Nuclear DNA Amounts in Macaronesian Angiosperms

12 Pages·2003·0.15 MB·English

Annals ofBotany92:153–164,2003
doi:10.1093/aob/mcg104, available onlineatwww.aob.oupjournals.org
Nuclear DNA Amounts in Macaronesian Angiosperms
JAN SUDA1,2,*, TOMA´Sˇ KYNCL2 and RADKA FREIOVA´2
1Department of Botany, Charles University, Bena´tska´ 2, Prague 2, 128 01, Czech Republic, and 2Institute of Botany,
Academy of Sciences, Pru˚honice 1, Prague, 252 43, Czech Republic
Received:25October2002 Returnedforrevision:30January2003 Accepted:4March2003
NuclearDNAcontentsfor104Macaronesianangiosperms,withparticularattentiononCanaryIslandsendemics,
were analysed using propidium iodide flow cytometry. Prime estimates for more than one-sixth of the whole
Canarian endemic flora (including representatives of 11 endemic genera) were obtained. The resulting 1C DNA
values ranged from 0·19 to 7·21 pg for Descurainia bourgeauana and Argyranthemum frutescens, respectively
(about 38-fold difference). The majority of species, however, possessed (very) small genomes, with C-values
<1·6 pg. The tendency towards small nuclear DNA contents and genome sizes was confirmed by comparing
average values for Macaronesian andnon-Macaronesian representatives of individual families, genera and major
phylogeneticlineages.OurdatasupportthehypothesisthattheinsularselectionpressuresinMacaronesiafavour
small C-values and genome sizes. Both positive and negative correlations between infrageneric nuclear DNA
amountvariationandenvironmentalconditionsonTenerifewerealsofoundinseveralgenera.ª2003Annalsof
BotanyCompany
Keywords:C-value,CanaryIslands,endemic,flowcytometry,genomesize,nuclearDNAcontent,Macaronesia.
INTRODUCTION Oceanic islands typically show a high degree of
endemicity. Macaronesia harbours at least 30 endemic
Oceanicislandsplayanimportantroleinmaintainingglobal
genera(Bramwell,1976;Kunkel,1993)andtheproportion
biodiversity. It has been estimated that they harbour
ofMacaronesianendemicspeciesforindividualislandshas
approximately one-sixth of vascular plant species, a large
beenestimatedatbetween4%(GraciosaintheAzores)and
proportion of which is endangered (World Conservation
27 % (La Palma in the Canary Islands) (Hobohm, 2000).
Monitoring Centre, 1992). The Macaronesian phytogeo-
The main archipelago, the Canary Islands, is by far the
graphic region encompasses five assemblages of volcanic
richestarea,withabout570endemicspecies(about40%of
archipelagos in the eastern Atlantic Ocean (the Azores,
native plants) (Francisco-Ortega et al., 2000). Such a high
Madeira, the Salvage Islands, the Canary Islands and the
number of endemics could be attributed to the great
Cape Verde Islands), situated between 15 and 40(cid:176)N. The
diversity of habitats on the Canaries where six major
flora of this region is diverse and complex. The strongest
ecological zones have developed (Fernandopulle´, 1976). A
phytogeographicconnectionshavebeenproposedtobewith
broadrangeofgeologicalages(between0·8and21million
theMediterraneanbasinandnorth-westernAfrica;apparent
years) (Carracedo, 1994), a varying degree of substrate
linkswithsouth-easternAfricaandneotropicalregionscan
erosionandtheproximityoftheAfricancontinentmayalso
also be traced (Bramwell, 1986; Panero et al., 1999). A
contribute to the species richness. Adaptive radiation
distinct feature of indigenous plant species is a high
(divergent evolution in response to different ecological
proportion of woody life-forms in otherwise herbaceous
pressures) and vicariance (divergence due to geographic
groups, Echium and Sonchus being two prominent exam-
isolation) seem to be the main processes favouring the
ples. Analysis of growth-form composition also reveals a
diversification of ancestral plant types into several related
high percentage of succulents and a low abundance of
taxa (Crawfordet al.,1987).
geophytes and annuals (Shmida and Werger, 1992). The
The flora of Macaronesia, and of the Canary Islands in
Macaronesian flora has traditionally been suggested to
particular, has been subjected to numerous karyological
represent the relictual fragment of a subtropical Tertiary
studies (e.g. Larsen, 1963; Borgen 1969; Bramwell et al.,
plantbiotaoncewidespread inEurope and northern Africa
1976;Dalgaard,1991).Averylowincidenceofpolyploidy
(Bramwell,1976).However,modernphylogeneticanalyses
wasrepeatedlyconfirmed.Onthebasisof453species(304
of several Macaronesian plant groups (Aeonium,
Macaronesian endemics and 149 non-endemics) described
Argyranthemum, Bencomia, Echium) have not provided
cytologically,Borgen(1974)concludedthatonly26·6%of
support for a relict origin, and indicated relatively recent
endemicsand27·8%ofthetotalfloraarepolyploids.These
insulardiversificationfromcontinentalancestors(Emerson,
percentages may alter to a certain extent as some species
2002).
