The species of Walsura and Pseudoclausena genus novum (Meliaceae)

56 Pages·1994·10.4 MB·English

by  Clark, T P

BLUMEA 38 (1994) 247-302
The species of Walsuraand
Pseudoclausena genus novum (Meliaceae)
T.P. Clark
DepartmentofPlant Sciences, South ParksRoad, Oxford0X1 3RB,U.K.
Summary
The Indo-Malesian genus WalsuraRoxb. isrevised andthecloselyrelatednewgenus, Pseudoclausena,
issegregatedfrom it.Walsura consists ofthree sections ofwhich one(Ruswala) isnewlydescribed,
and thirteenspeciesofwhich three (W. dehiscens, W.pachycaulonand W.sarawakensis) arenewly
described. One new combination is made (W. trifoliolatasubsp.acuminata).The Malesian genus
Pseudoclausenaconsistsofonespecies (P. chrysogyne),formerly Walsurachrysogyne, and W. ve-
lutina isreduced toanewformaofit.Asummary ofthe taxonomic history ofthe species is given.
Notesonmorphology(includingmicro-features ofthe leafsurfaceandpollen),wood,fruitand seed
anatomyand chromosome andchemotaxonomic studiesare included andseed dispersalsystemsare
considered. Variation within the genera and speciation and biogeographyare discussed. Noteson
economicbotanyaregiven.All speciesaredescribed andakeyispresented.
Introduction
Sincethelastmonographic treatment(De Candolle, 1878)ofthespecies includedin
thisrevision something in excess of95%ofspecimens currently availableforstudy
havebeencollectedand72% (i.e.28 out of39)specific names havebeen published
withinWalsura.Of these new species, manywere published with littleattemptat
comparison with previously describedones, hence synonymsabound. Of the four-
teen species recognised here, threeare newly described, and(forthisrevision) five
havebeenstudiedin thefieldandflowering materialofone(W. dehiscensT. Clark)
wascollectedforthefirsttime.Inthelightofinfraspecific variationdemonstratedby
materialcollectedsinceDeCandolle'srevision, five ofhistwelvespecies have been
or needtobe reduced, andhis key to thespecies is foundtobe largely basedon in-
accurately describedcharacters (which in some cases could havebeen avoidedby
closeexaminationofany specimen ofthespecies concerned). All ofthis, together
withtheremovalhereofseveralspecies toanewclosely related genus,necessitatesa
newmonographic treatment,so thatmaterialmaybecorrectly identifiedandtheaffini-
tiesandrelationships ofthespecies beunderstoodmoreclearly.
Theproblem of generic delimitationin the TrichiliaP. Browne(Africa & New
World) - Heynea Roxb. ex Sims (Asia) - Walsuracomplex is an old chestnut in
meliaceoustaxonomy.Heynea has always been distinguished from Walsuraprinci-
') Part ofathesis successfully submitted forthe degree ofD.Phil, in the University ofOxford
248 BLUMEA Vol. 38, No. 2, 1994
pallyon thebasis offruitdehiscence, andusing thesamecharacterBentvelzen(1962)
reducedHeynea to Trichilia, its species becoming T. connaroides(W. & A.)Bent-
velzenand T.sinensisBentvelzen.Inthispaper, forconvenience, thesespecies will
bereferredtoasHeynea spec. Theproblems ofgeneric delimitationintheTrichilieae
havebeeninvestigated using an assortmentofmacro- andmicro-morphological and
anatomicalfeaturesand this whole question (Clark, 1990) will be dealtwith ina
separatepaper.Ithasbeen concludedhoweverthatWalsuraand anew genusbased
on W. chrysogyne arequite distinct generawithinthe tribe(see below).
Wherethe term ‘W. chrysogyne etal.' isused belowitrefers collectively to the
formerly recognised species W. chrysogyne, W. brachybotrys, W. celebica, W. gla-
bra, W. borneensis, W. hosei, W.palawanensis and W. velutina.ThetermWalsura
sensu stricto referscollectively toallotherWalsuraspecies.
