biodiversity...genetic differentiation between willow populations 17 mycology 18 ectomycorrhizal...
TRANSCRIPT
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Biodiversitytaxonomy, Genetics and ecologyof sub-Arctic Willow scrub
A collaborative research project by the scottish Montane Willow research Group
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introduction 3
sub-arctic willows 4
sub-arctic willow scrub 6
the situation in scotland today 7
research questions 8
study sites 9
taxonomy 10
Patternsofhybridizationamongsub-arcticwillowsinScotland 11
PatternsofhybridizationbetweenS. arbusculaandS. lapponum 12
DynamicsofhybridizationbetweenS. arbusculaandS. lapponum 13
Genetics 14
Sexualversusasexualreproduction 15
Geneticdiversitywithinwillowpopulations 16
Geneticdifferentiationbetweenwillowpopulations 17
Mycology 18
EctomycorrhizalfungiassociatedwithS. herbacea 19
Sub-arcticwillowsandrustfungi(Melampsoraspp.) 20
Ectomycorrhizalcolonizationpotentialofuplandsoils 21
ecology 22
Herbivoryandseedproduction 23
PredictingthepotentialdistributionofS. arbuscula 24
Herbivoryandseedlingestablishment 25
Conservation implications 26
Taxonomy 26
Genetics 26
Mycology 28
Ecology 29
Further information 30
Contents
Allphotographicimagesincludedinthisreportweretakenbymembersoftheprojectduringthecourseoftheresearch.
Thespeciesdistributionmapsonpages4-5arereproducedfrom:Preston,C.D.,Pearman,D.A.andDines,T.D.(Eds.)(2002).NewAtlasoftheBritishandIrishFlora.OxfordUniversityPress.©Crown,2002.
Citation:ScottishMontaneWillowResearchGroup(2005).Biodiversity:taxonomy,geneticsandecologyofsub-arcticwillowscrub.RoyalBotanicGardenEdinburgh.
PrintedonReviveSpecialSilk,madefrom30%FSCfibre,30%de-inkedpost-consumerwaste,30%virginfibreand10%millwaste,byMeigleColourPrintersLimited.
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Sub-arcticwillowscrubisoneoftherarestandmostendangeredhabitatsintheUK.ItisalmostentirelyrestrictedtotheScottishmountainswhereitformsacomponentofthemontanescruboccurringabovethenaturaltreeline.
Remainingsub-arcticwillowscrubexistsasisolatedpopulationsthatareconsideredtoberemnantsofaformerlymorewidespreadpost-glacialvegetationtype.Thesesurvivingfragmentsarethesubjectsofacuteconservationconcernand,withoutintervention,manypopulationsareindangerofterminaldecline.
TherareandthreatenedstatusofthisvegetationtypeisrecognizedbyitsinclusioninAnnexIoftheEuropeanHabitatsDirectiveandsubsequentprioritizationforconservationwithintheUK.Oneofthespeciesincludedinthisvegetationtype,S. lanata,islistedintheBritishRedDataBookofVascularPlantsandisthesubjectofaSpeciesActionPlanthatsetsouttargetsforitsconservation.
Thisbookletpresentsasummaryofthefindingsofalargecollaborativeresearchprojectthatranfrom2002-2005andaimedtoprovidetheunderpinningscientificresearchrequiredfordeterminingthemostappropriatestrategiesformanagementandspeciesrecoveryprogrammesforsub-arcticwillows.
introduction
A C o l l A B o r At i v e r e s e A r C h p r o j e C t �
Salix lapponum
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Willows(Salix spp.)belongtothefamilySalicaceaethatconsistsofdioecious(separatesexes),catkin-bearingtreesandshrubswithsimple,alternateleaves.Salixspeciesarebelievedtobeprimarilyentomophilous(insect-pollinated)andpartiallyanemophilous(wind-pollinated).Thesmallseedsarecharacteristicallyenvelopedinlong,soft,silkyhairsanddispersedbywind.
MontanewillowscrubcommunitiesinScotlandconsistofmixturesofspecieswhich,elsewhere,havearctic-subarctic-alpinedistributions(S. arbuscula, S. lanata, S. lapponum, S. myrsinites, S. reticulata)andwillowspeciesofgeneralnortherlydistribution(S. herbacea, S. myrsinifolia, S. phylicifolia).
Fivespeciesofsub-arcticwillowandoneofthemorecommon‘northerly’willowswereincludedinthisresearchproject.
Salix arbuscula (Mountain willow)Conservationstatus:SCARCE.
Salix herbacea (dwarf willow)Conservationstatus:COMMON.
sub-arctic willows
Recordedin3210x10kmsquaressince1970,allinScotland.
Recordedin33510x10kmsquaresinGreatBritainsince1970.
Salix lapponum (downy willow)Conservationstatus:SCARCE.
Recordedin8310x10kmsquaresinGreatBritainsince1970.
Mapkey1987-1999Native1970-1986NativePre-1970Native
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S. lanata SpeciesActionPlan
S. lanataisincludedintheBritishRedDataBookofVascularPlants.Itisextantatonly14localitiesinScotlandandonlyfiveofthesepopulationsarecurrentlyconsideredtobeviable.TheSpeciesActionPlanforS. lanataincludesthefollowingtargets:
ensurethatallpopulationsarerestoredtoastatecapableofregeneratingby2008
ensurethateachpopulationwillconsistofatleast50plants(orthesustainablemaximumforthesite)by2008
reintroducethespeciestotwoformersitesby2003.Salix lanata (Woolly willow)
Conservationstatus:RARE&VULNERABLE.Recordedin1310x10kmsquaressince1970,allinScotland.
sub-arctic willows
Salix myrsinites (Whortle-leaved willow)Conservationstatus:SCARCE.
Salix reticulata (net-leaved willow)Conservationstatus:SCARCE.
Recordedin5910x10kmsquaressince1970,allinScotland.
Recordedin1810x10kmsquaressince1970,allinScotland.
A C o l l A B o r At i v e r e s e A r C h p r o j e C t �
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sub-arctic willows
Sub-arcticwillow scrub
Underfavourableconditions,sub-arcticwillowscanformextensivescrubcommunities.InGreatBritainthesehavebeenclassifiedundertheNationalVegetationClassificationasW20–Salix lapponum–Luzula sylvaticascrub.Thistendstooccuronmoist,relativelybase-richsoilsinrockysituationswithanorthtoeastaspect,generallyataltitudesfrom600mtoover900m.Adegreeofsheltermaybefavourabletoscrubdevelopmentandtheremaybeapositiveassociationwithlatesnow-liewhichofferssomeprotectionfromspringfrostsandbrowsing.
