Colonization of experimentally arranged resource patches - a case study of fungivorous beetles

2010·0.92 MB·

by  Anne Sverdrup-Thygeson

©EntomologicaFennica.15December2010
Colonization of experimentally arranged resource patches
– a case study of fungivorous beetles
AnneSverdrup-Thygeson
Sverdrup-Thygeson,A.2010:Colonizationofexperimentallyarrangedresource
patches–acasestudyoffungivorousbeetles.—Entomol.Fennica21:139–150.
Thestudyfocusesonacolonizationexperimentofbeetles,usingsporocarpsof
tinder fungus Fomes fomentarius. Initially, a mapping of all sporocarps of F.
fomentarius and its inhabitants was made in a 225 ha area of boreal forest in
southernNorway(controldataset).62%ofthesporocarpscontainedoneormore
beetleindividuals.Experimentalsporocarpswerethenplacedoutforthreeyears,
collectedanddissected.21%ofthesewerecolonized.Thecomparisonbetween
control and experiment showed that species assemblages were rather similar.
Successfulbetween-treecolonizationandreproductioninexperimentalsporo-
carps by the darkling beetle Bolitophagus reticulatus was observed. Cis
jacquemartiicolonized14%oftheexperimentalsporocarps,andtherewasnoef-
fectofdistancefromknowndispersalsourcesoncolonizationforthisspecies.
ThisindicatesthatC.jacquemartiiwaswellabletolocateandcolonizenewsub-
stratewithinthescalecoveredinthestudy.
A.Sverdrup-Thygeson,NorwegianInstituteforNatureResearch,Gaustadalléen
21,NO-0349Oslo,Norway;E-mail:[email protected]
Received15February2010,accepted18August2010
1.Introduction wood in the forest is well below natural condi-
tions (Siitonen 2001). Some saproxylic species
Dispersalisabasicpropertyinecologyandinflu- havealreadydisappeared;severalhundredmore
ences the life history of an organism in several arelistedonvariousnationalRedlistsinNorth-
ways.Infragmentedlandscapesoftoday’sworld, ernEuropeasindangerofextinction(Balevièius
thedispersalofmanyspeciesisimpeded,asthey 1992,Lilleleht1998,FinnishEnvironmentInsti-
face isolation between their suitable habitat tute 2000, Gärdenfors 2005, Kålås et al. 2006).
patches.Onesuchgroupofspeciesisthesapro- Theaccumulatingeffectofintensiveforestman-
xylicinsects(Speight1989);theinsectsdepend- agementhasalsobeenshowntoindicateanex-
ent on dead and decaying wood or other sapro- tinction debt in saproxylic insects in Finland
xylic organisms such as wood rotting fungi for (Hanski2000).
theirsurvival.Althoughmodernforestmanage- The need for better knowledge on how for-
ments,e.g.inFennoscandia,strivestoaccommo- estryaffectssaproxylicspeciesisthereforecriti-
date the requirements of forest living species cal.Severalstudieshavebeenconductedtoeluci-
throughstandardsofsustainableforestmanage- date the mechanisms of dispersal in saproxylic
mentandprinciplesofforestcertification,com- beetlesinFennoscandia(Sverdrup-Thygeson&
parisonsindicatethattheamountofcoarsedead Midtgaard1998,Ranius&Hedin2001,Jonsson
140 Sverdrup-Thygeson (cid:127) ENTOMOL.FENNICAVol.21
2003, Gibb et al. 2006b) and other regions phagous beetle Bolitophagus reticulatus (e.g.