TAXONOMIC HISTORY
WilliamRoxburgh describedthe genusWalsurainFloraIndica (1832), having in-
validly published thenamein his HortusBengalensis (1814). In 1832, heincluded
only two species (W. piscidia Roxb.and W. robustaRoxb.). The genustherefore
appeared justtoo lateforincorporation inAdriendeJussieu'srevisionofthefamily
and itsspecies thenknown, published intoto in 1832. Jussieudid howeverpublish
(1830) anew species ofHeynea (H. trifoliolata) andit was not until 1940that its
synonymy with W. piscidia was pointed out (by Harms). Walsurarobusta was re-
movedfromthegenusby Roemer(1846) to anew genusSurwala, butwas reinstated
in WalsurabyHiem(1875)whereithasremained.
Walsurapinnata was described by Hasskarl from Javain 1855andW. gardneri
by ThwaitesfromSriLankain1858.Clausenachrysogyne, described by Miquel in
theRutaceaein1861,was transferredto Walsuraby Bakhuizen f.(1968) as the cor-
rectnamefor thewide-ranging andhighly variablespecies W.multijuga King(1895).
Walsura trichostemonwas also describedbyMiquel(1868) andKurz(1875) reduced
Wallich's unpublished W. villosa intoit, though DeCandolle(1878) chose tokeep
thesetwo species separate.
Thenfollowedtwo importantregional floristicaccounts. Hiern in J.D. Hooker's
FloraofBritish India(1875) keyed outand describedeight species ofWalsura (in-
cluding W. tubulatafrom Sikkim as new) and Kurz in his ForestFlora ofBritish
Burma (1877) didthesameforseven species,butalso illegitimately reducedHeynea
Roxb.ex Sims (one species) tothe genus. Walsuraoxycarpa Kurz, fromtheAnda-
mans, was also first describedin 1875. 1878saw thepublication ofCasimirdeCan-
dolle'sepic species revisionoftheMeliaceaeinwhichhedescribedandattemptedto
key outtwelvespecies of Walsura, including onenewspecies (W. thwaitesii)I.Harms
(1896, 1940) gavea description ofthegenusbut little or noinformationonindividu-
alspecies, andin theearlierwork follows Kurz(1877) in including Heynea (at sec-
tionstatus) butreinstateditas a distinctgenusin 1940.
Since 1895, severalspecies names havebeenpublished (see synonymies below),
particularly based onmaterialfromBorneo, southeasternIndo-ChinaandthePhilip-
pines. Only threeare maintainedin thisrevision, namely W. bonii Pellegrin (1910)
T.P.Clark: Species of Walsura and Pseudoclausena genus novum 249
and W.poilanei Pellegrin (1944), bothfromVietnamand W. monophylla Elmerex
Merrill(1954, published invalidly by Elmerin 1937) from thePhilippines.
Pennington (1965) gives thefullestdescriptionofthegenus(butnot species) to
dateandincludesobservationsofwoodstructureandpollen morphology. Pennington
andStyles (1975) inthemostrecent generic monographof thefamilyhaveaslightly
abbreviated versionofPennington's earlierwork on Walsuraandalso briefly discuss
itsrelationship withothermembersofthetribe.
MORPHOLOGICAL NOTES
Habit
Allspecies inwet evergreenforestare predominantly sub-canopy trees,butin dry-
zoneevergreenforestinSriLanka, W. trifoliolataattainsthesameheight as theother
canopytrees (Holmes, 1956).Walsuragardneri ofSriLankais invariably atreeletto
less than 3.5 mtall andits crown is more densely twiggy thanin any otherspecies.
All species,withthenotableexceptionofW.pachycaulon, haveslendertwigs.Leaves
can beall along theshoot(e.g. W. robusta)ior clusteredaround theshootapex(e.g.
W.pinnata ‘villamilii’).