DevelopedscrubcommunitiestendtobedominatedbyS. lapponumwhichisthecommonestandmostwidelydistributedofthesub-arcticwillowsbutcanincludesomeoralloftheotherspeciesaswellashybrids.Associatedvascularplantsincludesub-shrubssuchasVaccinium myrtillus, V. vitis-idaeaand Empetrum nigrum;tallherbssuchasAlchemilla glabra,Rhodiola rosea, Oxyria digynaandSaussurea alpina;smallherbssuchasAlchemilla alpina, Thalictrum alpinumandPolygonum viviparum.
S. lanatawithOxyria digyna S. arbusculawithSaxifraga aizoides
WelldevelopedwillowscrubatCorrieSharroch,GlenDoll
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sub-arctic willows
The situation in Scotland today
BasedoncomparisonswithScandinaviaandthedistributionofsuitableterrain,itisgenerallyconsideredthatsub-arcticwillowscrubwasoncemorewidespreadinScotlandthanitistoday.Cuttingforfirewoodandcharcoal-burningcoupledwithmorerecentintensificationofgrazingpatternsinuplandareashasresultedinasituationwheremontanewillowcommunitiesarenowlargelyrestrictedtoinaccessibleledges.Consequently,willowpopulationsaretypicallysmallandisolatedandofacuteconservationconcern.
Remainingwillowscrubisconfinedlargelytoinaccessibleledges
Samplinginaccessiblewillows
A C o l l A B o r At i v e r e s e A r C h p r o j e C t �
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Conservationactionrequiresunderpinningscientificresearch.Attheoutsetofthisprojectitwasapparentthatthereareanumberofknowledgegapsthatneedtobeaddressedifconservationtargetssetforsub-arcticwillowinScotlandaretobeachieved.Examplesoftheseareasfollows.
WillowsarenotoriousfortheirtaxonomiccomplexityandnumeroushybridcombinationshavebeenrecordedintheUK.Dosub-arcticwillowsexistasseparatewell-definedtaxonomicentitiesforwhichconservationplanscanbedevisedorishybridizationsoextensivethatthesewillowsshouldeffectivelybetreatedasonelargeaggregate?
Smallandisolatedplantpopulationsareoftenfoundtobelowingeneticdiversity.Thistendstolimittheircapacitytorespondtobothacuteandchronicenvironmentalchange.Furthermore,smallnumbersofindividualsinpopulationscanleadtoproblemsthroughinbreedingdepression.Therefore,hasthefragmentationofwillowscrubresultedingeneticallydepauperatepopulationsthatmaybelackinginvigourandill-equippedtorespondtofutureconditions?
Inattemptingtorestorewillowscrub,isenoughknownaboutassociatedorganismssuchasfungi?Forexample,itisknownthatspeciesofSalicaceaeformmycorrhizalassociations.Isthissomethingthatshouldbetakenintoaccountwhenwillowsarebeingplanted?
Grazingofwillowseedlingsandsaplingsbyherbivoresinhibitsnaturalregenerationofwillowscrub.However,herbivoresmayaffectthereproductivecapacityofwillowsinotherways.Forexample,howdoesremovalofshootsbysheepandreddeerinfluencecatkinproduction,seedsetandhencepopulationviability?
research questions
Researchaims:Ourresearchwascarriedoutunderfourbroadheadings:taxonomy,genetics,mycologyandecology.
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Sampleswerecollectedfrommanysitesrepresentingthefullrangeofsub-arcticwillowdistributionacrossScotland.However,intensivecross-cuttingresearchwascarriedoutatfourfocalstudysites.
study sites
BenLawersEffectoflargeandsmallmammalherbivoryonreproductivebiologyofS. arbuscula,seeddispersal,potentialestablishmentsites,ectomycorrhizalcolonizationpotentialofsoils.
MeallnanGabhar,BenLuiHybridizationstudiesofS. lapponumandS. arbuscula.
CorrieSharrochAssessmentofclonalgrowthofS. lanataandS. lapponum,assessmentsoftaxonomicstatus,rustinfection,insectherbivoryandphytochemistryofS. lanata,S. lapponumandS. myrsinites.
MeallGhaordiadhAssessmentofclonalgrowth,ectomycorrhizalcolonizationandinsectherbivoryofS. herbaceaontheridge-top.HybridizationstudiesofS. lapponumandS. arbusculaonthecragsbelow.
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Willowsarewell-knownfortheirtendencytohybridise.Therearecurrently64willowhybridcombinationsrecordedintheUKbutwedonotknowtheextenttowhichhybridizationoccurswithinnaturalpopulations.Dowillowspecieslimitsremainwell-definedwithonlyoccasionalhybridizationeventsorishybridizationinfactmuchmorefrequentandwidespread?Underwhatcircumstancesdoeshybridizationoccur?
Thisisimportantfromaconservationperspectiveasthedevelopmentofappropriatestrategiesandtargetsrequiresasoundunderstandingofthetaxonomicstatusoftheplantswewishtoprotect.Forexample,ifonestrategyforconservationistoaugmentexistingpopulationsorestablishnewonesbyplanting,shouldeffortsbemadetoavoidinclusionofhybridsamongplantingstock?Orarehybridsinfactsocommoninnaturethatinclusionofhybridsinrestorationprogramsisinevitable?
Astherangeofphenotypicvariationinwillowhybridsispoorlyunderstoodwedevelopedmoleculartoolsthatwouldenableustodiscriminatebetweenspeciesanddetecthybrids.Toprovidecomplementarydatawealsoemployedphytochemicaltechniquesthatwerefoundtosuccessfullydistinguishspecies.Wethenusedthesetoolstogetherwithmorphologicalmethodstoinvestigatethreetopics.
1. Patternsofhybridisationamongsub-arcticwillowsinScotland.2. PatternsofhybridizationbetweenS. lapponumandS. arbuscula.3. DynamicsofhybridizationbetweenS. lapponumandS. arbuscula.
taxonomy
SamplingS. lapponumatDrumochterPass
S. lapponum
S. x pseudoglauca
S. arbuscula
LeafmorphologyofS. lapponum,S. arbusculaandtheirhybrid,S. x pseudoglauca
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A C o l l A B o r At i v e r e s e A r C h p r o j e C t 1 1
Whatcanmolecularstudiestellusaboutthepatternsofhybridizationamongsub-arcticwillowsinScotland?Ishybridizationcommonorrare?
ManysamplesofelevenspeciesofwillowwerecollectedfromsitesacrossScotlandaswellasexamplesofhybridsidentifiedbytheirmorphology.Wealsocollectedsamplesfrommorphologicalhybridspecimensfromanextensiveex-situcollectionofnativewillows.DNA-fingerprintingtechniqueswereappliedanddataanalysedtodetectpatternsofhybridization.
Theextentofhybridizationappearstobelimitedwithmosthybridsoccurringonlyoccasionally.AnexceptiontothisishybridizationbetweenS. arbusculaandS. lapponumwhichoccursfreelyatsomesites.
