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Arthropod communities in fungal fruitbodies are weakly structured by climate and biogeography across European beech forests

Authors:
  • Nationalpark Bayerischer Wald

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Aim The tinder fungus Fomes fomentarius is a pivotal wood decomposer in European beech Fagus sylvatica forests. The fungus, however, has regionally declined due to centuries of logging. To unravel biogeographical drivers of arthropod communities associated with this fungus, we investigated how space, climate and habitat amount structure alpha and beta diversity of arthropod communities in fruitbodies of F. fomentarius. Location Temperate zone of Europe. Taxon Arthropods. Methods We reared arthropods from fruitbodies sampled from 61 sites throughout the range of European beech and identified 13 orders taxonomically or by metabarcoding. We estimated the total number of species occurring in fruitbodies of F. fomentarius in European beech forests using the Chao2 estimator and determined the relative importance of space, climate and habitat amount by hierarchical partitioning for alpha diversity and generalized dissimilarity models for beta diversity. A subset of fungi samples was sequenced for identification of the fungus’ genetic structure. Results The total number of arthropod species occurring in fruitbodies of F. fomentarius across European beech forests was estimated to be 600. Alpha diversity increased with increasing fruitbody biomass; it decreased with increasing longitude, temperature and latitude. Beta diversity was mainly composed by turnover. Patterns of beta diversity were only weakly linked to space and the overall explanatory power was low. We could distinguish two genotypes of F. fomentarius, which showed no spatial structuring. Main conclusion Fomes fomentarius hosts a large number of arthropods in European beech forests. The low biogeographical and climatic structure of the communities suggests that fruitbodies represent a habitat that offers similar conditions across large gradients of climate and space, but are characterized by high local variability in community composition and colonized by species with high dispersal ability. For European beech forests, retention of trees with F. fomentarius and promoting its recolonization where it had declined seems a promising conservation strategy.
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Diversity and Distributions. 2019;25:783–796.  wileyonlinelibrary.com/journal/ddi 
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 783
Received:23April2018 
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  Revised:18O ctober2018 
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  Accepted:11November2 018
DOI:10.1111/ddi.12882
BIODIVERSITY RESEARCH
Arthropod communities in fungal fruitbodies are weakly
structured by climate and biogeography across European beech
forests
Nicolas Friess1| Jörg C. Müller2,3 | Pablo Aramendi4| Claus Bässler2|
Martin Brändle1| Christophe Bouget5| Antoine Brin6| Heinz Bussler7|
Kostadin B. Georgiev2,3| Radosław Gil8| Martin M. Gossner9|
Jacob Heilmann‐Clausen10| Gunnar Isacsson11| Anton Krištín12| Thibault Lachat13,14|
Laurent Larrieu15,16| Elodie Magnanou17,18 | Alexander Maringer19| Ulrich Mergner20|
Martin Mikoláš21,22| Lars Opgenoorth1| Jürgen Schmidl23| Miroslav Svoboda21|
Simon Thorn3| Kris Vandekerkhove24| Al Vrezec25| Thomas Wagner26|
Maria‐Barbara Winter27| Livia Zapponi28| Roland Brandl1| Sebastian Seibold29
1DepartmentofEcology‐AnimalEcology,FacultyofBiology,Philipps‐UniversitätMarburg,Marburg,Germany
2BavarianForestNationalPark,Grafenau,Germany
3FieldStationFabrikschleichach,DepartmentofAnimalEcologyandTropicalBiology,UniversityofWürzburg,Biocenter,Rauhenebrach,Germany
4Vermungsgade,Copenhagen,Denmark
5Irstea,'ForestEcosystems'ResearchUnit,Nogent‐sur‐Vernisson,France
6INPT–Ecoled'IngénieursdePurpan,UMR1201DynaforINRA‐INPT,UniversityofToulouse,Toulouse,France
7AmGreifenkeller1b,Feuchtwangen,Germany
8DepartmentofEvolutionary,BiologyandEcology,InstituteofInvertebrateBiology,FacultyofBiologicalSciences,UniversityofWroclaw,Wrocław,Poland
9ForestEntomology,SwissFederalResearchInstituteWSL,Birmensdorf,Switzerland
10CenterforMacroecology,EvolutionandClimate,NaturalHistoryMuseumofDenmark,UniversityofCopenhagen,Copenhagen,Denmark
11SwedishForestA gency,Hässleholm,Sweden
12InstituteofForestEcolog ySAS,Zvolen,Slovakia
13SchoolofAgricultural,ForestandFoodSciencesHAFL,BernUniversityofAppliedSciences,Zollikofen,Switzerland
14SwissFederalResearchInstituteWSL,Birmensdorf,Switzerland
15INRA ,UMR1201DYNAFOR ,ChemindeBordeRouge,UniversityofToulouse,CastanetTolosanCedex,France
16CRPFOC ,Tolosane,France
17SorbonneUniversités,UPMCUnivParis06,CNRS,BiologieIntégrativedesOrganismesMarins(BIOM),Banyuls/Mer,France
18Réser veNaturelleNationaledelaForêtdelaMassane,Argelès‐sur‐Mer,France
19GesäuseNationalPark,Admont,Austria
20ForestCompanyEbrach,Ebrach,Germany
21FacultyofForestryandWoodSciences,CzechUniversityofLifeSciencesPrague,Prague,CzechRepublic
22PRALES,Rosina,Slovakia
23Ecologygroup,DevelopmentalBiolog y,DepartmentBiology,UniversityofErlangen‐Nuremberg,Erlangen,Germany
24ResearchInstituteforNatureandForestINBO,Geraardsbergen,Belgium
25NationalInstituteofBiology,Ljubljana,Slovenia
ThisisanopenaccessarticleunderthetermsoftheCreativeCommonsAttributionLicense,whichpermitsuse,distributionandreproductioninanymedium,
providedtheoriginalworkisproperlycited.
©2019TheAuthors.Diversity and DistributionsPublishedbyJohnWiley&SonsLtd.
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26Depar tmentofBiolog y,UniversityofKoblenz‐Landau,Koblenz,Germany
27ForestResearchInstituteofBaden‐Würt temberg(FVA),Freiburg,Germany
28CentroNazionaleperloStudioelaConservazionedellaBiodiversitàForestale"BoscoFontana",Marmirolo,Italy
29TerrestrialEcolog yResearchGroup,DepartmentofEcologyandEcosystemManagement,TechnischeUniversitätMünchen,Freising,Germany
Correspondence
SebastianSeibold,TerrestrialEcology
ResearchGroup,Depar tmentofEcology
andEcosystemManagement,Technische
UniversitätMünchen,Freising,Germany.
Email:sebastian.seibold@tum.de
Funding information
RudolfandHeleneGlaserFoundation;
MinisterstvoŠkolství,Mládežea
Tělovýchovy,Grant/AwardNumber:CZ.0
2.1.01/0.0/0.0/16_019/0000803;Česká
ZemědělskáUniverzitavPraze,Grant/
AwardNumber:CIGANo.20184304
Editor:AnnaTraveset
Abstract
Aim:ThetinderfungusFomes fomentariusisapivotalwooddecomposerinEuropean
beechFagus sylvaticaforests.Thefungus,however,hasregionallydeclinedduetocen
turiesoflogging.Tounravelbiogeographicaldriversofarthropodcommunitiesassoci
atedwiththisfungus,weinvestigatedhowspace,climateandhabitatamountstruc ture
alphaandbetadiversityofarthropodcommunitiesinfruitbodiesofF. fomentarius.
Location:TemperatezoneofEurope.
Tax o n:Arthropods.
Methods:Werearedarthropodsfromfruitbodiessampledfrom61sitesthroughout
therangeofEuropeanbeechandidentified13orderstaxonomicallyorbymetabar‐
coding.WeestimatedthetotalnumberofspeciesoccurringinfruitbodiesofF. fom en
tarius in European beech forests using the Chao2 estimator and determined the
relativeimportanceofspace,climateandhabitatamountbyhierarchicalpartitioning
foralphadiversityandgeneralizeddissimilaritymodelsforbetadiversity.Asubsetof
fungisampleswassequencedforidentificationofthefungus’geneticstructure.
Results:ThetotalnumberofarthropodspeciesoccurringinfruitbodiesofF. fomentarius
acrossEuropeanbeechforestswasestimatedtobe600.Alphadiversityincreasedwith
increasingfruitbodybiomass;itdecreasedwithincreasinglongitude,temperatureand
latitude. Beta diversitywas mainly composed by turnover.Patterns of beta diversity
wereonlyweaklylinkedtospaceandtheoverallexplanatorypowerwaslow.Wecould
distinguishtwogenotypesofF. fomentarius,whichshowednospatialstructuring.
Main conclusion: Fomes fomentariushost s a l a r g e n u m b er o f a r th ro p o ds i n Eu r o p e a n
beechforests.Thelowbiogeographicalandclimaticstructureofthecommunities
suggeststhatfruitbodiesrepresentahabitatthatoffers similarconditionsacross
largegradientsofclimateandspace,butarecharacterizedbyhighlocalvariability
incommunitycompositionandcolonizedbyspecieswithhighdispersalability.For
European beech forests, retention of trees withF. fomentariusandpromotingits
recolonizationwhereithaddeclinedseemsapromisingconservationstrategy.