(Schiegg 2000, Grove 2002, Starzomski & Nilsson 1997, Rukke & Midtgaard 1998, Sver-
Bondrup-Nielsen2002,Buseetal.2007),butthe drup-Thygeson & Midtgaard 1998, Olberg &
interpretationofdispersalpatternsisnotstraight- Andersen 1999, Jonsell et al. 2003, Jonsson
forward.Caremustbetakenwhenextrapolating 2003).
between spatial scales, and when extending the A relevant question in field experiments is
temporalfocus.Especially,theeffectofrarebut whether the assemblages colonizing the experi-
successfullongdistancedispersaleventsishard mentalresourcepatchesareindeedrepresentative
toevaluate,andsucheventsareeasilymissedin ofthetrueassemblagesinhabitingthenaturaloc-
fieldstudies. currencesoftheseresources.Thisisimportantin
Onechallengeindispersalstudiesofinsectsis ordertojudgetherelevanceoftheresultsofsuch
tofindsoundmethods.InareviewpaperRanius fieldexperimentsandtoevaluatewhetherexperi-
(2006) lists several examples of possible meth- mentally arranging empty resource patches is a
ods,suchascapture-recapturemethods,teleme- soundmethodtouse.Thishasbeendonefordif-
try,studiesofoccurrencepatterns,geneticstud- ferenttypesofresourcespreviously:Jonselletal.
ies, observations of flight in field or in lab, and (2004)showedthattheassemblageinartificially
colonizationexperiments.Inthispaper,Ifocuson created high stumps mimic that of natural high
the latter; colonization experiments under full stumps,andJanssonetal.(2009)statethatamong
scalefieldconditions. beetles found in hollow oaks which were either
Lately,fieldexperimentshavebecomeacom- tree-hollowspecies,birdnestspecies,orwoodrot
monmethodforstudyingdispersal,colonization species, 70% were also found in the artificial
and resource utilization by saproxylic insects. boxes. The beetle fauna in sporocarps has also
Severalsmallandlargefieldexperimentsinbo- been compared earlier, as Jonsell et al. (1999)
realforesthavecreatedemptyresourcepatches– found the fauna in experimental sporocarps of
oftenarrangingthemincertainpatternsrelatedto tinderfungusFomesfomentarius(L.ex.Fr.)and
management,distancefromcolonizationsources FomitopsispinicolaFr.(Karst.)tobecomparable
etc.–andplacedthemoutwithinthenaturaldis- to the communities in natural sporocarps from
tribution area of relevant species (or sometimes nearbyareas.IntheJonselletal.study,theexper-
outside,seeNilssen1984).Thetypeofnewre- imentaltinderfungussporocarpswerefreshand
source patches range widely in scale and type; onlyplacedoutforashorttimeperiod(7weeks).
fromforeststands“treated”withcertainretention Thesporocarpsweremountedonwoodenboards
levels or with forest fire (Eriksson et al. 2006, (meanttoinvestigatebetween-treecolonization),
Hyvärinen et al. 2006), via artificially created or nailed to stems of dead birches bearing old
highstumpsandlogs(e.g.Schroederetal.1999, sporocarpsoftinderfungus(tostudywithin-tree
Sverdrup-Thygeson & Ims 2002, Gibb et al. colonization). No between-tree colonization by
2006a, Johansson et al. 2006a, Johansson et al. B.reticulatuswasobservedinthatstudy.
2007,Fossestøl&Sverdrup-Thygeson2009),ar- Iwantedtostudythebeetlecommunityintin-
tificialnestboxesthatimitatecavitiesinold,hol- derfungusinanexperimentalset-upthatresem-
lowtrees(Janssonetal.2009),tosporocarpsof bled the natural situation as much as possible.
fungi(Jonselletal.1999,Jonsson&Nordlander Most of the associated beetle species utilize the
2006). sporocarpsaftertheyaredead,thereforeIchose
Sporocarpsoffungiconstituteclearlydefined tousedeadsporocarpsandtomountthemonre-
resourcepatchesforthebeetles,manyofwhich centlydeadbirchstumps;theirnaturalsubstrate
aremonophagousonspecificfungi.Tinderfun- in the study area. As dead tinder fungus sporo-
gusiscommonlydistributedovermostofFenno- carps can remain intact for years (e.g. Nilsson
scandiaandhostsseveralsuchbeetlespecialists. 1997), and the flight period of B. reticulatus is
Thesecharacteristicsmakethesystemanattrac- short(Jonselletal.2003),Ialsofeltitnecessary
tivemodelsystem,andahandfulofstudiesoftin- toextendthetimeofexposureoftheexperimental
derfungusanditsinhabitantshavebeencarried sporocarpstothreeyears.
