Comparative vegetative anatomy of Neosparton darwinii and N. ephedroides (Verbenaceae) - Sociedad Argentina de Botánica

Bol.Soc.Argent.Bot. 37 (1-2):63

-

70. 2002

COMPARATIVE

VEGETATIVE ANATOMY

OF

NEOSPARTON

DARWINII

AND

N.

EPHEDROIDES(VERBENACEAE)

PAULA M.HERMANN,ALEJANDROC. CURINOand PAMELA GEDDES1

Summary:Neospartondarwiniiisendemictothecoastal dunes of Pehuen-cóandoneofthe four speciesof

thegenusendemic toArgentina.It is considered an “endangeredspecies”because of the extreme restriction ofitsarea of occurrence. Neospartondarwinii isawoodyshrub withglobosespikesof yellowish-cream

coloredflowers.Itsseedsareheavily parasitized bya bruchid, so its reproduction Isbasically vegetative.

Primaryrootsaretriarch to heptarch.Thecylindrical, ridged,stemiscovered bya thick cuticle; cyclocitic stomataand hairsoccur inthe furrows,fibers intheridges,andscattered sclereidsIn the chlorenchymatous cortex. Collateralvascular bundles surroundaparenchymaticpith. The ephemeralleavesare decussately

arrangedand nodesare unilacunarwith two traces. The primaryvascular system is of theclosedtypeand

consistsoffoursympodia,eachmirroringtheonenexttoit.Neosparton ephedroidesoccursin disjunctareas

and is very similar to N. darwinii.Thepresenceofcortical sclereidsInthe stemofthelattersuggeststhat they are only one speciessince this character-absencevs. presenceofsclereids-seemed themostevident to

separatethem. Thus,we conclude that thepopulation of Pehuen-có is another population of N.ephedroides and,on the basisof priority, N. darwinii isasynonym of thelatter.

Keywords: Neosparton darwinii, Neospartonephedroides, vegetativeanatomy, root anatomy, stem anatomy, leaf anatomy, synonymy.

Resumen:Anatomía vegetativa comparadade NeospartondarwiniiyN. ephedroides(Verbenaceae).

Neospartondarwiniies endémica de las dunas costeras dePehuen-cóyuna de las cuatro especiesdel

género,endémicodeArgentina. Está considerada como una “especie amenazada” porla extrema restric¬ cióndesu hábitat. Es unarbusto leñosocon espigas brevesde flores colorcrema amarillento. Lassemillas

sonintensamente parasitadas porunbrúquido ylareproducciónes básicamentevegetativa. Las raíces primariasson triarcas aheptarcas. Eltallo cilindrico,estriado, estácubiertoporuna cutícula gruesa;en los surcoshayestomasciclocíticos y pelos,fibrasenlas costillasyesclereídasenla corteza. Hacecillos colaterales rodeanuna médulaparenquimática.Lashojasson efímeras, decusadas, y los nudos unilacunares condostrazas. El sistema vascular primarioes deltipocerradoyconsisteen cuatrosimpodios; cadauno esuna imagen especular del contiguo. Neospartonephedroides habitaen áreasdisyuntasyes muy pareci¬ doa N.darwinii. Lapresenciade esclereídas corticalesen estaúltima especie sugiere queson sólo una especieyaque estecarácter-ausenciavs.presencia de esclereidas-parecíaser el más evidente para sepa¬ rarlas.Concluimosquela de Pehuén-cóes unamásde laspoblacionesdeN.ephedroides y,enbasealas '

prioridades, N. darwiniies un sinónimodeaquella especie.

Palabras clave:Neospartondarwinii, Neosparton ephedroides,anatomía vegetativa, anatomíaradical,ana¬ tomía caulinar,anatomía foliar,sinonimia.

long by 1.5 kmwide (Zalba & Villamil, 1989;

Zalba

&Nebbia, 1999)—extendingEast and West of

Pehuen-có,asmallvillageontheSouth ofthe

Prov-INTRODUCTION

The genusNeosparton Griseb. is endemic to

Argentina and consists of four species: N. ince ofBuenosAires,Argentina (Fig.1). Ithas been considered a“vulnerable species” (Villamiletal.,

ephedroides Griseb., N. darwinii Benth. & Hook.

f., N. aphyllum(Gillies& Hook.)Kuntze and N. 1996)or an“endangeredspecies” (Zalba & Nebbia, 1999) becauseof theextremerestriction of itsarea (Troncoso," 1974).

patagonicum Tronc.

