Biodiversity of Wasp Species (Insecta: Hymenoptera) in Burned and Unburned Habitats of Yellowstone National Park, Wyoming, USA

15 Pages·1996·5.4 MB·English

by  J A Lockwood

J.HYM.RES.
Vol.5,1996,pp.1-15
BiodiversityofWasp Species (Insecta: Hymenoptera) in Burned and
Unburned Habitats ofYellowstone National Park, Wyoming, USA
JeffreyA.Lcxtkwood,ScottR.Shaw,andJaneM.Struttmann
DepartmentofPlant,Soil,andInsectSciences,UniversityofWyoming,Laramie,Wyoming
82071-3354,U.S.A.
—
Abstract. FourmonthsofMalaisetrappingintwoburnedandunburnedhabitats,2yrafter
the 1988 fires inYellowstone National Park (YNP), resulted ina total of603species from36
familiesofHymenoptera.ThemajorityofthespecieswereIchneumonoidea(607o).Theunburned
habitatspeakedat107and113speciesduringa2-weeksamplingperiod,whilethecorresponding
burnedhabitatshad maximaof88and90species. Hymenopteranspeciesdiversity(Shannon-
Wiener)wasprimarilyafunctionofrichness,withevennessdifferingonlyslightlybetweenhab-
itats(range78-98%).Diversityandrichnessinburnedsitesweregenerally75-85%ofthevalues
inunburnedsites.Thetwoburnedhabitatshadgreatercommunitysimilarity(23.5±4.6%)than
that found between adjacentburned and unburned habitats ateithersite (13.8 ± 1.9%).The
unburnedhabitatshadrelativelylowcommunitysimilarity(12.4±5.4%),indicatingasurprisingly
highdegreeofbetween-patchendemisminmaturelodgepolepineforests.Thisendemismalso
suggeststhepossibilitythatspeciesmayhavebeenextirpatedfromsomeburnedhabitatsinYNP.
Comparisonoftrophicassociations,includinginferenceofrelative(ordinal)hostabundancefrom
parasitoidabundance,indicatethatburnedhabitatsweredominatedbyherbivoresofnonwoody
plantsandunburnedhabitatsarecharacterizedbyfungivoresanddetritivores.Thesefindingsare
consistentwithobservationsthatburnedsitesweretypifiedbytheestablishmentofgrassesand
forbsandthelossoflitter,whichwouldhavebeenconcomitantwithadecelerationofarthropod-
andfungal-mediatedorganicdecomposition.Therewasnoevidenceofdeadwoodhavingpro-
videdamajorsourceofnutrientsforinsectsinburnedhabitats,andtherewasnoevidenceof
insectoutbreaksintheregionofourtrapsites.
INTRODUCTION suggests that extremely large-scale fires
4P0a0Tr,hk0e00(1Yh9Na8P8o)r,fi4re5Ws%yioonmfYitenhleglp,oawrsUktSo(AnCe,hrNibasutHeronnnseaedln ho^(fC^ah^vtr^ehiessbtmteeuanedgsnineeindp.heajtrIdtanel.otsh1fei9es8tn9hc)eio,nncth1aei9txs8atts8otirhrtyoaipvsohefiicmnYpefoivNrreeP-rs
edtiealt.ed198t9h)a.tKonveirgahltlasnpedciWeasllraiccehn(e1s9s89w)opurled- c^gh^atngteoscionnseicdoelorgitchaaltcsotnrdiiktiingonsquaalnidtaptriov-e
graduallyincreaseoveraperiodof25yr, messesmayresultfromincreasing(orde-
eventually surpassing that of the old creasing)thescaleofreference(Allenand
growthforestpriortothefires.Theyalso Hoekstra1992).
