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ISSN 1346-7565 ActaPhytotax,Geobot.56(3):241-246(2005)
Chromosome Numbersof isodon(Lamiaceae) inJapan
TADASHI YAMASHIROi KAZUOSUZUKIi" and MASAYUKI MAKI2
iDepartment ofLi jSlcieenee st,heult yofintagrate danAdr Stcsiences, TVie U7iiversi otfy 7bkushima ,7bkttshima,
770-8502 lapan; 2Division ofEcol oangdEyvolutionai:F BiologB Graduate St'hoo olfLi jSZciiences 7,bkoku
Uhivensic Axoba, Sendai ,980-8578 lapan.
Somatic chromosome numbers were counted in sevcn species and six varieties oflsodon occurring in
Japan, All of the taxa had 2n - 24 chromosomes, indicati ntghat they are diplei Fdo.r al1 taxa except L
umhrosus var. hakusanensi asnd I. ,iaponicu sc,hromosome numbers are reported here fbr the firs ttime.
The results suggest that diversifica tiin oJnapanes etaxa of Isodon has occurrcd at the diploi ldevel e,ven
though some reticulation had bcen suggested by a prelimjnar myolccular study.
Key words: chromosome number, tsedbn, Japan, Lamiaceae
Ivodb n(Bent hS.ch)rad .ex Spach (Larniac ceoma-e) reported 2n = 24 fbr Rabdosia umb,vsa (Maxim.)
prise sapproximately 100 species having a ca]yx Hara var. hakusanensis (Kudo )Hara [= isodon
with ene larg eupper tooth and fbur small lower umbrosus (Maxim, H)ara var. hakusanens i(sKudo)
ones, as well as thos ehaving a calyx with five equal K. Asano].
or subequal teeth, or three upper teeth and two From apreliminary phylogenet istcudy using
lower ones (Li 1988), The genus is widely distrib-sequence variations of chloroplast DNA, origins of
uted from the Far East to Africa; in Japan, seven some Japanese taxa of Lsodon are revealed to be
species and six varieties are currently known complex, probably involvin greticulate evolution
(Murat a& Yamazaki 1993) .Coroll asizes of the (Dohzon eot al. 2004). For example, f. inj7ext thsas
Japanes etaxa of Xsoclo nvary greatl aynd are known two di ffere nhtaplotype osfcp DNA, whjch belong
to correspond well to thei rpQllinato srpecies (Suzukito differ eclnadtes, suggcst{ng that the species orig-
l992a, b, Suzuki & Akazome 2000) ,offering good inated from differc nttwo lineages .Because, in
examples ofplant-pollinator mutualism. plants r,eticulation is very often accompanied by
At presen to,nly limite dameunt of infbrmation polyploidizat i(oHnegar t& yHiscock 2005) ,it is
on chromosome numbers are available fbr lsodon possibl tehat allopolyploidization is rclevant to the
(Darling t&o nWylie 1955, thc Index to Plant origin of some Japanes etaxa of lsodon .Accord-
Chrornosom eNumbers l 956 - 2000). Tb date ,chro- ingly c,hromosome numbers are essential infbrrna-
mosome counts are published for only two taxa of tion fbr uncoycring thc speciation proces sin the
the genus in Japan; Suzuka (195 0re)ported the Japanese taxa ofLgodon. In this study, we report the
chromosome number of Plectranthus ,iaponicus somatic chrornosome numbers of lsodon occuning
(Burmf,)Koidz,[-lsodon.iaponicu(sBurmf,) inJapan.
Hara] to be 2n = 24, and Wakabayashi (1973)
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Materialsand Methods Results Discussion
and
Living stocks were collected from natural popula- All 13 taxa investigat iend this study had a chro-
tions of seven species and six varieties of lsodon in mosome number of2n = 24, representing diploi odf
Japan (Tabl e1) ,and were cultivated in pots fi11edx - 12 (Fig s1,, 2), All chromosomes of 13 taxa
with soil in the nursery of the University of observed in this study were similar to ea¢h other in
Tbkushima ,Taxonomic treatment softhe taxa fo11ow size. The length softhe chromosomes varied from
Murata & Yamazaki (1993). O,7 to 1.4 pm. The centromeric positions of the
For the observation ofsomatic chromosomes, chromosomes were obscure,
root tips were pretreate idn a 2 mM 8-hydrox- The chromosome counts {n the presen tstudy
yquinolin aequeous solution for 3.5 hours at room are consistent with those of two previous studies
ternperature. The root tips were then fixe dwith a reporting 2n = 24 for lsodon umbiosus var. haku-
mixture of 1OO % ethanol and acetic acid (3 l:) for saensis (Wakabayas h19i73) and I .japonicus
30 minutes and preserve dat 5 OC until observa- (Suzu k1a95e). For all taxa except I uinbrosus var.