Neosparton darwinii is endemic to the coastal occurrence andthe tourist expansion of the lo-dunes of Pehuen-có.It occursinavery restricted cality; thus, athorough biological study is neces-

.

area—a2,300 ha band paralleltotheshore,25km sarY toprovide abetterunderstanding ofits

mor--

-

: phology, reproductive biology,etc. to try to

pre-1

Departamentode Biologia, BioquímicayFarmacia,Univêr- ventits extinction due tohabitat modificationsas sidadNacional del Sur,SanJuan670,8000Bahia Blanca,

Bol.Soc. Argent.Bot. 37 (1-2) 2002

Beingendemic to sucharestrictedzone, very

fewauthors have studiedthisspecies.Bentham & Hooker (1876) described the first specimencol¬ lected byCharlesDarwinonOctober 2, 1832 dur¬ ing the voyage of the Beagleas a newspecies: N.

darwinii.Lateron,Troncoso (1957, 1974)consid¬

eredit intaxonomic works where exomorphology

ingeneral andanatomy ofthe stem aredescribed. Morerecently,Zalba (1989) characterized thedis¬ persionofthespecies, considereditswayof

propa¬

gation,

phenology,

andproposedapossibleconser¬

vationstrategy.This study has led the Municipality

of CoronelRosales to declareN. darwiniiapro¬ tectedspecies.

Michetti

etal. (1994) and Zalba & Nebbia (1996, 1999) concluded that the reduced

distributionand the lack ofits range expansionmight berelatedtoreproductiverestrictions rather than

to limitations on availability of adequate or favourablehabitats. In addition, fruits and seedsare

heavily parasitizedpreventing seed germination

(Nebbia &Zalba,2001),and seriouslycompromis¬

ingsexualreproduction. This is anotherreason to consideritsprotection against anthropogenic en¬

croachment.

I

l

Salta

'? •À

•'Mendoza

BuenosAires

\

Pampa

,

• \

1

'4*

Fig. 1.PopulationdistributionofNeosparton darwinii (rectangle) and N.ephedroides(circles),

Neosparton darwinii has been

described

asthe _{covered by fungi and growth stopped.No other}

only species in the genus lacking sclereids _{treatments were tried since the aimwas toobtain} (Troncoso, 1957), the mostconsistent feature to _{primaryrootsforanatomicalstudy;weused} adven-separateit fromN.ephedroides. Sclereids do oc- _{titiousroots t0 describeroot morphology.}

cur,however, inthe stemcortex ofN. darwinii,

which makes it even more similar to N. Herbarium specimens

examined:

Neosparton

darwinii. Type: Argentina,Prov. Buenos Aires.

ephedroides.Thus,acomparativestudy ofthe veg- _{MonteHermoso, outsideofBahiaBlanca,coastof} etative structuresofbothspecies has been under- _{Patagonia, Darwin 528, 2-X-1832 (K). Prov.} BuenosAires,Pdo. CoronelDorrego, 1 al

5-XI-allyshould be maintainedastwodifferenttaxaand j_{924, Doello Jurado (BA 24-1711). Pdo. Coronel}

to describe the anatomyofaspecies considered _{RosaiesÿDos iegUas al Norte de Monte Hermoso,}

“vulnerable”or“endangered”. j_{894ÿAmeghino (LPS 21934); Pehuen-Có,}

19-XI-1962,Cabrera y Fabris 14910 (SI); 31-X-1985, . Villamil y Cazzaniga 3444 (BBB); 11-XI-1984,

Villamil 9621 (BBB).'

takeninan attempt tofindoutwhether they

actu-MATERIALS

AND

METHODS

Neosparton ephedroides.Prov. La Pampa. Material of Neosparton darwinii and N.. Dep. 25 de Mayo,Ruta aColoniaChica,a1300m ephedroides was collected by severalcollectors del ViveroProvincial,20-X-1989, Villamil 6578

includingthe authors. Thevastmajorityofthe ob- (BBB); EntreColonia Chica y 25 de Mayo,

26-XI-servationsweredoneonfixedmaterial collected"at 1980, Steibel y Troiani 6466 (BBB). Prov.