KEY WORDS
deadwood,Fagus sylvatica,Fomes fomentarius,insects,invertebrates,restoration,saproxylic,
sporocarp
1 | INTRODUCTION
Most parts of the temperate zone of Europe—from the Iberian
Peninsula to the Black Sea and from southern Italy to southern
Sweden—are naturallycoveredby forestsdominated by European
beechFagus sylvatica (Fig ure 1). These forests, however,have de‐
clined over recent centuries due to deforestation until around
1800,andsincethenduetoconversiontoconifer‐dominated(Pinus
sylvestris,Picea abies)plantations(Dirkx,1998;Schelhaas,Nabuurs,&
Schuck,2003).Historicdeforestationanddegradationhaverecently
been reinforced by large‐scale clear‐cutting of old‐growth beech
forestsin regionsthat,until recently, were rather unaffected (e.g.,
intheCarpathians;Vanonckelen&VanRompaey,2015;Mikolášet
al.,2017).Sincethe distributionofEuropean beechisrestricted to
thetemperatezoneofEurope,theEUhas acknowledgeditsglobal
responsibilitybylistingseveraltypesofbeechforestasNatura2000
    
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habitats(CounciloftheEuropeanUnion,).Furthermore,someofthe
lastnaturaloralmostnaturalEuropeanbeechforestsarepartofthe
UNESCO World Heritage “Ancient and PrimevalBeech Forests of
theCarpathians andOther RegionsofEurope”(http://whc.unesco.
org/en/list/1133).Despitethesecommitmentstoconservingbiodi
versityinEuropeanbeechforests,ourunderstandingoflarge‐scale
driversof biodiversity inbeechforests remainslimited,hampering
systematic conservation planning, given prevalent area conflicts
(Ammeretal.,2018;Kouki,Hyvärinen,Lappalainen,Martikainen,&
Similä,2012;Margules&Pressey,2000).
ThespeciespooloforganismsassociatedwithEuropeanbeech
forestscanbeexpectedtobestructuredacrosslargespatialscales
reflecting different underlying mechanisms. European beech was
one of the last tree species to recolonize central and northern
EuropefromitsmajorrefugiainsouthernEuropeafterthelastgla‐
ciation and is still expandingits range towards the north andeast
(Magri, 2008). Understorey plant diversity in European beech for‐
estsreflectsthishistoryandisdeterminedbydistancetothenear‐
estknownmajorrefuge(Jiménez‐Alfaroetal.,2018;Willner,Pietro,
&Bergmeier,2009).Inaddition,populationsofEuropeanbeechmay
alsohavepersistedinmicrorefugiaincentralEurope(Robin,Nadeau,
Grootes,Bork,&Nelle,2016).Duetoitshighcompetitivenessand
climate tolerance,Europeanbeech covers a widerange of climatic
conditions (Figure 1; Brunet, Fritz, & Richnau, 2010), which might
structurecommunities(Heilmann‐Clausenetal.,2014).Towardsits
ecologicalrangelimits,increasingpresenceofothertreespeciesand
arthropodsassociatedtothesetrees (Brändle&Brandl,2001)may
furtherinfluencetheregionalspeciespool.
These natural drivers ofcommunity structure in beech forests
interact with anthropogenic factors. Forest clearing and forest
manageme nt have been more intens e in western than in e astern
Europeresultinginagradientofhabitatlossofnaturalbeechforest
and conse quently fragme ntation of these fo rests from eas t–west
(Abrego,Bässler,Christensen, & Heilmann‐Clausen, 2015;Kaplan,
Krumhardt, & Zimmermann,2009;Larsson,2001). Manyspecialist
speciesforold‐growthbeechforestshavethusbecomerarerorlo‐
callyextinctinwesternEuropeandcantodayonlybefoundineast‐
ernEurope(Eckeltetal.,;Speight,1989).
Onsmallerspatialscales,speciescommunities canbe affected
bytheregionalclimate acting as environmental filterasshown for
wood‐inhabitingbeetlesandfungiinbeechforests(Bässler,Müller,
Dziock,&Brandl,2010;Mülleretal.,2012)andminutetree‐fungus
beetlesinfruitbodies(Reibnitz,1999).Moreover,notonlylarge‐scale
gradients of anthropogenic pressure can influence communitiesin
FIGURE 1 Mapofthe61samplingsitesofthisstudy.ThegreenareadepictsthepredictedcurrentdistributionofEuropeanbeech
Fagus sylvatica(Brusetal..,2011).ThenumbersinthemapcorrespondtothestudysiteIDinsupportinginformationAppendixS2and
AppendixS3:TableS3.1.Circlesindicatethe52studysitesforwhichdataonallarthropodswereavailable;squaresindicatetheninesites
forwhichonlybeetledatawereavailableandwhicharepartoftheanalysesinSupportinginformationAppendixS4.Blackfillingindicates
siteswithactiveforestmanagementandwhitefillingindicatesunmanagedsites.Leftinset:AtypicalexampleofaEuropeanbeechtree
withfruitbodiesofFomes fomentarius. PhotographbyThomasStephan.Rightinset:Meanannualtemperatureandannualprecipitationof
allstudysites(filledcirclesandsquares(seeabove))and10,000randomlysampledpointsinthedistributionofF.sylvaticarepresentingthe
climatespacewherebeech‐dominatedforestsareoccurring
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beech forests butalsothe amountofavailablehabitat at localand
landscapescales(Fahrig,2013;Seiboldetal.,2017)andtheconnec
tivityofhabitat patches (Abrego et al., 2015; Nordén et al.,2018;
Rukke,2000).
Fun giareth emainbiot icagent sofwooddecom posit ionan dt heir
myceliaandfruitbodiesareanimportantfoodformanyarthropods
astheycontain higherconcentrationsofnutrientsstoredin amore
ac ces sibl efor mtha ninundec ayed woo d(Fi lipi ak,S obczyk, &Weine r,
2016;Merrill&Cowling,1966;Stokland,Siitonen,&Jonsson,2012).
Inparticular,fungalfruitbodies,especiallypolypores,serveashabi
tatformany fungicolousarthropod species(Schigel,2012).Studies
ofthediversityandcompositionoffungicolousarthropodcommuni
tieshavesofarbeenrestrictedtolocalandregionalscales,andgen
erallyindicatethatmanyarthropodspeciesarehost‐specific(Jonsell
&Nordlander,2004;Komonen,2001).Occurrenceandabundanceof
fungicolousarthropodspeciesonsingletreesandforeststandsde
pendonhabitatavailability(Rukke,2000).Attheregionalscale,turn
overinspeciescompositionhasbeenfoundtobehighamongfungal
host spe cies, but low amon g sites across host sp ecies (Komonen,
2001).Sofar,nostudyhasinvestigateddiversitypatternsoffungic
olousarthropodsatcontinentalscales(Schigel,2012).
ThetinderfungusFomes fomentariusisoneofthemaindecom
posersofwoodinmanybeechforestsinEurope.However,F. fomen
tarius has a much l arger range tha n European bee ch covering the
temperate and boreal zones of Europe, Asia and Nor th America.
Outsidebeechforests,itoccursespeciallyinriparianandborealfor
estsonBetula,Populus, Alnus orotherhardwoodtrees(Matthewman
&Pielou,1971;Reibnitz,1999;Rukke,2000).Asawhite‐rotfungus,
itcan efficiently break down lignocellulose andcontributes tothe
death ofweakenedliving trees, thus promoting naturalforest dy‐
namics(Butin,1989).Itsfruitbodiesandthecreateddeadwoodare
habitatformanyarthropodspecies (Schigel,2012).Their commu
nitycompositionislargelyaffectedbythephysicalconditionsofthe
fruitbodieswhichchangewithongoingdecomposition(Dajoz,1966;
Reibnitz, 1999; Thunes &Willassen, 1997).Thus, in order to cap‐
ture the w hole local com munity occur ring in F. fomentarius differ
entstagesofdecompositionhavetobetakenintoaccount(Graves,
1960).
Treescolonized by the fungus have been suggested as afocal
habitat for biodiversity conservation in beech forests (Larrieu
et al., 2018; Mül ler, 2005). Howe ver, due to centuri es of logging
and direct persecution for phytosanitary reasons, populations of
this fungus have declined orbecamelocally extinctin many areas
(Vandekerkhove etal., 2011;Zytynskaet al.,2018). Toguide con‐
servation planning andstrategies inEuropeanbeechforests, such
asthe selectionof areastobe setaside forconservation(Bouget,
Parmain,&G ilg ,2014)orforacti verestoratio nbyde adwoodenrich
ment(Dörfler,Gossner,Müller,&Weisser,2017), it isnecessaryto
understandhowarthropodcommunities—whichrepresentthelarg
estfractionofanimalbiodiversityinforests—arebiogeographically
structured.
In this study, we reared arthropods from fruitbody samples of
F. fomentarius across the whole distributional range of European
beech.Ouraimsweretoestimatealphaandbetadiversityofarthro
podsinfruitbodiesofF. fomentariusandtodise nt angletheeffect sof
post‐glacialrecolonizationofitshosttree,macro‐climate,anthropo
genicpressureandhabitatamountondiversitypatterns.Specifically,
weexpected (a) decreasing alphadiversity and increasingnested
nesswithlatitudeduetotherecolonizationhistoryofbeech,(b)de
creasingalphadiversity and increasing nestednessfromeast‐west
due to the an thropogenic l and use histor y, (c)i ncreasing tur nover
withincreasingdifferencesinmacro‐climaticconditionsacrossboth
latitudinalandlongitudinalspace,and(d)increasingalphadiversity
withincreasinghabitatamountatlocalandlandscapescales.
2 | METHODS
2.1 | Collection of Fomes fomentarius fruitbodies
We collected fruitbodies from 61 beech‐dominated forest sites
across the distributional range of F. sylvatica (Figure 1) between
JuneandAugust2013.Thesesiteswerechosentocoverthenatural
distributionofF. sylvatica,aswellasthefullrangeofclimaticcondi‐
tions withinthis area(Figure1).Wewerenot abletoincludesites
from someparts of thedistributionalrange,for example southern
England,whereF. fomentarius isalmostabsentforhistoricalreasons
(Abreg o, Christensen, B ässler, & Ainswort h, 2017). Sites were lo‐
cated inunmanaged (36) and managed forests (25); both manage‐
mentcategorieswereevenlydistributedacrossEurope(Figure1).