Exudate
Allspecies seemto lack exudateofany sort in slash barkandwood.Mostofthe
species haveglands onthe undersurfaceoftheleaf, however. Thesehave beenob-
servedinW. tubulata(cultivated underglass atOxford) toexudesmallquantitiesof
sweet colourless liquid and theglands producing it are, therefore, probably extra-
floralnectaries. A colourlesssweetstickyexudatehasalsobeenreported (Penning-
ton 7815, Selangor) from thearilof W.pinnata.
Bark
Observations ofbark morphology are sparse but seemto beof sometaxonomic
value.Mostspecies have smoothishouterbarkbutthat ofW. trifoliolata is deeply
fissured.Observations ofsome species are completely lacking.
Leaves
1) Walsurasensustricto
Theleafis unifoliolate(W. gardneri, W. monophylla andoccasionally in W.pin-
nata ‘cochinchinensis’) or imparipinnate withlateralleafletpairs opposite (neversub-
opposite). Theprimary rachis is slightly swollen atthepointofinsertionof thepeti-
olules, as is the petiolule immediately belowthebase ofthelamina, and theleaflet
herecan oftenbeslightly geniculate. Theunifoliolatespecies have asecond petiolule
swelling eitherjust below or continuouswith theswelling atthelaminabase.The
largestleaves are foundin W. sarawakensis, atup to 80 cm long. Walsura trifolio-
lataand W. tubulatahaveone-jugate leavesand mostspecies ofWalsura are two-
jugate. Three-jugate leavesoccur in W. sarawakensisand inW. pinnata ‘villamilii’
andthefour-(and rarely five-)jugate stateoccurs in W.pachycaulon only. Walsura
trifoliolata subsp. trifoliolataandW. tubulatagrownfrom seed attheOxford Botanic
250 BLUMEA Vol. 38, No. 2, 1994
Garden bothproduced undividedleavesinthe early stages and thelatterwas still
producing asmall proportion ofsuch leaveswhen five years old (and flowering).
All species havepapillate epidermis ontheabaxialsurfaceoftheleafletlaminato
some degree. Thisgives thesurfacea glaucous (in life)or matt(when dried)appear-
ance.Itshouldbenotedthatleafepidermis is describedas 'glaucous (in vivo)', this
implies thatitis matt(in sicco) also.Eachepidermalcellconcernedhas one dome-like
projection (complete withcuticularsculpturing) ofthe outer periclinal wall. Species
differintheextentto whichthe abaxialsurface is covered, varying fromonly inthe
islets betweenthe smallest veins(giving thesurface a white dottedappearance) in
W. robustaand (to alesserextent) inW. oxycarpa, toall areasexcept themidriband
costae, asin W.pachycaulon. Heynea species also haveapapillateabaxialepidermis.
Foliar trichomesrange from theprostrate 2-armed trichomes ofW. trifoliolata
to prostrate simple trichomes(in e.g. W. bonii) totheerectsimple trichomesof W.
poilanei. All are unicellular. Stomatalsubsidiary cell arrangementis actinocytic
(sensu Wilkinson, 1979) and epicuticular wax (as found in Owenia species) is
absent.
Venationpatterns donot seemtobeof great use taxonomically. However,costae
frequency is a goodcharacterwith somespecies andW.pinnata ‘villamilii’ isexcep-
tionalin having incomplete costae. These are 1/4-3/4thelength ofnormalcostae
and taperdistally,butformostoftheirlength are thesamewidthandprominence as
complete costae.
2) Walsura chrysogyne etal.
This groupexhibits awiderangeofleafdivision, fromone-to seven-jugate, with
two-,three-,or four-jugate being thecommonest states.The primary rachisandpe-
tioluleswellings typical ofthe other Walsuraspecies are very slight or completely
lacking inthesespecies and, whilstmostspecimens haveopposite leaflets, asmall
proportion have theslightlysubopposite state.Venationpatterns seemtoprovide no
taxonomiccharacters.