Pehuen-có,ProvinceofBuenosAires,Argentina Mendoza.Dep. Malargüe, Bardas Blancas, 14-XI-(N. darwinii) and by Route 20near25 de Mayo, 1969,Ancibor,Cano,

Crespo

(SI 90129);entre

Province of La Pampa (N. ephedroides) (Fig. 1). AguaBotadayArroyoChequenco,I-1942,Ruiz Leal Despite fungicide treatments geñninationes- _{7700 (BA 46381). Prov. Salta, Dep. Cafayate,}

says for Neosparton darwiniiwereunsuccessful; _{Médanos de Cafayate, 1-1943, Castellanos (BA} only one seedgerminatedandas soon asaverysmall 46953); X-1948, Cárdenas 4222 (LIL 532043);

portionofthe radicle emerged itwasimmediately cauce seco del Rio Santa María, 22-X-1948,

Burkart 17634 (SI). Dep. Guachipas,

Quebrada

de (Fig. 2B). The hypodermal layer has larger cells with Guachipas, XII-1896, Spegazzini (LPS 21979). thinner walls (Fig. 2B). Therest ofthe cortical

Prov. Catamarca.Dep. Andalgalá, Campos del cells—approximately 5-14 layers—havevery thin

Arenal, 10-III-I916,Joergensen1731 (BA 23968); walls,areisodiametric incrosssection and rather Dep. Antofagasta

de

la Sierra, Antofagasta de la elongated in longitudinal section,increasing insize Sierra,26-11-1981,Cabrera,Botta,Deginani32564 toward thecenterofthecortexanddecreasing

to-(SI); 17-11-1974, Ulibarri 641 (SI); 6-IV-1950, ward the endodermis (Fig. 2B). Large intercellular Vervoorst 730 (LIL 362694); 1-1885, Philippi (SGO spacesoccuramong thecortical cells (Fig. 2B). The 42500); Dep. Tinogasta, Agua Negra,7-II-1930, endodermal cellsaresmall, squarishandpresentthe

Castellanos(BA 30/603);VallecitoaAgua Negra, characteristic casparian thickenings. The vascular 11-1930,Schreiter 6314 (LIL);Dep. Santa Maria, cylinderis surrounded bya one-,sometimestwo-,

Camino SantaMaríaal Cajón,I-1915,Castillón(LIL layered pericycle;its cellsaresimilar to those of 32413); FuerteQuemado, 19-X-1948,Cozzo (BA theendodermisexceptforthe absence ofcasparian 52800); Dep. Belén, Río Hualfín, X-1875, thickenings.Primary xylem forms 3-7armsof pro-Schickendantz 105 (CORD). Prov. Tucumán. Dep. toxylem alternatingwith3-7groupsofphloem cells.

Tqfi, Rio Santa María,3-II-1935,Castellanos (BA Thecenter ofthevascular cylinderisoccupied by anarea,variableinsize,of sclerified parenchyma 14807).

Herbarium material wasrestored following cells (Fig. 2C). Venning’s technique (1953).Both fresh andre¬

stored herbarium materialwere fixedinformalin- Stem

acetic-acid-alcohol,dehydrated inanethyl

alcohol-tertiary butyl alcohol series and embeddedin

Paramat. Cross and longitudinal sectionswere cut node shows it is circular and ridged (Figs. 2D, G), at10 pm,stainedwith safranin-fast green and 6b- the ridges being 24-37. Theepidermisis commonly served underacompound microscope.Leaveswere biseriate(Fig. 2G),occasionallyuniseriateat the cleared following Dizeo de Strittmatter’stechnique furrows andthree-, seldom four-seriate at the (1973). Observationswererecorded through draw- ridges.Itis covered byathickcuticlewhichthins markedlyoverthecyclociticstomatathatoccurin

the furrows (Fig. 2E). Thisareaisprotected from

waterloss through theoccurrenceofdifferentsorts

ofhairs in and very closetothe furrows (Figs. 2D,

,G).There arelong,unicellular,cylindrical,hairs

,

depleted of cytoplasmatmaturitybutwith cuticu¬ lar teeth; 4-cell-headedhairs;and,less frequently,

palisade-cell-headedhairs. At theridges, directly

beneath the epidermis, there is agroup of fibers arranged inatriangle,the base of which is in

con-A:Anatomy.Across section of thestemfilter¬

ings and photomicrographs.