Forarthropodrearing,wecollected10fruitbodiesofF. fomentar
iuspersitefoll owi nga stand ardizedpro toc ol.A ssem blagesi nhab iting
fruitbodiesofbracketfungichangewithongoingfruitbodydecom
position.Therefore,wesampledfruitbodiesatdif ferentsuccessional
stagesofdecay.Ateachsite,samplingincludedfruitbodiesattached
towoodthathadjustrecentlydiedandwerestillmoist(3to4fruit
bodies)andfruitbodiesthathadbeendeadforalongertime(6to7
frui tbodies).Thelatterwer ee itherdrywhens tillatta chedtowoo d(3
to4fruitbodies)orwetwhenlyingontheground(3to4fruitbodies).
Thissamplingprotocolaimedatcoveringmostoftheavailablehab
itatheterogeneityrepresentedbythefruitbodies.Thetotalvolume
sampledpersiterangedbetween0.2and21.7kg(mean:2.7kg)and
didnotrepresent the local availabilityoffruitbodies as transporta
tionandrearinglogisticsrestrictedthesampledvolume.
In additi on, we collect ed samples of li ving fruitb odies to anal‐
ysethe geneticstructure withinthe population of F. fomentarius in
Europe.Fromthesesamples,weappliedamicrowave‐basedmethod
toextractDNA(Dörnte&Kües,2013)andamplifiedsequencesfor
theinternaltranscribedspacer(ITS)regionandtheelongationfactor
α(efa)genebytouchdownPCR(fordetails,seeSupportinginforma
tionAppendixS1).
2.2 | Arthropod rearing
Toreararthropods,allfruitbodiesofthesamesite(fromnowoncalled
“sample”) w ere put into a cardbo ard box (25cm×25cm×50cm)
in an unheated well‐ventilated storage room with a seasonal
    
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FRIESS E t al.
temper ature regime. A tra nsparent collec ting jar was att ached to
eachboxandfilledwith90%ethanoltocollectarthropodsattracted
tolight.Collectingjarswereemptiedeverytwomonthsandarthro
podsinside theboxeswerecollectedbyhand. Rearingwascarried
outfor12monthsforeachsample.
2.3 | Arthropod identification and classification
Reared ar thropod specimens were stored in ethanol and beetles
were determined to species level by taxonomists. The remaining
fauna was identified by metabarcoding using next‐generation se
quencin g carried out by Adv anced Identific ation Methods G mbH
(Munich,Germany;fordetails,seeSupportinginformationAppendix
S1).Arthropodsequenceswerematched against the publicly avail
able DNA barcode library within the Barcode of Life (BOLD
v4.boldsystems.org; Ratnasingham & Hebert, 2007). Laboratory
problemsimpededtheuseofnext‐generationsequencingforsam
plesfromninesites(Figure1).
Weconsideredallspeciesthatwererearedfromfruitbodysam‐
ples,includingspeciesthatusehollowfruitbodiesas shelterorde‐
velopattheinterfacebetweenfruitbodiesandwhite‐rottenwood.
However, since this i ncludes specie s that do not intera ct directly
with the fruitbody, we additionally analysed the data excluding
these species.Basedon literature,we classified species orgenera
thatare knownto feeddirectly on thefungaltissue or exclusively
preyuponmycetophagousspeciesas“fungispecialists”(Supporting
informationAppendixS2);andweclassifiedallspeciesaccordingto
theirtrophiclevelasconsumers(i.e.,speciesthatfeedonnon‐animal
tissue),predators(i.e.,speciesthatfeedonanimaltissue)orparasit‐
oids(i.e.,speciesthatdeveloponorwithinsinglehostorganismsand
ultimatelykilltheirhost).
2.4 | Environmental predictor variables
Coordinatesofeachsitewererecordedin the fieldusinghandheld
GPSdevices(SupportinginformationAppendixS3,TableS3.1).We
extracteddataonall19bioclimaticvariablesforeachsitefromthe
WorldClim database (Hijmans, Cameron, Parra, Jones, & Jarvis,
2005).Sincebioclimaticvariablesareoftencorrelated,weperformed
aprincipalcomponentanalysisonthecorrelationmatrixfortemper
atureandprecipitationvariablesseparately(i.e.,temperature:BIO1
–11;precipitation:BIO12–19).Thefirsttwoprincipalcomponents
explainedmostofthevariationinbothdatasets(temperature:75%;
precipitation:91%;SupportinginformationAppendixS3,TableS3.2)
andweresubsequentlyusedasaproxyforbioclimaticconditionsat
thesites.Thefirstprincipal componentsrepresented a gradient in
meantemperatureorprecipitationwithhighvaluesindicatingsites
withoverallhightemperatureorsumsofprecipitation,respectively.
Thesecondprincipalcomponentsrepresentedagradientinseason
ality withhigh values forsites displaying hightemperature orpre‐
cipitationseasonality,respectively.
Too btain a proxy f or landscap e‐scale habi tat amount an d an‐
thropogenicpressure,we calculated the proportionofforestcover
surroundingthe sitesforradiifrom 100 to 5,000m(100‐msteps).
Forest coverwithina radiusof700maround siteshadthehighest
independenteffectonalphadiversity,andthus,thisradiuswascho
senforfurtheranalyses(SupportinginformationAppendixS3,Figure
S3.1).WeuseddatabasedonLandsatsatelliteimagesfromtheda‐
tabaseonGlobalForestChange(Hansenetal.,2013),whichisavail‐
ablewithaspatialresolutionofapproximately25metresperpixel,
withvaluesrangingfrom0to100perpixelencodingtheproportion
ofcanopyclosureforallvegetationtallerthan5minheight.Toeval‐
uatetheroleofsamplesize(asaproxyforlocalhabitatamount)for
alphaand betadiversity,werecordedthetotal dryweightoffruit‐
bodiespersampleafter12monthsofrearing.Proportionsofforest
coverwerelogit‐transformedandsamplesizewasloge‐transformed.
2.5 | Statistical analyses
AllstatisticalanalyseswerecarriedoutusingR version3.3.2(RCore
Tea m, 2016) .T he main analyses i ncluded beetl es identified t axo‐
nomicallyandallotherarthropodsidentifiedbymetabarcodingand
werethus restricted to the52sites for which metabarcoding data
wereavailable.Additionalanalyseswereconductedforbeetledata
fromall61siteswithbeetleabundances(seeSupportinginformation
AppendicesS4andS5).
Toestimate the overall species pool, we calculated the Chao2
estimator, as implemented in the vegan package version 2.4–3
(Oksan en et al., 2018). The Chao2 es timate is a functi on of spe‐
ciesoccurringonceortwiceinthedatasetandoffersrobustlower
bound es timation for sp ecies richnes s based on inciden ces under
theassumptionthatrarespecieshavesimilardetectionprobabilities
(Chao, 1987). Cal culations were b ased on data for a ll species and
separatelyforfungispecialistsandeachtrophicguild(i.e.,consumer,
predator a nd parasitoid ) on the 52 sites. In ad dition, we use d the
rarefaction–extrapolation framework based onsp eciesincidences
acrossallsites(Chaoetal.,2014).WeusedHillnumberoftheorders
0(species richness),1 (the exponential of Shannon's entropy) and
2(the inverse of Simpson's concentration)to analyse thediversity
ofrare andcommonspecies within one framework. We used 999
replicated bootstraps to calculateconfidence intervalsaround the
species‐accumulationcurves using the iNEXT package (Hsieh, Ma,
&Chao,2016).
Alphadiversitywascalculatedasthenumberofspeciespersite.
Toestimate therelative importance of thepredictor variables, we
performedhierarchicalpartitioning—asimplementedinthehier.part
package version 1.0–4 (Walsh & Mac Nally,2013)—based ongen‐
eralizedlinearmodels.Forthegeneralizedlinearmodels,wechose
aquasipoissonerrordistributionanda log‐linkfunctionin orderto
accountforfrequentlyobservedoverdispersioninmodelsofcount
data.Ple asenotethatalternativelych oosingmod elsincludin ga no b
serva tion‐level ran dom effect o rm odels with a neg ative‐binomia l
errordistributiondidnotalterthemainresults.Themodelsincluded
alphadiversity as the dependentvariableandspace(latitude,lon
gitude),climate(meantemperature,temperatureseasonality,mean
precipitation,precipitation seasonality)andhabitatamount(forest
788 
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cover,sample size)aspredictor variable sets. Allcalculations were
performedseparatelyforallspecies,fungispecialistsandeachtro
phicguildonthe52sites.
BetadiversitywascalculatedastheSørensendissimilarityamong
all 52 sites using presence–absence information. The community
compositionofall speciesandfungi specialistswasvisualized using
non‐metricmultidimensionalscaling(NMDS).Subsequently,wefit
tedtheenvironmentalvectorsofspace,climateandhabitatamount
to the resulting ordination as implemented in the envfit function
using the vegan package. In ad dition, we per formed an a nalysis of
similarityin ordertotest for groupdifferences in communitycom
position a mong managed and un managed sites, as wel l as among
biogeographicalregionsagainusingvegan (seeSupportinginforma
tionAppendixS3forfurtherdetails).Furthermore,wedecomposed
beta diversity in its turnover and nestedness components based
onthe Sørensenindexfamilyas implementedinbetapart (Baselga,
Orme,Villeger,Bortoli,&Leprieur,2017).Theturnovercomponent
representsbetadiversityintroducedbythereplacementofspecies
betweensites,whilethenestednesscomponentrepresentsthebeta
diversityintroducedbytheremoval/gainofspeciesbetweensites.
Toestimatethe relativeimportanceofthepredictor variables (lati
tude,longitude, meantemperature,temperatureseasonality,mean
precipitation,precipitationseasonality,forestcoverandsamplesize)
for beta diversity, we calculated generalized dissimilarity models
(GDMs)asimplementedinthegdmpackage(Manionetal.,2017)for
totalbetadiversity,andturnoverandnestednesscomponentssep
arately. GDMs allow theanalysis of spatial patternsof community
compositionacrosslargeregions under consideration of nonlinear
relationshipsbetweendissimilarityincommunitycompositionalong
environmentalgradients(Ferrier,Manion,Elith,&Richardson,2007).
