Beatty&Provan—ClonaldiversityinH.monotropa
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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.
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