out the past 15 years, especially on the mono- InthisstudyIfocusontheuseofexperimental
ENTOMOL.FENNICAVol.21 (cid:127) Colonizationofexperimentalsporocarps 141
resourcepatchesintheformofsporocarpsoftin- possible, avoiding sporocarps diverging too
derfungus.Withaclose-to-naturalexperimental muchinsize,decayorhumidity.Thesporocarps
set-up,Iinvestigatewhetherthecolonizingbeetle wereplacedinasuperfreezerat–70°Cforsev-
assemblages, including the much studied B. eraldaysinordertokillallbeetleindividualsin-
reticulatus,arerepresentativeoftheassemblages side. The sporocarps were then attached at 1 m
in naturally occurring sporocarps in the same heighton2mhighfreshlycutbirchtrees(10–15
area.Ialsowanttoinvestigatewhatfactorsinflu- cmdiameter).Thebirchtreepolesweremounted
ence the colonization of empty experimental vertically at random points in the study area,
patches,especially towhatdegreethecoloniza- avoiding the border towards non-mapped areas
tion ofempty habitat patches relates to relevant (Fig.1).
dispersalsourcesinthesurroundingforest.This Theexperimentalsporocarpswereleftinthe
was done by placing out empty sporocarps in a forestfor3summersandcollectedinthelatefall
study area where the distribution pattern of the of the third year. 3 sporocarps were destroyed
relevantfungivorousspecieswasmappedinad- overthecourseoftheyears,sothefinalnumber
vance,atascaleofsomehundredsofhectares. of replicates was 77. All sporocarps were dis-
sectedatonce,andspecieswereidentifiedandre-
corded. In order to avoid possible confounding
2.Methods frompre-experimentbeetleindividualskilledin
the freezing process and still not decomposed,
Thepresentstudyisbasedontwoperiodsoffield onlylivingbeetleswereusedinfurtheranalyses.
work.First,in1992,allsporocarpsoftinderfun- I calculated colonization rate as the propor-
gusF.fomentariuswithina225haareaofboreal, tionofsporocarpsthatwereinhabitedbyatleast
spruce dominated forest 60 km east of Oslo in one beetle individual. I compared colonization
south-eastern Norway were recorded and ratebetweentheexperimentandthecontrolboth
mapped(Fig.1).Thefungusgrewondeadbirch by comparing observed rates, and by a re-
trees which could be found as single trees or in sampling procedure. In the resampling, I ran-
groupsamongtheborealconiferoustreespecies domlyselected77sporocarpsfromthepoolofthe
(seeSverdrup-Thygeson&Midtgaard(1998)for 367 control sporocarps 10,000 times, and re-
moredetaileddescriptionofstudyarea).Oneach corded the resulting resampled distribution of
tree with F. fomentarius sporocarps, one third meancolonizationrate.Thiswasdonetoelimi-
(butalwaysatleastone)ofthedeadsporocarps natedifferencesduetounevennumberofsamp-
wascollectedandrearedisolatedfor2monthsin lingunitsofexperimentalandcontrolsporocarps.
alaboratoryat20°C.Finally,allsporocarpswere Inaddition,Iwantedtocomparethecharac-
dissectedtofindbeetlespecimensremainingin- teristicsoftheoccupiedexperimentalsporocarps,
side. This result represents the naturally occur- withasimilarnumberofcolonizedcontrolsporo-
ring beetle community in tinder fungus in the carps. In order to achieve this, I ran a similar
area.Basedontheassumptionthatpresenceofa resampling procedure (10,000 iterations) in
beetlespeciesinonesporocarponatreeisarea- which a subsample of 16 colonized sporocarps
sonableindicationofpresencealsointheremain- (i.e.thenumberofoccupiedsporocarpsintheex-
ing,uncollectedsporocarpsonthattree(asshown periment)wereselectedrandomlyfromthepool
for Bolitophagus reticulatus (Linnaeus, 1767) of367controlsporocarps.Ithenrecordedthedis-
(Tenebrionidae)inSverdrup-Thygeson&Midt- tribution of the resampled cumulative species
gaard (1998)), this presence denotes a potential richness(foreachsetof16sporocarps),species
dispersal source for the species (excluding of richnesspersporocarps,andnumberofindividu-
course the trees with only one sporocarp). This alspersporocarpintheexperimentalsporocarps.