Whereitispossibletodistinguishmorphologicalhybrids,hybridizationinsub-arcticwillowsappearstofollowoneofthreepatternsA,BorC(Figures1and2):
taxonomy
Patterns of hybridization among sub-arctic willows in Scotland
Figure 1/PatternA.Morphologicalhybridsaremolecularlyintermediate(e.g.,S. auritaxS. repens).
Figure 1/PatternB.Morphologicalhybridsareeitherintermediateoraremorecloselyalliedtoeitheroftheparentspecies,suggestingback-crossing(e.g.,S. herbaceaxS. lapponum).
Figure 1/PatternC.Morphologicalhybridsalwaysfallwithintherangeofmolecularvariationofoneorbothparentspecies(e.g.,S. capreaxS. lapponum).Asnogeneticallyintermediateindividualsoccur,itiscurrentlydifficulttosaywhethertheobservedpatternisduetoback-crossingorextrememorphologicalvariationintheparentspecies.
Figure �.Patternsofhybridizationbetweensub-arcticandmontanewillowspecies.SeeFigure1fordescriptionofpatterns.
Figure 1.Threepatternsofhybridizationamongsub-arcticwillows.Distancebetweenpointsapproximatestherelativegeneticsimilarityofpairsofsamples.Seelegendtextfordescriptions.
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taxonomy
Patterns of hybridization
betweenS. arbuscula and
S. lapponum
Arethepatternsofhybridizationthatwerevealedforparticularhybridcombinationsconsistentacrosssitesorcanwedetectdifferencesbetweensitesthatmightthenoffersomeinsightsintofactorsthatinfluencethisprocess?
TwositeswereselectedwhereS. arbusculaandS. lapponumgrowtogether(MeallGhaordiadhandMeallnanGabhar,BenLui).Patternsofhybridizationatthetwositeswerecomparedusingacombinationofmorphologicalandmoleculartechniques.
Thepatternsofhybridizationatthetwositesweredifferent.AmuchhigherincidenceofmorphologicalhybridswasrecordedatMeallGhaordiadhthanatMeallnanGabhar.
AtMeallnanGabhar,themorphologyofthetwohybridsfoundwasclearlyintermediatebetweentheparentspecies.However,theirmolecularfingerprintsclusteredwithintheparentspecies(Figure3).Thisindicatesthatthesehybridindividualsareprobablyderivedfromback-crossingofhybridstoeitherparentwiththetransmissionofmorphologicalcharacterstatesfromtheotherparent.
AtMeallGhaordiadh,themorphologyofmostofthehybridswasalsointermediate.However,themoleculardataweremorecomplexwithsomehybridsfallingwithintherangeoftheparentsandsomebeingintermediate(Figure3).Thepresenceofintermediateindividualsleadstomoreofageneticcontinuumbetweenthetwospeciesatthissite.
Thesedataindicatethatpatternsofhybridizationbetweenthesametwospeciescanvarybetweensites.
Figure �.Comparisonofmorphological(A)andmolecular(B)variationinS. arbusculaandS. lapponumandhybridsbetweenthematMeallnanGabhar(1)andMeallGhaordiadh(2).
A1 B1
A2 B2
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A C o l l A B o r At i v e r e s e A r C h p r o j e C t 1 �
taxonomy
Dynamics of hybridization between S. arbuscula and S. lapponum
HavingdetecteddifferentpatternsofhybridizationatMeallGhaordiadhandMeallnanGabhar,weaimedtoinvestigatefactorsinvolvedinmaintainingspeciesbarriersandthecircumstancesunderwhichhybridizationbetweenS. lapponumandS. arbusculaoccurs.
Atthetwositeswecountedtherelativenumbersofplantsofthetwospeciesandrecordedthefloweringtimeofalargenumberoftaggedplantsatweeklyintervalsduringthefloweringseason.
Relativeabundancesofthetwospeciesweredifferentatthetwosites.AtMeallnanGabhar,thenumberswereroughlyequal.However,atMeallGhaordiadhthereweremanymoreindividualsofS. arbusculathanofS. lapponum (ca.30:1).
TheassessmentoffloweringdatesshowedacleartendencyforS. lapponumtoflowerbeforeS. arbusculaatbothsites(Figure4).
AtMeallnanGabharneitherofthehybridsfloweredduringthetwoyearsofobservation.AtMeallGhaordiadh,morphologicalhybridsweredetectedthatfloweredatintermediatedatesbetweenthetwospeciesaswellasoutwiththerangeofoverlapbetweenthefloweringtimesbetweenthetwospecies(Figure4).Thiscouldincreasetheprobabilityofintrogressionthroughback-crossingineitherdirectioniftherewasnoselectionagainsthybridgenotypes.
Thesedataareconsistentwithhybridizationtheorythatpredictsthatwheretwospecieswiththepotentialtohybridizeco-occurindisproportionatenumbers,hybridizationismorelikelytotakeplace.Wherefertilehybridsaregeneratedasinthepresentcase,introgressionofgenesbetweenspeciesmayaccentuatethebreakdownofspeciesbarriers.
Figure �.FloweringdateofS. arbuscula,S. lapponumandtheirhybrid,S. x pseudoglauca,attwosites.
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GeneticsFragmentationofvegetationcoverintosmallandisolatedpopulationscanresultinseriouslossesofgeneticdiversitywhichcanhinderaspecies’abilitytorespondtobothacute(short-term)andchronic(long-term)environmentalchange.Smallpopulationscanalsobeaffectedbyinbreedingdepressionduetotheincreasedchanceofmatingamongrelatedindividuals.Subsequentexpressionofdeleteriousrecessiveallelescanresultinreducedvigourandfitness.
Itisbelievedthatsub-arcticwillowpopulationsintheUKareremnantsofapreviouslymorewidespreadvegetationtype.Giventhesmallsizesandpatchydistributionofmanyoftheremainingpopulations,itispossiblethattheyconsistofrelatedindividualswithlowlevelsofgeneticdiversity.Suchpopulationswouldbeapoorsourceofdonormaterialforreintroductionprogrammes,andmaythemselvesbepoorcandidatesforconservationmanagementduetointrinsiclowlevelsoffitness.
Theamountofgeneticdiversityavailableinremainingpopulationsisrelatedtotheamountofsexualreproductionoccurringwithinandbetweenthem.Willowsarealsocapableofreproducingasexuallyviathespreadofclonalsuckersandattheoutsetofthisprojectwedidnotknowwhethersub-arcticwillowsreproduceprimarilysexuallyorasexually.Anunderstandingofthiscrucialaspectofwillowbiologyisnecessaryifrestorationprogrammesaretosuccessfullyimitatenaturalpopulations.
Wedevelopedmoleculartoolsthatwouldenableustodifferentiateindividualwillowgenotypes.Thesetoolswerethenappliedtonaturalpopulationsofsub-arcticwillowsacrossScotlandtoinvestigatethreetopics.