traditionally regarded as diploids (e.g. Canarina,
Convolvulus, Crambe, Micromeria) might actually be
*Forcorrespondence.Fax[phone],[email protected] polyploid in their origin. Nevertheless, the frequency of
Annals of Botany 92/1, ªAnnals of Botany Company 2003; all rights reserved
154 Suda et al.—Nuclear DNA Amounts in Macaronesian Angiosperms
TABLE1. List of localities of Macaronesian endemics used in the present study
No. Locality Coordinates Altitude(m)
1 Tenerife:Can˜adasdelTeide,rockcrevicesinValledeChin˜oque,northofElSanatorio 28(cid:176)14¢20¢¢N16(cid:176)36¢10¢¢W 2180
2 Tenerife:Can˜adasdelTeide,rockcrevicesandvolcanicsandseast-south-eastofParadorNacional 28(cid:176)13¢20¢¢N16(cid:176)37¢10¢¢W 2180
delasCan˜adashotel
3 Tenerife:Can˜adasdelTeide,rockcrevicesalonghikingtrailwestofColmenarhill 28(cid:176)15¢50¢¢N16(cid:176)33¢10¢¢W 2060
4 Tenerife:Can˜adasdelTeide,ElPortillo,volcanicsandsalonghikingtrailnearMontan˜adelas 28(cid:176)17¢40¢¢N16(cid:176)33¢40¢¢W 2000
ArenasNegrashill
5 Tenerife:Can˜adasdelTeide,RiscosdelaFortalesa,rockcrevicesatthetopofthemountain 28(cid:176)18¢50¢¢N16(cid:176)35¢50¢¢W ~2150
6 Tenerife:Pinuscanariensisforestalongtheroadapprox.1kmsouthofMiradoresdelaCumbre, 28(cid:176)21¢50¢¢N16(cid:176)28¢00¢¢W 1970
nearMontan˜aAvosahill
7 Tenerife:MargaritadePiedra,rockcrevicesinBarrancodelaZarza 28(cid:176)20¢30¢¢N16(cid:176)31¢30¢¢W 1420
8 Tenerife:Aquamansa,Fayal-brezalcommunityalongtheroadapprox.1kmsouth-westofthevillage 28(cid:176)21¢30¢¢N16(cid:176)30¢30¢¢W 1160
9 Tenerife:LosPinos,wallnexttoroadinthevillage 28(cid:176)22¢50¢¢N16(cid:176)30¢50¢¢W 520
10 Tenerife:Anaga,CasaCarlos,rockcrevicesinlaurelforestalongtheroadnearPicodelIngleshill 28(cid:176)31¢50¢¢N16(cid:176)15¢30¢¢W 940
11 Tenerife:Anaga,LomodeLasBodegasvillage,laurelforestnearChinobrehill 28(cid:176)33¢20¢¢N16(cid:176)10¢50¢¢W 770
12 Tenerife:Anaga,Chamorgavillage,rockcrevicesinBarrancodeRoqueBermejoandlaurelforest 28(cid:176)34¢N16(cid:176)09¢W 0–600
fragmentsnorth-eastofthevillage,nearMontan˜aTafadahill
13 Tenerife:Anaga,Tagananavillage,rockcrevicesinRoquedeEnmedio 28(cid:176)34¢00¢¢N16(cid:176)12¢40¢¢W 330
14 Tenerife:ValledeGu¨´ımar,succulentcommunity(cardonal)northofPuertodeGu¨´ımar 28(cid:176)18¢00¢¢N16(cid:176)22¢20¢¢W 30
15 Tenerife:Gu¨´ımar,Pa´jaravillage,rockcrevicesinLaderadeGu¨´ımar 28(cid:176)17¢30¢¢N16(cid:176)25¢30¢¢W 840
16 Tenerife:Teno,Mascavillage,rockcrevicesinBarrancodeMasca 28(cid:176)17¢30¢¢N16(cid:176)51¢W 0–600
17 Tenerife:Teno,LasPortelasvillage,rockcrevicesalongtheroadnearLaTabaiba 28(cid:176)19¢30¢¢N16(cid:176)51¢10¢¢W ~650
18 Tenerife:Teno,rockcrevicesinRoqueElFraile 28(cid:176)21¢40¢¢N16(cid:176)53¢40¢¢W 220
19 Tenerife:Teno,succulentcommunity(cardonal)nearPuntadeTeno 28(cid:176)20¢40¢¢N16(cid:176)55¢00¢¢W 40
20 Tenerife:Vilaflor,Pinuscanariensisforestalongtheroadapprox.5kmnorthofthetown 28(cid:176)10¢40¢¢N16(cid:176)38¢40¢¢W 1880
21 Tenerife:Fronto´ndeSanMiguel,succulentcommunity(tabaibal)invalleynearthevillage 28(cid:176)06¢40¢¢N16(cid:176)36¢50¢¢W 730
22 Tenerife:Adeje,rockcrevicesinBarrancodelInfierno 28(cid:176)08¢10¢¢N16(cid:176)42¢30¢¢W 490
23 LaPalma:CalderadeTaburiente,rockcrevicesnearMiradordelosAndenes 28(cid:176)45¢40¢¢N17(cid:176)52¢00¢¢W 2330
24 LaPalma:forestalongtheroadapprox.1kmnorth-westofTagojahill(north-westofSantaCruz 28(cid:176)43¢20¢¢N17(cid:176)47¢10¢¢W 1110
delaPalmacity)
25 LaPalma:CalderadeTaburiente,sandyareasapprox.1·5kmnorth-north-westoftheCentro 28(cid:176)40¢00¢¢N17(cid:176)51¢20¢¢W 950
deVisitantes
26 LaPalma:CalderadeTaburiente,sandyareasalongtheroadapprox.0·5kmsouth-eastoftheMirador 28(cid:176)41¢40¢¢N17(cid:176)51¢10¢¢W 1210
delaCumbrecita
27 LaPalma:Jedeyvillage,sandyareasalongtheroadSSEofthevillage 28(cid:176)34¢50¢¢N17(cid:176)52¢40¢¢W 700
28 LaPalma:CalderadeTaburiente,leg.Hanneken(Bot.GardenBerlin) – –
29 GranCanaria:Ayacata,basalt,leg.Royl(Bot.GardenBerlin) – 1330
30 GranCanaria:Moya,BarrancodelLaurel,leg.Royl(Bot.GardenBerlin) – 600
31 GranCanaria:MontanadeArucas,north-coast,leg.Royl(Bot.GardenBerlin) – 400
32 GranCanaria:Maspalomas,silicate,leg.Royl(Bot.GardenBerlin) – –
33 Fuerteventura(Bot.GardenBerlin,orig.seedsfromBot.GardenErlangen) – –
34 Lanzarote:Famara,basalt,leg.Royl(Bot.GardenBerlin) – 300
polyploid species, at least amongst the endemic elements, phylogeneticmarkersinevolutionarystudies(Leitchetal.,
would remainstrikingly low. 1998).CorrelationsbetweennuclearDNAamountandplant
The extensive karyological literature contrasts with the phenology (Grime and Mowforth, 1982), life history
almost complete lack of information about nuclear DNA (Bennett, 1972) or sensitivity to frost (MacGillivray and
amounts of Macaronesian plants. Hitherto, only 12 esti- Grime, 1995) indicate the utilization of C-values as
mates of C-value (the DNA amount in the unreplicated ecological indicators. Although such information was
haploidnucleusirrespectiveoftheploidylevelofthetaxon) based on 3500+ estimates of angiosperm C-values, further
ranging from 0·54 pg in Aeonium haworthii to 8·63 pg in targeted work is essential for better representation of
Ranunculus cortusifolius have been completed (Cerbah taxonomic groups, geographic regions and plant life forms
etal.,1999;BennettandLeitch,2001;Hansonetal.,2001; (Bennett et al., 2000). The principal goal of current work
Ellul et al., 2002). Nuclear DNA amount is undoubtedly a was to improve our knowledge of nuclear DNA amount
keycharacter,withmanyusesinvariousbiologicalfields.It from a geographic point of view. Macaronesia was chosen
has been employed as an effective tool for distinguishing as an appropriate region because of the high level of
taxa in several groups of vascular plants, e.g. in Petunia endemismthatenabledthecomparativestudyofpatternsof
(Mishiba et al., 2000) and Helleborus (Zonneveld, 2001). nuclear DNA amount variation in a phytogeographically
Moreover,ananalysisofgenomesizecanevenrevealnew distinct area. Moreover, a conspicuous concentration of
taxathathavesofarbeenneglected(GreilhuberandSpeta, plantbiotaatriskistobefoundthere;ithasbeenestimated
1985). There is increasing demand for C-values as a that 41 % of Canarian endemic flora is endangered
Suda et al.—Nuclear DNA Amounts in Macaronesian Angiosperms 155
(I.U.C.N., 1983). Therefore, there is an urgent need for =1·11pg),LycopersicumesculentumMill.‘Stupnicke´poln´ı
various biological data applicable to conservation biology tycˇkove´ rane´’ (2C = 1·96 pg), Glycine max (L.) Merrill
(Bennett et al.,2000). ‘Polanka’(2C=2·5pg),ZeamaysL.‘CE-777’(2C=5·43pg)
andPisumsativumL.‘Ctirad’(2C=9·09pg)(Dolez˘eletal.,
1992, 1994; Lysa´k and Dolez˘el, 1998). Selection of a
MATERIALS AND METHODS suitable standard followed these criteria: (1) the smallest
ratio between the 2C-values of an analysed plant and the
Plant material
internal standard to minimize the potential non-linearity of
SeedsofmostspecieswerecollectedontheCanaryIslands flow-cytometer measurements; (2) at least 12 % difference
during 2000–2001 (Table 1). The Botanical Garden in in2C-valuesoftheinternalstandardandsampletoexclude
Berlinprovidedseedsofanadditionaleightspecies,mostof bias due to very close or overlapping peaks; and (3) the
whichwerealsooriginallysampledinthefield.Seedswere sameinternalstandardwasusedforallspeciesbelongingto
germinated on wet filter papers in Petri dishes, and plants onegenus.Thecrudesuspensionwasfilteredthrougha42-
werecultivatedunderthesameconditionsinaglasshouseat mm nylon filter and centrifuged at 150 g for 5 min. The
the Experimental Garden of the Institute of Botany in pellet was resuspended in 100 ml fresh Otto I buffer and
Pru˚honice,Prague(50(cid:176)00¢N,14(cid:176)30¢E).Vouchersarekeptin samples were incubated for 30 min at room temperature.