notedthatsomespecies(e.g.,barkbeetles) Before the 1988 fires, managers antici-
would likely outbreak shortly after the pated the development of a new biotic
fire.Thereliabilityoftheseforecasteddy- communityimmediatelyfollowingabum,
namicsiscontingentuponthesimilarityof withinsectsquicklyutilizingthenewfood
fires investigated in previous research sources provided by the freshly killed
(Taylor1969, 1973, 1974;Taylorand Bar- trees(Despain1978).Basedonexperience
more1980; Knight 1987)tothosethatoc- withsmallerfires,itwaspositedthatfew
curred in 1988. Although someevidence vertebrates and no species, were lost in
JournalofHymenopteraResearch
the 1988 fires (Christensen et al. 1989, (>95%) of which were not documented
Schullery1989,Skinner1990).Whilesome priortothefires.AsMinshalletal.(1989)
insect populations were undoubtedly re- noted, a more complete faunal database
ducedbythefires,therewereseveralob- and systematic sampling are essential in
servationsthatsuggestedthatinsectswere assessing the impacts of the fires to the
recoveringwithinayear(McEneaney[YNP biodiversity of YNP (Christensen et al.
Ornithologist]hiCarr1990,Skinner1990, 1989, Schullery 1989, Roemhild 1994).
Varley[YNPChiefofResearch] inJeffery Simply put, without empirical data it is
1990), and anecdotal evidence indicated not possible to assess predictions of the
possible outbreaks of species capable of rateandformofecologicalrecovery.
exploiting fire-damaged trees (Romme The central questions related to the
and Despain 1989, Skinner 1990). Quali- short-termeffectsoftheYNPfiresonbio-
tativeobservationsindicatedthattherate diversityare:1)hasspeciesdiversity,rich-
of recolonization for some taxa was ex- ness, or evenness increased in the time
traordinarilyrapid.Skinner(1990)report- since the fires, 2) are any species found
ed finding black bears feeding on abun- only inburned areas (suggestingthepo-
dant, large wood wasps while they ovi- tentialforenhancedrichnessordiversity)
posited in the smoldering stumps, and or unburned areas (suggesting thepossi-
Lewin (1988) forecasted a resurgence of bility of extirpation from YNP), and 3)
insects exploiting the new growth of have there been any insect outbreaks of
grassesandherbs.Suchevidencewasex- fire-adapted species? Initial studiesdem-
tendedintoamoregeneralpredictionthat onstrated that in the 2 yr following the
biodiversitywasorwouldbeenhancedby fires insect species diversity in the litter
thefires(KnightandWallace 1989,Rom- habitatwerealmostinvariablyreducedin
me and Despain 1989, Varley in Jeffery burned locations relative to unburned
1989,1990).Conversely,Elfring(1989)and sites, although diversity consistently in-
Conniff (1989) warned that reported re- creasedinburnedsitesfrom1989to1990
covery rates were overestimated (Elfring (Lavigneetal.1990).Becauseextrapolating
1989,Conniff1989). fromthishabitattotheforestecosystemis
The observations and predictions re- problematical,weundertookanintensive
garding the recovery offire-adapted and studyoftheHymenopteraasanindicator
otherinsectspeciesformanimportantand taxon [sensii Cook 1976, Sheehan 1984,
compellingbasisfordevelopingandtest- Munn 1988, Hawksworth and Ritchie
ing ecological hypotheses. However, the 1993)in1990.
controversysurroundingcompetingclaims The Hymenoptera were chosen as the
ofecologicalrecoverypersistslargelydue indicator ofbiodiversitybecause: 1) they
to a lack of quantitative ecological data. areeasyandcost-effectivetocollect,2)the
Despitetheintriguingobservationsofin- parasiticspeciesrelyonawidespectrum
sectfauna,therearenopublisheddatare- ofherbivoroushosts,3)theparasitoidsof
latedtothepost-fireterrestrialinsectfau- herbivorous insects provide an indirect
naofYNP.Therehaveonlybeenabouta but effective measure of biodiversity of
dozenpublishedstudiesofentomological thislowertrophiclevelandthecondition
researchwithintheParkinthelast20yr, ofthe vegetativecommunity, and 4) one
and the only relevant, quantitative data ofus(SRS)isahymenopteransystematist,
wererestrictedtothelitterhabitat(Lavig- facilitating identification work [see Noss
neetal. 1990). Indeed,theinsectfaunaof (1990), Spellerberg (1991), and Hawk-
YNP has been estimated to range from sworth and Ritchie (1993) formorecom-