The abaxial leafletsurfaceis non-papillate. Thetrichomesareerect, simple and
multicellularandcompound stellates(i.e. aggregations ofsimple hairsas opposed to
thestellatetrichomesproperfoundinsomeothergeneraof theTrichilieae) alsooccur
(butvery sparsely). Stomatalsubsidiary cellarrangementis paracytic (sensu Wilkin-
son, 1979)andepicuticular wax isabsent.
Inflorescence
Inall species the inflorescenceis athyrse which maybe very shortand denseas
in W. brachybotrys (=W. chrysogyne) and W. dehiscens (as short as 0.8cm) or
long andopenas in W. trichostemonand W.pachycaulon (up to30cm inthelatter).
Walsuratrifoliolata frequentlyhas denseheadsofflowers attheendsofthesecond-
ary rachides, afeaturerareinotherspecies. Allspecies have adenseindumentumon
theinflorescence, andin mostthis consistsofminutesimple trichomes only. In W.
trichostemonthetrichomesare sodense asto give theinflorescenceavelutinouscov-
ering. Two-armedtrichomesalso occur (sparsely) in thisspecies. InW. trifoliolata,
W. gardneri andW. oxycarpa two-armedtrichomespredominate on thepeduncle and
arereplaced onallotherpartsby simpletrichomes.
T.P.Clark: Species of Walsura and Pseudoclausena genus novum 251
Flower
Most species seem tohavehermaphrodite flowersonly, butin W. trifoliolata, W.
pinnata and W. chrysogyne et al. hermaphrodite or (on differenttrees) only male
flowersoccur. Walsura robustaseems tobe dioeciousbutmayalsoexhibittheher-
maphroditecharacter.
Aestivationmay vary considerably withinasinglespecimen, fromvalvatetoim-
bricateand, although muchusedinthepast asa characterin thesespecies, is consid-
eredtobeoflittletaxonomicvalue.
Walsurarobustais theonly species withdiscretefilamentsonly, allotherspecies
havinganandroeciumwhichis tubularbelowwithdiscretefilamentsabove. Thepro-
portion ofthetotalandroecium length (excluding anthers) whichis atubeprovides a
usefultaxonomiccharacter. Theformoftheapex ofthefilamentis in most species
bifidto some degree,butin W. boniiis truncate.
Allspecies ofWalsurahave ashallowcylindrical diskabovetheovary aroundthe
stylebase,butapartfrom W. robustawhereitispubescent, it isvery constant andis
oflittle taxonomic use. Walsurachrysogyne etal.lack a disk completely, however.
Allspecies havea densecovering ofbristle-liketrichomesontheovary (being partic-
ularly denseinW. chrysogyne) butonlyinW. tubulatadotheyextendupthestyle. The
stigma is normallycapitate toconical, butin W. dehiscensaratherelaborateconeon
top ofacap-like structureexists andin lifetheupperpart isalso coveredby alayer
ofcolourlessgel-like substance,unknownelsewhere inthegenus.
Pollen
Pollenmorphology inthese species isfairly uniform, as itis across the tribeand
across thefamily (unlike similar-sizedgroups ine.g.Compositae). The grains are
single, generally apolar and4-(or 5-)zono-colporate (neversyncolpate) andprolate-
spheroidal to sub-prolate. Walsurachrysogyne etal.grains are25.6-28.8 x 19.2-
19.7pmand thosein otherWalsura species are 30.0-53.6x 24.0-41.6gm, with
W. robusta having the smallest grains and specimens ofW. pinnata the largest.
Micro-puncta may be well definedor poorly defined,which may provide a taxo-
nomiccharacter,buttheformof thecomplex apertureis probably thebest character,
particularly thelength andshape oftheendoaperture andtheformofitsends.