datasetisdenoted‘controldataset‘. Ialsowantedtoevaluatetheeffectofdistance
InApriltwoyearslater,80deadbutlittlede- fromknownsourcesofdispersalforaspecies,if
cayed sporocarps of F. fomentarius were col- sufficient data for the monophagous species
lectedfromahighdensityareawestofOslo.Care couldbeattained.Asitturnedout,thiscouldonly
wastakentomakethesampleashomogeneousas bedoneforonespecies(CisjacquemartiiMellié,
142 Sverdrup-Thygeson (cid:127) ENTOMOL.FENNICAVol.21
Fig.1.Mapofthestudy
areashowingthepositions
oftheexperimentaltinder
fungussporocarpsandthe
controlsporocarps(alltrees
withnaturallyoccurringtin-
derfungussporocarps).The
experimentalsporocarps
colonizedbyBolitophagus
reticulatus(squares)and
Cisjacquemartii(triangles)
aremarked,aswellasthe
experimentalsporocarps
notcolonizedbyeitherof
thesetwospecies(large
points).Thecontrolsporo-
carpsaremarkedwith
small,darkpoints.
ENTOMOL.FENNICAVol.21 (cid:127) Colonizationofexperimentalsporocarps 143
Table1.Beetlespeciesfoundin367sporocarpsofFomesfomentariusinthecontrolstudyandin77sporocarps
intheexperiment,withabundance(no.ofindividuals),numberofoccurrences(no.ofsporocarpsitwasfoundin)
foreachgroup.
Species Abundance Occurrences Abundance Occurrences
incontrol incontrol inexperiment inexperiment
Cisjaquemartii 2,466 181 167 11
Bolitophagusreticulatus 1,121 96 5 1
Cislineatocribratus 159 26 1 1
Ciscastaneussyn.C.nitidus,C.ater 48 10 16 2
Dorcatomadresdensis 20 6 – –
Leptusapulchella 16 14 – –
Ropalodontuscornutum 12 3 – –
Rhizophagusdispar 11 6 – –
Ennearthroncornutum 9 5 – –
Triplaxrussica 6 2 – –
Leptusafumida 5 4 4 4
Cisbidentatus 4 3 – –
Cerylonfagi 3 3 – –
Lygisopterussanguineus 3 1 – –
Acruliainflata 2 2 – –
Dinaraeaaequata 2 2 – –
Scaphisomaagaricinum 2 2 – –
Agonumfuliginosum 1 1 – –
Ampedusnigerinus 1 1 – –
Anaspisrufilabris 1 1 2 2
Athetamyrmecobia 1 1 – –
Atreluslongiceps 1 1 – –
Biotomacrenata 1 1 – –
Chryptocephaluspunctigel 1 1 – –
Dinaraealinearis 1 1 – –
Gyrophaenaboleti 1 1 – –
Gyrophaenasp. 1 1 – –
Lordithonlunulatus 1 1 – –
Malthodessp. 1 1 – –
Phratoravitellinae 1 1 – –
Quediusplagiatus 1 1 – –
Rhyncoluschloropus 1 1 – –
Notiophilusbiguttatus – – 1 1
Phloeocharissubtilissima – – 1 1
Dorcatomachrysomelinus – – 1 1
Salpingusruficollis – – 1 1
1848(Ciiidae)),astheothershadtoofewoccur- fered and the water content of the sporocarps
rences.Icalculatedthedistancefromeachexperi- upon collection varied accordingly. Therefore,
mentalsporocarptotheclosesttreeinthecontrol volume(calculatedasthevolumeof¼ofanellip-
datasetwithpresenceofC.jacquemartii,exclud- soid) and the water content (weight when col-
ingtreeswithonlyonesporocarp.Thecorrelation lectedattheendofexperimentminusweightafter
betweencolonizationanddistancetonearestin- dissectionanddryingat40°Cforoneweek)of
habitedtreewasthencalculatedbymeansoflo- thesporocarpsweremeasured.Ithenusedlogis-
gisticregression. ticregressiononthelog-transformedvariablesto
Although the experimental sporocarps were analyzewhetherdifferenceinsizeorhumidityin-
carefullypickedtomaximizehomogeneity,some fluenced colonization. All statistical analyses
variation in size was inevitable. Also, the field werecarriedoutinR(version2.10.0)(RDevel-
conditionsattherandomlychosenlocationsdif- opmentCoreTeam2007).