AllGDMswerecalculatedusingthedefaultofthree I‐splines.The
calculatedcoefficientfor each of the threeI‐splinesrepresentsthe
rateofchangealongathirdofthegradientoftheenvironmentalpre
dictorwhenkeepingallotherpredictorsconstant(i.e.,highvaluesof
thefirstI‐splineindicateahigh rateofchange alongthe first third
ofthegradient).Weestimatedtherelativecontributionofeachpre
dictorsetasthedifferenceinexplaineddeviationbetweenamodel
containingallpredictorsetsandamodel fromwhichthispredictor
setwasremoved(Legendre&Legendre,1998;Maestri,Shenbrot,&
Krasnov,2017).Allcalculationswereagainperformedseparatelyfor
allspecies,fungispecialistsandeachtrophicguildonthe52sites.
Dataforbeetlesincludingabundances wereavailable for all61
sites;wethusconductedsimilaranalysesforthisgroupasforallar‐
thropods(seeSupportinginformationAppendicesS4andS5).These
analysesconsideredtheinfluenceofincreasingnumbersofindivid
ualsonalpha diversity andtheeffectof space,climate and habitat
amountonabundance‐baseddissimilaritiesofthebeetlecommuni
ties. He re, we used Bray–Cur tis dissimil arities and de composed it
intothetwocomponentsbasedonbalancedvariationinabundance
(i.e., individuals of some species ata site are substituted by equal
numbersof individualsat anothersite)and dissimilarityintroduced
byabundancegradients(i.e.,individualsarelostwithoutsubstitution
fromonesitetotheother;Baselga,2013).
3 | RESULTS
In total, we identified 216 arthropod species emerging from fruit‐
bodiesof F. fomentariusfrom52sites.Speciesbelongedto13or
ders, with highest species richness found in Diptera ( n=72) and
Coleoptera(n=71;Figure2;SupportinginformationAppendixS2).
The majority oftaxa (n=179) couldbe assigned to species bythe
taxonomist or by alignment of operationaltaxonomic units (OTUs;
see Supporting information Appendix S1)with existing databases.
Theremaining37OTUsnotassignedtoaspeciesweremostlymem
bers ofthe Cecidomyiidae (Diptera), for whichbarcodes were not
availableinthedatabases.Weidentified74speciesasfungispecial‐
ists.Concerningtrophicguilds,weclassified131speciesasconsum
ers, 68 speciesaspredatorsand17species as parasitoids.Genetic
analysisofF. fomentariussamplesrevealedtwogenotypesthatwere
previouslyidentified aspossiblesympatric crypticspecies(termed
genotype“A”and“B”;Judova,Dubikova,Gaperova,Gaper,&Pristas,
2012).However,intraspecificgeneticvariationamongsiteswasvery
lowandgenotypeBoccurredonlyatfiveofoursiteswidelyspread
overthesamplingarea(SupportinginformationAppendixS1).
Chao2 est imators indic ated an overall s pecies pool of 5 87(S E
=103) for all specie s, 249(S E =181) for fungi spe cialists, 40 2 (SE
=104) for consumer s, 163 (SE =43) fo r predators an d 42(S E =24)
for parasitoids associated with F. fomentarius in European beech
forest s. The observed effec tive number of typical species (q=1)
was87,whilethe observedeffective number of dominant species
(q=2)was 44 (Supporting informationAppendix S3, Figure S3.3).
Manyofthedominantspecieswereconsumers,such as beetles of
the family Ciidae, the Tenebrionidae Bolitophagus reticulatus, the
micro‐mothScardia boletellaandCecidomyiidaesp.3(Figure3).The
most frequent par asitoids were the hyme nopterans Astichus spp.
andascuttlefly(Phoridae).Beetlesincludedfourspeciesconsidered
tobe “primeval forest relicts” (Eckeltet al., ), namely Bolitophagus
interruptus, Bolitochara lucida, Teredus cylindricus and Philothermus
evanescens, whi ch were each found at on e site (Slovenia, France ,
southernItalyandSweden,respectively).
FIGURE 2 Piechartoftheproportionofspeciesfromdifferent
arthropodordersrearedfromfruitbodiesofFomes fomentariusfrom
52beech‐dominatedforestsitesacrossEurope.Theoverallnumber
ofdeterminedspecieswas216
    
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FRIESS E t al.
Consideringallarthropods,themeanspeciesnumberpersite
was16(SE=6) with thelowest number (six species) foundin the
German Wetterauandthe highestnumber(36 species)locatedin
Abruzzo,Italy.Inthequasipoissonmodels,ourpredictorvariables
explained20%ofthedevianceinalphadiversityforallspeciesand
26% for the fung i specialists (F igure 4). The explain ed deviance
decreased from consumers(22%) topredators (16%)and parasit
oids(6%)correlatedtothenumberofspeciesofthetrophicguilds
(Table 1).According to hierarchical part itioning, habitat amount,
thatisforestcoverandsamplesize,explainedmostoft hedeviance
inourmodels(Fig ure4).Alp hadiver sit yofa llspecies,fungisp ecial
is t s ,cons u mersa n dpred a torsi ncrea s e dwit h incre a sing s amples ize
(Table1,Figure5a)andthatofconsumersalsoincreasedwith in
creasingforestcover.Moreover,alphadiversityofallspecies,fungi
specialistsandconsumersdecreasedwithincreasinglongitudeand
thatoffungispecialistsalsodecreasedwithlatitude.Alpha diver
sityoffungispecialistsandconsumersadditionallydecreasedwith
increasingmeantemperatureandprecipitation(Table1).Mostef
fects,however,wereonlymarginallysignificant(Table1).
Ordinationofthecommunitycompositionofallspeciesas well
asfungispecialistsrevealedlargedifferencesincommunitycompo
sition acrossour study sites(Supporting informationAppendixS3:
Figure S3 .2). Except for a si gnificant ef fect of samp le size on the
communitycompositionofallspecies(r2=0.13,p < 0.05), environ‐
mentalvariableswerenotsignificantlycorrelatedwiththeaxesofthe
NMDS(SupportinginformationAppendixS3;FigureS3.2A&D).In
addition,wefoundnodifferencesincommunitycompositionamong
managedandunmanagedsites,aswellasamongbiogeographicalre
gions(SupportinginformationAppendixS3:FigureS3.2).Thelargest
proportionofdissimilaritywasduetoturnover,ratherthannested‐
nessforallspecies(98%),fungispecialists(96%)andalltrophicguilds
(consumer:97%;predator:99%;parasitoids:97%).Theproportionof
devianceexplainedbyGDMswasbelow15%foroverallbetadiver‐
sity,nestednessandturnoverinallgroups(Figure4).Forallspecies,
wefoundamarginallysignificantincreaseofdissimilarityintroduced
bynestedness with increasinglongitudinal distance between sites
(Table2).Nosinglepredictorhadasignificanteffectonbetadiver‐
sityoffungispecialists andconsumerspecies (Supportinginforma‐
tionAppendixS3,TableS3.4&TableS3.5).Dissimilarityinlatitudinal
distancehadasignificantpositiveeffectontheoverallbetadiversity
aswellasontheturnovercomponentforpredatorsandparasitoids
(Suppor ting inform ation Append ix S3, Table S3.6 and Table S3 .7).
Additionally,wefoundasignificantincreaseinoverallbetadiversity
aswellasindissimilarityduetoturnoverwithincreasingdissimilarity
ofsamplesizeforpredators.
Our a n a l ysesfo r b e e t l esfroma l l61 sitesi n c l u d e dabundan c e data
for123 species (Supporting information AppendixS5).Here,alpha
diversitywasstronglyaffectedbysamplesize(Figure5;Supporting
informationAppendixS4,TableS4.1).Thenumberofbeetlespecies
increased with fungal sample size as the range in samplesize was
consider ably higher acr oss all 61 sites (Figure 5b) th an across the
subset of 52 sites (F igure 5a). Beetl e community co mposition was
FIGURE 3 Rank‐incidenceplotofall216arthropodspecies
rearedfromfruitbodiesofFomes fomentariusfrom52beech‐
dominatedforestsitesacrossEurope
FIGURE 4 Relativecontributionofpredictorsetsinexplaineddevianceofalphaandbetadiversityanditscomponentsturnoverand
nestedness.Alphadiversitywasmodelledusinggeneralizedlinearmodelsandtherelativecontributionisbasedonhierarchicalpartitioning.
Betadiversityisbasedonpresence–absencedataanditscomponentsweremodelledusinggeneralizeddissimilaritymodelsandtherelative
contributionwascalculatedasthe“pure”effectofthepredictorsetontheoverallexplaineddevianceofthemodel.Allanalyseswere
conductedforallspeciesandfungispecialistsseparatelyandforthetrophiclevelsconsumer,predatorandparasitoids.Barcoloursrepresent
thepredictorsetswithspaceinblack,climateinlightgrey,habitatamountinwhiteandthedeviancesharedbythepredictorsindarkgrey
Parasitoids
Predator
Consumer
Fungi specialists
All species
01020
Alpha diversity
0510 15
Beta diversity
0510 15
Turnover
0510 15
Nestedness
Space
Climate
Shared
Habitat
amount
Explained deviance
in alpha-diversity (%)
Deviance explained exclusively
by sets of variables (%)
790 
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affec ted by dissimilarit y in sample size and longitude. Here, bee
tle commu nities showed i ncreased rat es of turnover and balanc ed
changes of abundances withlongitudeand increased ratesofnest
ednessandabundancegradientswithsamplesize.Ourmodelsforall
beetle species explainedupto59%of the deviance in alpha diver
sity,34% inSørensen dissimilarity and 19%inBray–Curtisdissimi
larity(SupportinginformationAppendixS4,TableS4.1;FigureS4.1).