WOODANATOMY
Themostdetailedconsiderationsof woodanatomyinthesespecies are by Pennington
(1965) andDatta& Samanta(1983), witha summaryofPennington's earlierwork
in Pennington & Styles (1975). The woodofW. robustadiffersin somesmall fea-
tures tothatofW. trifoliolataand W.tubulata, andW. chrysogyne hasamuchlarger
vesselporedensity (308/sq.mm) thantheseotherthreespecies (at 81-154/sq.mm).
Thepaucity ofdataonindividualspecies howeverseverely limitsthediscussionof
taxonomic worthofwoodanatomicalfeatures.
Mehrotra(1989) has describedanewspecies of Walsura, W. deccanensis, onthe
basis ofwoodanatomicalcharactersoffossilmaterial. He gives a detaileddescrip-
tionofthewoodstructure ofthisfossiland comparesitwithwoodsamples ofextant
252 BLUMEA Vol. 38,No. 2, 1994
species ofWalsura (W. robusta, W. piscidia = W. trifoliolata, W. villosa = W. tri-
chostemonand W. glauca = W.pinnata), Heynea, Dysoxylum BlumeandLansium
Corr. Serr.
FRUIT STRUCTURE AND SEED DISPERSAL
ThefruitofWalsurarobusta, W.trifoliolata and W.pinnata is aberry consisting ofa
pericarp0.3 to2.3 mm thick.Theouter, andmuchthethickest,layer is parenchyma-
tous andtheinnerlayer is sclerenchymatous. Theinnerlayer canbefurtherdivided
into an outer layer ofsclereidsand aninner layer offibres. There are no sutures in
thefruitwall. Theseed, enclosedinathick(0.2-1.7 mm) succulentaril-like struct-
ure, is connectedtothepericarp viaaseptum whichintwo-seededfruitsdividesthe
fruitcavity into two locules. Walsura robusta isoddinhaving prostrate trichomes
(similarto thosefoundonthe leafbutalittlelonger) ontheinnersurfaceoftheperi-
carp (i.e. of the fibrous layer), a featureunknownelsewhere in this genus or the
family. Thepericarp andseptumstructuresof W. dehiscensare basically very similar
tothose oftheabovespecies except thatthereare longitudinal linesofweakness in
thewallatthefourwings andtheseptumruns betweentwoofthese, i.e. septicidal-
ly. Dehiscence canoccur ateitherofthetwo pairs ofsutures,but normallyseems to
happen (at leastinitially) atthe two withtheseptum attached,causing theseptumto
split intotwo membranoushemi-septa. This dehiscence, ifonly weak, is unknown
elsewherein thegenus.
The fruitofW. chrysogyne, W. brachybotrys and W. velutinadiffers consider-
ablyfrom thatoftheabovespecies, externally initsasymmetric appearanceandan-
atomically in completely lacking sclerenchyma tissueor welldefinedpericarp layers
or aseptum(or anything analogous to aseptum). Theleathery natureofthepericarp
isdueto veryhigh levelsoftannininthe cells(compared withlowlevelsintheabove
species). No aril-likestructure ispresent.
Cheek(1989) hasmadea detailedsystematic study of seedanatomyinthefamily
andexaminedtheseeds ofW. pinnata, W. dehiscensand W. chrysogyne. Thelatter
heconcludedtobesignificantly differentfromthe othersprincipallyinthatitlackeda
fleshy arilandthenormalmeliaceousseed-coatstratification.
Afruiting tree ofSpecies A,withafruitvery similarmorphologically andanatom-
icallytothatof W.pinnata, hasbeenobserved inthefield(Semengoh, Sarawak). The
fruitswere eaten wholeand in large quantities by the BorneanGibbon(Hylobates
muelleri).Squirrels removedthepericarp and atethearil(an operationinvolving great
dexteritysincethe 'aril' is firmlyattachedto therestof theseed), discarding theseeds
whichfellto theground around theparenttree. Thefollowing day, all seedsonthe
ground wereremoved, however, presumably byrats. Nootherobservationsrelating
topossible dispersal systems inthesespecies areknown.