144 Sverdrup-Thygeson (cid:127) ENTOMOL.FENNICAVol.21
Fig.2.Boxplotsoftheresultsofresamplingeither77sporocarpsfromthecontrol(thenumberofexperimental
sporocarps)(a)or16colonizedsporocarpsfromthecontrol(thenumberofcolonizedsporocarpsintheexperi-
ment)(b–d).–a.No.ofcolonizedsporocarps.–b.No.ofindividualspercolonizedsporocarps.–c.Speciesrich-
nesspercolonizedsporocarp.–d.Cumulativespeciesrichnessincolonizedsporocarps.Thestardenotesthe
observedmeanvaluefromtheexperimentalsporocarps.The25and75percentileandthemedian(indicatedby
theboxandthelineinside),mean(indicatedasasquare),confidenceinterval(arrowheads),minimumandmaxi-
mumvalues(”whiskers”)andoutliers(dots)areshown.
3.Results mostcommonspecies,with63%oftheindividu-
als, while B. reticulatus was the second most
3.1.Controldataset commonwith29%oftheindividuals.
367 dead sporocarps were collected from 204
birchtreesinfectedwithtinderfungusinsidethe 3.2.Experimentaldataset
studyarea.62%ofthesporocarpscontainedone
or more beetle individuals. In total, the sporo- The77sporocarpsintheexperimentalsetupwere
carpscontained3904adultindividualsrepresent- colonized by 199 individuals from 10 different
ing32beetlespecies(Table1). beetlespecies,ofwhich5speciesweresingletons
47%ofthespecieswereonlypresentinone (50%) (Table 1). Only 16 of the 77 sporocarps
individual(singletons). C. jacquemartii wasthe (21%)werecolonizedbyoneormorespecies.In
ENTOMOL.FENNICAVol.21 (cid:127) Colonizationofexperimentalsporocarps 145
addition to the beetles, larvae of Raphidioptera
sp.(Diptera),werefoundin10sporocarpsanda
Camponotus sp. (Hymenoptera) queen was
foundinonesporocarp.
3.3.Comparisonwithassemblage
innaturallyoccurringsporocarps
Thecolonizationrateoftheexperimentalsporo-
carpswasfarlowerthantheproportionofinhab-
ited sporocarps in the complete control dataset,
and bootstrapping also confirmed that this low
proportion was not a likely result when repeat-
edly resampling 77 sporocarps fromthecontrol
dataset(Fig.2a).
Still, when considering the sporocarps that
actuallywerecolonized,theresamplingshowed
thattheydidnotdiffersomuchfromthecontrol
dataset.Thecumulativespeciesrichness,thespe-
ciesrichnesspersporocarps,andthenumberof
individuals per sporocarp in the experimental
sporocarpsallwerewithintheconfidenceinter-
valsofthecontrolsporocarps(Fig.2b–d).
Therelativecontributionofeachofthemost
abundantspecieswassomewhatdifferentinthe
experimentandthecontroldataset(Fig.3).The
threemostcommonspeciesoccurringintheex-
perimental sporocarps were among the 4 most
commonspeciesinthenaturallyoccurringsporo-
carps, but in the experimental sporocarps, one
species dominated the assemblage with 84% of
theindividuals.Inthecontrolsporocarps,onthe
other hand, two species constituted almost 2/3
and1/3each.
Themaindifferencewasthelowcolonization
oftheexperimentalsporocarpsbyB.reticulatus.