12,000 to "tens of thousands" ofspecies pletedescriptionsofthedesired qualities
(Clark et al. 1989), the vast majority ofabiodiversityindicatortaxon].Logisti-
Volume5,1996
cal, financial, and regulatory limitations resultinginmissingdata(northernburned
restrictedourstudytoasingleyearofin- siteonJuly7;southernunburnedsiteon
tensivedatacollection,2yrafterfires,so July14;northernburned,northernunbur-
weadoptedthestrategyofcomparingad- ned, and southern burned sites on Sep-
jacentburned and unburned areastoad- tember 7). Thecollectionswerestored in
dresstheeffectsofthefiresandthenature 70% ethanol and returned to the labora-
oftherecovery. tory where the Hymenoptera weresepa-
MATERIALSANDMETHODS riadteendt.ifiTehdetoHysumbefnaompitleyr(ainwseormeepcraespeasregde,-
Tv^^ositesinYellowstoneNationalPark nus,ancioccasionallyspecies),andsorted
werechosen forsettingpairsofTow2nxes2- to morphospecies. Voucher specimensof
styleMalaise traps (approximately all morphospecies are deposited in the
X2m;GoldenOwlPublishers,Lexington Rocky Mountain Systematic Entomology
Park,MD).Thenumberofsitesandtraps Laboratory, UniversityofWyoming, Lar-
swtarsainltismitaenddbyYNloPgisptoilcialciaensdrreegsaorudricnegcotnh-e amiWee. examined the hymenopteran com-
frequency and intensity of trap monitor- munitystructurefromtheperspectivesof
ing.Thesesitesrepresenteddifferentfires diversity, evenness, and richness (Kotila
withinYNP(whichmergedintotheSnake 1986).Aswithallsamplingmethods.Mal-
River fire complex) and therefore func- aise traps are biased in the groups that
stiitoenseidncalsudetrdueabruerplniecdathesa.bitTahteanndoratnheurnn- tflhyeiyngcol<l2ectm(e.ag.b,ovperimgarroiulnydsmlaelvlelin(sMeactt-s
burned (control) habitat, 5.4 and 5.8 km, thews and Matthews 1971, Darling and
respectively, from the South Entrance to Packer1988)).However,theapplicationof
thePark.Thesouthernsitesincludedase- diversityindicestoselected portionsofa
v(ceornetlryolb)uhranbeitdat,ha4b.i0taatndan2d.3aknmufnrboumrntehde b1i9o9t5i)ciscoapmpmruonpiritayte(ea.sg.l,onKgapapseltlheereetsulatls.
SouthEntrance.Controlhabitatswerese- are interpreted inthecontextofthecon-
lected to represent topographic and pre- straints of the sampling methodology
sumed vegetative characteristics of the (Southwood1978).
burned areas prior to the fires. Malaise Diversity (ameasureofboththeabun-
trappingishighlyefficientbutmaybein- danceandequitabilityofspecies)wasex-
fluenced by the local conditions, so trap pressed using theShannon-Wienerindex
positioning and microhabitat conditions (H) (Southwood 1978).Thismeasurewas
werereplicatedaspreciselyaspossiblebe- chosen because: 1) it is normally distrib-
tween sites. As such, physical proximity uted(Taylor1978),2)itismoreappropri-
wassecondarytotheecologicalcharacter- atethantheSimpson-Yuleindex,whichis
istics. stronglyinfluencedbytheunderlyingdis-
unTbhuernterdapsarweeasr,eaibnoaudtja5c0e0ntmburfnreodmatnhde stpriebcuiteison(Mfaoyr s1a97m5p)l,e3s)wititwhasmomroeretahpanpro1-0
edgeofthebum.Trapswerefirstsetdur- priate than the Berger-Parker index be-
ingthelastweekofMay,1990.Owingto causetherewereseveralcasesofco-dom-
YNP regulations that trapsbeconstantly inant species, 4) it is dependent onboth
"attended", they could only be left in evenness and richness (Magurran 1988),
placefor2-wkintervals. Insectswerecol- and 5) it is perhaps the most commonly
lected from the trapsonJune 10 and 14, encountered index in the literature (Ma-
July7and14,August11and19,andSep- gurran 1988, Spellerberg 1992) and was
tember7.Trapsweredamagedbyweath- used in the analysis of litter arthropod
er,wildlife,orvandalson fiveoccasions. communitiesaftertheYNPfires(Lavigne
JournalofHymenopteraResearch
etal. 1990).ThedisadvantagesofusingH threetimeblocks: spring(before21 June,
sapuroresee,tdhawttiotthhteohueitnSdieamxbpsisosloaunt-peYuurmleeleaynirniednleagxtiv[(eaSsomueotaph--- aN(anfdt=er141)A,Aueugaguruslstyt,,sNuNm=m=e34r)),(asbnoedtawsleatetoenas2lu1lomJwmueanrne
wood1978)],butwewereparticularlyin- equalnumberofdatapointsineachblock
terestedincomparisonsbetweencommu- and eliminate the confounding effects of
nitiesfromburnedandunburnedhabitats, phenology.
