High clonal diversity in threatened peripheral populations o(7)

Beatty&Provan—ClonaldiversityinH.monotropa

Page7of8

TheobservedlowlevelsofclonalitysuggestthatmostgenetsinthepopulationsofH.monotropastudiedarefertileandthatreproductionispredominantlysexual.Theobservedlevelsofinbreeding,however,werehighinalmostallofthepopulationsstudied.ApreviousstudyonthereproductiveecologyofthegenusMonotropaandtherelatedgenusMonotropsisidenti eddifferencesinlevelsofautogamousseedsetinthetwocolourmorphsofH.monotropathatarefoundinNorthAmerica(KloosterandCulley,2009).Boththeredandyellowforms(theyellowformbeingthemorphfoundinBritainandIreland)werehighlyself-compatible,butonlytheyellowformsetsubstantialamountsofautoga-mousseedafterself-pollination.Thus,itislikelythatthehighlevelsofinbreedingobservedinthepopulationsinthepresentstudyaretheresultofself-pollination,particularlygiventhesmallnumbersofindividualsinmostofthepatches.Beingself-compatible,however,meansthatH.monotropadoesnotfacethesameproblemsofcompletelossofsexualreproductionand/orrapidpopulationextinctionthatcanthreatenpopulationsofobligatelyoutcrossingclonalplants.Wheremateavailabilityislimitedinsuchspecies,orwherepopulationsarecomprisedofasmallnumberoflargeclones,manyofwhichareoftenrelated,self-incompatibiltymechanismsandstigmasaturationviaself-pollinationcanleadtosexualreproductivefailureandsubsequentextensivelossofgeneticvariation(e.g.Willietal.,2005;ScobieandWilcock,2009).Nevertheless,ongoinginbreedingremainsapotentialthreattothefragmented,peripheralpopulationsinvestigatedinthepresentstudy.

Conservationimplications

Inthepresentstudy,thetransientnatureofH.monotropawasnotedatboththepopulationlevelandattheindividuallevelwithinpopulations.Evenlargepopulationshavebeenobservedtodisappearwithinafewyears(LocktonandWalker,2010),whichposesaproblemwhentryingtoestimatecensusnumbersforthespecies,astheactualnumbersofindi-vidualswillnotbetrulyknownifasurveywascarriedoutinanysingleyear.Furthermore,anadditionalissuewhenattemptingtoidentifycensusnumbersforH.monotropaistheincidenceofclonalgrowth.Asaerialspikesdonotnecess-arilyrepresentseparategenets,theymayinfactrepresentmul-tiplerametsofthesamegenet.Geneticanalysesoversuccessiveyearsthereforeprovidevitalinformationonthedynamicsofthesethreatenedpopulations.Althoughthepresentstudyonlyconsidereda2-yearperiodateachlocation,nosigni cantdifferenceswereobservedingeneticdiversityorcompositionofthepopulationsbetweensuccessiveseasons,withtheexceptionofasingledecreaseindiversityinonepopulation.GiventhehighlevelsofinbreedinginNorthernIreland’sremainingpopulationsofH.monotropa,however,furthergeneticmonitoringwouldbeadvisabletoensurethatgeneticdiversityismaintained.Iflevelsofgeneticdiversityweretodroptotheextentthatsomeformof‘geneticrescue’isrequired,thenthegeneticdistinctnessbetweenpopulationsrevealedbytheAMOVAanalysesshouldbetakenintoaccount,bothintermsofpossiblymaximizinggeneticdiver-sity,butstillconsideringthepotentialforoutbreedingdepression(Frankham,2010).Furthermore,thesmalland

fragmentednatureofremnantpopulations,withlownumberscon rmedbythecapture–recapturecalculationacrosssucces-siveyears,leavesthemvulnerabletostochasticextinctionevents.

SUPPLEMENTARYDATA

andconsistof25distributionmapsofindividualswithineachpopulation.

