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20Methods
formedateachstep0Ward’smethodwasusedasaveryeffectivewaytocreate
clustersofsmallsize(Ward1963),whereastheManhattandistancewasused
toreducetheinfluenceoflargeindividualdifferencesinthebiomassofspe-
cies(outliercases;e0g0000001–196058gd0w0/001m2)0Therelevanceofselected
vegetationunits(communities)wasevaluatedbyone-wayANOSIMwith
theBray-Curtisdistancemeasure(Bray,Curtis1957)inthePASTprogram0
ANOSIM(ANalysisOfSIMilarities)isanon-parametrictestofsignificant
differencebetweengroups(for15specieswithF>5%),basedondistance
measures,whichareconvertedtoranks(Clarke1993)0Thetestisbasedon
comparingdistancesbetweengroupswithdistanceswithingroups0ANOSIM
ismainlyusedforecologicaltaxa-in-samplesdata,wheregroupsofsamples
aretobecompared0TheBray-Curtisdistancemeasurewasusedbecauseof
theconstructionofdata(sampleswithspeciesbiomass):itispossiblythemost
widelyusedabundancebasedmeasure,duetoitsstrongrelationshiptoeco-
logicaldistanceundervaryingconditions0Thedifferences(R,forp<00001)
betweeneachgroup(plantsamples)aregiveninthetable0
Fortheselectedvegetationunits(communities)thefollowingwerecalcu-
lated:Shannon–Wienerdiversityindex(Hl),Pielou’sevennessindex(II),as
wellasindicesofdominance(DI),constancy(CI),importance(II),fidelity(FI)
andfrequency(F)ofspecies0Speciesdiversitywasdeterminedonthebasisof
theShannon–WienerindexHl(Shannon,Weaver1949;Huston1996),accord-
ingtotheformula:HI=–S[(mj/m)•logmj/m],where:mj–biomassofspeciesj
inthesample[gd0w0],m–plantbiomassinthesample[gd0w0]0Pielou’sindex
ofspeciesevennessdistributionIl(Pielou1966;Pielou1974;Piernik2008)was
calculatedaccordingtotheformula:II=HI/Hmax,whereHl–valueofthe
indexforthesamplewithnumbernofspecies,Hmax–maximumvalueofthe
indexforthesamplewithnumbernofspecies(Hmax=logn)0
Thefidelityindex(FI)isameasureoftherelationshipbetweenaspecies
andthecommunity(Peinadoetal02013)0Itwascalculatedaccordingtothe
formula:FI=a/b•100%,wherea–speciesbiomassinthecommunity,b–
biomassinallthecommunitiesin161lakesunderstudy0Fourcategoriesof
fidelityweredistinguishedforthespeciesinthecommunities:differential
(>95%),typical(FI50–95%),accompanying(FI5–50%)andforeignspecies
(FI<5%)0Thedifferentialspeciesoccurredwithhighbiomassexclusivelyor
almostexclusivelyinagivenvegetationunit(community)andtheircombina-
tionwascharacteristicofonlyonecommunity0Thetypicalspeciesoccurred
withconsiderablebiomassorregularlyinacommunitybutwereconnected
toseveralcommunitiessimilarintermsofhabitat0Theaccompanyingspe-
cies(companions)wererareinacommunity,occurredwithlowbiomassand
hadnovisiblerelationshipwiththecommunity0Theforeignspeciesweread-
