinflictedbytheleaf-cutting antAcromyrmex (Farji Breneretal.,
1992).
In somecases, myrmecophytism canbe detrimentalto thehost-plant becauseof
damage doneby destructivevertebratepredators ofantbrood. Damage tomyrmeco-
phytes by woodpeckers and mammalswas often observed(Davidson & McKey,
1993;Maschwitz etal., 1994a). In C.buwaldaewe recognized thesame phenome-
nonpresumably causedby arodent. Six out ofeight plants found(=75%) showed
damaged stemparts. Similartracesofdestructionwereobserved inhost-plants ofthe
myrmecophytic ant genusCladomyrma, i.e., inNeonauclea,Drypetes, andinSaraca
(unpubl. results). Somepredators seemto learnwheretofindtheantprey sincemost
otherhost-plants inthevicinity suffereddamageas well.Butwhiletheproportion of
damaged plants in apopulation appearstobe ratherlow, the impact of vertebrate
damage onthemaintenanceofmyrmecophytic associationsis not easily assessed.
ACKNOWLEDGEMENTS
Wearegratefultothe directoroftheHerbarium /Hortus Botanicus,Leiden,Prof.P.Baas,foraccess
totheherbarium material. Wethank Mr. K.M.Kochummen andDr. L.G.Saw foraccess totheher-
barium attheForest Research InstituteMalaysia(FRIM) atKepong, Malaysia, and for theirkind
helpwith plantidentification.R.Klein and an anonymousrefereeprovidedmany valuable comments.
This study wassupportedbytheDeutsche Forschungsgemeinschaft(DFG).
230 BLUMEA —Vol. 41, No. 1, 1996
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