GERMINATION
(afterPennington& Styles, 1975)
Cryptocotylar, cataphylls minute,followedby spirallyarranged simpleentireeophylls.
SeeFigure 3forillustrationofW. trifoliolata seedling.
T.P.Clark: Species of Walsura and Pseudoclausena genus novum 253
CHROMOSOMES
Walsuratrifoliolatais theonly species studiedcytologically. Itschromosomecount
isn= 14, 2n=28 (Ghosh, 1961; Khosla& Styles, 1975; Datta&Samanta, 1977).
CHEMOTAXONOMY
Chatterjee & Kundu (1968) described a new pentacyclic alcohol, which they call
Walsuranol, from Walsuratubulata, butthey couldnot findlimonoidsinthisspecies.
Taylor (1984), however,reports theoccurrence ofvariouslimonoidsintheotherIn-
dianspecies, W. trifoliolata.Purushothamanetal.(1985) andUmadevi etal.(1988)
have also madechemicalstudiesofW. trifoliolata. Nootherspecies seems tohave
beeninvestigated froma chemotaxonomicviewpoint.
VARIATION WITHIN THEGENERA
Walsura was first dividedintosections by Hiern(1875) whenhereduced Roemer's
(1846) genusSurwalato Walsuraas themonospecific section containing W. robus-
ta. Allotherspecies wereaccommodatedin sect. Euwalsura. Harms (1896) main-
tainedthese two sections and addeda third(un-named) which included W. trijuga
(Roxb.) Kurz (=Heynea trijuga).In 1940,when Harms reinstated thegenus Hey-
nea, heincludedthisspecies theresetting upanother,third, sectionwithin Walsura,
calledNeowalsura, toaccommodateW. glabra Merrill.However, thisspecies is here
(see below) movedtoPseudoclausena.
ThesectionEuwalsurais heremaintained, anditsnameamendedslightly (to con-
formtotheInternationalCode) assection Walsura, andsection Surwalaisalso main-
tained.Anewsection is describedto accommodateW. dehiscensandis calledRus-
wala. SectionRuswalais characterisedby thedehiscentfruitof itsone species, and
sectionSurwala byseparatefilamentsandby trichomes on theinnersurfaceofthe
pericarp. Theordering ofthesections posed some problems, particularly withre-
spect toRuswala.Fruitanatomicalevidence(seeabove) seemstosuggestthatsection
Surwala (i.e. W. robusta), maybenearer toHeynea thansection Walsurais. Within
sectionWalsura thereis greatdiversity with,perhaps, thosespecies centred on W.
pinnata (see below) being themost differentfrom W. robusta. Theposition ofsec-
tionRuswala (W. dehiscens) dependslargely on howthesepticidal capsule character
is treated.Ifitisregarded as asmallevolutionary step from/toaloculicidalcapsule
thenitisbest placed ontheHeynea sideofsectionRuswala. If, however, itis con-
sidered quite different, and probably the product/origin ofa completely different
evolutionary line, thenit should probably be placed furtheraway, possibly beyond
section Walsura.Itis thissecondjuxtapositioning whichis accepted here. This deci-
sion is supported by W. dehiscens having a stigma form unlike thatfound in any
otherspecies ofWalsura or Heynea. Its very shortstaminaltube(c. 1/5 ofthetotal
length oftheandroecium) is nearer tothe discretefilamentsstateofW. robustathan
most species ofthegenus,but it couldbe pointed out that W. gardneri (in section
Walsura) canhave atubeas shortas 1/8thetotallength oftheandroecium.
254 BLUMEA Vol. 38, No. 2, 1994
Accepting this order(i.e. sect.Surwalai-sect. Walsurai-sect. Ruswala), anevo-
lutionary orderingcan thenbespeculated. IfTrichiliais seen asthecoregenusofthe
tribewithHeynea as amodifiedversionofanAfricanTrichiliaspecies, thentheevo-
lutionary trendcouldbe seento be: Trichilia-Heynea-Walsura (sect. I, Surwala-
sect.II, Walsura-sect.Ill, Ruswala) with thesepticidally dehiscentspecies W. de-
hiscens being arelatively recentinnovationderivedfrom thenormalberry-bearing
Walsurastock.