theprivateherbariumofthefirstauthor.Thegreatmajority Subsequently, 1 ml of staining solution Otto II (0·4 M
ofspeciesiscurrentlybeinggrownattheBotanicalGarden Na HPO .12H O)supplementedwithpropidiumiodideand
2 4 2
of the Charles University,Prague. RNAse(bothat50mgml–1)wasaddedand,afterincubation
In total, 104 Macaronesian angiosperms with various for 30–45 min at room temperature, fluorescence intensity
distribution patterns were analysed; seven of these were of isolated nuclei was measured using a Partec PA II flow
endemictoMacaronesia,56endemictotheCanaryIslands, cytometer (Partec GmbH, Germany) equipped with an
32 endemic to Tenerife, six endemic to La Palma, and the argon ion laser (488 nm). The flow rate did not exceed 50
endemics of Lanzarote, Fuerteventura and Gran Canaria fluorescenteventspersecondinahugemajorityofspecies,
were represented by one species. Seven genera (Allago- andthefluorescenceofatleast5000particleswasrecorded.
pappus, Dicheranthus, Gesnouinia, Lugoa, Plocama, Two histograms for each sample were recorded and only
Tinguarra and Todaroa) were endemic to the Canary when both peaks were symmetrical and of approximately
Islands, and Argyranthemum, Isoplexis, Pericallis and equal height were analyses taken into account when
Schizogyne are the Macaronesian genera-endemics. The calculating the C-value of an analysed plant. When
plants were classified into 20 families and 14 orders converting picogram values to base pairs, 980 megabase
according to current phylogenetic views (Stevens, 2002), pairs(Mbp)wereassumedtobeequivalentto1picogramof
and all but three (Asparagus umbellatus, Dactylis smithii, DNA (Bennett et al., 2000).
Dracunculus canariensis) belong to the Eudicots. The vast
majority of species was perennial; Senecio teneriffae and
Chromosome counts
Volutaria canariensis being the only two exceptions.
Chamaephytes clearly prevailed from a life-form point Observations were made on root tip cells of germinated
ofview [theterminologyoflife-formsfollowsthecategor- seedlings. Samples were pre-treated with a saturated
ies adopted in the World Checklist and Bibliography solution of p-dichlorbenzene or 1-monobromnaphtalene
Series database at Royal Botanic Gardens, Kew, UK for 3 h at room temperature, fixed in 3 : 1 ethanol : acetic
(www.rbgkew.org.uk/wcb/index.html)]. Considering the acidovernightat4(cid:176)Candkeptin70%ethanolatthesame
ecologicalprofileofthepresentspeciesset,representatives temperature. After maceration in 1 : 1 hydrochloric
of five major zones covering an altitudinal range of more acid : ethanol for 60 s, the root tip cuttings were squashed
than 2300m were included. in lacto-propionic orceine. As a rule, at least three mitoses
per plant andtwo individuals per species were counted.
Flow cytometry
Statistical analyses
To reveal potential intrapopulation variability in nuclear
DNA amount, three to six plants from each species were DNA amount data were analysed with the SAS 8.1
measured simultaneously in the first step. As one narrow statistical package using ANOVA, CORR, GLM and
peak with unimodal distribution was always obtained, one UNIVARIATE procedures (SAS Institute, Cary, NC,
individual per species was randomly selected and analysed USA).DifferencesinDNAcontentbetweenspecieswithin
further. Each plant was measured at least three times on a genus were tested by ANOVA, and Tukey’s procedure
differentdaysbythesameoperator,andadifferentleafwas was applied to compare mean values. Differences in C-
used for each analysis. valuesbetweenmajorangiospermlineagesofMacaronesian
Nuclearsampleswerepreparedfromayoungfreshintact plants were analysed using the GLM procedure because of
leaf. Approximately 50mm2ofleaftissuewasco-chopped anunbalanceddesign.DifferencesinC-valuesandgenome
with an appropriate volume of internal standard in 1 ml of sizes between Macaronesian vs. non-Macaronesian repre-
ice-cold Otto I Buffer (0·1 M citric acid, 0·5 % Tween 20) sentatives were tested using the signed rank test on paired
usinganewrazorblade(Otto,1990).Thefollowinginternal datatoavoidproblemsofdatanon-linearity.TheSpearman-
standards were employed: Raphanus sativus L. ‘Saxa’ (2C rank correlation coefficient was employed in testing
156 Suda et al.—Nuclear DNA Amounts in Macaronesian Angiosperms
(2n),sand ocality 147 20 10 17 12 21262121612 11212 14 3 19161516188121 2336121622124
rn L
hromosomenumbedistributionpatter CVofsampleDistribution(%)pattern§ 3·71–4·88C2·28–2·67T 1·89–3·02T 2·26–3·18T 1·84–2·60T 1·84–2·82C 1·86–2·39T1·54–2·64P1·82–2·39T2·02–3·29C2·54–3·67C2·50–2·97C 1·79–2·83C2·05–3·10T4·06–4·53C 3·49–4·74C 1·88–3·08C 3·94–4·41C2·23–2·96C4·11–4·49T3·57–3·85T2·76–3·73T2·88–4·53C2·08–3·37C5·72–8·57T 5·64–7·67P5·43–7·68T4·99–6·56T6·07–7·79C3·60–4·18C2·89–3·65C2·10–3·27C3·49–4·44T