RESULTS

Neosparton darwinii is awoodyshrub 2-2.20

mhighthatgrows on coastal dunes in Pehuen-có

contributing to fixing them.Itsridgedbranches

seemaphyllousduetothe early falling of the small leaves. Inflorescencesareglobosespikesof15-25

yellowish-creamcolored flowers ofapeculiar, tactwith theepidermis(Figs. 2D, G). It is flanked by elongated chlorenchyma cells resembling the ratherunpleasant,odor. They bloom from Septem¬

bertoNovember and fruitsmaturefromNovember

toJanuary.Reproductionthroughseedsseemsal¬

mostnonexistent since theyareheavily parasitized by abruchid,Lithraeus

_ferreroi

(Belenguer & Ferrero, 1994). Reproductionis thus essentially vegetative,via stolonswith adventitiousrootsatthe

nodes,

which

areresponsible for dune fixation.

palisadeparenchymacells of leaves (Figs. 2D, G). This tissue flankingoneside ofafiber trianglecon¬

tinues inaband 3-4 cell layers thick beneath the epidermis of the furrowsto the flank of the fiber triangleofthecontiguousridge.Thus, each furrow is surrounded byahemicycle (orhorseshoe-shaped band) ofpalisade chlorenchyma (Figs. 2D,G). Closertothecenterofthestem,chlorenchymacells are larger andmoreisodiametric, and scattered

amongthem there appearsclereids,solitary orin groupsoftwoto seven,mostcommonlycloserto

the furrows -(Figs. 2D, G). They are very thick Root

Theepidermisoftheprimary roothas‘rather

Bol.Soc. Argent.Bot. 37(1-2) 2002

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Fig. 2. A

-

G:Neospartondarwinii:leaf,rootandstem.A:leaf,centralportion,x45.B: tetrarchprimaryroot,x80. C:vascular cylinder of heptarchprimaryroot,x58.D:partofa stemshowingfour ridgesandcorrespondingfurrows.Notice sclereidsatarrowheads, x 54.E:part of a furrow withcyclociticstomatainsurfaceview,x270.F:sclereidinstemcortex,x135. G:detailof ridges, furrows,and sclereids (arrowhead), x 157. A-D, G: cross sections. E, F:longitudinalsections. References: abe, abaxialepidermis;_ade/adaxialepidermis;e:

epidermis. •

walled, roundish incrosssection (Figs.2D,G), and

elongatedlongitudinally (Fig. 2F). Continuingto- js_basedonthe threenodes thatoccurbetween the ward thecenterof thestemtherearescatteredpack- apical meristem and the beginning of secondary ages of fibers that correspondto the fiber cap of growth.Leaves aredecussatelyarrangedand nodes, the collateral primary vascular bundles (Fig. 2D) areunilacunar withtwotraces.The primaryvascu-

-and beneaththese;primaryphloemissquashed be- larsystem,illustrated in Fig. 3, is of the closedtype tweenthe fiber caps and secondary phloem.Be- aftdconsists of four sympodia. Closetoeach node

tween contiguous fiber caps, cortical cells are the axial bundle of eachsympodiumbranches pro-smaller and abut directly into secondaryphloem duringonelateral leaftrace to oneside andhalf (Fig. 2D). The two cortical layers closestto the medianleaftraceplusasmall budtrace tothe other.

secondaryphloem have smallcrystals.Continuing Thispatternisrepeatedalternately alongthestem. onto thecenterofthestem,cambium leadsonto Eachsympodiumis the mirror image of theone next

secondary xylemand thisto remnantsofprimary toit. The lateraltraces traversealmostacomplete xylem(partof primaryvascular bundles). Thecen-, intemodebefore enteringthe corresponding leaf.