tion. For observation, root tips were macerated with hakt{saen sanids L 1'aponicu sc,hromosome numbers
a mixture of IN HCI and 45 % acetic acid (2: 1at) are reported here for the fir sttime. [[:w otaxa close-
60 OC for 30 seconds, then stained in 2 9" 6aceto- ly related to the Japanese members, Rabdosia excisa
orcein solution for an hour, The meristematic parts (Maxim ,Ha)ra [= lsodon ex;cisus (Maxim .K)udo]
ofthe root tips were squashed in 2 % aceto-orcein and R. 1'aponi cvaar. gtaucocaly Mxaxim. [= Iyodon
on slide glass and were observed by using a micro- J'aponicus var. glaucocalyw (Maxim .H). W. Li],
scope at 1500 magnification. Chromosome num- also have chromosome number of 2n [: 24
ber sof at leas tthree cells for each individu awelre (Sokolovs keta aLy a1986) .According to a previous
counted at somatic metaphase. series ofthe Index to Plant Chromosome Numbers
1laBL E1, List oftaxa, localiti eaisi,d chromesome number's ofIsodon examined in thi sstudy.
[[hrlen Locality Chromosome
number(2n)
L qffLtsusL Mt. Ogasa-yam aF,ukuroi City .Shizuoka Pref. 2424242424M2424
tnjTexus Mt.BizanT,bkushimaCityl,bkushimaPref.
TsushimaIslandsN,agasakPiref.
L y'crponic"s Ohgisawa, Ohmachi City ,Nagano Pref,
1[byama,NakaTbwn,TbkushimaPref.
L lengitubus Entrance of Mt. Shakaga-dake ,Yabe Tbwn, Fukuoka Pref,
Sawadani,Naka Tbwn,TbkushimaPref.
L shikokianus Mts, Ishiduchi-sa nS,aijye City ,Ehime Pref.
var. intermeditts Mt, Ketsu-zan ,Ybshinogawa City ,Tbkushima PreL
var. occidentalis Mt. [[bdagatak eO,bama City ,Fukui PreE 24242424242424
L tricocarp"s Mts.Izumigatake,SendaiCityM,iyagiPref.
L umbres"s Abe Pass, Shizuoka City ,Shizuoka Pref,
var. excisiqflexus Atsumi Spa, Atsumi Ibwn, Yamagata Pref,
var. hakusanensis Ohgisawa, Ohmachi City ,Nagano Pref.
var. Iatijbtius Yhshaj iPnass, Minami Alps City Y,aiiiana sPhrief,
var. Ieucanthzas Ichinos eHeights ,Enzan City ,Yamanashi Pref,
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Decelnber 2005 YAMASHIRO et al Chromosome Numbers oflsodon （Lam 置aceae ） m Japan 243
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Flc l Microphotogrdphs of somat 且c chlomosQmes at metaphase of Japancse／sodon A Isodon etiuses’ B ∬ノnflexus し ノ
Japontcu“ Dllongitubus E ∫shikoinanus var sinkolaanus F ∬shikoluani ’∫var intertnedius C F explanatory drawlngs
o世Cand F， respeLtlvcly Sc翫lc bar represent 号5μm
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RG 2 Mlcrophotograph〜of gomatlc chromosomcs at metaphase of Japanese lsodon A I shikokianu 〜var ‘丿ccidenta ’lv B I tnc
ocaTpus C Jsodon unめroyus var umbt り5恥 D ∬umbrosus var exeigin17exzay’ E 1 巴〃nbrosus var hakuhanens iFs∫umbTosus
var latifol iuGs J l〃nbrcハt［s var ’eucanthuT Seale bar represents 5 y皿 E expla皿atory drawmg ofE Scale bar repre 』ent 、5叫m
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December 2005 YAMASHIRO et al,: Chromesome Numbcrs ofIsedon (Lamiac eina Jeap)an 245
(195 -6 2000) and Darlingto &n Wylie (1955 o)nl,y in progres san,d will elucidate the speciation process
2n = 24 (o rn =12), 28 [on liyn Plect,unth ucaslyci- in the taxa.
Benth.(=lsodon (BenthH,.)W. Li)
nus calycinus
(d eWet 1958) ]and 42 [on liyn L ramosissimus The authors thank Mr. R. Morita for technic aalssistance
(Hook f,. )Codd (Morto 1n998) ]are reported for and Ms S. Horie fbr collecting the plant materials. This
lsodon sensu Li (1988 s)ug,gesting that all Japanese study was supported by a Grant-in-Ai fdrom the Japan
taxa of lsodon are diploi dT.his is supported by MMMi.nistr yof Education ,Science ,Sport sand Cultur eto
the results of enzyme electrophoresis, by which
additional gene duplications were not detected References
(Maki data)A.
et at, unpublished recent molecular
phylogenetic study on Ocimeae revealed that R Darlingto nC,, D, & A. P, WYIie .1955. Chromoseme
ealycinms, with a chromosome number of2n == 28, is atlas of fiowerin gplants 2.nd ed. George Allen &
not contained in the clade comprised of lsodon Unwin, London.
