CYTOTAXONOMICSTUDIES IN THE EUPHORBIACEAE, SUBTRIBE PHYLLANTHINAE' GRADY L. WEBSTER and J.R. ELLIS Departmentof Biological Sciences, Purdue University,Lafayette, Indiana and Galton Laboratory,University College, London, England ABSTRACT WEBSTER, GRADY L. (Purdue U., Lafayette,Ind.), and J. R. ELLIS, Cytotaxonomicstudies in the Euphorbiaceae, subtribePhyllanthinae. Amer. Jour. Bot. 49: (1): 1X18. Illus. 1962.-Chromosome numbersare reportedfor 18 species of mostlyWest Indian Euphorbiaceae, subtribe Phyllanthinae, 13 of these for the first time (including the firstpublished count for the genus Margaritaria). For 4 species, a number differentfrom previous determinationshas been recorded. The base chromosomenumber in Breynia, Fluggea, Margaritaria,and most species of Phyllanthusappears to be 13. However, in Phyllanthus subg. Isocladus haploid numbers of 8 and 18 were observed.One species, Phyllanthuspulcher, is a sterile hexaploid (n - 39) of presumablyhybrid origin. The cytological data do not support Perry's suggestionthat annual taxa are primitivein the Euphorbiaceae. THE 7,000 species of the famllyEuphorbiaceae regarded as unequivocallyconfirmed. The few presentsuch a vegetativeand floraldiversity that workerswho have studiedtaxa of the subtribein- systematictreatment of the grouphas alwaysbeen clude Perry (1943), Raghavan (1957), Raghavan controversial.Not only have there been many and Arora (1958), JanakiAmmal and Raghavan schools of thoughtin delimltingtaxa withinthe (1958), and Thombre(1959). family,but its recognitionas a naturalgroup has In the presentcontribution we wish to report been seriouslyquestioned on the basis that it is the resultsof cytologicalobservations on 18 spe- polyphyleticin origin.Hutchinson (1959) suggests cies belongingto 4 generaof subtribe Phyllanthinae, derivationof the familyfrom at least 4 different most of which are eithernative to or cultivated orders(Blixales, Tiliales, Malvales, and Celastrales). in the West Indies. In view of the paucityof data Erdtman (1952), on the basis of palynolog,ical availableup untilnow, we believethat these counts studies,has suggestedpossible relationshipswith are moresignificant than a similarnumber of mis- theBuxaceae and Thymelaeaceae.Hurusawa (1954) cellaneousreports in moreextensively studied taxa. proposes a division of the Euphorbiaceaeinto 4 However,the tentativeand exploratorynature of families. our conclusionsmust be recognized,since even In contrastto such familiesas the Gramineae, withthe addition of therecords in thispaper, chro- Leguminosae,and Compositae,the Euphorbiaceae mosomenumbers are knownfor only about 3% have been relativelylittle studied cytologically. Of of thespecies of Phyllanthus. the 7,000 species, fewerthan 250 have been re. MATERIALS AND PROCEDUREs-Studies weremade portedon, and the bulk of the countsare in the ofplants growing in thefield in theWest Indies dur- singlegenus Euphorbia. The subfamilyPhyllanthoi. ing thesummer of 1959,and werelater supplemented deae has been especially under-represented.as by observationson plantsgrown in the greenhouses heretoforecounts have been publishedon less than at Purdue. Observationsof mitoticchromosomes 2%o of the 1500 species. In the subtribePhyllan. were made fromroot-tip squashes. Root-tipswere thinae,which includes about 1000 species (700 of pre-treatedfor 2-3 hr in a saturatedsolution of thesein Phyllanthus),counts have been published paradichlorobenzene,fixed overnightin acetic al- for only 8 species, and only I of these may be cohol,hydrolyzed in 1 N HCI at 60 C for 18 min stainedin Feulgen 1 Receivedfor publication May 12, 1961. for2 hr and squashedin aceto- carmine.For meiotic Field workfor this studywas carriedout in the West observations,buds were col- Indies during the summersof 1959 and 1960. The work was lectedin thefield and fixeddirectly in aceticalcohol supported by the National Science Foundation (Grant in whichthe acetic acid componenthad been sat- G-7148). uratedwith ferricacetate; the antherswere then The authorsare indebted to Mr. Kim Miller for valuable dissectedfrom the male flowers assistance in collecting and preparing material. Acknowl- and squashed in edgementfor assistance is also due to the directorsand staffs aceto-carmine.Voucher herbarium specimens of the of cooperatinginstitutions in the West Indies, includingthe plantsstudied have been depositedin the Kriebel Instituteof Jamaica (Kingston), U. S. AgriculturalExperi- Herbarium,Purdue University(PUL). ment Station (Mayaguiez), Universityof Puerto Rico Agri- RESULTS AND DISCUSSION-In 1 cultural ExperimentStation (Rio Piedras), Institutede la Table are pre- Recherche Agronomique (Basse-Terre), Imperial College sentedcounts made by us for 18 speciesbelonging of Tropical Agriculture (Port-of-Spain), and the Dept. of to 4 generaof the subtribePhyllanthinae, of which Agricultureand Marine Products (Nassau). 