C.jacquemartiiwasthemostabundantspeciesin
Fig.3.Theproportionsofthefivemostabundantspe-
bothdatasets,with84%oftheindividualsinthe ciesintheexperimentalsporocarps,forbothexperi-
experimentand63% inthecontrol. Thesecond mentalsporocarpsandthenaturallyoccurring(con-
most abundant species in the experiment, Cis trol)sporocarps.
castaneusHerbst,1793(syn.C.alter,C.nitidus)
(Ciiidae),with8%oftheindividuals,wasranked foundinoneindividualinoneoftheexperimental
asthefourthmostabundantspeciesinthecontrol sporocarps.
with1.2%oftheindividuals.
B.reticulatusrangedthirdintheexperiment 3.4.Single-speciesanalysisofcolonization
with3%oftheindividuals,andsecondinthecon-
trol with 29% of the individuals. Cis lineato- 3.4.1.Cisjacquemartii
cribratusMellié,1848(Ciiidae),whichwasthe
third most common species in the control, was Only one beetle species colonized a sufficient
146 Sverdrup-Thygeson (cid:127) ENTOMOL.FENNICAVol.21
numberofexperimentalsporocarps(morethan5) colonizationofasuitablepatchofacertainsizeis
to justify single-species analyses, namely C. dependentnotonlyonthedistancefromsuitable
jacquemartii.Thiswasthemostabundantandthe sourcesandthesizesofthese,butalsoondura-
mostcommonlyoccurringspecies,havingcolo- tion.Thecumulativechanceofadispersalevent
nized 14% of the sporocarps during the three reaching the patch will increase with time, al-
yearsoftheexperiment(Table1andFig.2). thoughitmightbecounteractedbytheslowdete-
When analyzing the presence/absence of C. riorationofthepatch.Whenreachinglatestages
jacquemartii as the response variable and dis- ofdecay,thesporocarpwillnolongerbeasuit-
tancetothenearestotherinhabitedtreeasthepre- ablehomefortheassociatedspecies.Thisalsore-
dictorvariable,therewasnoeffectofdistanceto latestoanotherfactorpossiblyaffectingthecolo-
known dispersal sources (Logistic regression, nizationrate–whethertherelevantspecieswere
¤2=0.08,R2=0.001,p=0.8), abletolocatetheexperimentalsporocarpsinan
Eventhoughthevarianceinvolumeoftheex- efficientway.Severalfungivorousinsectsrelyon
perimentalsporocarpswaslimited(rangingfrom olfactorycuesinfindingsuitablesubstrate(Jon-
0.09dm3to0.4dm3),thesporocarpswhichwere sell & Nordlander 1995, Jonsson et al. 1997,
colonized were significantly larger than those Johanssonetal.2006b),eitherintheformofphe-
that were not colonized (Logistic regression, romones or through attraction to specific com-
¤2=4.285,R2=0.06,p=0.04).Ifoundnosuchef- poundsreleasedfromthehost.Fäldtetal.(1999)
fect of water content (Logistic regression, did detect ethanol and acetic acid from newly
¤2=0.014,R2=0.0002,p=0.91). dead F. fomentarius sporocarps, which may be
importantinattractinginsects.AlsoJonselletal.
3.4.2.Bolitophagusreticulatus (2003) found thattrapsbaited with ethanolor a
combinationofethanolandthefungusattracted
B. reticulatus had colonized at least one sporo- B.reticulatus.Mostspeciesthathavetheirlarval
carp,where5livingimagineswerefoundwhen developmentinF.fomentariusovipositindeador
dissecting the sporocarps. This experimental dyingfruitingbodies(Fäldtetal.1999),buteven
sporocarp was 55 m away from the closest B. though I used birch tree poles for mounting to
reticulatus-inhabited sporocarp. In addition, 12 mimictheodorsofdecayingbirch,olfactorycues
sporocarpscontainedatotalof27deadimagines, connectedtothedyingstageofthesporocarpwill
but as explained in Methods, dead specimens bemissed.Thiscouldhaveinfluencedthecoloni-
wereexcludedfromanalyses. zationrate.