1.Theextentofsexualversusasexualreproduction.2.Theamountofgeneticdiversitywithinwillowpopulations.3.Theamountofgeneticdifferentiationbetweenwillowpopulations.
DNAmicrosatellite‘fingerprints’ SamplingS. lapponumatCreagMegaidh
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A C o l l A B o r At i v e r e s e A r C h p r o j e C t 1 �
Genetics
Sexual versus asexual reproduction
Sexualrecruitmentinwillowpopulationsoftenappearstobeverylimitedandweknowthatwillowshavetheabilitytospreadvegetativelyviasuckers.Whatproportionoftheindividualbushesthatweobserveinapopulationisderivedfromsexualreproductionandwhatproportionfromasexual,vegetativegrowth?
Leafsampleswerecollectedfromover400closelyspacedbushesofS. lanataandS. lapponumatCorrieSharrochandfromS. herbaceaat90pointsonanexposedridge-topatMeallGhaordiadh.Samplesweregenotypedusingmoleculartechniques.
99%ofS. lanataand95%ofS. lapponumsamplesrepresenteduniquegeneticindividuals.
28%oftheS. herbaceasamplesrepresenteduniquegeneticindividuals.Sampleswithidenticalgenotypesshowedstrongspatialaggregationwithonegenotypebeingatleast8macross(TransectF,Figure5).
DespitefieldobservationsofsexualreproductioninS. lanata andS. lapponumbeingrare,thisappearstobetheirmainmechanismofreproductionanddispersal.ThepatternobservedinS. herbaceasuggestsgreaterlevelsofclonalgrowthandpatchformation.Thismatcheswellwiththematformingrhizomatousgrowthofthespeciesandthemoreopenhabitatinwhichitoccurs.
Figure �. DistributionofS. herbaceagenotypesalongsixtransectsof8mlengthatMeallGhaordiadh(nottoscale).Circlesofthesamecolouraresampleswiththesamegenotype.Thephotographshowsflagsmarkingoneofthetransects.
S. lanataandS. lapponumatCorrieSharroch.Ourresultssuggestthattherearemanygeneticindividualsresultingfromsexualreproductionratherthanfewindividualsresultingfromclonalgrowth.
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Geneticdiversity(A)
Aisthemeannumberofallelesperlocus(ie,thenumberofvariantsofeachgeneticmarker).Thisisasensitiveindicatorofgeneticbottlenecks.
Genetics
Genetic diversity within willow
populations
Manyoftheremainingpopulationsofsub-arcticwillowsinScotlandaresmallandisolated.Suchpopulationscanlackgeneticdiversityduetolownumbersofindividualsandinsufficientgeneflowtoensurenewgeneticcombinations.AreScottishsub-arcticwillowpopulationsgeneticallydepauperate?
LeafsamplesofS. lanata(rare),S. lapponum(scarce)andS. herbacea(common)werecollectedfromatotalof19sitesacrossScotlandandsubjectedtoDNA-fingerprinting.
Therewasnodifferencebetweenthethreespeciesindiversitylevelswithinpopulationsinspiteoftheirdifferentabundance.
Thedatasetsshowedverylittlecorrelationbetweenpopulationsizeandlevelsofgeneticdiversity.InS. lanata,thelargestpopulationcontainsthehighestdiversity(CoireCheap),butsomesmallerpopulationsalsohavehighdiversity.Forexample,thesmallpopulationof12individualsatCaenlochanhasthesamelevelofdiversityasthelargerpopulationof243individualsatCorrieSharroch(Figure6).
Thelevelsofgeneticdiversityandthelackofcorrelationbetweenpopulationsizeanddiversitysuggesteitherhighlevelsofgenefloworlimiteddivergencesincefragmentation.
Figure �.Relationshipbetweenpopulationsizeandgeneticdiversity(A)inS. lanata.
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A C o l l A B o r At i v e r e s e A r C h p r o j e C t 1 �
Geneticdistance(Fst)
Fstisameasureofgeneticdifferentiationbetweenpopulations(ie,theproportionoftotalgeneticdiversityattributabletobetweenpopulationvariation).Avalueof1indicatesthatpopulationsarecompletelydifferentandavalueofzeroindicatesthatpopulations areidentical.
Genetics
Genetic differentiation between willow populations
Inadditiontogeneticdiversitywithinpopulations,anothercomponentofinter-andintraspecificgeneticdiversityisthelevelofgeneticdifferentiationbetweenpopulations.Thisisimportantbecauseweneedtoknowtowhatextentthefullrangeofgeneticdiversitywithinaspeciesisrepresentedwithinanyonepopulation.Thishasimplicationsforthetargetingofconservationresourceswheretheaimistoconservegeneticdiversity.Measuringpopulationdifferentiationalsoallowsustoassesstheimpactofisolationbyofferingimportantinsightsintolevelsofpollenandseeddispersalbetweenpopulations.
UsingthesameDNAfingerprintdataasfortheanalysisofgeneticdiversitywithinpopulationsofS. lanata,S. lapponumandS. herbacea,weexaminedthelevelofgeneticdifferentiationbetweenpopulations.
Allthreespeciesshowedsomeevidenceoflowbutsignificantpopulationdifferentiation.
ThehighestpopulationdifferentiationwasfoundinS. herbaceaandthiswassignificantlygreaterthanthatfoundinS. lapponum(Figure7).S. lanatahadasimilarlevelofdifferentiationtoS. herbacea,thoughthiswasnotsignificantlydifferenttoeitheroftheotherspecies.ItisunclearwhythecommonspeciesS. herbaceashowshigherpopulationdifferentiationthanthemorescarcespeciesS. lapponum.
WhatcanbeconcludedisthattherarityofS. lanataisnotassociatedwithhighpopulationdifferentiation.Thissuggestseitherhighgenefloworlimiteddivergencesincefragmentation.Itisnotpossibletodistinguishbetweenthetwoatpresent,butthelatterseemsmostlikely.Thelongevityofwillowsmayhaveledtolimitedgenerationssincethepopulationshavebeenfragmentedandhencelimitedopportunitiesfordifferentiationviageneticdrift.
Figure �.Meanpercentagevariationbetweenpopulationsforthreespeciesofsub-arcticwillow.
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Associatingwithmycorrhizalfungibenefitsplantsbyenhancingtheircapacitytoacquirelimitednutrients.Onetypeofmycorrhizalassociation,theectomycorrhiza(seebox)isconsideredtobeparticularlyimportantinuplandenvironmentswheredecompositionprocessesareslowandmuchofthesoilnitrogenisboundinorganicmatter.Communitiesofectomycorrhizalfungiareoftenverydiverse.Isthisdiversityrelatedtodiversityofhostgenotypes?Understandingthisrelationshipisimportantifwearetomimicnaturalpopulationsinrestorationprogrammes.Furthermore,successfulestablishmentofplantedwillowsmayrelyontheabilityofyoungplantstoformectomycorrhizalassociations.Douplandsoilstargetedforrestorationhavesufficientectomycorrhizalinoculum?