Var iable slinkedtoha bit atamountconsis tentl yexplainedmos toft he
devianceinmodelsofspeciesrichness,overallcommunitycomposi
tionandcommunitydissimilarityduetonestedness,whilevariables
linkedtospatialdistanceexplainedmostofthedevianceduetospe
ciesturnover(SupportinginformationAppendixS4).
4 | DISCUSSION
Overall,our results indicatethatfruitbodiesof F. fomentariusform
an important micro‐habitat in European beech forests, host inga
rich fauna (estimat ed ~600 art hropod species). Howe ver, t he ar
thropod communities included about 30 dominantspecies which
occurredatmost sitesacrossEurope andcan beconsideredtypi
cal for fr uitbodies of F. fomentarius. Moreover, there was a lar ge
number of species thatuse F. fomentarius fruitbodiesoccasionally.
The latter groupincludes fungicolousspecies usingawiderrange
offungal hosts (e.g.,Bolitophagus interruptus,Coleoptera,which is
more common on Ischnoderma spp.),speciesthatfeedonwhite‐rot‐
ten wood (e.g ., Corymbia scutellata, Coleoptera) or fu ngal mycelia
and spec ies that use cavi ties inside fru itbodies sim ply for shelter
(e.g. , Amaurobius fenestralis, Aranaea)or that benefit from arthro
podprey(e.g.,Plegaderus dissectus, Coleoptera).Alpha diversity in
creasedwithsamplesizeanddecreasedwithlongitude,latitudeand
temperature.Despitethelargeextentcoveredinourstudy(approx.
1,80 0km in latitude an d 3,000km in lo ngitude), beta dive rsity—
which wascharacterized by high turnover—wasnot structured by
drivers associated withspace, the biogeographyofF. sylvatica and
habitat amount. Moreover, increasing nestedness and decreasing
TABLE 1 Z‐valuesandexplaineddevianceofgeneralizedlinearmodels(quasipoissonfamily)withthenumberofspeciesofallspeciesor
withinguildsasresponsevariables.Significanteffectsareindicatedbyboldtypesetting.PC1andPC2refertothefirsttwoaxesofthe
respectiveprincipalcomponentanalysesoftemperatureorprecipitationvariables(seeMethodssection)
Predictor set Predictor All species Fungi specialists Consumer Predator Parasitoids
Space Latitude −1.36 −1. 98 ** −1 .70 ** −0.08 0.93
Longitude −1. 77** −2 .1 2* −1. 8 2** −1 . 0 8 −0.34
Climate Temperature(PC1) −1 .7 2** −1. 90** −1. 92 ** −0.48 −1. 0 0
Temperature(PC2) −0.82 −0.79 0.43 −1.24 0.31
Precipitation(PC1) −1.41 −1. 3 0 −1. 5 7 −0.68 −0.01
Precipitation(PC2) −0.31 0 .13 −0.45 0.74 −1. 49
Habitatamount Forestcover 1. 26 0.94 1.45 0.13 0.13
Samplesize 1.75** 2.20*1.55 2.20*0.17
Explaineddeviance 0.20 0.26 0.22 0.16 0.06
Note. aSignificancelevels:*p<0.05,**p < 0.1
FIGURE 5 Relationshipbetween(a)thenumberofarthropodspeciesperfruitbodysampleandsamplesize,thatisthetotalweightof
the10sporocarpssampled,of52sitesand(b)thenumberofbeetlespeciesperfruitbodysampleandsamplesizeincludingall61sites.
Circlesindicatethe52studysitesforwhichdataonallarthropodswereavailable;squaresindicateninesitesforwhichonlybeetledata
wereavailableandwhicharepartoftheanalysesinSupportinginformationAppendixS4.Blackfillingindicatessiteswithactiveforest
management,whitefillingindicatesunmanagedsites.Asimpleregressionlineandconfidenceintervalareshown.Axesarelog‐transformed
(a) (b)
    
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FRIESS E t al.
alpha diversity towards theeast follow not the continental gradi
entofincreasinglanduseintensityfromtheCarpathianstowestern
Europe.
Post‐glacial dispersal lags have been identified as one of the
driving mechanisms causing patterns of alpha and beta diversity
acrossEuropeinplants,insectsandvertebrates(Pinkertetal.,2018;
Svenning, Fløjgaard,&Baselga,2011;Svenning,Normand,&Skov,
2008).Incontrast,betadiversityofsaproxylicbeetleswasshownto
behigherbetweensitesthanbetweenelevationalzonesandbiore‐
gions(Mülleretal.,2012).Wefoundonlyaweakdecreaseinalpha
diversityoffungispecialistswithlatitudeandnosignificanteffectof
latitudinaldistanceonbetadiversityofallarthropodsandthetrophic
guildsinF. fomentarius fruitbodies.Onlypredatoryspeciesshowed
an increased rate in turnover with increasing latitudinal distance:
the rateof change in species composition was highest atlow lati‐
tudes (Supportinginformation Appendix S3,TableS3.6).There are
several potentialexplanations as to why post‐glacialrecolonization
ofthemainhost treespecies appears to be ofminor relevance for
communitiesofarthropods occurring inF. fomentariusfruitbodies.
For instance, species associated with fungal fruitbodies ingeneral
displayhighdispersalabilities(Komonen&Müller,2018).Flightmill
experiments showedadispersal ability of Neomida haemorrhoidalis
and Bolitophagus reticulatus(bothColeoptera;bodylength:6–8mm
and 6 – 7.5mm, respectively; Wagner & Gosik, 2016) of>30km
and>100km, respectively (Jonsson, 2003). Additionally, there is
evidence thatthegenetic distance offungivores doesnotincrease
with geographic distance, indicating the absence of dispersal lim
itation ( Kobayashi & S ota, 2016). Another poss ible explanatio n is
thatalthough European beechis the mainhost of F. fomentarius in
temperateEuropetoday,otherhoststhatrecolonizedEuropemuch
earlier—suchasbirch—arealsofrequentlyused(Judovaetal.,2012).
IfF. fomentarius recolonizedEuropewiththelattertreespecies,its
arthropods may have had more time for recolonization and thus
post‐glacialdispersallagsarelesslikelytobeimportant.Last,ifmi‐
crorefugiaofEuropeanbeechalsooccurredincentralEurope(Robin
etal.,2016),recolonizationpathwaysmay becomplexandnotwell
describedbylatitudeusedasaproxyfordistancetomajorrefugiain
southernEurope.
TABLE 2 CoefficientsofthreeI‐splines(i.e.,1,2and3)fromtheGDMofoverallbetadiversity,turnoverandnestednessofallarthropod
species.Significant(p < 0.05)ormarginallysignificant(p<0.1)P‐valuesfortheI‐splinesofthepredictorvariablesafter999permutations
areindicatedbyboldtypesettingPC1andPC2refertothefirsttwoaxesoftherespectiveprincipalcomponentanalysesoftemperatureor
precipitationvariables(seeMethodssection)
Response matrix Predictor set Predictor
I‐spline
Sum of
coefficients P1 2 3
Overallbeta Space Latitude 0.155 0.007 0.003 0.165 0 .11
Longitude 00.067 00.067 0.42
Climate Temperature(PC1) 0 0 0 0 0.99
Temperature(PC2) 0.017 0 0 0.017 0.68
Precipitation(PC1) 0 0 0 0 0.99
Precipitation(PC2) 0.061 0 0 0.061 0.35
Habitatamount Forestcover 00.016 00.016 0.73
Samplesize 0.12 0 0 0.1 2 0. 24
Turnover Space Latitude 0.116 00.054 0.170 0 .24
Longitude 0 0 0.082 0.082 0.46
Climate Temperature(PC1) 0 0 0 0 0.99
Temperature(PC2) 0.004 00.030 0.034 0.65
Precipitation(PC1) 0 0 0 0 0.99
Precipitation(PC2) 0 0 0 0 0.99
Habitatamount Forestcover 00.018 0.001 0.019 0.73
Samplesize 0.121 0 0 0.121 0.25
Nestedness Space Latitude 0.001 0 0 0.001 0.70
Longitude 0.132 0 0 0.132 0.07
Climate Temperature(PC1) 0.013 0 0 0.013 0. 51
Temperature(PC2) 0 0 0 0 0.98
Precipitation(PC1) 0.010 0 0 0.010 0.57
Precipitation(PC2) 0.018 0 0 0.018 0.47
Habitatamount Forestcover 0.05 0 0 0.05 0.27
Samplesize 0 0 0 0 0.97
792 
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   FRIESS Et al.
Agradientofdecreasinganthropogenicpressurefromwesternto
easternEuropeexplainswhymanyspecialistspeciesofold‐growth
forest s have become rar e or extinct i n western Europ e (Eckelt et
al.,;Ódoretal.,2006;Speight,1989).Wethusexpectedtofindan
increase of fungicolous arthropod alpha diversity with increasing
longitu de, but in fac t we observed a we ak decrease . Additionall y,
wefoundamarginallysignificant increaseincompositionaldissim
ilarity due to nes tedness with incre asing longitudinal distance of
the overal l arthropo d community. Howeve r,the r ate of change in
compositionduetonestednesswashighestatlowlongitudes,while
explanatory power was low and nestedness did not account for
more than4%of compositionaldissimilarity(Table 2). Forbeetles,
we found an in creased rate in tu rnover and balance d changes of
abundanceatthelowerendofthelongitudinalgradient(Supporting
informationAppendixS4, TableS4.4). In parallel to thegradient of
historicanthropogenicpressure,thereisaneast–westclimaticgradi
entfromoceanictowardsmorecontinentalclimates,whichisshown
byamoderatecorrelationbetweenclimatevariablesandlongitude
(Supporting information Appendix S3, TableS3.3). Bothdecreasing
alphadiversityandincreasingnestednesswithincreasinglongitude
aswellasincreasedbeetleturnoveratlowlongitudesare inconsis‐
tent with t he expected ef fect of histor ic anthropogen ic pressure,
butmayalsobeexplainedbyamilderclimateinthewest.However,
wehavetopointoutthatwewerenotabletocollectF. fomentarius
samplesinthewesternmostregions(e.g.,England)duetotherarity
offruitbodiesofF. fomentarius.Moreover,manyofoursites,alsoin
western Europe,werelocatedinunmanagedforests(Figure1)and
althoug h forest manage ment had no eff ect on overall co mmunity
composition(SupportinginformationAppendixS3,FigureS3.2),the
gradientofanthropogenicpressuremaybelesspronouncedacross
oursitesthanatalandscapescale.