SectionII, Walsura,accommodates themajorityofthespecies andis herefurther
dividedinformally into two species groups.Group 1 is definedby thosespecies re-
maining when Group 2 is removed. Group 2 is centred on thehighly variableand
widely distributedspecies W.pinnataandis confinedtothe Malesianendofthedistri-
butionofthegenus.Whilstthe minorcharacters defining itare notsufficienttomerit
segregation as aseparatesection, itisconsideredusefultoinclude thetwo groupsin
thecurrentrevision.
Group2is definedby thefollowing characters, taken collectively: i)petiole ad-
axially flattenedto shallowly canaliculatealong itswholelength (i.e. tofirst node);
ii)leaflaminaabaxialsurface glabrous or verysparsely pubescent; iii) allleafveins
clearly prominent (in sicco) onabaxialsurface; iv) flower buds, justprior toopen-
ing, less than4.6mm long. Walsura tubulatafromDarjeeling is mostsimilarto the
Group2 species (but differs inflowersizeandin twig bark lenticellation) and, per-
haps, provides thelinkbetween the two groupsand, possibly, between theIndian/
SriLankan species andtheMalesianspecies.
Walsura chrysogyne et al. are considered so differentfrom allotherspecies of
Walsura(see morphological andanatomicalnotes aboveandthekey and diagnosis
below) thatthey areremovedtoanew genus,Pseudoclausena.
Thetaxonomicdivisionofthegenerainthisrevision isthereforeasfollows:
WALSURA
Section I Surwala(M.Roemer) Hook.f.
1. W. robusta Roxb.
Section II Walsura
GROUP 1
2. W. trifoliolata (Adr.Juss.) Harms
subsp. trifoliolata
subsp.acuminata(Trimen) T.Clark, hereinvalid; nobasionym
3. W. tubulataHiern
4. W. trichostemon Miq.
5. W. gardneri Thw.
6. W. boniiPellegrin
7. W. oxycarpaKurz
8. W.poilanei Pellegrin
T.P.Clark: Species of Walsura andPseudoclausena genus novum 255
GROUP 2
9. W.pinnata Hassk.
‘pinnata’
‘cochinchinensis’
‘villamilii’
10. W.pachycaulon Mabb.ex T.Clarkhereinvalid, fornom.nud.
11. W. sarawakensisT.Clark
12. W. monophylla Elmerex Merr.
Section III Ruswala T.Clark
13. W. dehiscens T.Clark
+ threespecies (14, 15& 16), incompletelyknown
PSEUDOCLAUSENA
17. P. chrysogyne (Miq.) T. Clark
formachrysogyne
‘chrysogyne’
‘multijuga’
‘brachybotrys’
formavelutina(Ridley) T.Clark
GEOGRAPHICAL DISTRIBUTION AND SPECIATION
ThespeciesofWalsura(excl. W. chrysogyne etal.) occurinIndia(west totheWest-
ern Ghatsand northto Darjeeling), SriLanka, theAndamanIslands, Burma,Thai-
land, Indo-China, Yunnan, Hainan, the MalayPeninsula, Sumatra, Java, Borneo,
thenorthernandwestern Philippines (Luzon to Palawan),Sulawesi, Halmaheraand
western NewGuinea(Manokwari). Walsura chrysogyne et al. occur in peninsular
Thailand, theMalay Peninsula,southernSumatra,Borneo, thesouthernPhilippines
(Samar, Leyte, MindanaoandPalawan), Sulawesi, Halmahera, Seram andwestern
NewGuinea.Distributionmapsformostindividualspecies are givenbelow.