terofthestemisoccupied byathin-walled paren- The halvesofthe

median

tracefusewith each other

atthe level of thenextnode and continueupwards B: Primary vascular system.Thisdescription

chymaticpith (Fig. 2D).

glandularmulticellularhairs occur onthe adaxial surface of youngleaves. Acrosssection of the leaf showsasmall portionof collenchyma inthemar¬

gins; thissametissueoccurshypodermally inthe centralzone—approximately the length occupied

byfourtosevencentralnerves(Fig. 2A) of the 27-36observed incrosssection. This tissue formstwo tothree layers under the abaxial epidermis andone to twounder the adaxialone.Vascularbundlesare

collateral andoccurina rowfrom margintomar¬

gin ofthe leaf,somewhat closertothe abaxial epi¬ dermis. Toward the adaxial surface, the mesophyll consists of rectangular, rather long, chlorenchyma cells vaguely reminiscent ofpalisadeparenchyma

(Fig. 2A); lackofstratificationmakes the tissue lose the characteristic appearance of palisade paren¬ chyma.

_Quite

compact toward the margins and adaxial surface,large intercellularspaces andmore

irregularcellsoccurtoward thecentergivingit the

aspectofaspongyparenchyma. Twotothreecen¬

tral bundlesaresurroundedby acollenchymatous

parenchyma thatreaches thesubepidermalcollen¬ chyma ofthe abaxial side of the leaf, whereas to¬

ward the adaxial sideit consists of threeto four cell layers whichnarrowtowards theleaf surface

until theycontactthechlorenchymaorthesubepi¬ dermal collenchyma. Scattered throughout theme¬

sophyllsomedegrading cells (they stain rather red¬ dish) may befound(Fig. 2A);similarly,numerous

starch grains occuressentially toward the adaxial surface.

\

C

D

.

_CJ

/

\

\

Fig. 3. Primaryvascularsystemalongthethree nodes betweenthe

apical meristem andthebeginning of secondary growth.

References:C )leaf; mainbundle ofsympodium;

-

leaf

trace; budtrace.

(fused) formostpartof anotherintemode,thustra¬ versingalmosttwointemodes;itneverreaches the base of the leaf,however,commonly fadingout

closetoit,sometimes fusingto eitherone ofthe

lateraltraces, orbifurcating, with each resulting branch fusingtoalateraltrace.Both lateraltraces

branch immediatelyatthebase ofthesessile leaves andcontinueaparallelcourse

upward

ortheymay fusesomewhere between the middle and the distal

partofthe leaf.

Neosparton ephedroides is also endemic to

Argentinaandoccursinthree widelyseparated, dis¬ junct,areas(Fig. 1); 1) NEofCatamarca, S of Salta and NW of Tucumán (Troncoso, 1957); 2) S of Mendoza (Troncoso, 1957); 3) W of La Pampa (Covas, 1965).Itisawoodyshrub2-3mhighwith similar characteristics tothose described for N. darwinii. The globose spikes bear 11-21 flowers also similarincolor andodortothat species.

Roots, stemsand leaves look like those of N. darwinii althougha slightvariationoccursinthe

number ofridgesofthe stem,being21-33 inN. ephedroides; several of the specimens observed lacked cortical sclereids,and the small number of leaves availableof N. ephedroidesshow alarger

amount of collenchymaonthe abaxialside; this, however,maybeaquitevariable feature.

Althoughinalower degree, flowers in thisspe¬ ciesarealsoparasitized apparentlybyColeóptera

Leaves

Theephemeral leaves are decussate, small,

simple,sessile,somewhat fleshy,slightlyconnate at the base, oblong-lanceolateto ovate-spathulate with smoothmargins,glabrousonthe abaxial side'

and hairyonthe adaxialone.Variablein size,the smallerones are4mmlong by 2mmwide whereas thelargerones are10mmlong by4mmwide;oc¬

casionally they reachalengthof 15mmandawidth of 7 mm. Both epidermis consist of cells that are squarishtorectangularbothinsurfaceview andin cross section (Fig. 2A); the outer wallsarerela¬ tively thick. A thin cuticle coversthe epidermis. Stomataoccur onboth adaxial and abaxial sidesof

the leaves (Fig. 2A) andareessentiallyanomocitic,

showing in some cases a slight tendency to cyclocitic.