Environme ntal filtering by climatic dr ivers is often an imp ort‐
ant mecha nism struc turing commun ities (Cadot te & Tucker, 2017;
Kraftetal.,2015),includingdeadwood‐associatedinsectsandfungi
(Bässleretal.,2010;Mülleretal.,2012;Seiboldetal., 2016).Being
poikilothermic,arthropodsgenerally benefit fromhighertempera
tures (Sc howalter, 2006). However, we foun d a marginally sig nifi‐
cantnegativeeffectoftemperatureonalphadiversity.Onepossible
explana tion is that frui tbodies are dr ier and thus les s suitable for
somespeciesinwarmerclimates.However,ingeneralbetadiversity
wasnotaffectedbydissimilarityinclimaticconditions.Thissuggests
thatclimate is ofminorimportance for arthropodsassociatedwith
F. fomentarius despiteconsiderablevariabilityin climaticconditions
withinoursamplingrange(Figure1).
Theamountofavailablehabitatisoneofthefundamentaldriv‐
ers of biodiversit y (Fahrig, 2013; MacAr thur & Wilson, 1967). In
Europe, hu man activiti es over millennia have re duced the fores ts
and features of old‐growth stands (overmature and dead trees),
whichhasledtoadeclineofmanysaproxylicinsects(Seiboldetal.,
2015).Forestcover is only a coarse proxy for theamountofhab‐
itat available tospecies associated with dead wood or fruitbodies
ofF. fomentarius,astheamountof theiractualhabitat—dead wood
orfruitbodiesofF. fomentarius,respectively—canvaryconsiderably
within beech forests depending, for example, on current forest
management(Abregoetal.,2015;Bässler,Ernst,Cadotte,Heibl,&
Müller, 2014). This was als o reflected by t he time need ed to find
tenfruitbodiesofF. fomentarius inthepresentstudy,whichranged
fromminutestodays.Nevertheless,wefound thenumber of con‐
sumersamongfungicolousarthropodsandfungispecialistsamong
beetle s to increase with f orest cover (70 0m radius aroun d sites).
Consistentwithresultsofearlierstudiesthatfoundapositiveeffect
offruitbody availability on fungicolousbeetlediversity atregional
scales(Araujo,Komonen,&Lopes‐Andrade,2015;Rukke,2000),we
foundthenumberofarthropodspeciestoincrease withincreasing
fruitbodybiomass.Althoughourmeasureoffruitbodybiomassdid
notreflecttheabundanceofF. fomentarius atthesites,basedonour
resultscoveringarangeoffruitbodybiomassfrom0.4to21.7kgand
earlierfindingsatregionalscales(Araujoetal.,2015;Rukke,2000),
weexpectmorefungicolousarthropodspeciesinforestswithmore
fruitbodiesofF. fomentarius.
Forbeetles,samplesizestronglyaffectedthenumberofspecies
evenwhenaccountingforabundance,whichsuggeststhathabitat
heterogeneityincreaseswithfruitbodybiomass(Supportinginfor
mationAppendixS4,TableS4.1).Here,largersamplesseemtopro
videmoredifferenthabitatniches, forexample through different
stages of d ecomposition wi thin and among fr uitbodies (Dajoz et
al., 1966) similarl y as shown for coar se woody debri s (Seibold et
al.,2016).Concerningcommunitycomposition, only the totalbeta
diversity and turnovercomponent of predatory arthropods were
affected by sample size.However, abundance‐baseddissimilarity
in community composition ofb eetleswas affec ted by longitude
and sample size. Here, dissimilarity due to abundance gradients
(analogous to nestedness) increased with sample size. Overall,
this indic ates that loc al habitat amo unt is an impor tant driver of
alphadiversityoffungicolousarthropodcommunitiesand,atleast
for fungicolous beetle communities,an impor tant driver of beta
diversity.
BasedontheITSregion,Judovaetal.(2012)havesuggestedthat
populationsofF. fomentarius arecomprisedoftwosympatriccryptic
species;this hasbeen confirmedbyPristas, Gaperova,Gaper,and
Judova(2013)usingtheefagene.Onegenotype,termedgenotype
A, has b een suggested to b e prevalent on Europ ean beech whil e
the other,termed genotype B, isadditionally found on other host
species (Judova et al.,2012).Our geneticanalysisofF. fomentarius
supports this, as all but 5 of 36 of our samples—all sampledfrom
Europeanbeech—belongedtogenotypeA.Nevertheless,theoccur
renceofgenotype BonEuropeanbeechinthePyrenees,southern
Italy, Belgium andDenmark is a noteworthyresult(Supportingin‐
formationAppendixS1).Thelowintraspecificvariationamongsites
renderedananalysisoftheinhabitingarthropodcommunitybased
ongenetic differencesfruitless.Furtherstudiesareneeded to test
the hypothesis that F. fomentarius of genotype B hos ts arthro pod
communitiesdifferentfromgenotypeA.
Inour analyses, we incorporated variables whichare knownto
bestrongdriversoflarge‐scale differencesin communitycomposi‐
tion(Dobrovolski,Melo,Cassemiro,&Diniz‐Filho,2012;Soininen,
    
|
 793
FRIESS E t al.
Lennon,&Hillebrand,2007;Zellweger,Roth,Bugmann,&Bollmann,
2017).Fur thermore,weaccountedfordifferencesinhabitatspe cial
ization andtrophic level,forestmanagementintensityand biogeo‐
graphicalregionsandevenconsideredthegeneticpropertiesofthe
fruitbodies.Nevertheless,whileourmodelsexplainedconsiderable
proportions ofvariationin alpha diversity most of the variation in
thecommunity compositionofarthropods occurringinfruitbodies
of F. fomentarius remained unexplained. Although explaining the
full variation in community composition was beyond the scope of
this study, these results appear surprising. We suggest three di‐
rections for future studies. First, future studies investigating the
community composition ofar thropods occurringin fruitbodies of
bracket fungishouldfocus on factors driving communitycomposi‐
tion at local scales.This mayincludethe amount of fruitbodies at
thesiteandlandscapescalewhichrepresenthabitatavailabilityand
mayaffectpopulationdynamicsviaincreaseddispersalsuccessand
rescueeffects givensufficientpatchconnectivity(Gonzalez,2005;
Snäll&Jonsson,2001;Venier&Fahrig,1996).Furthermore,studies
could inves tigate the ef fects of mic roclimate as me diated by can‐
opyopennessand forestsuccessional stage, whichwereshown to
generate largedifferencesincommunitycomposition in saproxylic
organisms (Hilmers etal., 2018;Seibold et al., 2016).Second, fur‐
therstudiesneedtoincludearthropodcommunitiesinfruitbodies
ofF. fomentariusonotherhost treespecies, suchas Betula spp. or
Populus spp.,andinvestigatepotentialalternativepost‐glacialrecol
onizationroutes.Third,to betterunderstand scale‐dependency of
communityturnover,futurestudiescouldcoverthewholerangeof
F. fomentariusincluding NorthAmericaandEast Asia.Forinstance,
theTenebrionidaeBolitophagus reticulatus isaubiquitousspeciesin
F. fomentarius fromEurope to Korea(Jung,Kim,&Kim, 2007), but
iscompletelyreplacedby itsrelative Bolitotherus cornutus inNorth
America(Matthewman &Pielou,1971),indicating thatthere might
beastrongerbiogeographicalstructuringofthecommunityatsuch
largerscales.
OurresultsshowedthatfruitbodiesofasinglefungusF. fomen
tarius pro vide habi t attoahi ghn u mberofar t h ropo d s,th e rebycon
tributingconsiderablytobiodiversityinEuropeanbeechforests.
Conside ring the respon sibility of Europ ean countries t o protect
biodiversityinthisecosystem,werecommendmakingthepromo
tion of bra cket fungi as F. fomentarius an inte grated goal of for
estconservationstrategiesinEuropeanbeechforests.Theweak
biogeographicalstructuringandhighturnoverofcommunitiesbe
tweensites suggestthataprioritizationofcertainregionswithin
Europeisofminorimportancewithregardtoarthropodcommu
nitiesinF. fomentarius. Instead,werecommendthatconservation
should rangefromtheprotectionofforestswhere F. fomentarius
ishighlyabundantand inhabitedbyEurope‐widerarearthropod
species(e.g.,intheCarpathianMountains),totheretentionofin
dividualhabitattreesanddeadwoodwithfruitbodiesofthespe
ciesfromharvestingandsalvagelogging(includingunintentional
destructionbyloggingmachinery)throughoutEurope,andtothe
reintroductionof thespecies to regions(e.g., in westernEurope)
whereithasbecomeextinctandrelictpopulationsarelacking(for
methodssee Abrego etal., 2016).The example of the region of
Flanders,Belgium,showsthat F. fomentarius isabletorecolonize
areaswhereitwasformerlyextinctfromafewrelictpopulations
ifbee chd eadwoo dan dha bita ttr eesare ret aine d(Vande ke r khove
etal.,2011).Furthermore,manyfungicolousarthropodsareable
totrack F. fomentarius populationsrecolonizingsuitablehabitats
due to their high dispe rsal ability ( Vandekerk hove et al., 2011;
Zytynska et al.,2018). In addition topositiveeffects onspecies
associated with its fruitbodies, promoting F. fomentarius will po
tentially help to restore fundamental ecosys tem processes and
natural forest dynamicsinbeechforests as itisthe primaryde
composerofbeech woodand an importantagent of treesenes
cence and de ath. Species a ssociated with b roadleaf dead wo od
andsunnycondi tio nsi nfores t smaya lso benefitfro mga pscreated
when beech trees are killed byF. fomentarius. As F. fomentarius
provideshabitat,shapesfurtherhabitatcharacteristicsanddrives
ecosys tem processes, it c an be considered a key stone modifie r
orecosystemengineerinEuropeanbeechforests(Mills,Soule,&
Doak,1993).