Walsurapinnata, attheIndo-China-Malesianendoftherange, is acomplex spe-
cies(sensu Pennington & Styles, 1981), whichmay correspond to an ochlospecies
(White, 1962).Suchaspecies is highly variableandoccupies awidegeographic range
butis not divisibleintosubspecies. Onepopulation may containtwo or more distinct
morphologicalentitieswhichdonot intergrade, buttheintermediatesmay (now)occur
inanotherpopulation farremovedgeographically. Closely relatedto W.pinnata are
atleastthreeotherspecies, alldistributedwithinitsrangeandeachofverysmallrange
(viz. W. sarawakensisand W.pachycaulon in Borneo, and W. monophylla onPala-
wan).IfW. chrysogyne et al.are treatedas one species (see below) thenthisis also
acomplex species andis limitedto theMalesianregion (Whitmore, 1984;equivalent
tothe 'Malaysian region' ofVan Steenis, 1950),north tothe isthmusofKra andto
LuzoninthePhilippines andsoutheasttoNewGuinea.
256 BLUMEA Vol. 38,No. 2, 1994
By contrast,thosespecies intheIndiato continental-Malesiaendoftherangeare
predominantly monotypic, taxonomically isolatedspecies (sensu Pennington &Styles,
1981),eachofwhich is separable fromall otherspecies by several diagnostic char-
actersandis notdivisibleintosubspecies, W. dehiscens beingtheonly species from
outsidethisrangewhichfallswithinthiscategory. Walsuratrifoliolatais the only spe-
cies withinthisrangewhichcouldbe describedas apolytypic species, i.e.whichon
the basisofmorphological characters, supplemented by geographical orecological
evidence, canbesubdividedintotwo or moresubspecies.
Walsurarobustaseemstobeoflargely coastaloccurrence whilstW.trichostemon,
with asimilarrange,occurs muchfurtherinlandas well.The velutinousindumentum
ofthelattermay account foritstoleranceof amorecontinental(i.e.seasonal) climate.
Themajority of specimens ofthe densely velutinousP. chrysogyne formavelutina
are fromlocalitiesabove300 maltitude, possibly forsimilarreasons. Walsuragard-
neriofSriLanka seems tobelimitedto hillcountry, although itsshootsand leaves
are glabrous, andthesubspecies of W.trifoliolata generally occupy differentclimatic
zones (see below), this being mostpronounced in SriLanka.The distributionofW.
monophylla inPalawanseems to betheonly onewhich correlateswith anedaphic
factor, thetrees being largely restrictedtoultrabasicsoils.
ECONOMIC BOTANY
Mostofthewidely occurring species seemtobeusedlocally as asource ofhard,du-
rabletimber2and W. robusta (in combinationwithother timbers) hasbeenusedin
papermanufacture(Hossain & Siddique, 1970). The specific epithet ofW.piscidia
Roxb. (=W. trifoliolata)reflects thewidespread practice inIndiaof using thebark in
fishing. Thebark is stripped offthetree,brokenupandthrownintothe waterwhence
a toxincoming fromitkillsthe fish(which floattothesurfaceand can becollected)
but doesnotrenderthe fishflesh inedible(Roxburgh, 1832:388). Mostspecies of
Walsuraareknowntohaveasucculentarilwhichis sweet andediblebutnoevidence
ofitsuse as ahumanfoodstuffcan be found.
Biomassproduction in dryevergreen forest(in Thailand) dominatedby Hopea
ferrea, Walsura trichostemon, Memecylon ovatumandHydnocarpus ilicifolius has
beenstudiedby Sabhasari(1971).
SYSTEMATICTREATMENT
— Leaflet abaxial epidermis papillate, flower withwell-defineddisk; ovary 2-
locular;fruitsymmetrical; pericarp withsclerenchyma layer Walsura
— Leafletabaxial epidermis non-papillate; flower lacking disk; ovary 4- or5-
locular; fruitasymmetric; pericarp lacking Sclerenchyma . . Pseudoclausena
2) Thepropertiesofthe timberofW.trifoliolataarelisted inNazmaet al.(1981:221-222).