Mbp),cspecies CVofinternalstandard(%) 2·60–3·572·21–2·66 1·67–2·92 1·99–2·81 1·54–2·48 1·83–2·65 1·74–2·541·27–2·231·65–2·252·01–2·762·52–3·561·84–2·24 1·92–2·861·61–2·942·79–3·56 3·38–4·08 2·01–2·99 2·82–3·382·38–3·212·90–3·432·55–3·702·49–3·392·70–3·761·95–2·522·56–3·52 2·41–3·323·23–4·342·63–2·992·68–3·452·84–3·652·85–3·281·84–2·853·27–4·12
1pg=980thesample, LifeInternalorm**standard‡ CGCP CP CP CP CP CPCPH/CPCPClNPLCL ClGPCZSHR SHR CL NPGClNPGCGCGCGCGHZCR CRCRCRCRCLCGGPHG
asepairs(andardandmilies Genomesize(2CDNAamount/ploidylevel)(pg)f† 0·886·84 6·89 7·07 7·14 7·21 7·096·696·975·711·280·40 1·433·560·44 0·43 <0·71 0·350·350·310·320·310·332·180·19 0·220·230·220·220·751·121·981·55
ndmegabnternalstom20fa ylevel(x)† 22 2 2 2 2 222224 422 2 >2 66666622 22222242
air d
msofesf Ploi
NAcontentinpicogracoefficientsofvariance04Macaronesianspeci 1CDNA1CDNAamountamount(Mbp)2n(pg)¶ 10·888622036·84A670318* 56·89A675218* 67·07B692918 57·14B699718 47·21C706618 67·09B69481886·69D655618*56·97E683118*65·7155961831·2812542040·7977432 22·8527933463·56348920*10·44A43122 10·43B42122 20·71696~30* 11·06A10393011·06A103930!*10·93A9113010·95B931~30!*10·92A902~30*20·99C9703022·1821361410·19A18614* 10·22BC21614!*10·23B22514!*10·22BC2161410·22C21614*030·757351611·1210981493·9538712811·55151918*
nuclearDdardused,calityfor1 2CDNAamount6s.e.(pg) 1·7560·013·6960·0 13·7760·0 14·1460·0 14·2860·0 14·4160·0 14·1860·013·3960·013·9460·011·4360·02·5660·01·5860·00 5·7160·07·1160·00·8960·0 0·8660·0 1·4360·0 2·1260·02·1360·01·8660·01·9060·01·8560·01·9860·04·3560·00·3860·0 0·4560·00·4660·00·4560·00·4460·01·4960·02·2460·07·9060·03·1060·0
T2.2CnuclearDNAcontentwithstandarderror,1CABLEploidylevel,unreplicatedgenomesize,life-form,internalstanoriginallo TaxonFamily Allagopappusdichotomus(L.fil.)Cass.AsteraceaeArgyranthemumadauctum(Link)AsteraceaeHumphr.ssp.adauctumArgyranthemumadauctum(Link)AsteraceaeHumphr.ssp.dugourii(Bolle)Humphr.Argyranthemumbroussonetii(Pers.)AsteraceaeHumphr.ssp.broussonetiiArgyranthemumfoeniculaceum(Willd.)AsteraceaeWebbexSch.Bip.Argyranthemumfrutescens(L.)Sch.Bip.Asteraceaessp.frutescensArgyranthemumgracileSch.Bip.AsteraceaeArgyranthemumhaouarytheumHumphr.&Bramw.AsteraceaeArgyranthemumteneriffaeHumphr.AsteraceaeArtemisiathusculaCav.AsteraceaeAsparagusumbellatusLinkAsparagaceaeBupleurumsalicifoliumR.Br.inBuchApiaceaessp.aciphyllum(WebbexParl.)Sund.&Kunk.Canarinacanariensis(L.)VatkeCampanulaceaeCarlinaxeranthemoidesL.fil.AsteraceaeCeropegiadichotomaHaw.Apocynaceae(incl.Asclepiadaceae)CeropegiafuscaBolleApocynaceae(incl.Asclepiadaceae)Cheirolophusteydis(Chr.Sm.inBuch)Asteraceae´G.LopezConvolvulusfloridusL.fil.ConvolvulaceaeConvolvulusperraudieriCoss.ConvolvulaceaeCrambearboreaWebbexChristvar.indivisaSvent.BrassicaceaeCrambelaevigataDC.exChristBrassicaceaeCrambescaberrimaWebbexBramw.Brassicaceae´CrambestrigosaL.¢Her.BrassicaceaeDactylissmithiiLinkssp.smithiiPoaceaeDescurainiabourgeauana(Fourn.)BrassicaceaeO.E.SchulzDescurainiagilvaSvent.BrassicaceaeDescurainiagonzalesiiSvent.BrassicaceaeDescurainialemsiiBramw.BrassicaceaeDescurainiamillefolia(Jacq.)Webb&Berth.BrassicaceaeDicheranthusplocamoidesWebbCaryophyllaceaeDorycniumeriophtalmumWebb&Berth.FabaceaeDracunculuscanariensisKunthAraceaeErigeroncalderaeHans.Asteraceae
Suda et al.—Nuclear DNA Amounts in Macaronesian Angiosperms 157
y
calit 29227113081811231231 1212 26 126101213258 51233112117916243114 14310 3423198
o
L
n
Distributiopattern§ MCCCMMTCPTM TC C TTMTTPC TCFCCCCTTPGC CCC LCCC
79718455162 62 6 4207157 404713425617 916 4096
CVofsample(%) 3·55–4·83·41–4·93·81–4·85·54–6·93·24–4·03·85–4·82·99–3·53·85–4·03·23–4·03·81–6·75·08–5·4 1·78–2·52·01–3·0 2·78–4·1 3·60–4·22·21–3·42·09–2·92·12–2·85·18–6·15·11–6·34·32–5·7 4·48–5·84·43–5·92·98–3·53·67–4·82·27–2·94·89–7·14·12–4·93·97–4·53·00–4·83·93–5·34·53–5·54·72–5·5 2·76–3·42·45–3·53·73–4·9 3·86–4·93·32–5·02·38–3·32·94–3·5
CVofinternalstandard(%) 2·11–3·012·01–3·172·56–3·032·70–3·452·62–3·382·98–3·482·31–3·162·43–3·012·29–3·202·12–3·542·28–3·08 1·97–2·871·59–2·27 2·30–3·09 2·28–2·892·25–3·022·03–2·822·12–2·953·65–4·593·29–3·993·19–4·12 3·20–4·083·20–4·212·52–3·342·65–3·492·45–2·872·82–4·412·40–3·252·24–3·252·32–2·672·46–3·002·42–3·132·51–2·94 2·49–3·281·87–3·132·18–2·85 2·29–2·992·26–2·992·53–2·912·76–3·33
nternalandard‡ LLRLRRLGGLL PP L LLLPRRR RRGRLLLLLLLL GZL LLGR
Ist
Lifeorm** CCCNPNPCHCHCC HH C HHHH/CCCC CCCHCCHHCHHClNP CHC CCNPH/C
Genomesize(2CDNAamount/ploidylevel)f(pg)† 0·290·270·320·510·250·201·140·25(1·03)0·510·51 5·452·62 0·56 0·610·620·625·97?(<0·38)(<0·36) <0·37<0·370·860·270·670·180·230·240·190·200·190·50 1·092·300·48 0·500·560·70(0·47)
x)†
(
level 44224428(2)22 22 2 2242?>2)>2) >2>22246666662 222 224(2)
y ((
d
oi
Pl
* * **** * * *
ed 2n 282822204040656?2222 1412 22 14142818??? 303014163260606060606022 182012 121244?