Quite

abundant simple unicellular and

Bol. Soc.Argent.Bot. 37 (1-2)2002

blumei) (Balfour &Philipson, 1962)—themain difference beingthat in thisspecies,the leafcen¬

tral bundle doesnotdisappear before reaching the base of the leaf (it commonly doesinN.darwinii) butinsteadbifurcates, each resulting bundle fusing

toeach lateral bundle (anotherofthepossibilities inN.

darwinii

).

Therearenodescriptions ofrootsand leaves

foreither of thetwospecies priortothosereported here,thus comparisonsare notpossible.

We agree with the observations of Troncoso (1957) and Bõcher & Lyshede (1972) withrespect toN. ephedroides.There are, however,some dis¬ crepancies with the latter studiesinwhich cortical sclereidsaredescribedasbeing radially elongated incrosssection; only inoneofourspecimens this isso,while in theresttheyarerather roundjustas

in

N. darwinii. Bõcher &Lyshede(1972)referto twotypesofhairsin this species: the “cutinized

coveringhairs”and the glandular hairs (head

two-celledwith large nuclei);wehavefound,however,

thesame three types asinN. darwinii,including theglandularonewithpalisade-celledhead that they describe only for N. aphyllum.

The presence

of

corticalsclereidsinthe stem ofN. darwinii magnifies its similarity to N.

ephedroides, since this character—absence vs.

presence of sclereids—seemedthe mostevident.

to separateboth species (Troncoso, 1957). The other characters used by Troncoso (1957)—height,

number of ridges in thestem,bract/calyx length, insertedvs.exertedstamens—donotreally con¬

tributetoaseparation of thetwospecies. There is muchoverlap in height (2-2.20min N.darwinii; 2-3minN.ephedroides),inthe number of ridges

in the stem(24-37 in N. darwinii', 21-3.3 in N.

ephedroides) and in bract/calyx length (>in N. darwinii',<inN. ephedroides), andwehave found didynamousstamens—twoexerted andtwoinserted

ones—inboth species. Thus, the fivedifferences pointedoutby Troncoso (1957)to separatethetwo

species areinsufficient traits for identification. Mostofthespecimens of N.ephedroides lack¬ ing cortical sclereidsbelongtoarather restricted

zonearound the borders between the Provinces of Catamarca, Salta andTucumán,inthevicinity ofthe river Santa Maria.This couldbe driven byphysical

conditions—climatic,edaphic, etc.—but it also demonstrates that whereas in N.ephedroides cor¬

tical sclereids may beabsent,this hasrarelybeen observedsofar in N. darwinii.

ofthe family Nitidulidae (Belenguer, pers. comm.); onlyadults have beenseeninthe flowers andsofar havenotbeenidentified.

DISCUSSION

AND

CONCLUSIONS

Our observationson the stemof N. darwinii

areinaccordance with those of Troncoso (1957)

except withrespectto the occurrence of cortical

sclereids;whereasthis author didnotdetect sclere¬ ids—acharacter that she usedtoseparatethis spe¬ cies from N. ephedroides—our studies indicate that they almost alwaysoccur in the formerspe¬

cies (with theexceptionofyoungstemswith little

or no secondary). Moreover, the specimenof N.

darwiniicollected by Doello JuradoonNov.1924 (BA 24-1711),cited by Troncoso (1957) as one

ofthetwospecimens sheobserved,possessescor¬

tical sclereids; the other one, collected by

Ameghino in 1894,however,doesnot.Neverthe¬

less, among the materialcollectedbythe authors and other collectors in many differentopportuni¬ ties and from differentplants,lackofsclereids has

neverbeen found.