sporobtlheematreilcaatli.viItnyaodfditthiiosn,iHndeisxnowtassennsoit- twTeoenahsasbeistsatstheandtasxiotnesom(ii.ce.,ocvoemrlmaupnibtey-
tivetothecharacteroftheratioofspecies similarity),weusedadirectcalculationof
toindividualsanditisdominatedbythe percentsimilarity(Kotila1986).Thismea-
abundant species (May 1975), but these sureofsimilarityprovidesresultsconsis-
qualitiesdidnotconstitutedisadvantages tentwithothercommonexpressions[e.g.,
inHtahveicnogntcehxtosoefnoHuraaspptlhiecamteiaons.ureofdi- J1a9c90c)a]r,d'wshiccohefgfiicvieenetqua(lChwreisitgihatnsteonalletspael-.
versity,weused theShannon-Wienerin- ciesand thereforetendtoplaceexcessive
dex ofevenness (Kotila 1986). This mea- significance on rare species (Southwood
sureistheratioofthemaximumvalueof 1978). Lnourstudy, rarespeciesarecon-
H (assuming that the individuals were ceptually very important, so overempha-
evenly distributed among the species) to sizingtheircontributiontothecommunity
therealizedvalueofH.Assuch,thismea- wasnotconsideredaseriousshortcoming.
sureofevennessrangesfrom0.0to1.0. Some coefficients of similarity take rela-
Weexpressedthespeciesrichnessasthe tive abundance into consideration (e.g..
numberofspecies.Althoughthismeasure BrayandCurtis1957),buttheseapproach-
has the clear advantage of simplicity, it es have other shortcomings (Austin and
hasthedisadvantageofoversensitivityto Orloci1966).
numerically rare species. Findley (1973) Tounderstand how theentirecommu-
andHendricksonandEhrlich(1971)have nitystructureoftheburnedandunburned
criticized restrictingexpressionsofdiver- habitatsdiffered,wherepossible,weclas-
sitytothenumberofspeciespresentwhile sified theHymenopteraintotrophiccate-
failingtoconsidertheformsandfunctions goriesbasedonthelowesttaxonomiclev-
ofthespecies.However,ourassessmentof el of identification (Borror et al. 1989).
speciesrichnessavoidsthispitfallinthat Clearly,thereareexceptionstothesegen-
weemployedconcomitantanalysesofdi- eralcategories,butthisapproachwascon-
versityand wehavea good understand- sistentlyappliedacrossallsamplesandal-
ingoftheecologicalfunctionsofthespe- lowed us to make reasonable inferences
cies in the taxon of interest. Given the abouttrophicstructureintheconimunity,
samplingconstraints,theuseofnumerical includingthoseelementsthatwerenotdi-
speciesrichnessisappropriate(Magurran rectly sampled (e.g., plants, non-hyme-
198W8)e. used analysis of variance (MSU- cnaoupsteertahnehmeirsbsiivnorgess,amfpulnegsivworeerse,beatcl.a).ncBeed-
STATsoftware,version3.2) toassessdif- between burned and unburned samples
ferencesintheecologicalmeasures(diver- andrepresentedsimilartimesofyear,we
sity, evenness, richness) betweenburned were able to validly pool the available
andunburned habitats;anarcsinetrans- data across dates and sites to avoid the
formation was applied toevenness (Sne- problemoflowsamplesizesingenerating
decorandCochran 1980). Measuresfrom anoverallexpressionofcommunitystruc-
the sites representing each habitat type ture in burned and unburned habitats.