u
Contin 1CDNAamount(Mbp) 56852931450050040211179801009500500 53412568 549 59860812155851431372353 3633638432651313539666715559588559490 10682254470 4905491362461
2BLE 1CDNAamount(pg)¶ 0·58A0·54B0·320·510·51A0·41B1·141·001·030·51A0·51A 5·45A2·62B 0·56 0·61A0·62B1·24C5·970·44A0·38B0·36C 0·37CD0·37BD0·860·271·340·55A0·68B0·73C0·57D0·60E0·57D0·50 1·092·300·48A 0·50B0·56C1·390·47A
A 3 4
T 12111121111 61 1 0121111 111121120111 351 1111
DNAunt6(pg) 60·060·060·060·060·060·060·060·060·060·060·0 60·060·0 60·0 60·060·060·060·060·060·060·0 60·060·060·060·060·060·060·060·060·060·060·060·0 60·060·060·0 60·060·060·060·0
2Camos.e. 1·161·080·641·021·010·812·281·992·051·011·02 0·905·23 1·13 1·221·242·481·940·880·760·72 0·740·751·720·552·681·091·361·461·151·201·141·00 2·194·600·97 1·001·112·790·93
1 1
e)
Family BrassicaceaeBrassicaceaeUrticaceaeUrticaceaeClusiaceaeClusiaceaeAsteraceaePlantaginaceaeAsteraceaeLamiaceaeLamiaceae PlumbaginaceaePlumbaginaceae Brassicaceae FabaceaeFabaceaeFabaceaeAsteraceaeLamiaceaeLamiaceaeLamiaceae LamiaceaeLamiaceaeAsteraceaeLamiaceaeCaryophyllaceaeAsteraceaeAsteraceaeAsteraceaeAsteraceaeAsteraceaeAsteraceaeApocynaceaecl.AsclepiadaceaAsteraceaeApiaceaePlantaginaceae PlantaginaceaePlantaginaceaeRubiaceaeCaryophyllaceae
n
(i
k
c
Taxon Erysimumbicolor(Hornem.)DC.Erysimumscoparium(Brouss.exWilld.)Wettst.ForsskaoleaangustifoliaRetz.Gesnouiniaarborea(L.fil.)Gaud.HypericumcanarienseL.HypericumgrandifoliumChoisyHypochoerisoligocephala(Svent.&Bramw.)LaIsoplexiscanariensis(L.)Loud.LactucapalmensisBolleLavandulabuchiiWebbvar.buchiiLavandulamultifidaL.ssp.canariensis(Mill.)Pit.&Pr.Limoniummacrophyllum(Brouss.)O.KuntzeLimoniumpectinatum(Ait.)O.Kuntzevar.pectinatumLobulariacanariensis(Webb)Borgenssp.palmensis(Christ)BorgenLotusdumetorumWebbexMurr.Lotuscampylocladus(Webb&Berth.)LotusglaucusAit.Lugoarevoluta(Chr.Sm.inBuch)DC.´MicromeriaglomerataPerezMicromeriaherpyllomorphaWebb&Berth.MicromeriahyssopifoliaWebb&Berth.var.hyssopifoliaMicromerialachnophyllaWebb&Berth.MicromeriavariaBenthamssp.variaNaupliussericeus(L.fil.)Cass.NepetateydeaWebb.&Berth.Paronychiacanariensis(L.fil.)Juss.Pericallisappendiculata(L.fil.)B.Nord.´Pericalliscruenta(L.¢Her.)BollePericallisechinata(L.fil.)B.Nord.´Pericallislanata(L.¢Her.)B.Nord.Pericallispapyracea(DC.)B.Nord.Pericalliswebbii(Sch.Bip.)BollePeriplocalaevigataAit. PhagnalonumbelliformeDC.PimpinellacumbraeLinkPlantagoarborescensPoir.ssp.arborescensvar.arborescensPlantagofamaraeSvent.PlantagowebbiiBarn.PlocamapendulaAit.Polycarpaeaaristata(Ait.)DC.
158 Suda et al.—Nuclear DNA Amounts in Macaronesian Angiosperms
ocality 1028515121271621023712321226123 6125238912126 2725114 ‘Saxa’
L s
n u
CVofinternalCVofstandardsampleDistributio(%)(%)pattern§ 2·77–3·192·68–3·03C2·55–3·683·03–5·11C2·78–3·202·67–3·38C2·34–3·322·44–2·68C2·06–3·081·75–2·66C2·92–3·842·17–3·94C2·49–3·053·45–4·69M3·07–4·023·55–5·55T3·10–4·024·10–4·62C2·80–3·422·91–3·69T2·50–3·032·80–3·23C1·64–2·372·83–3·46C2·86–3·252·56–2·93C2·54–3·002·98–3·69C2·52–3·233·09–3·74M3·25–4·072·45–3·03C2·98–4·782·80–4·40T2·59–3·732·29–3·88T 1·77–2·842·04–3·44C1·75–2·372·04–3·30T1·86–2·802·11–3·40T2·15–3·122·73–3·84P2·90–3·652·59–3·14C2·80–3·092·57–3·11C2·24–3·042·33–3·06T3·32–4·264·21–4·63C2·88–3·812·54–3·89C 2·72–3·632·08–2·71C2·50–3·081·86–2·46C2·55–3·072·42–3·11T2·81–3·132·62–3·62C 9·09pg);R,Raphanussativ micryptophyte;T,therophyte.