ACKNOWLEDGEMENTS
Wearegratefultoallthosewhohelpe dinthef iel da ndinthelabo
rator y to conduct the s tudy, Svitlana Los for p roviding sampl es
fromCrimea,BorisBücheforidentificationofbeetlesandJérôme
Morinière for laboratory support in DNA barcoding. We thank
Emily Kilham for linguistic revision of the manuscript. Nicolas
Friessreceivedascholarship fromthe RudolfandHeleneGlaser
Foundation organized in the “Stifter verband für die deutsche
Wissenschaf t.”M.MikošandM.Svobodaweresupportedbythe
Czech Universityof LifeSciences, Prague (CIGANo. 20184304)
andbythe institutional project MSMT CZ.02.1.01/0.0/0.0/16_0
19/0000803.
ORCID
Nicolas Friess https://orcid.org/0000‐0003‐0517‐3798
Jörg C. Müller https://orcid.org/0000‐0002‐14091586
Simon Thorn https://orcid.org/0000‐0002‐3062‐3060
Sebastian Seibold https://orcid.org/0000‐0002‐7968‐4489
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BIOSKETCHES
Nicolas Friessresearchfocusesonlocaltolargescalepat
ternsofbiodiversityinterrestrialecosystemsandtheassociated
processes.
Jörg C. Müller's re search focuses on forest biodiversity, from
ecological mechanisms toconservation strategies intemperate
forests,withaspecialfocusondeadwood‐relatedorganisms.
Sebastian Seibold's research focuses on the conservation of
biodiversity in forest ecosystems, particularly associated with
dead wood , and the impor tance of biodi versity for eco system
functioning.
SUPPORTING INFORMATION
Additional supporting information may be found online in the
SupportingInformationsectionattheendofthearticle.
How to cite this article:FriessN,MüllerJC,AramendiP,etal.
Arthropodcommunitiesinfungalfruitbodiesareweakly
structuredbyclimateandbiogeographyacrossEuropean
beechforests.Divers Distrib. 2019;25:783–796. ht tps://d o i .
org /10.1111/ddi.12882
... [37,38]), but usually within one taxonomic group or trophic guild at a time. The studies that have considered all arthropods are either exploratory, i.e. not inferring community patterns based on host traits [17,26,36], or limited to one or two fungal hosts [25,35,39]. However, to get a solid understanding of the effects of host traits in the fungi-arthropod system, we need to assess arthropod communities across different hosts. ...
... The most common families we identified consist mostly (Bolitophilidae, Mycetophilidae and Oppidae) or partly (Chironomidae and Cecidomyiidae) of fungivorous species [27,79,80]. However, fungivores may not necessarily be dominant, as our annotations are largely unresolved at the species level and predators could make up to a third of the faunal composition in fruit bodies [25,39]. At the order level, true flies and oribatid mites were dominant, which we expected based on earlier rearingbased studies on living fruit bodies of wood-decay fungi [17,26,27,34]. ...
Article
Full-text available
Biological communities within living organisms are structured by their host's traits. How host traits affect biodiversity and community composition is poorly explored for some associations, such as arthropods within fungal fruit bodies. Using DNA metabarcoding, we characterized the arthropod communities in living fruit bodies of 11 wood-decay fungi from boreal forests and investigated how they were affected by different fungal traits. Arthropod diversity was higher in fruit bodies with a larger surface area-to-volume ratio, suggesting that colonization is crucial to maintain arthropod populations. Diversity was not higher in long-lived fruit bodies, most likely because these fungi invest in physical or chemical defences against arthropods. Arthropod community composition was structured by all measured host traits, namely fruit body size, thickness, surface area, morphology and toughness. Notably, we identified a community gradient where soft and short-lived fruit bodies harboured more true flies, while tougher and long-lived fruit bodies had more oribatid mites and beetles, which might reflect different development times of the arthropods. Ultimately, close to 75% of the arthropods were specific to one or two fungal hosts. Besides revealing surprisingly diverse and host-specific arthropod communities within fungal fruit bodies, our study provided insight into how host traits structure communities.
... So far, there have been rather few studies on the relationships between a whole set of TreMs and the abundance and diversity of forest-dwelling species. For example, birds' and bats' species richness was positively related to TreM diversity , while invertebrates showed positive associations with specific TreMs, like fruiting bodies of fungi or cavities (Friess et al., 2019;. Therefore, a better understanding of the links between a comprehensive set of TreMs and forest dwelling taxa may help to identify valuable habitat trees and provide a foundation for monitoring of some aspects of forest biodiversity. ...
Thesis
Full-text available
Forests are undergoing through a slow but steady process of forest area change, which happen to be different across countries. Predictions of future scenarios highlight the role of agriculture in shaping land-use change in Europe, with possible local benefits for forests. Thus, the role of management in shaping the forests of the future will increase according to the World’s demand for timber, clean water, biodiversity, clean air and other ecosystem services. Research is testing and developing new management strategies to halt completely biodiversity loss. The threats faced by biodiversity in managed forests constitute the challenges of future forest ecological research. The response of birds to environmental changes is a consequence of the close-knit species-habitat relationships they evolved and are adapted to. Adaptations to the forest environment are structural, behavioural and physiological. The alteration of the forest structures and their spatial allocation across landscapes creates threats to bird populations that need to be taken into account in conservation-oriented forest management. The present thesis aims to assess the numerical response of the bird assemblage to forest structures and its relevance for management. The general aim is focused on close-to-nature forest management and on the retention of structural elements as a conservation tool. The numerical response of the bird assemblage is investigated in terms of species diversity and abundance. The general aim is achieved by focusing on the following research questions: i. Which forest and landscape characteristics best explain the abundance and diversity of forest birds? ii. Which management practices can be developed for the conservation of birds in managed forests? This thesis is carried out within the framework of the ConFoBi Research Training Group (Conservation of Forest Biodiversity in multiple-use landscape of Central Europe). ConFoBi assesses whether and how structural retention measures contribute to the conservation of forest biodiversity in multiple-use landscapes of the temperate zone. The research programme of the present thesis has been implemented in the southern Black Forest, Germany, as a model system for temperate forests. The Black Forest is a forest-dominated low mountain range within a multiple-use landscape typical of central Europe, where 135 quadratic 1-ha-plots where selected within the forested areas. Plots were selected along two major environmental gradients: forest vertical complexity, represented by the number of standing dead trees found in each plot; landscape composition, represented by the amount of forest cover within 25 km2 surrounding each plot. All plots were inventoried by measuring the diameter of every tree (above 7 cm diameter at breast height) and the amounts of laying and standing dead wood. Because habitat trees are an important structural element in retention approaches, for each study plot the 15 largest trees were mapped and their existing microhabitats (such as hollows, cracks, and cavities) quantified. Landscape patterns were described using a range of metrics, including amount of forest cover and landscape metrics. Bird data were collected by employing point counts performed at the centre of each plots and repeated two or three times per sampling season (2017-2018). Abundance and diversity of birds were analysed using hierarchical N-mixture models and generalized linear (mixed) models, respectively. The results highlight that current retention practices are well below the retention levels needed by the bird assemblage to have abundance and diversity similar to those of unharvested forests, assessing the levels around 40-60% of retained trees. Retention practices can, however, be improved by retaining trees of higher ecological importance. Trees with a diameter 20 cm larger than the surrounding trees, with cavities, rot holes or concavities can potentially fulfill the habitat requirments of a large array of species, including woodpeckers and the related cavity-users community. The presence of those trees across the landscape can ensure the continuity of resources, while favouring more natural tree species composition will benefit bird species diversity. The response of the entire bird assemblage to the configuration of forest patches indicates that in landscapes with less aggregated forest patches, the abundance of the bird assemblage can potentially be lower than in landscapes with closer forest patches. I conclude that the establishment and assemble of the bird community is a hierarchical spatial process. Small environmental elements determine the occurrence and observed abundance of populations. The location of such elements determines which species and how many individuals of each species are found across the landscape. Over the entire landscape, the amount of available habitat and its configuration determines how many species can be found at a given site. Therefore, I suggest a hierarchical set of actions should be considered, each benefiting birds at different levels of biological organization and spatial scale. Actions to preserve forest area and avoid fast land-use changes should have higher priority. The provisioning of large trees and deadwood would then ensure that the forests retain those structures and functions that support the establishment of bird populations in optimal habitats.
... For example, the presence of perennial fungal fruiting bodies on European beech (Fagus sylvatica) very likely refers to the tinder fungus (Fomes fomentarius). The fruiting bodies of the tinder fungus was found to serve as habitat for up to 600 different arthropod species (Friess et al., 2019). Whereas the presence of perennial fungal fruiting bodies on silver fir (Abies alba) may refer to Phellinus hartigii, which presumably interacts with different arthropods compared to the tinder fungus (cf. ...