(burnedand unburned)werepooledinto Analysisoftrophicassociationsinburned
Volume5,1996
andunbumedhabitatswasperformedus- Table1. SpeciesrichnessofHymenopterafromYel-
ingchi-squaretests(Siegel1956). alroewsatrornaengNeadtiionnadlesPcaernkd,i2ngyroradfetrerotfhsepe1c9i8e8sfriirceshn(etsasx)a
RESULTS
Taxon
TheMalaisetrapsamplesyieldedatotal
of2,331 hymenopteranspecimens, repre-
senting603species(morphospecies)from
36families(Table 1). Themajorityofthe
species were Ichneumonoidea (60%);
Chalcidoidea comprised 16% of the spe-
cies,andProctotrupoideamadeup9%of
the species. The aculeate Hymenoptera
comprisedonly10%ofthespecies.
Speciesdiversityincreasedsharplyfrom
earlyJune throughJulyand thengradu-
allyincreased untilSeptemberinallsites
(Fig.1).Thesharpdropindiversityacross
allsitesonthesecondsamplingdatewas
associatedwithanunusualcoldfrontthat
caused snow atboth samplingsites. The
valuesand dynamics ofspeciesdiversity
inburnedandunbumedhabitatswerere-
markably similar between sites. At both
sites,thespeciesdiversityinburnedhab-
itats was generally lower than in unbur-
ned habitats throughout thesummer, al-
though theindicesconvergedinlateAu-
gsiugsntifoircaSnetpltyem(bFer<.D1.i0v2e,rsPi>t0y.d3i0d)nboettdwieffeenr
burned and unbumed sites in spring or
claatnetlysu(mFme=r,5.68b,utPd=iv0e.r0s7i)tygrweaatsersiingniufni--
bumedhabitatsinearlysummer.
Thechangesinspeciesdiversityappear
tohavebeenlargelyafunctionofspecies
richness (Figs. 2). As with the trends in
diversity, the number of hymenopteran
species was significantly (F= 7.74, P =
0s.u0m5)megrre,atweirthinnuonbsiugmniefdicahnatbi(tFat<si0n.5e2a,rlPy
sr 0.50)differencesinothertimeperiods.
Richness generally increased throughout
thesummer.Atsite1,thenumbert^fspe-
cies in the unbumed habitat increased
rapidly in the first 6 wk of the survey,
while the species richness in theburned
habitatincreasedmostrapidlylaterinthe
summer. At site 2, species richness in-
creasedatarelativelyconstantrateinboth
JournalofHymenopteraResearch
>
cu
aI
o
c
c
1
o
155 170 185 200 215 230 245
Julian date
J(Fuciligry.c;l1e.2s1)5Sah=nadn3nnAoourngt-uhWseitre;nne2(4rs5qduia=vree2rss)Sietspyatmienpmlbueenrbs)iu.tresn,ed2(yrdaasfhteerdtHhnee)fiarensdibnuYrnNePd((Jsuolliiadnlidnaet)eha1b5i5tat=s,4atJutnhee;s1o8u5th=ern4
unburnedandburnedhabitatsafterJune. evennesswasgreaterthan80%inallsam-
Attheendofthesummer,thenumberof ples.Therewasageneraltrendofdecreas-
speciesdeclinedinalllocationsexceptthe ingspeciesevennessinunburnedhabitats
burned habitat at site 1. At both sites, acrossthesummer,buttherewasnodis-
more species were found in unburned cernibletrendofevennessinburnedhab-
habitatsthaninburnedhabitatsthrough- itats.