LifeInternalorm**standard‡ HRHLH/CRCGHGCPHLCRHGHGCGTPHGCGCGCGCGCG HPHPHPHPHLCLHLNPGHL HLHLHLTL ‘Ctirad’(2C= H,succulenthe
Genomesize(2CDNAamount/ploidylevel)(x)† f(pg)† 0·44?0·451·781·893·120·690·430·260·260·980·881·891·021·020·891·010·91 2·552·592·582·611·431·441·310·751·22 1·441·331·370·40 P,Pisumsativum ophanerophyte;S
T2ContinuedABLE 1CDNA2CDNA1CDNAamountPloidylevelamount6amount(Mbp)2nTaxonFamilys.e.(pg)(pg)¶ PolycarpaealatifoliaWilld.Caryophyllaceae0·8960·0030·44B431182PolycarpaeasmithiiLinkCaryophyllaceae1·0960·010·54C529??PolycarpaeatenuisWebbexChristCaryophyllaceae0·9160·0030·45D44118!*2Pterocephalusdumetorum(Brouss.exWilld.)Coult.Dipsacaceae3·5660·011·78174418*2Reichardialigulata(Vent.)Kunk.&Sund.Asteraceae3·7860·011·89185216*2RumexlunariaL.Polygonaceae12·4760·096·23A6105364RumexmaderensisLowePolygonaceae1·3860·010·69B676202SalviabroussonetiiBenthamLamiaceae0·8660·010·43421222ScrophulariaglabrataAit.Scrophulariaceae2·0660·011·03A1009568ScrophulariasmithiiHornem.ssp.smithiiScrophulariaceae2·0860·011·04B1019588Seneciopalmensis(Chr.Sm.inBuch)LinkAsteraceae1·9660·010·98A96020*2SenecioteneriffaeSchultzBip.Asteraceae5·2660·022·63B2577606SeseliwebbiiCoss.Apiaceae3·7960·021·891852222SchizogyneglaberrimaDC.Asteraceae2·0560·011·02A1000182Schizogynesericea(L.fil.)DC.Asteraceae2·0560·011·02A1000182SideritiscanariensisL.Lamiaceae3·5660·011·78A1744444SideritismacrostachysPoir.Lamiaceae4·0360·032·01B1970~36*4´´SideritisoroteneriffaeNegrın&PerezLamiaceae3·6560·011·82C1784444var.oroteneriffaeSileneberthelotianaWebbCaryophyllaceae5·1160·042·55A249924!*2SilenelagunensisChr.Sm.exChristCaryophyllaceae5·1960·012·59BC253824*2SilenenocteolensWebb&Berth.Caryophyllaceae5·1660·012·58C252824*2Silenepogonocalyx(Svent.)Bramw.Caryophyllaceae5·2360·012·61B255824!*2SonchusacaulisDum.-Cours.Asteraceae2·8660·031·43A1401182SonchuscongestusWilld.Asteraceae2·8760·021·44B1411182SonchusradicatusAit.Asteraceae2·6260·021·31C128418*2Telinecanariensis(L.)Webb.&Berth.Fabaceae3·0060·031·50147048!*4Tinguarramontana(WebbexChrist)Apiaceae2·4560·021·221196222A.Hans.&Kunk.TodaroaaureaParl.Apiaceae2·8760·011·441411222Tolpislaciniata(Sch.Bip.exWebb&Berth.)WebbAsteraceae2·6660·031·33A1303182TolpiswebbiiSch.Bip.exWebb&Berth.Asteraceae2·7560·011·37B134318*2VolutariacanariensisWagenitzAsteraceae1·6060·010·80784324 *Chromosomenumbersdeterminedinthepresentwork;!,newspeciesrecord.Allothercountsweretakenfromliterature.Anassumedploidylevelandgenomesizegiveninparentheses.† ´´ˇ´´G,Glycinemax‘Polanka’(2C=2·5pg);L,Lycopersicumesculentum‘Stupnickepolnıtyckoverane’(2C=1·96pg);‡ (2C=1·11pg);Z,Zeamays‘CE-777’(2C=5·43pg).C,CanaryIslands;F,Fuerteventura;G,GranCanaria;L,Lanzarote;M,Macaronesia;P,LaPalma;T,Tenerife.§ Lettersindicategroupoftaxawithinthesamegenusthatarenotsignificantlydifferentata=0·05.¶ **C,Chamaephyte;ClG,climbinggeophyte;ClNP,climbingnanophanerophyte;G,geophyte;H,hemicryptophyte;NP,nan
Suda et al.—Nuclear DNA Amounts in Macaronesian Angiosperms 159
s
m
r
spe M57) 5 55 3
anangio steridsII non-(n=3 3·90·41·83·05·124·82·9
onesi Eua M=42) 2·610·550·901·43·387·210·57
r n
a (
c
a
ndnon-M eridsI non-M(n=280) 2·210·330·91·42·8415·30·85
a st
here) Eua M=24) 0·780·270·430·511·052·010·37
n
d (
e
at
M;estim dsII non-M(n=152) 1·380·050·551·121·768·70·58
( osi
nesian) Eur Mn=12) 0·550·190·220·550·920·990·22
o1 (
r0
a0
geneticlineagesofMacmBennettandLeitch,2 EurosidsI MMnon-M07)(n=9)(n=721) 20·762·350·320·120·510·650·611·1581·122·3531·527·480·510·55
phyloM;fro udicots non-(n=2 6·10·20·72·19·679·30·4
formajor(non- Basale M(n=14) 2·090·440·581·952·616·23–
s
set 7)
M8 5 4 5
ue n-14 0·50·12·55·83·97·40·9
C-val nocots no(n= 1 112
1 o
M
of 3) 783875
cs Mn= 2·41·21·72·13·03·9–
sti (
riptivestati cots non-M(n=1929) 3·270·050·851·654·1579·330·7
desc Eudi 1) s.
elected M(n=10 1·690·190·510·991·787·210·51 picogram
S n
T3.ABLE Phylogeneticlineage MeanMinimum25%quartileMedian75%quartileMaximumMode Allvaluesi
160 Suda et al.—Nuclear DNA Amounts in Macaronesian Angiosperms
FIG.1. 1C DNA amount distribution (pg means) of 104 Macaronesian
speciesinvestigated.
whether infrageneric DNA amount variation (mean values
for individual species) correlated with the altitude and
environmental characteristics (climatic data were taken
from Fernandopulle´,1976).
RESULTS
Chromosome counts
Table2givesachromosomecountoranestimatednumber
for 35 Macaronesian angiosperms; eight of these represent
newspeciesrecords.Specialattentionwaspaidtotaxafrom
FIG.2.Flow-cytometrichistogramsshowingthedifferencein2Cnuclear
the supracanarian zone (generally above 2000 m altitude). DNA content for species with the smallest DNA amounts, Descurainia
Thechromosomecountsfor63othertaxaweretakenfrom bourgeauana and D. lemsii (A), and species with the highest DNA
the literature, and the number of chromosomes for six amounts,ArgyranthemumhaouarytheumandA.frutescens(B).Nucleiof
both species in the genus were isolated and stained with propidium
species isapparentlyunknown.
iodide simultaneously. Small G2 peaks represent the nuclei of
An analysis of ploidy level revealed the following:
Descurainiawithdoubled(4C)nuclearDNAcontent.
diploids, 63 taxa; tetraploids, 16 taxa; hexaploids, 13 taxa;
and octoploids, three taxa. The proportion of polyploid
plantswastherefore33·7%.Despiteusuallybeingregarded
as diploids, Crambe species were included amongst the
hexaploids on the basis of comparative genome mapping
results (Leitch and Bennett, 1997). Three taxa with a basic
chromosomenumberhigherthan13wereexcludedfromthe
comparisonasitwasuncertainwhethertheywerediploidor
polyploid(Grant,1971),andtheomissionalsoappliedtosix
species which lacked an exact chromosome count.