(Pat oetn al. 2004), although L ramosissinzas with 2n Dohzono, I. ,K, Hiei, M. Maki & K. Suzuki. 2004. Floral
42has been its diversificat sieolencted by plura plollinat osprecies:
= not examined, and phylogenetic
the case of bumbLebee pollinati soysntem. Proceeding
position remains still unclear. It is probable that ofthe 36th Symposium of the Societ yfbr the Study
species having a basi cchromosome number ofx = of Specie sBiolegy. pp 1-1-6. (i nJapanese).
14 are phylogenetica lilnydependen otflsodon. Ifx De Wet, J, M, J. 1958. Chromosome numbers in
= 14 is another basic chromosome number of Plectranthu asnd related genera .South Africa nJ.
Sci.54:153-156.
lyodon,I isdiploid L is
calycinus and ramosissinus
triploid. Hegarty ,M. J .& S. J .Hisock. 2005. Hybrid speciation in
Consequentl yi,t is unlikely that polyploidy pPlhaynttosl :.n1e6w5 : i4n1s1i-g4h2 t3fs.rom rnolecular studies. New
plays a roie in the speciation of the Japanes etaxa of Li, H.-W. 1 988. Tlaxonomi creview ofIsodon (Labiatae).
lsodon ,and it is probabl ethat their diversificatio n J, Arnold Arbor .69: 289-400.
occurs at the diploi ldevel I.n other words, the puta- Morton, J, K. 1998, Chromosome number and poly-
tive reticulative evolutions suggested in the group ploidy in the fior aof Cameroon Mountain. Opera
would haye occurred at the diploi ldeve lW,e should Bot. 121: 159-177.
Muratq G.& T.Yarnazaki,1993,lsodon,in:Iwatsuki,K.,
the introgresshiyvberidization
consider possibili tofy T. Yamazaki, D. E. Boufford & H. Ohba, (eds.),
or diploi hdybri dspeciation in the taxa suspected of F]ora ofJapan 3a: 309-314 .KDdansha, Tbkyo.
reticulative evolution in the preliminary study. Paton ,A. J, ,D. Springat eS,. Suddee, D. Otieno ,R. J.
Because several hybrids between the Japanese taxa Grayer ,M, M, Harley ,F. WMis, M. S. J ,Simmonds,
of lsodon have been reported (Mura t&a Yamazaki M, P, Powell & V Savolaine n2.004. Phyloncny and
m1a9jo9r3) , ronlaetu rianl t hhe yebvorliutdiioznat iofot nhmeay t ahxaav .eI t ipsl iamypeed ra- ebPvhaoylslueotigd oennone te .f t Ehbvraoelse. i 3 pl1als:n ad2s7 ta7il-ld 2i9eD9sN .A(O criegimones. aLae b,iMaolt.ae)
tant to assess to what extent these hybrids have fer- Sokolovskaya ,A, P,, N, S, Probatova & E. G. Rudyka.
tility, 1986. A contribution te the study of chromosome
For investigat ioofn natural hybridizati oorn numbers and geographica ]distribution of somc
hybrid speciation in plants ,molecular works using species of the famil Lyamiaceae in the Sovie fta reast,
Bot.Zur.71i195-200.
more than one kind of marker are very effective S u z uka, O.19 50, Chromosome in
(Hegar&tHyiscock 2005),Molecularphylogenet- numbers pharmaceu-
tical plant sI .Rep, lnst K.ihara Biol .4:57-58.
ic studies on lsodon in Japan employing sequence Suzuki ,K, 1992a .Bumblebee pollinato rasnd pollina-
variations ofchloroplast and nuclear DNA are now tion ecotypes oflsodbn umbpvsus and Z Shikoldanus
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246 APG Nbl. 56
(Lamiacea PeL )S.pec, Biel .7: 37-48. (Lamiace aande )it srelation to fruit-s aentd seed-sct.
. 1992b ,Speciatio onf lsodon and it spo]]inators, J. PL Res. I13: 149-155,
ln: Inoue, K, & T, YUmoto. (eds. B)i,ology of Wakabayashi, M. 1973. Chromosome number of
Pollinator-Plant Mutualism: 61-79, Heibonsya, Rabdosia umbrosus (Maxim .H)ara var. hakusanen-
Tbkyo, (i nJapanese) sis (Kudo H)ara, Acta Phytotax G,eobot. 25: 153. (in
. & Y, Akazome. 2000, Flexibilit yof pollinator- Japanese)
flowe rrelationship in lsodon umbrosus and 1 eLt7iisus
ReceivedJiil2y3,2005; Sleptember13,2005
accepted
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