RustfungiinthegenusMelampsora(seebox)canhavedevastatingeffectsonwillowsgrowninplantations.Infectionepidemicscanleadtoseriousreductionsinbiomassproductionwhichmaylimitreproductivepotential.Wesoughttoassesslevelsofinfectioninwildpopulationsofsub-arcticwillowandtoexaminethedistributionofMelampsoraspeciesamongdifferentwillowspecies.
Identificationofectomycorrhizalfungionplantrootsandrustfungionleavesisextremelydifficultusingmorphologyalone.Weusedmoleculartechniquestoidentifythesefungiandtherebyinvestigatethefollowingthreetopics.
1.TherelationshipbetweenS. herbaceagenotypediversityandtheectomycorrhizalfungi thatcolonizetheirroots.
2. TherelationshipbetweenwillowspeciesandthediversityofMelampsorarustfungithat infecttheirleaves.
3. Theectomycorrhizalcolonizationpotentialofsoilstargetedforplantingofsub-arctic willowsforrestoration.
Ectomycorrhizas
Ectomycorrhizasaremutuallybeneficialrelationshipsbetweenplantsandsoilfungithatformasheatharoundroottips.Thefungiobtaincarbonassimplesugarsfromtheplantsandinreturnprovideplantswithnutrientsabsorbedfromthesoilthroughextensivenetworksofthread-likecells(hyphae).
Mycology
Melampsora rustfungi
MelampsorarustfungiarepathogenicBasidiomycetesthatinfectplants.Theyhavecomplicatedlifecyclesthatinvolveuptofivedifferentsporestages.
EctomycorrhizasofaCortinariusspecieswithS. herbaceaMelampsorarustinfectingS. myrsinites
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Mycology
Ectomycorrhizal fungi associated with S. herbacea
Whatistheectomycorrhizalfungaldiversityassociatedwithmontanewillowroots?Doeswillowgeneticdiversityinfluenceectomycorrhizalfungaldiversity?
WeusedDNAfingerprintingtechniquestoidentifyS. herbaceagenotypesandtheectomycorrhizalfungiassociatedwiththeirrootsat90samplingpointsontheridge-topatMeallGhaordiadh.
Wefound20speciesofectomycorrhizalfungiontherootsofS. herbaceaatMeallGhaordiadh(Figure8)andanadditional13specieswerecollectedthereasfruitbodies.
Bycomparingthedistributionofwillowgenotypesandfungiwefoundthatovershortdistances(1-2m)therewasaslightlyhigherprobabilitythatroottipsfromthesamewillowgenotypewouldbecolonizedbythesamefungalspeciescomparedtoroottipsfromdifferentwillowgenotypes.
Ectomycorrhizalfungaldiversityappearstobehighgiventheunproductivenatureofthehabitat.Thisdiversitymaybepromotedbywillowgeneticdiversityatsmallspatialscales.
Montane ectomycorrhizal fungi in Scotland
Thetotalnumberofectomycorrhizalfungirecordedinassociationwithsub-arcticandmontanewillowspeciesinGreatBritainnowstandsat105.Ofthese,24speciesareconsideredtobearctic-alpinespecialistsfoundonlyinthishabitat.Therestcanbefoundinlowlandsituationsaswell.DuringthisprojectwediscoveredtwonewBritishrecords(Cortinarius phaeopygmaeusandCortinarius inconspicuous)andonenewScottishrecord(Cortinarius subtorvus).
Amanita nivalis Russula nana
Figure �.PercentageofsoilcoresinwhichectomycorrhizalfungiwererecordedonroottipsofS. herbacea(n=90).
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WillowsarepronetoinfectionbypathogenicrustfungiinthegenusMelampsora.Thesecanhavedevastatingeffectsinuniclonalplantationsofwillowgrownforfuel.Arenaturalpopulationsofsub-arcticwillowsalsoaffected?Areallspeciesequallysusceptibletoinfection?Whatistherelationshipbetweensub-arcticwillowspeciesdiversityanddiversityofrustfungi?
Wescoredanumberofwillowspeciesfromonesiteforrustinfectiononaten-pointscale.WealsocollectedrustsamplesfromawidersetofwillowspeciesfromacrossScotlandformolecularidentification.
Mycology
Sub-arctic willowsand rust fungi
(Melampsora spp.)
Figure 10.PhylogenetictreeshowingtherelationshipbetweenrustDNAsequencesandhostidentity.EachterminalpointonthetreerepresentsauniquerustDNAsequence.Linesbetweenterminalpointsrepresentgeneticdistancebetweensequences.
Figure �.RustinfectionscoresrecordedatCorrieSharrochinSeptember2003.Theboxesinthegraphrepresenttheinterquartilerangecontaining50%ofthevalues.Thehorizontallineintheboxesisthemedianvalue.Thewhiskersextendtothemaximaandminima.
WefoundthatdifferentrustDNAsequencestendedtoclusterondifferentspeciesorgroupsofspeciesofwillows(Figure10).
Thesedataprovideanimportantframeworkwithwhichtocarryforwardourunderstandingofthetaxonomyandecologyofthisgroupofpathogensinnaturalpopulationsofwillows.
WillowspecieswerefoundtovaryintheirsusceptibilitytoinfectionbyrustfungiinthegenusMelampsora(Figure9).S. lanatawasmuchlesssusceptiblethanS. lapponumandS. myrsinites.
SusceptibilitytoinfectionvariedgreatlyamongindividualsofS. lapponumandS. myrsinitesatthesamesite(Figure9).Thissuggeststhattheremaybeastronggeneticinfluenceonrustsusceptibility.
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Mycology
Ectomycorrhizal colonization potential of upland soils
Itisknownthatwillowsformectomycorrhizasandnumerouslaboratorytrialshaveshownthatectomycorrhizasarebeneficialtoplants.Sowhenwillowsareplantedduringrestorationprojectsistheresufficientectomycorrhizalinoculumavailableinsoilsorshouldwillowsbeinoculatedbeforeplanting?
ToassesstheectomycorrhizalcolonizationpotentialofuplandsoilsweusedabaitingtechniqueinwhichuncolonizedS. lapponumcuttingswereplantedintouplandsoilsanddugupafter14monthstoassesstheirectomycorrhizalcolonization.Wecomparedthecolonizationpotentialassociatedwithtwodifferentuplandplantcommunities:onedominatedbygrassandtheotherbyVaccinium myrtillus.
70%ofcuttingswerecolonizedtosomeextentbutanaverageofonly20%ofroottipspercuttingwascolonized.
Onlyfivetaxaofectomycorrhizalfungiwereidentified.