Nuclear DNA amounts
Table 2 shows 2C DNA content (pg) andstandard error,
1C DNA content expressed in picograms and megabase
pairs, number of chromosomes and ploidy level, genome
size (calculated as 2C DNA value/ploidy level), life-form,
internalstandardused,coefficientsofvariance(CV)ofboth
theinternalstandardandplantanalysed,speciesdistribution FIG.3. Flow-cytometric histogram obtained after simultaneous analysis
of propidium iodide-stained nuclei of Lycopersicum esculentum (L.e.;
pattern and original locality for 104 taxa from 20 families.
internalstandard)andRumexmaderensis.Occurrenceofnucleiwith2C,
Prime C-values represent 98 % of the estimates in the 4Cand8CDNAamountsindicatesendoreduplication.
Suda et al.—Nuclear DNA Amounts in Macaronesian Angiosperms 161
present species set; only Hypochoeris oligocephala and differed significantly. Somatic tissues of five taxa (Cero-
Plocamapendulahave been analysed previously. pegia dichotoma, C. fusca, Dicheranthus plocamoides,
Flow-cytometric measurements yielded histograms with Polycarpaea smithii and Rumex maderensis) underwent
CV values ranging from 1·27 to4·78 %(mean 2·85%) for endoreduplication,andthreepeakscorrespondingtonuclei
internal standards, and 1·54 to 8·57 % (mean 3·57 %) for with 2C, 4C and 8C DNA content were observed. Flow
analysedplants,dependingonthetaxon,DNAamountand histogramsofparticularinterestareshowninFigs2and3.
thequalityofsamplepreparation.ACVvaluenotexceeding
the arbitrary level of 3 % was achieved in 69 and 47 % of
Correlation of C-value with environmental conditions
internal standard and analysed plant acquisitions, respect-
ively. The standard error of the mean described the Correlations between C-value and altitude, average
difference in 2C-values between individual runs of the annual temperature, humidity and rainfall were calculated
samespeciescausedbycytometerinstability,non-identical in genera where at least three species from Tenerife were
sample preparation, etc. Values smaller than 1 % of the available.ThenuclearDNAamountinArgyranthemumwas
plant 2C DNA amount were attained in 82 % of taxa; the negativelycorrelatedwithaltitude(r=–0·806,P<0·0001,
limit of 2 % was never been exceeded. Therefore, the data n = 8) and annual rainfall (r = –0·783, P < 0·0001, n = 8),
on nuclear DNA content can be regarded as reliable. and positively correlated with mean annual temperature
1C nuclear DNA contents obtained in the present study (r = 0·704, P < 0·0001, n = 8). The number of species in
rangedfrom0·19pginDescurainiabourgeauanato7·21pg other genera was too small to permit meaningful compari-
in Argyranthemum frutescens, representing a difference of sons so the results were treated only as tendencies. The
approx.38-fold(Table2;Fig.1).However,themajorityof DNA amount in Silene and Micromeria followed the same
species(71%)fellintothelowerpartoftherange,withC- trends as in Argyranthemum (with the exception of a non-
values between 0·2 and 1·6 pg. Genome sizes had a range significantcorrelationwithaltitude).Acompletelydifferent
very similar to that of 1C DNA content, with hexaploid pattern of variation was observed in Crambe and Sonchus
Pericallis appendiculata having the smallest genome where nuclear DNA content increased with higher mean
(0·18 pg). The highest genome size was found in diploid altitude and rainfall, and decreased with average annual
Argyranthemumfrutescens.Comparisonofmeanvaluesfor temperature.TheDNAamountinPericalliswasnegatively
Macaronesian vs. non-Macaronesian (taken from Bennett correlated with relative humidity (r = –0·616, P = 0·0005,
and Leitch, 2001) representatives of individual genera and n=4).However,thisrelationshipmaybebiasedtoacertain
families affirmed the tendency towards small C-values and extentasthegenuscomprisedspeciesoftwogrowth-forms
genomesizesinMacaronesiantaxa(datanotshown).Atthe (chamaephytes P. appendiculata and P. lanata possessed
rankoffamily,bothC-valuesandgenomesizesofendemic significantly smaller genomes than hemicryptophytes
plants were significantly smaller (P < 0·01, n = 20) than P. echinata and P. cruenta).
thoseofnon-Macaronesiantaxa,andthecomparisonsatthe
generic level brought identical results (P = 0·017, n = 22).
Artemisia,ReichardiaandRumexwerethemostprominent
DISCUSSION
exceptions, with Macaronesian representatives having
larger C-values. Although species from 56 genera were Nuclear DNA amounts for 104 Macaronesian angiosperms
includedinthestudy,only22generawereemployedinthe from56generaand20familieswereestimatedinthisstudy.
foregoing comparison as no previous C-value data were Speciesfromthisphytogeographicregionhavebeenunder-
available for the remaining 34 genera. Small nuclear DNA represented in previous investigations of nuclear DNA
amounts in Macaronesian native flora were also confirmed amount,andonly12estimateswereavailable(Cerbahetal.,
in data sets taking the phylogenetic position of the species 1999; Bennettand Leitch, 2001; Hanson et al., 2001; Ellul
into account. Selected descriptive statistics for major et al., 2002). The present paper therefore increases know-
angiosperm lineages clearly indicate that non-Maca- ledgeofnuclearDNAcontentinMacaronesianangiosperms
ronesian plants possessed larger C-values that their byalmostninetimes.Thirty-fourofthe56genera(60·7%)
Macaronesiancounterparts(Table3).Macaronesianspecies werepreviouslywithoutC-valuesandthepresentestimates
of particular interest with very low DNA amounts include thusrepresentthefirstdataonnuclearDNAcontent.Ahuge
Nepeta teydea (1C = 0·27 pg; the smallest C-value among majority (93 %) of taxa analysed was restricted to the
EuasteridsIIandeventheAsteridsasawhole),Micromeria Canary Islands. A comparison with recent figures on
spp.(1C=0·36–0·44pg;verysmallC-valuesinEuasterids Canarian flora (Francisco-Ortega et al., 2000) indicates
II) and Pericallis appendiculata (1C = 0·55 pg; the second thatinformationonC-valueandgenomesizeformorethan
smallestC-valueinEuasteridsI).Average1CnuclearDNA one-sixth (approx. 17·9 %) of Canarian endemics was
amounts 6 s.d. for main phylogenetic lineages of obtained. It should, however, be emphasized that there are
Macaronesian plants were as follows: Eurosids II, significantdifferencesconcerningboththetotalnumberand
0·55 6 0·33 pg; Eurosids I, 0·76 6 0·42 pg; Euasterids I, the proportion of endemic plants given by various authors.