Thelowcolonizationratesexperiencedinthe
study differ from those of a field experiment in
4.Discussion andclosetoabirchforestinSweden(Jonsellet
al.1999),wherelivingsporocarpsofF.fomenta-
4.1.Lowexperimentalcolonizationrate riuswereremovedfromtreesandplacedoutfor
only one summer. In that study, all sporocarps
The proportion of experimental sporocarps that placed inside the birch forest with high natural
hadbeencolonizedthreeyearsafterbeingplaced abundanceofF.fomentariuswerecolonizedbyat
outintheforest,iswellbelowtheproportionof least one species, and ca 75% when placed out
inhabitednaturalsporocarpsinthecontrol(21% 150metersawayfromthebirchforest,inamono-
vs.68%).Severalfactorscanservetoexplainthis culture of spruce. The proportion of natural F.
difference.Forone,thecolonizationrateisprob- fomentarius sporocarps that were inhabited by
ablyunderestimated,asonlybeetlesaliveatthe beetlesisnotgiven,butitwasprobablyhigh.
endpointofthefieldstudywasconsidered.This In addition to differences related to decay
wasdonetoavoidconfoundingcolonizingindi- stage of sporocarps, the difference between the
vidualswithindividualsthathadbeeninthefun- studiescanbeduetothefactthatthesporocarps
gus before the onset, and ensure a conservative ofJonselletal.(1999)wereplacedoutwithinand
ratherthaninflatedjudgementofcolonization. closebyasignificantsourceofdispersalforthe
Inaddition,thepatternreflectsthatsuccessful relevant species, while the presence of such a
ENTOMOL.FENNICAVol.21 (cid:127) Colonizationofexperimentalsporocarps 147
‘mainland’ (sensu Harrison & Taylor 1997) is studieshaveshownthatC.jacquemartiiismore
missinginmystudyarea.Instead,sporocarpsin- abundant in larger sporocarps (Jonsell et al.
habited by different species are spread out over 2001), which fits with the results on sporocarp
theentire225haarea(seeFig.1). size.
In addition to C. jacquemartii, C. castaneus
was also found to have colonized a few experi-
4.2.Resemblanceofnatural mentalsporocarps(Table1,Fig.2).C.lineatocri-
speciescommunities bratus was only found in one experimental
sporocarp, even though it was common in the
Although a low proportion of the experimental control sporocarps. Dorcatoma dresdensis
sporocarps in the study was colonized (Fig. 1), Herbst,1792(Ptinidae),amonophagousspecies
the assemblage in colonized sporocarps is still rankingasthefifthmostabundantspeciesinthe
rather similar to the natural communities in the control,wasnotfoundtohavecolonizedanyof
tinderfungusinthearea,withrespecttonumber the new sporocarps. The reason for this is not
ofindividualsandspeciespersporocarp.Thereis clear, but could be related to dispersal abilities,
atrendofhighercumulativespeciesrichnessin competition,ordifferencesinfactorstriggeringa
the experimental sporocarps, indicating that the dispersalevent.
(cid:1)-diversityintheexperimentalsporocarpsmight Jonselletal.(1999)foundthatthebeetlesbe-
be higher, but the difference is not significant. longingtothegenusDorcatomaweremoresuc-
Such a pattern could make sense if placing out cessfulincolonizingdistantpatchesthanspecies
empty,deadsporocarpscouldbeseenasawayto ofthegenusCis,eventhoughthelatteraremore
removetheeffectsofspeciessuccessionandin- widelydistributedandmorecommoninFenno-
terspecificcompetition,byintroducingemptyre- scandia. This does not fit with my results. As
source patches in a decay stage where it would Ranius(2006)pointsout,thelackofdataonthe
usuallybefilledupwithestablishedspecies. populationsize(thenumberofpotentialcoloniz-
TheCis-speciesthatwerecommoninthecon- ers)couldlimitthegeneralizationsoftheJonsell
trol, Cis jacquemartii, Cis lineatocribratus and etal.(1999)results.Also,differencesintheex-
Cis castaneus (syn. C. alter, C. nitidus) are all perimentalsetupscouldbealikelyexplanation.