ACKNOWLEDGEMENTS

WeareextremelygratefultoRobertandHannahNorthridgeforprovidingtheCo.Fermanagh2007samples,RobertBeattyforassistancewithsampling,RalphForbesforhelpfuldiscussions,andNeilReidforGISadvice.Wearealsogratefultothreeanonymousrefereesforcommentswhichgreatlyimprovedthemanuscript.Thisresearchwassup-portedbyaPhDstudentshipawardedtoGemmaBeattybytheDepartmentofAgricultureandRuralDevelopment,NorthernIreland.

LITERATURECITED

AlbertoF,Arnaud-HaondS,DuarteCM,SerraoE.2006.Geneticdiversity

ofaclonalangiospermnearitsrangelimit:thecaseofCymodoceanodosaintheCanaryIslands.MarineEcologyProgressSeries309:117–119.

ArakiK,ShimataniK,OharaM.2007.Floraldistribution,clonalstructure,

andtheireffectsonpollinationsuccessinaself-incompatibleConvallariakeiskeipopulationinnorthernJapan.PlantEcology189:175–186.

Arnaud-HaondS,BelkhirK.2007.GeneClone:acomputerprogramto

analysegenotypicdata,testforclonalityanddescribespatialclonalorganization.MolecularEcologyNotes7:15–17.

AugeH,NeufferB,ErlinghagenF,GrupeR,BrandlR.2001.Demographic

andrandomampli edpolymorphicDNAanalysesrevealhighlevelsofgeneticdiversityinaclonalviolet.MolecularEcology10:1811–1819.BeattyGE,parativephylogeographyoftworelatedplant

specieswithoverlappingrangesinEurope,andthepotentialeffectsofclimatechangeontheirintraspeci cgeneticdiversity.BMCEvolutionaryBiology,inpress.

BeattyGE,McEvoyPM,SweeneyO,ProvanJ.2008.Range-edgeeffects

promoteclonalgrowthinperipheralpopulationsoftheone-sidedwinter-green(Orthiliasecunda).DiversityandDistributions14:546–555.BidartondoMI,BrunsTD.2001.Extremespeci cityinepiparasitic

Monotropoideae(Ericaceae):widespreadphylogeneticandgeographicstructure.MolecularEcology10:2285–2295.

BillinghamMR,ReuschTBH,AlbertoF,SerraoEA.2003.Isasexual

reproductionmoreimportantatgeographicallimits?AgeneticstudyoftheseagrassZosteramarinaintheRiaFormosa,Portugal.MarineEcologyProgressSeries265:77–83.

BooyG,HendriksRJJ,SmuldersMJM,vanGroenendaelJM,VosmanB.

2000.Geneticdiversityandthesurvivalofpopulations.PlantBiology2:379–395.

BrownJH.1984.Ontherelationshipbetweenabundanceanddistributionof

species.AmericanNaturalist124:255–279.

CaughleyD,GriceD,BarkerR,BrownB.1988.Theedgeofrange.Journal

ofAnimalEcology57:771–785.

EckertCG.2002.Thelossofsexinclonalplants.EvolutionaryEcology15:

501–520.

EckertCG,SamisKE,LougheedSC.2008.Geneticvariationacrossspecies’

geographicalranges:thecentral-marginalhypothesisandbeyond.MolecularEcology17:1170–1188.

EcksteinRL,O’NeillRA,DanihelkaJ,OtteSA,Ko

¨hlerW.2006.Geneticstructureamongandwithinperipheralandcentralpopulationsofthreeendangered oodplainviolets.MolecularEcology15:2367–2379.

Downloaded from at Queens University of Belfast on January 21, 2011

百度搜索“77cn”或“免费范文网”即可找到本站免费阅读全部范文。收藏本站方便下次阅读，免费范文网，提供经典小说教育文库High clonal diversity in threatened peripheral populations o(7)在线全文阅读。