outJulyand August.Theunburnedhab- The hymenopteran communities from
itatspeakedat107and113species,while burned and unburned habitats at both
the corresponding burned habitats had siteswere to20%similaracrossthesum-
maximaof88and90species. mer (Fig. 4). Community similarity of
Species evenness was generally higher burned and unburned habitats ranged
inunburnedhabitatthaninburnedhabi- from to 14% at site 1, with a general
htaatds (sFiiggnsi.fi3c)a.ntIlnydegerde,ateurnb(ufrn=ed7.7h1a,biPtat=s ttirmeen.d tAotwasridtse i2n,crceoasmimnugnisitmyilarsiitmyilawriitthy
0.03)evennessthandidburnedsitesdur- ranged from 16 to20%, with nodiscern-
ing the spring, but no significant differ- ible trend during the summer. The hy-
ences were found during thesummer (f menopteran community similarities from
^ 0.25, P s: 0.72). Except foronesample thetwoburnedhabitatsrangedfrom5to
from theburned habitatatsite 1,species 30%throughoutthesummer.Atonlyone
Volume5,1996
120
100
«3 80
a
o
60
en
o
o
c^ 40
20
O
155 170 185 200 215 230 245
Julian date
Faingd.2n.ortShpeercnie(ssqruiacrhense)sssainmpulnebusirtnese,d2(ydrasahfteedrltihnee)fiarnesdibnuYrnNePd((Jsuolliiadnlidnaet)eha1b5i5ta=ts,4aJtunteh;e1s8o5ut=he4rnJu(lcyi;rcl2e1s5)
=3August;245=2September).
timewascommunitysimilarityofthetwo structure(X'=298.4,8df,P<0.0001;Ta-
burned habitats less than that found be- ble 2). In burned habitats parasitoid
tweentheburnedandunburnedhabitats groupsassociatedwithherbivoresonorin
withinasite. foliagebut not in wood (e.g., Dryinidae,
Thecommunity similaritybetween the Microgastrinae,Hormiinae,andplatygas-
two unburned habitats was consistently trids) were significantly more frequent
lower than between theburned habitats. than in unburned habitats (X- = 118.4, 1
The unburned habitats had community df,P<0.0001).Thedominationofthistro-
similarities ranging from to 30%, with phicgroupinburnedhabitats(71%ofthe
higher similarities later in the season. hymenopteranfauna) indicated thatvari-
Thus,thesimilaritybetweenhymenopter- ousgrassesandforbswereprovidingthe
an communities in widely separated, primary food source. This hypothesis is
burned habitats was greater than that further substantiated by the significantly
foundeitherbetweenburnedandunbur- higher frequency (X- = 24.8, 1 df, P <
ned habitats at a single site or between 0.0001)ofnectar-feedingHymenopterain
widelyseparated,unburnedhabitats. these habitats as well. The herbivores of
Analysis of trophic associations in nonwoodyplantsandnectar-feedingspe-
burned and unburned habitats revealed ciescomprisedonly52%ofthehymenop-
significant differences in community terancommunityinunburnedhabitats.In
JournalofHymenopteraResearch
1.0
CO .9
CO
Qi
Si
>
.8
d
I .7
o
a
a
C/3 .6
155 170 185 200 215 230 245
Julian date
J(Fuciligry.c;l3e.2s1)5Sah=nadn3nnAoourngt-uhWseitre;nne2(4rs5qeuva=reen2sn)eSsespsatmiepnmlbueenrbs)iu.tresn,ed2y(rdaasfhteerdtlhiene)fiarensdibnuYrnNePd((Jsuolliiadnlidnaet)eha1b5i5tat=s,4atJutnhee;s1o8u5th=ern4
burned habitats, woody herbivores (i.e., were infrequently found inburned habi-
Siricidae) and parasitoidsofwoodyherbi- tats (9%), suggesting that the litter com-
vores(e.g.,Dolichoniitusiinperntor(Kriech- munity and decompositional processes
baumer), Rhyssa alaskensis (Ashmead), mayhavebeenadverselyaffectedbyfire.
gwTaresirtacesrpsis(siPgrnpoiivsfasioncdacinhstelrVy)i,emraoencrkde,OAfdlroleonqdtuooercinoitlso(ncXr-a^ssps.i=)- TheresultsoDfIoSuCrUsSuSrIvOeyNsofhymenop-
43.6, 1 df, P < 0.0001) than inunburned teranspecies diversityin YNP2yrafter
habitats,wherethesetrophicassociations thefiresallow usthe firstopportunityto
comprised only 1% ofthe Hymenoptera. addressempirically thecentral issues re-
In unburned habitats, parasitoidsoffun- latedtotheeffectsofthefiresonterrestrial
givoresand detritivores (e.g., Diapriidae, biodiversity. Our findings 2 yr after the
Proctotrupidae, Megaspilidae, and Cera- firesareparticularlyrelevanttoecological
phronidae) were significantly more fre- and management discussions of short-
quentthaninburnedhabitats(X-=200.0, term recoveryinYNP(Lewin1988,Rom-
1 df,P<0.0001).Beingthemostcommon meandDespain1989,McEneaney/'/;Carr
trophic association (32%), these parasit- 1990,Skinner1990,VarleyinJeffery1990).