Becketal. (1982)pointoutthat “closedvascu¬

larsystems occur inboth woody andherbaceous

species,butare morecommon,_{amongherbaceous}

species”. N. darwinii is anotherwoody species to

haveaclosed primary vascular system. Thesame

authorshave founda strongcorrelation between closedsystemsand decussate phylotaxy, which is also thecase with N. darwinii.Furthermore,they indicate that “closedsystems arecommonly char¬ acterized byan evennumber of axialbundles,often 4...,6...,or 8...”. Four axialbundlesoccurin N.

darwinii.

“Closedsystemsdiffer from open systemsin being regularlyreticulate”where“theaxial bundles ofsympodia areconnected by the fusion of leaf

traces..., or the axial bundles themselvesanasto¬

mose...”.The firstpart ofthis statementbyBeck

etal. (1982) isinaccordance with the characteris¬ tics of the primary vascularsystemof N.darwinii

where axialbundlesareconnectedbythefusionof leaftraces,those that makeup what would be the median leaftrace.

Incomparing N. darwinii1sprimary vascular

systemwith those of otherspecies

studied,

wehave foundthatit isverysimilartothat ofaLamiaceae—

Solenostemon scutellarioides(L.) Codd (=Coleus

Itisnotuncommontofindspecies withadisjunct distribution suchas occurswithN. ephedroides', how¬

ever, asdifficulties arise todetectclear differential characteristics between this species and N darwinii

,

the tendency existstoconfirm theiridentitiesonthe basis of their place of origin. The distribution of N. ephedroides in three distant areas asstated above,

makes possiblesomespeculation: if the northernmost

populations—those of Catamarca, Salta and Tucumán—occurlittleover1000kmapartfromthose inthe south ofMendoza,and these are 300 kmaway

fromthose of25de Mayo (La Pampa), the distance between that locality and Pehuen-có—550km—does

not seem animportant isolation factor that will lead

tocontemplate the populationatPehuen-cóas adif¬ ferentspecies. Bõcher & Lyshede (1972) consider that the absence ofNephedroides from the provinces of La Rioja, SanJuanand north of Mendoza could be attributedtoclimatic factors since this region consti¬

tutesthe,driestpartofthemostelevatedareasofthe argentinewesternregion. Noobservations have been made of the conditions occurring between the south ofMendoza and 25 de Mayoorbetween thelatter and

Pehuen-có,but heretoo,edaphicreasons or someoth¬

erscouldberesponsible for the distribution of the species in disjunctareas.

itsextinction since each population adds genetic diversitytothe speciesgenepool (Ehrlich & Daily, 1993; Myers, 1994). Another important consider¬ ation is that it is the onlyonethatoccursinacoastal habitat and that this environment could beafactor ofselection towards certainphenotypes that may eventuallybecome a new species; this could then certainlybe called N. darwinii.

ACKNOWLEDGMENTS

Partof this workwasdone withagrantofthe Department of BiologytoP. M.Hermann.We thank thecollectors of plant material and the curatorsof the Herbaria citedabove,particularly Dr. M. Muñoz

Pizarro,thecuratorofthe Herbarium of the Museo Nacional de HistoriaNatural, Santiago, Chile, who allowed the specialtreatmentofa type specimen,

aswellasProf. M. B. Mújica for critically reading themanuscript.

BIBLIOGRAPHY

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“Especie indudablemente muy vecina de N. ephedroides. Aún requieresermásestudiadaabase de mejores ejemplares que los actualmente disponibles...”.Moreover,one ofthe labelsonthe

typespecimen observedatthe RoyalBotanic Gar¬ dens (Kew) Herbarium reads: “Neosparton ephedroides Griseb. [TYPE ofN. Darwinii Benthr], Identified by H. N. MOLDENKE and cited by him in hisMonograph ofthe Genus.November,1938.” The mentionedmonograph, however,has apparently

neverbeen published since the sameauthor cites N. darwiniias a valid species in a later work (Moldenke, 1941), andsodid Troncoso(1957)and Múlgura (1999). Basedonthe abovediscussion, it is concluded thatwe aredealingwith onlyone en¬

tityatthespecies level and the binomial N. darwinii should become asynonym of N. ephedroides for priority reasons. Therefore, the population at

Pehuen-có is Neosparton ephedroides Griseb,

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Recibido el 11 de Marzo de2002,aceptadoel 22 de Abril de 2002.