Thetwoplantcommunitiesdifferedinthecompositionofinocula(Figure11).ThegrasscommunitywasdominatedbyLaccaria proximaandanunidentifiedspeciesintheorderPezizaleswhiletheVacciniumcommunitywasdominatedbyThelephora terrestriswhichwasentirelyabsentfromthegrasscommunity.Therewasnodifferenceinwillowperformanceintermsofleafbiomassproductionbetweenthetwoplantcommunities.
Thesedatasuggestthatectomycorrhizalinocula,probablyspores,arewidespreadintheseuplandsoilsbutlowindiversity(e.g.,comparethefivetaxaofEMfungiherewithFigure8)andabundance.Thedifferencesinthespeciesoffungipresentinthetwoplantcommunitiesmaybeinfluencedbythevegetationitselfortheedaphicconditionsofthesoil.
Figure 11.Frequency(percentageofcuttingscolonized)andabundance(averagepercentageofrootspercutting)ofectomycorrhizalfungiingrass-dominated(G)andVaccinium-dominated(V)habitats.Errorbarsforabundance=standarderrorwheren>2.
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ecology
Theecologicalfactorsleadingtothecurrentrestricteddistributionofmanymontanewillowspeciesneedtobeassessedifthedownwardtrendinrangeandnumbersistobepreventedorreversedthroughrestorationprojects.Thisrequiresinformationonallaspectsofthelifecyclefromgrowthandreproductiontoseeddispersalandseedlingestablishment.
Aparticularemphasisofthisareaofresearchwasaninvestigationoftheroleofherbivoryonkeystagesinthelife-cycleofmontanewillows.Theroleofsheepanddeerinpreventingregenerationofwoodyperennialsbyremovingseedlingshasbeenwelldocumented.However,largeherbivoresmayimpactwillowsinotherways.Forexampletowhatextentdoesthebrowsingofwillowshootslimittheresourcesavailableforseedproduction?
Oneoftheproblemsassociatedwithremovinglargeherbivoresaltogetheristhatadenseswardofrankgrasscandevelop.Thismayreducethenumberofsuitablegerminationandestablishmentsitesforregeneratingplants.Whensuitablemicrositesarelimited,thenseedproductionanddispersal,sufficienttoensurethattheyareexploited,becomescrucial.Developmentoftallgrassmayalsoencouragegrowthofpopulationsofsmallherbivoressuchasvolesandslugs.Towhatextentiswillowregenerationlimitedbydispersal,suitableestablishmentsitesandseedlinglossestosmallherbivores?
Understandingtheserelationshipsbetweenherbivoresandwillowgrowthandreproductionmayhelpusindevelopingstrategiesforthemanagementoflargeherbivoresinordertoencourageregeneration.
S. lapponumPollination
S. lapponumSeedset
S. lapponumSeedlingestablishment
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ecology
Herbivory and seed production
Aswillowsaredioecious,successfultransferofpollenbetweenmaleandfemaleplantsiscrucial.Pollentransferiscarriedoutprimarilybyinsectsthatareattractedbyflowers.Browsingbylargeherbivoreshasthepotentialtoremovelargeproportionsoffloweringshoots.Howdoesthisaffectthereproductivepotentialofthewillowsbothintermsoftheabilitytoattractinsectsandintheeffectoftheresultingresourcelimitationonviablefruitproduction?
WecomparedindividualsofS. arbusculathatwereprotectedfrombrowsinginexclosureswithunprotectedindividuals.Catkinsfromsomeindividualsineachtreatmentwereprovidedwithsupplementalpollen.Plantswerescoredfornumberofcatkinsproduced,numberofripeandunripefruitspercatkinandnumberofseedsperripefruit.
Wefoundthat,irrespectiveofbrowsing,seedproductionvariedsignificantlyfromyeartoyearprobablyduetovariationintheweather(Figure12).
Browsingreducedtheamountofseedproducedperplot,particularlyinyearswhentheweatherwasbad(Figure12).
Overall,handpollinationresultedinagreaterproportionofripefruitcomparedtonaturallypollinatedcontrols.Thiseffectwasgreaterinbrowsedindividualsthanunbrowsedindividualssuggestingthatbrowsedplantsaremorepollenlimitedthanunbrowsedplants(Figure13).
ThedatasuggestthatbrowsingofadultplantshasanegativeimpactonthereproductivesuccessofS. arbusculathroughareductioninattractivenesstopollinatinginsects.
Figure 1�.Meannumberofseedproducedperplotinbrowsed(control)andunbrowsed(exclosure)plots(errorbars=95%confidenceintervals).
Figure 1�.Meanproportionofripefruitunderdifferentbrowsingtreatments(errorbars=95%confidenceintervals).HPrepresents‘handpollinated’.
S. arbusculamale S. arbusculafemale
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ecology
Predicting the potential distribution
of S. arbuscula
WeaimedtoassessthepossibilityofusinginformationonassociatedspeciesandenvironmentalconditionstopredictthepotentialdistributionofS. arbusculaatthelargerscaleswithinasiteasawayofassessingthepotentialforpopulationexpansion.
Vegetationandenvironmentalvariablessuchasaltitude,aspect,slope,swardheightandsoildepthwererecordedinover200quadratsintheLochannaLairigecatchmentatBenLawers.SomequadratswerelocatedclosetoorwithinexistingS. arbusculastandsandothersrandomlydistributedwithinthecatchment.Thesedatawerethenusedtomodeltheexistingdistributionandpredictpotentialdistribution.
Populationexpansionwillonlybepossiblewhereseedisdispersedawayfromparentplantstosuitablesitesforgermination,establishmentandgrowth.WeaimedtoquantifytheamountofS. arbusculaseedbeingdispersedawayfromparentplants.
Inboth2003and2004,over300stickytrapsweresystematicallyarrangedwithinandupto80mawayfromastandofS. arbusculaatBenLawers,andleftinplacefor2monthsfrommid-Junetomid-August.
InspiteofabundantseedproductionbythestandofS. arbusculaoverthetwoyears,only11seedswerecaught,allononetrapat20mawayfromthestandin2003.Observationssuggestthatmuchofthefertileseedremainedwithinthebushandwaswashedintothegroundbeforethesilkyhairsthataiddispersalwerefullydriedout.
Limitedseeddispersalmaybeafactorinhibitingpopulationexpansion.
ThedistributionofS. arbusculaisdeterminedbythepresenceofopen,moderatelyfertileareasonsteepslopes.
Ifotherreproductivefactorsarefavourable,thereispotentialfortheexpansionofS. arbusculaduetothepresenceofsuitablehabitatwithincurrentstandsandelsewhereintheLochannaLairigecatchment(Figure14).