mainly developing in F. fomentarius in Fenno- Thesecondmostcommonspeciesinthenatu-
scandia,althoughC.castaneuscanalsooccurin ralsporocarps,B.reticulatus,wasfoundtohave
PiptoporusbetulinusorFomitopsispinicola,and colonizedatleastoneexperimentalsporocarp,in
C.lineatocribratuscanoccurinF.pinicola(Thu- which5livingbeetleswerefound.Severalearlier
nes1994,Jonselletal.2001,Jonsell&Nordlan- papershavefocusedonthismonophagoustinder
der2002).BothP.betulinusandF.pinicolawere fungusbeetleandtheapparentmismatchbetween
present, but in very low numbers in the study thefactthatthespeciesisrathercommon,andon
area. theothersidethefactthatitsincidencepatternhas
C.jacquemartiiwasthemostsuccessfulcolo- beenshowntocorrelatenegativelywithisolation
nizerinthestudy,foundin14%oftheexperimen- (Rukke&Midtgaard1998,Sverdrup-Thygeson
talsporocarps(Table1andFig.2).Theresultof &Midtgaard1998).Recentexplanationstothis
thedistanceanalysisdoesnotindicateanycorre- distributionpatternandtheabsenceoftree-level-
lation between colonization and distance to colonization in earlier colonization experiments
sporocarpswithanestablishedpopulation. (Jonselletal.1999,2003)havefocusedontwo
ThespeciescompositioninF.fomentarius-in- facts:Thespeciesseemstohaveashortflightpe-
fected trees had been mapped two years earlier, riod(oneweek;Jonselletal.2003)andotherwise
andcouldhavechangedsomewhatinthemean- disperse mostly by walking (Nilsson 1997). It
time,andalsothespeciescompositioninthere- alsodisplaysattractiontothemixedodorsoftin-
maining sporocarps could differ from those derfungusandethanol(Jonselletal.2003).Inthe
reared. Differences in the characteristics of the present study, these factors were taken into ac-
experimentalsporocarps,suchasthesmalldiffer- count:theprolongedexposureoftheexperimen-
encesinvolume,alsoinfluencetheresult.Earlier tal sporocarps was intended to increase the
148 Sverdrup-Thygeson (cid:127) ENTOMOL.FENNICAVol.21
chance of colonization by including three flight References
periods,andtheuseoffreshlycutbirchtreesfor
mountingofexperimentalsporocarpswasmeant
Balevièius,K.(ed.).1992:Lietuvosraudonojiknyga[Red
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Thisindicatesthatthenaturaldispersaldynamics
Eriksson,M.,Lilja,S.&Roininen,H.2006:Deadwood
ofthespeciesoperateonaratherlongtimeframe
creationandrestorationburning:Implicationsforbark
compared to many other beetles, and that long
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4.3.Conclusion Fossestøl,K.O.&Sverdrup-Thygeson,A.2009:Saproxy-
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Fäldt,J.,Jonsell,M.,Nordlander,G.&Borg-Karlson,A.
cayingfungi,asshownbyseveralauthors(Jon-
K.1999:VolatilesofbracketfungiFomitopsispinico-
sell & Nordlander 2002, Komonen 2003). The
laandFomesfomentariusandtheirfunctionsasinsect
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fulcolonizer,wellabletolocateandcolonizenew 590.
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R. B., Hilszczanski, J., Johansson, T. & Danell, K.
the study. The field experiment further docu-
2006a:Effectsoflandscapecompositionandsubstrate
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availabilityonsaproxylicbeetlesinborealforests:a
latus.Theresultsindicatethatexperimentallyar- studyusingexperimentallogsformonitoringassem-
ranging empty resource patches is a sound me- blages.—Ecography29:191–204.
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J.,Alvini,O.&Danell,K.2006b:Wingloadingand
although there are certain differences in species
habitatselectioninforestbeetles:Arered-listedspe-
compositioncomparedtonaturalsporocarpsthat
cies poorer dispersers or more habitat-specific than
needsbestudiedfurther.Emphasisonmimicking common congenerics? — Biological Conservation
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