17 representeither different determinations ciom- 14 This content downloaded from 169.237.8.35 on Mon, 16 Sep 2013 14:22:41 PM All use subject to JSTOR Terms and Conditions January,1962] WEBSTER AND ELLIS-EUPHORBIACEAE 15 pared with previous reportsor counts recorded Margaritariahas not been reportedon cytologi- for the firsttime. For convenienceof comparison, callybefore, possibly because the commonest species publishedobservations by other workersare in- M. nobilisis disguisedin manybooks as a species cluded in the table,but are set in italic type.The of Phyllanthus.Cytologically, it agreesclosely with circumscriptionof the Phyllanthinaeand the Fluggeain havinga diploidcomplement of 26 chro- arrangementof subgenerictaxa withinPhyllanthus mosomes(Fig. 1). Margaritariaand Fluggea are, followsthe treatment of Webster(1956-58), which therefore,diploid genera, so faras we know,where- differsin a numberof respectsfrom the classifica- as Breyniais tetraploid.This relationshipis notun- tionof Pax and Hoffmann(1931). expected,since the formergenera have been con- It is interestingthat in the3 othergenera studied sideredprimitive on the basis of floraland vegeta- (besides Phyllanthus)x = 13. Perry'srecord of tivemorphology, whereas Breynia is obviouslymore 2n = 56 in Breynianivosa is questionable,inas- specialized. muchas we have found2n = 52 in meioticprepara- The 16 species of Phyllanthusreported on here, tionsof B. disticha(the correctname forthe same togetherwith 1 species (P. emblica) studied by plant). Likewise,his reportof 2n 16 in Fluggea Indian workers,represent 13 sectionsbelonging to obovatais probablyerroneous, for in our plantF. 8 subgenera.Although these species constituteless virosa the diploid number is clearly 26. Since than 3% of those in the genus,they are sufficient Fluggea obovata and F. virosa are synonymous fora preliminarysurvey of cytologicalrelationships namesfor the same plant,this large discrepancyin at the supraspecificlevel. reportedchromosome number suggests that perhaps One of the most strikingresults of our studies Perrv's determinationwas for some completely is the demonstrationthat the base numberin most differentplant. sectionsof Phyllanthusis 13, as in the 3 genera W.~ ~ ~ ~~~~~~~~~~~~I, ....S .. ...... .I Fig. 1-5. Chromosomesof Margaritaria and2800..... PI&yllantl&us.-Fig. 1. Margantaria nobilis, mitotic 2n 26 X diakm Fig. 2-3 Phyllathuspolgonoide, diakiesis, anphase I 2n = 1, X 1900 Fig. 4.PI&yllathuscarltnzenss sis, 2n =36, x 1900.-Fig. 5. Phyllantl&us2300~~~~~~~~~~~........ pulcl&er, anaphase I, x This content downloaded from 169.237.8.35 on Mon, 16 Sep 2013 14:22:41 PM All use subject to JSTOR Terms and Conditions 16 ANIERICAN JOURNAL OF BOTANY [Vol.49 mentionedabove, but that in 2 sectionsit is dis- Isocladus,which consists of specieswith unspecial- cordant.In P. polygonoidesof sect. Isocladus (not ized branching.On the otherhand, all taxa with West Indian but includedhere because of its in- n - 13 have phyllanthoidbranching (except for terest)n 8 (Fig. 2, 3), whilein P. caroliniensissect. Botryanthus).This would appear to suggest of sect.Loxopodium, n - 18 (Fig. 4). Perry'sre- thatthe taxa in subgenusIsocladus may be phylo- portof 2n - 28 in the latterspecies appears very geneticallyisolated fromthe other groups within dubious,even though he may have studieda differ- Phyllanthus.However, Arora (accordingto Janaki ent subspecies.It is noteworthythat sectionsIso- Ammaland Raghavan,1958) has reporteda chro- cladus and Loxopodiumboth belong to subgenus mosomecount of 2n - 52 forP. maderaspatensis, TABLE 1. Chromosomenumbers in the Phyllanthinae Taxon Chromosomenumber gam. spor. Reference or voucher collection Breynia disticha Forst. 26 Jamaica; Websteret al. 8069 56 Perry,1943a Fluggea 'obovata' 16 Perry,1943b Fluggea virosa (Willd.) Baill. 13 Jamaica; Proctor8131 Margaritarianobilis L. f. 26 Guadeloupe; Webster et al. 9157 Phyllanthus Subgenus ISOCLADUS Section ISOCLADUS P. polygonoidesNutt. ex Spr. 16 Texas; Johnston3547 P. maderaspatensisL. 52 Arora (cited by Janaki Ammal and Raghavan, 1958) Section LOXOPODIUM P. caroliniensisWalt. ssp. caroliniensis 28 Perry,1943C ssp. guianensis (Kl.) Webster 36 Martinique; Webster et al. 9200 Subgenus & section KIRGANELIA P. reticulatusPoir. 13 Webster and Wilson 5237 Subgenus & section CICCA P. acidus (L.) Skeels 26 Jamaica, cult. 14 Thombre,1959 Subgenus PHYLLANTHIUS Section EMBLICA P. emblica L. 28 Perry,1943 98 Raghavan, 1957 98-104 Janaki Ammal and Raghavan, 1958 Section URINARIA P. urinaria L. 26 Jamaica; Webster et al. 8177 52 Raghavan and Arora, 1958 Section PHYLLANTHUS P. amarus Schum. & Thonn. 26 Jamaica; Websteret al. 8025A