Figure 1�.PredicteddistributionofS. arbusculainonecatchmentatBenLawers.‘Predicted’referstoquadratspresentlywithoutS. arbusculawhereconditionsaresuitable.‘Willow’referstoquadratscurrentlywithS. arbuscula,‘Notwillow’referstoquadratswherenowillowcurrentlygrowsandareunlikelytobesuitableforwillowestablishment.MapreproducedfromOrdnanceSurveydatabypermissionofOrdnanceSurvey,©Crowncopyright.MLURIGD27237X2005.
seed dispersal
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ecology
Herbivory and seedling establishment
Figure 1�.EffectofslugsonproportionofS. arbusculaseedlingssurvivingindisturbedmicrosites(errorbars=95%confidenceintervals).
Figure 1�.EffectofmicrositetreatmentonproportionofS. arbusculaseedssurvivingasseedlings(errorbars=95%confidenceintervals).
Forseedthatdoesmanagetogetdispersed,whatarethefactorsthatdeterminethesuccessfulestablishmentofnewseedlings?Isseedandearlyseedlingmortalityaproblemandifsowhatiscausingit?
Anexperimentwascarriedoutinwhichsmallmammalswereexcludedfromsomeplotsbutnotothersandinwhichsub-plotswereeithermown(clippedto5cm),disturbed(allvegetationremovedtoleavebareground)orleftascontrols.Someofthedisturbedplotswereprotectedfromslugswithpellets.SeedofS. arbusculaandS. lapponumwassetoutintheplotsandtheirgerminationandsurvivalwasfollowedfor90days.Inaseparateexperimentone-year-oldseedlingswereplantedintoplotswiththesametreatments.
Disturbancestronglyfavouredgerminationandsurvivalofbothspecies.Noseedlingssurvivedinthecontrolplotsandonlyveryfewinthemownplots(Figure15).
Slugsstronglyreducedsurvivalduringtheearlystageofestablishment(Figure16).
Inspiteofanabundanceofbankvoles(Clethrionomys glareolus)inthearea,therewasnoeffectofsmallmammalsduringtheearlystageofestablishment.However,wefoundthattheycausedsignificantdamageto40%ofone-year-oldseedlings.
Successfulregenerationofwillowseedlingswasinfluencedbysluggrazingandavailabilityofsuitablemicrositeswithbaregroundforseeds.Smallmammalsreducegrowthofone-year-oldseedlings.
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Conservation implications
Taxonomy
Theoverarchingaimofthisprojectwastoprovidescientificunderpinningfortheconservationofsub-arcticwillows.Hereweseektosummarisethespecificimplicationsofourresultsfortheconservationofwillows.
Despitetheirformidablereputationfortaxonomiccomplexity,sub-arcticwillowsappeartohybridizeinfrequently.Ingeneral,whilehybridizationcanbeviewedasaprocessthatdoesoccurwithinthegenus,inthemajorityofcasesspeciesbarriersaremaintained.OneexceptiontothisisseeninpatternsofhybridizationbetweenS. arbusculaandS. lapponumwhichoccursfreelyatsomesites.
Whenconsideringtheconservationofagivenspecies,careshouldbetakentoavoidplantingmaterialderivedfromhybridizingpopulations.Tothisend,collectionofmaterialforplantingshouldbetargetedwherepossibletositesatwhichparentspeciesaregrowingaloneorwithfewotherwillowspecies.
Hybridizationisparticularlylikelytooccurwherethereareseriousimbalancesinspeciesabundance.DuetothefragmentarynatureofmontanewillowdistributioninScotland,differencesinrelativeabundancemightbemorepronouncedbetweencertainpairsofspeciesthanmighthavebeenthecaseinthepastwhenwillowscrubandthespecieswithinitweremorewidespreadandmorenumerous.Furtheraccelerationofthisprocessshouldbediscouragedbyavoidingthecreationofextremeimbalancesofspeciesabundanceinrestorationprogrammes.
Evidencesuggeststhatfloweringhybridsmayencouragefurtherhybridizationbetweentheparentspeciesincertaincircumstances,andassuch,knownhybridsshouldnotbedeliberatelyincludedinre-introductionprogrammes.Ifhybridlineagesaretobeactivelyincreasedinfrequency,thisshouldbedoneex-situwherenoeffectonthenaturalpopulationbalancewouldoccur.
S. x obtusifolia(S. lapponumxS. aurita)
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Conservation implications
Genetics
Despitetheirobviousabilitiesforclonalgrowthandthelackofobservedseedlingrecruitment,montanewillowspecieslikeS. lanataandS. lapponumreproducepredominantlybysexualreproduction.Thusrestorationprogrammesshouldfocusonlargenumbersofdifferentgenotypesiftheyaretomatchnaturalpopulations(ratherthanmultiplereplicatesofvegetativelypropagatedindividuals).
Managementtofacilitatesexualreproduction(e.g.,byavoidingexcessivelargemammalgrazing)andseedlingrecruitment(e.g.,creatingsuitableareas/conditionsforestablishment)isanecessarycomponentofwillowconservation.Willowpopulationsareunlikelytoexpandviavegetativegrowthanddispersal.
Evensmallwillowpopulationsshowhighlevelsofgeneticdiversityandlowlevelsofpopulationdifferentiation.Thereisnoevidenceofthembeingaffectedbymajorgeneticbottlenecksandhighlevelsofgeneticdrift.Althoughgeneflowbetweenfragmentedpopulationsispossible,itisunlikely.Morelikelyisthepossibilitythatthegeneticconsequencesofreducedpopulationsizesandphysicalisolationhavebeenlimitedbythelongevityofwillowsandalimitednumberofgenerationssincefragmentation.
Thepositiveaspectofthisisthateventhesmallestfragmentsrepresentausefulgeneticresource.Thesepatchesshouldnotbeconsidered‘dead-ends’beyondhope.Theyrepresentbothpotentiallyusefulsourcesasdonorsfornewpopulations/exsitucollections,aswellasreservoirsofdiversityfortheexpansionofexistingsites.Inthisrespect,itisnottoolatetorestoreandexpandpopulationsofthesespecies.However,thosefragmentswithpopulationsizesoflessthan50areofconservationconcernanditwouldtakefewgenerationsorenvironmentalcatastrophestolosediversityorwholeplants.Thusconservationactionintheneartomidtermisappropriate.
S. lapponum
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Conservation implications
Mycology
S. herbacea supportsahighdiversityofectomycorrhizalfungi.Manyofthesearearctic/alpinespecialistsfoundonlyinthesehabitats.S. herbacea shouldthereforebeviewedasanimportantcomponentofScottishbiodiversity.
Thebelow-groundECMcommunityassociatedwithS. herbacea wasdominatedbyspeciesthateitherdonotproducefruitingstructuresabove-groundorelseproducefruitingstructuresthatarecryptic.Thishighlightstheimportanceoflookingbelow-groundinordertoproperlyassessfungalbiodiversity.
TherewassomeevidencetosuggestthatovershortdistancesinS. herbacea bedsthecompositionoftheECMcommunitymaybeinfluencedbythegenotypeofthehost.Althoughitisnotpossibletoextrapolatedirectlytootherwillowspecies,thesedatatendtosupporttheprincipleofmaintaininggeneticdiversitywithinwillowpopulationsinordertomaintaindiversityofassociatedorganisms.