Thesis
Habitat trees – one of the key elements of integrative retention approaches in European forests – are increasingly studied regarding their benefits to forest biodiversity. In this regard, treerelated microhabitats (TreMs) and deadwood serve as indicators of forest biodiversity. Specific recommendations of amounts of deadwood to be retained in managed forest stands to support related taxa are available, but not for TreMs. Retention of habitat trees aims to increase availability of TreMs in managed forests. To be able to refine selection criteria for habitat trees, I focused in this thesis on factors affecting TreMs on living trees. Therefore, I calculated species specific diameter thresholds bases on TreM occurrences, I investigated the effect of tree maintenance on TreMs in urban areas and I evaluated the short-term value of the retention of habitat tree groups. Chapter 1. The aim of this chapter was to explain TreM occurrence from a qualitative perspective by considering their diversity. Tree diameter at breast height (dbh), tree species, and canopy class were useful predictors of TreM diversity. TreM diversity on broad-leaved trees was on average higher than in conifers of the same diameter. In contrast to TreM abundance their diversity saturated towards higher dbh levels. Those TreM saturation levels were used to derive diameter thresholds. Habitat trees support not only more, but also more diverse, microhabitats in comparison to crop trees. Chapter 2. In this chapter I further developed the findings of chapter one and focused on the calculation of species specific diameter thresholds to precise recommendations for selecting habitat trees. Based on the relation between TreMs and tree diameter as well as TreMs and species I derived diameter thresholds for 18 European tree species (13 broad-leaved, 5 coniferous). Those thresholds refer to statistically disproportionate high levels of TreM richness or abundance. Complementing other aspects that need to be considered during habitat tree selection processes in managed forest stands, I recommend to select habitat trees with or close to a dbh of 70 cm for broadleaves and 86 cm for conifers. The differences of dbh thresholds between broadleaves and conifers as well as between species indicate species specific TreM dynamic. Chapter 3. In the third chapter, I investigated the TreM availability on urban trees along a maintenance gradient in Montréal, Canada. Intensive tree maintenance in urban trees led to levels of certain microhabitats such as cavities and injuries that were comparable to natural, unmanaged forests. Light maintenance of urban trees encouraged more crown deadwood than typical and intensive maintenance levels. My results underline the importance of conserving and maintaining large living trees, especially in urban areas to provide tree microhabitats. These results also demonstrate the important role of intensive tree maintenance in stimulating tree microhabitat development in urban areas. Chapter 4. Here, I addressed the effectiveness of habitat tree group (HTG) retention in forests of Baden-Württemberg, Germany, 10 years after the introduction of the approach. Large living trees (LLTs), standing deadwood and TreMs were significantly more abundant in HTGs than in reference plots. When retaining 5 % of a forest stand area as HTG, old-growth attributes increased significantly at the stand scale: amount of LLTs doubled and its volume almost tripled, and standing deadwood increased on average by 25 %. However, quantities of both attributes remain below recommended minimum thresholds. Retaining 5 % of stand area in HTG had a significantly positive effect on woodpecker cavities, rot holes and exposed heartwood, whereas 15 to 25 % area in HTGs would be required to increase stand level abundance of concavities, exposed sapwood or crown deadwood significantly. Retention of HTGs enriched managed, multiple-use forests with old growth structural attributes. Yet, the selection of HTGs could be made more efficient by focusing on forest patches with high tree volume or low tree density and by further considering snags, tree species mixture and LLTs as well as less vital trees. Overall the findings of this thesis suggest, that common tree attributes (species, diameter, vitality, canopy class, life status) can be used to predict the occurrence of TreMs. Species specific diameter thresholds can help to identify trees with higher levels of TreM richness. The specification of tree attributes in regard to TreMs allow to optimize habitat tree selection procedures. In addition or absence of trees rich in TreMs, tree maintenance could increase structural diversity. Intensively maintained trees providing comparable amounts of TreMs to trees from long-term unmanaged forests emphasize the relevance of artificially induced structures. To consider a holistic view on trees as biodiversity relevant feature throughout the landscape, I propose to expand further TreM research to urban and rural trees. Regardless how TreMs evolved and in which landscape they occur, the relation between TreMs and related taxa needs to be specified to strengthen the biodiversity indicating function of TreMs. Results from current TreM inventories, that followed standardized procedures, allow a approximation of TreM occurrence on a landscape level by linking species and diameter information to observed TreM abundances. To better understand development and persistence of TreMs repeated inventories were needed. Finally, my results allow to refine selection criteria of habitat trees based on the presence of TreMs and the consideration of species specific diameter thresholds. Furthermore, in absence of TreMs or when minimum diameters were not reached, I propose the possibility of artificial TreM creation to be useful for structural enrichment.
... Wood-decaying fungi generally require high volumes of necromass, sometimes exceeding 300 m 3 /ha [23]. Many saproxylic beetles are linked to wood-decaying fungi [7,17,61,62]. The solar influence is essential for the abundance and diversity of saproxylic beetles [28,63,64], and at the same time, sun exposure can compensate for the amount of deadwood [23]. ...
Article
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Due to traditional forest management, the primary goal of which is the production of raw wood material, commercial forest stands are characterized by low biodiversity. At the same time, commercial forests make up the majority of forests in the Central European region, which means a significant impact on the biodiversity of the entire large region. Saproxylic species of organisms are a frequently used criterion of biodiversity in forests. Based upon the analysis of 155 scientific works, this paper defines the fundamental attributes of the active management supporting biodiversity as well as the preservation of the production function. Using these attributes, a model management proposal was created for three tree species, which takes into account the results of research carried out in the territory of the University Forest Enterprise of the Czech University of Life Sciences Prague, since 2019. The optimum constant volume of deadwood in commercial stands was set at 40–60 m3/ha, 20% of which should be standing deadwood. The time framework is scheduled for an average rotation period of the model tree species, while the location of deadwood and frequency of enrichment must comply with the rate of decomposition, the requirement for the bulkiest dimensions of deadwood possible, and the planned time of tending and regeneration operations in accordance with the models used in the Czech Republic. The goal of active management is to maintain the continuity of suitable habitats for sensitive and endangered species. The estimates of the value of retained wood for decomposition can be as high as 45–70 EUR/ha/year for spruce and beech, and about 30 EUR /ha/year for oak.
... For many studies, the area was one part of a larger study (e.g. Bouget Friess et al. 2019;Courbaud et al. 2017;Müller et al. 2015;Larrieu and Cabanettes 2012). However, this forest was sometimes specifically studied for impact of harvesting on soil chemistry (Larrieu et al. 2006), on hoverfly communities , on both deadwood and tree-related microhabitats amount (Larrieu et al. 2012), or on beetle communities (Brin et al. 2010). ...
... Positive correlations between TreMs and several taxa such as bats, birds and to a lesser extent (saproxylic) insects have been shown in earlier studies Basile et al. 2020a), and TreMs are considered valuable biodiversity indicators (Gao et al. 2015). Specific correlations between taxa and TreMs have, for instance, been reported for rare aquatic organisms in water-filled holes in trees (Gossner et al. 2016), arthropod species inhabiting conks of tree-decaying fungi (Friess et al. 2019), as well as cavity nesting birds in tree hollows (Puverel et al. 2019). An overview of associations between TreMs and taxa has been provided by Larrieu et al. (2018). ...
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Limited knowledge of dispersal for most organisms hampers effective connectivity conservation in fragmented landscapes. In forest ecosystems, deadwood-dependent organisms (i.e., saproxylics) are negatively affected by forest management and degradation globally. We reviewed empirically established dispersal ecology of saproxylic insects and fungi. We focused on direct studies (e.g., mark-recapture, radiotelemetry), field experiments, and population genetic analyses. We found 2 somewhat opposite results. Based on direct methods and experiments, dispersal is limited to within a few kilometers, whereas genetic studies showed little genetic structure over tens of kilometers, which indicates long-distance dispersal. The extent of direct dispersal studies and field experiments was small and thus these studies could not have detected long-distance dispersal. Particularly for fungi, more studies at management-relevant scales (1-10 km) are needed. Genetic researchers used outdated markers, investigated few loci, and faced the inherent difficulties of inferring dispersal from genetic population structure. Although there were systematic and species-specific differences in dispersal ability (fungi are better dispersers than insects), it seems that for both groups colonization and establishment, not dispersal per se, are limiting their occurrence at management-relevant scales. Because most studies were on forest landscapes in Europe, particularly the boreal region, more data are needed from nonforested landscapes in which fragmentation effects are likely to be more pronounced. Given the potential for long-distance dispersal and the logical necessity of habitat area being a more fundamental landscape attribute than the spatial arrangement of habitat patches (i.e., connectivity sensu strict), retaining high-quality deadwood habitat is more important for saproxylic insects and fungi than explicit connectivity conservation in many cases.
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Tree related Microhabitats (hereafter TreMs) have been widely recognized as important substrates and structures for biodiversity in both commercial and protected forests and are receiving increasing attention in management , conservation and research. How to record TreMs in forest inventories is a question of recent interest since TreMs represent potential indirect indicators for the specialized species that use them as substrates or habitat at least for a part of their life-cycle. However, there is a wide range of differing interpretations as to what exactly constitutes a TreM and what specific features should be surveyed in the field. In an attempt to harmonize future TreM inventories, we propose a definition and a typology of TreM types borne by living and dead standing trees in temperate and Mediterranean forests in Europe. Our aim is to provide users with definitions which make unequivocal TreM determination possible. Our typology is structured around seven basic forms according to morphological characteristics and biodiversity relevance: i) cavities lato sensu, ii) tree injuries and exposed wood, iii) crown deadwood, iv) excrescences, v) fruiting bodies of saproxylic fungi and fungi-like organisms, vi) epiphytic and epixylic structures, and vii) exudates. The typology is then further detailed into 15 groups and 47 types with a hierarchical structure allowing the typology to be used for different purposes. The typology, along with guidelines for standardized recording we propose, is an unprecedented reference tool to make data on TreMs comparable across different regions, forest types and tree species, and should greatly improve the reliability of TreM monitoring. It provides the basis for compiling these data and may help to improve the reliability of reporting and evaluation of the conservation value of forests. Finally, our work emphasizes the need for further research on TreMs to better understand their dynamics and their link with biodiversity in order to more fully integrate TreM monitoring into forest management.