0·7860·52pg;BasalEudicots,2·0961·85pg;Monocots, AlthoughMacaronesialacksanyendemicfamily,morethan
2·4761·36pg;EuasteridsII,2·6162·44pg.Apparently, 30 endemic genera can be found there (Bramwell, 1976;
there are some differences in mean C-values (one group Kunkel, 1993). This study encompassed species from 11
with 1C <1 pg, the other with 1C >2 pg); however, only endemic genera, thus representing about one-third of
Eurosids II/Euasterids II and Euasterids I/Euasterids II generic coverage.
162 Suda et al.—Nuclear DNA Amounts in Macaronesian Angiosperms
Theoverall1C-valuesobtainedherevariedfrom0·19pg speciationprocesses.Chromosomalsurveysonbothoceanic
inDescurainia bourgeauanato7·21pginArgyranthemum and more continental islands revealed chromosomal stasis
frutescens (about 38-fold difference). Nuclear DNA even though speciation has often been accompanied by
amounts for 12 Macaronesian angiosperms published pre- striking morphological divergence (Stuessy and Crawford,
viously differed approx. 16-fold, from 0·54 pg in the 1998).Dataobtainedinthepresentstudysupportaworking
Tenerife-endemic Aeonium haworthii to 8·63 pg in the hypothesis that small C-values are an evolutionary advan-
Macaronesian Ranunculus cortusifolius. By merging both tage under insular selection pressures. However, further
lists, we can conclude that C-values of Macaronesian targeted work isessential to test this theory.
vascular plants currently differ at least 45-fold. This is a Although several molecular analyses of Macaronesian
relatively narrow range compared with the approx. 1000- angiosperms have been published, meaningful comparison
fold variation in angiosperms as a whole (Bennett et al., betweenthephylogeneticpositionandnuclearDNAcontent
2000). However, it should be noted that very few is possible only in a few cases. In the genus Sideritis, two
Macaronesian monocots have been studied and there is a major clades were identified (Barber et al., 2000): one
strong possibility that the inclusion of additional taxa, e.g. comprised S. macrostachys (1C = 2·01 pg) and
from Liliaceae s.l., would extend the C-value range. Two S. oroteneriffae (1C = 1·82 pg); the other S. canariensis
species(Hypochoerisoligocephala,Plocamapendula)from fromLaPalma(1C=1·78pg).C-valuesratherreflectedthe
our collection have been analysed by previous authors sectionalclassification:S.macrostachys(sect.Creticae)had
(BennettandLeitch,1995;Cerbahetal.,1999).Bothvalues a substantially larger genome than the two remaining
weresimilaranddifferedbyonly3·5%intheformerandby species belonging to sect. Marrubiastrum. Nuclear DNA
4·3%inthelattertaxon,withourestimatesbeingnegligibly content variationthat parallelsthe taxonomic classification
smaller. is also known in the genus Pinus, for example (Hall et al.,
The majority of taxa analysed here possessed small 2000). Six Pericallis species from the present study
genomes, with 1C nuclear DNA amounts less than 1·6 pg. occupied four clades on the phylogenetic tree based on
They fall into the lowest third of the C-value database ITS sequences (Panero et al., 1999). P. cruenta (Tenerife,
comprisingabout3500recordsoffloweringplants(Bennett 1C = 0·68 pg), P. echinata (Tenerife, 1C = 0·73 pg) and
and Leitch, 2001). The estimates for Descurainia (0·19– P. papyraceae (La Palma, 1C = 0·6 pg) were grouped
0·23 pg) even approached the minimum known for the together, and P. webbii (Gran Canaria, 1C = 0·57 pg),
angiosperms. 1C DNA amount for Nepeta teydea repre- P. lanata (Tenerife, 1C = 0·57 pg) and P. appendiculata
sented the smallest value in the Asterids, and Pericallis (Tenerife, 1C = 0·55 pg) were each situated on a different
appendiculata had the second smallest C-value in branch (the position of the latter two species with woody
Euasterids II (only Leontodon longirostris possessed a stems was closer). Along with higher C-values for
smaller1CnuclearDNAamount).Comparisonsofaverage hemicryptophytes, the present data also indicate that there
C-values and genome sizes for Macaronesian vs. non- could be an inter-island differentiation in 2C-values
Macaronesian representatives of individual genera and between species of the same life form. Similar traces of
families confirmed the significantly smaller estimates for inter-islanddiversificationcanalsobefoundinothergenera
theformergroup.ObviousdifferencesinC-valueswerealso (e.g. Argyranthemum), and this question merits further
found whenmatchingdataformajorphylogeneticlineages study.
ofMacaronesianandnon-Macaronesiantaxa(e.g.meanand An increasing number of papers have investigated
median for the Macaronesian Eudicots were 1·93 and 1·67 correlations between DNA content and environmental
timessmaller, respectively). conditions. Altitude, average annual temperature, humidity
Leitch et al. (1998) analysed angiosperm C-values in a and rainfall on Tenerife were included as environmental
phylogenetic context and concluded that ancestral taxa variables inthe present study. Positivecorrelation between
probably possessed small genomes with 1C <3·5 pg. A nuclear DNA amount and mean annual temperature was
considerable proportion (86·5 %) of Macaronesian plants found in Argyranthemum; C-values in this genus were
meet this criterion, and more than two-thirds of them had negatively correlatedwithaltitude andannual rainfall. The
verysmallgenomes(definedas1C<1·4pg).Thesefindings same trends were also observed in Silene and Micromeria.
would support the relictual nature of Macaronesian flora PresentedresultsareinaccordancewiththepatternofDNA
(Bramwell,1976).However,recentphylogeneticinvestiga- amount variation in Berberis, where diploids with lower
tions of several endemic groups (e.g. Aeonium, DNA content grew in high-elevation habitats with greater
Argyranthemum, Bencomia, Echium) revealed the derived rainfall, and species with higher DNA content preferred
position of Macaronesian representatives indicating their sites with higher temperatures (Bottini et al., 2000).
recentorigin(Emerson,2002).Inmostcases,therehasbeen However, the nuclear DNA content divergence in Crambe
only a single colonization of the archipelago (Francisco- andSonchusfollowedacompletelyoppositetrendandtheir
Ortegaetal.,1997;Barberetal.,2000;Helfgottetal.,2000) C-valuesincreasedwithaltitudeandrainfallanddecreased
followed by a rapid speciation. Two theories may explain with temperature. As concluded by Grime and Mowforth
the smaller C-values of Macaronesian taxa in comparison (1982), large genomes in British flora have probably
with their non-Macaronesian counterparts: (1) there has evolved under low temperature conditions. In the last
been a loss of DNA since the archipelago was colonized; groupofgenera(Descurainia,Polycarpaea),nocorrelation
(2) ancestral species possessed small genomes and only with environmental traits was found, as previously noted
negligible changes have occurred during subsequent e.g.inthegenusLonchocarpus(PalominoandSousa,2000).