InoculaofECMfungiavailabletoplantedS. lapponum werefrequentintheuplandsoilsstudied.However,thediversityofinoculaandthecolonizationpotentialwerelowcomparedtootherstudiesofmontanehabitats.Trialstoassessthebenefitsofinoculumenhancementforwillowestablishmentshouldbecarriedout.
Althoughthereweredifferencesbetweengrass-dominatedandVaccinium-dominatedhabitatsinthecompositionofinoculaavailabletoplantedS. lapponum cuttings,nodifferenceinwillowperformancewasdetected.GiventhatwedonotatpresentunderstandtherelativebenefitsofdifferentECMfungitowillowsitisrecommendedthatchoiceofplantingsitecontinuestobedrivenbyconsiderationofedaphicconditionsthatareknowntobeimportanttowillowestablishment;forexamplesoilmoisture.
Therewasconsiderablevariationwithinspeciesinthedegreeofrustinfection.Susceptibilitytoinfectionislikelytohaveastronggeneticbasisandthesedatafurthersupporttheprincipleofmaintaininggeneticdiversitywithinwillowpopulations,inthiscasetominimisethechancesofcatastrophicpathogenepidemics.
Willowspeciesdiversitypromotesrustdiversity.Thistendstosupporttheviewthatthediversityoforganismsassociatedwithsub-arcticwillowscrubwillbeenhancedbyhavingmixturesofwillowspecieswhereenvironmentalconditionsallow.
Inocybe praetervisawithS. herbacea
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Conservation implications
Ecology
AllconclusionsbelowareforS. arbuscula.Extensionofthesepointsasgeneralitiestootherspeciesaretobeconsideredastentative,butshouldbepossibleaslongasspeciesdifferencesinecology,andsitedifferences,aretakenintoaccount.
Thelowfrequenciesofseedproductionand/orpoordispersalrecordedoverthecourseoftwoyearssuggestthatregenerationfromseedislikelytorequirecollectionandtranslocationofseedtonewsitesorwithinorclosetoexistingsiteswhicharealreadycolonised.
Moresuccessfulestablishmentfromseedwasrecordedinareaswheregroundwasexperimentallydisturbed.Scarificationormechanicalgrounddisturbancetorevealbaresoilcouldbeusedtopromoteestablishment.Thisisparticularlynecessaryinareaswhereagrassyormossymatformsthemainvegetationcommunity,andwouldbeunnecessarywherethesoilorothersubstrateisnaturallymobile,suchasflushedareasonsteeperslopes.Itissuggestedthatlarger(c.1m2)disturbedareaswouldreduceseedlinglossesduetopredationasthiswouldrenderalargerareaunsuitableforsmallmammalsandslugs.
Smallmammalsdidnothaveagreatinfluenceonveryearlyseedlingestablishmenteveninyearsofpeakabundance.However,smallmammalherbivorydidresultingreaterdamageofone-year-oldseedlingsalthoughthisdidnotnecessarilycauseseedlingmortality.Managersattemptingtoestablishwillowsmayconsiderplantingyear-oldseedlingsinbarepatchestoreducecompetitionandcoincidingplantingwithyearsoflowvoleabundance.
Exclusionoflargeherbivores(sheepanddeer)permittedmorevigorousvegetativegrowthofshoots,floweringandpollenandseedproduction.Limitingthenumbersoftheseherbivoresinareaswheretheirimpactsonthevegetationissignificantwouldpromotegrowthandsexualreproduction.However,thismeasurealonewouldresultinlittleornonewestablishmentfromseedgiventheotherfactorsreferredtoabove.
S. lapponumcatkins
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Further information
Inevitably,giventhenatureofthispublicationandspaceconstraints,theworkpresentedhereishighlysummarised.Ifyouwouldliketoknowmoreaboutthisprojectpleasevisitourwebsitewhichhasadditionalinformation,resourcesandphotographs.
http://rbg-web2.rbge.org.uk/willow/index.html
Foradditionalinformationpleasecontacttheprojectco-ordinatorsinthefirstinstance.
Dr.PeteHollingsworth Dr.GlennIason RoyalBotanicGardenEdinburgh MacaulayInstitute 20AInverleithRow Craigiebuckler EdinburghEH35LR AberdeenAB158QH tel+441312482883 tel+441224498200 Fax+441312482901 Fax+441224311556 [email protected] [email protected]
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AcknowledgementsScottish Montane Willow Research Group
royal Botanic Garden edinburgh Dr.PeteHollingsworth Dr.StephanHelfer DouglasMcKean AlanForrest Dr.JeremyMilne
Macaulay institute Dr.GlennIason Prof.RobinPakeman RosShaw
scottish Crop research institute Dr.JohnBrown Dr.JoanneRussell KonstantinaStamati
Biomathematics and statistics scotland Prof.DavidElston
scottish Agricultural College Prof.DaleWalters
university of edinburgh Dr.RichardEnnos
university of Aberdeen Dr.MarkYoung
Thanks
WewouldliketothanktheScottishExecutiveEnvironmentandRuralAffairsDepartmentforfundingthisprojectthroughtheCollaborativeFlexibleFund(SEERADCommissionNo.RBG/837/01).
Ourthanksareextendedtothefollowingindividualswhocontributedtotheprojectinavarietyofways:Prof.RoyWatling,Prof.RiittaJulkunen-Tiitto,DavidTennant,Dr.ChrisSydes,KenSlater,DavidMardon,AndrewWarwick,DianaGilbert,RobSoutar,Dr.IanAnderson,Prof.IanAlexander,SandieBlackie,RosAnderson,SvenRasmussen,VimiLomax,CatherineDickison,Dr.MichelleHollingsworth,AlexClark,Dr.ChrisWalker,KeithWatson,LynneTorvell,DavidSim,VeraThoss,JoanBeaton,KennyHood,BettyDuff,Dr.JaneSquirrell.
FinallywewouldliketothankthenumerouslandownersandstaffofScottishNaturalHeritagewhograntedusaccesstothewillowsandpermissiontoresearch.
GroupmembersonanearlyreconnaissancetriptoBenLawers
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Thisbookletsummarisessomeofthekeyfindingsfromacollaborativeresearchprojectentitled“Biodiversity: taxonomy, genetics and ecology of sub-arctic willow scrub”thattookplaceduring2002-2005.
TheprojectwasfundedbytheScottishExecutiveEnvironmentandRuralAffairsDepartment(SEERADCommissionNo.RBG/837/01).
Itinvolvedresearchersfrom:
RoyalBotanicGardenEdinburgh
MacaulayInstitute
ScottishCropResearchInstitute
BiomathematicsandStatistics Scotland
ScottishAgriculturalCollege
UniversityofEdinburgh
UniversityofAberdeen.