oidsindicatedtheimportanceofforestlit- Inthiscontext,webelievethattheconsis-
ter as a food source. These organisms tencyoithedatabetween thesesites,the
185
Julian
sF=iqgus.aqr4ue.asr)e,Cs)oa,nmd2muybnruiratnftyeedrsitamhniedlafriuirnetsybiuonfmYebduNrPnhaeGbduilthiaatabsnitwdaiatttshei(ns1o5ls5iidt=esli4(nedJauwnsieht;ehd1c8li5irncel=,es)s4,oJuuutlnhybe;ru2nm1e5sidt=eh3=abAictuiagrtculssets(,)s.onloidrtlhienrenwisitthe
qualityofthetaxonomicdata,andtheeco- exposed insect populahons survived the
logicalqualitiesoftheindicatortaxonal- severe burns. As such, it would appear
low us to draw some reasonable infer- thatagreatnumberofspecieshavereco-
enceswithrespecttotheeffectsofthefire lonizedburned habitats. Indeed, thespe-
onbiodiversity. As previously noted, al- ciesdiversityandspeciesrichnessinthese
though Malaise traps, and all other col- habitats reached about80% ofpresumed
lecting devices, arebiased in the groups pre-firelevelswithin2yr.Thus,itisevi-
thattheycollect,theapplicationofdiver- dentthatsubstantialrecoveryofbiodiver-
sity indices to the data is appropriate as sityhasoccurredsincethefires.
longas the interpretationoftheanalyses Therapidrecoveryofbiodiversityisnot
is developed in the context of the con- afunctionofanimpoverishedinsectfauna
straints of the sampling methodology priortothefires.Thenotion thatmature
(Southwood1978).Inthislight,wecanbe- lodgepole pine forests are biological de-
gintoaddressthethreecentralquestions serts(RommeandDespain1989)isclearly
raisedpreviously. — erroneous. The diversity and richness of
Hasbiodiversityincreasedsincethefires? Hymenoptera in the unbumed habitats
Althoughwedonotknowwhatthestatus was5-to10-foldgreaterthanthatreport-
ofbiodiversitywasimmediatelyfollowing ed for sagebrush habitats in Wyoming
thefires,wecanreasonablyinferthatfew (Christiansen et al. 1990). If we assume
10 JournalofHymenopteraResearch
Table2. TrophicassociationsofHymenopteracollectedfromburnedandunburnedhabitatsofYellowstone
NationalPark,2yrafterthe1988fires
Percentofsamplefrom
IH'phii.jj'^ocijtion habitat(n.individuals)
(representdtiM's)
parasitoidofherbivoresonorinfoliage 51(750) 71(844)
(mostichneumonidsandbraconids)
parasitoidofherbivoresinwood 1(21) 6(73)
(doryctineandhelconinebraconids)
parasitoidofdetritivores,fungivores,andotherlitterassociates 32(464) 9(104)
(diapriids,proctotrupids,orthocentrineichneumonids,alysiineandopiinebraconids)
nestprovisioningpredator 3(41) 3(38)
(sphecids,pompilids,vespids,chrysidids)
herbivoreonorinfoliage 1(15) 1(9)
(tenthredinids,argids,xyelids,eurytomids,cynipids)
herbivoreinwood (1) (2)
(siricids)
nectar-pollenfeeder 1(12) 4(42)
(apoids)
scavenger 11(157) 5(60)
(formicids)
hyperparasitoid (5) 1(9)
(mesochorineichneumonids)
thatHymenopteraaccountfor20%ofin- andinsectcommunitiesdivergewithfor-
sect species richness based on North estrecovery.
American estimates (Schaefer and Kosz- Earlier work has suggested that the
tarab1991),thenanold-growthlodgepole greatestdiversityofselectedplant(herbs,
pine habitat is likely to include 500 to shrubs,and trees)andselectedvertebrate
1,000insectspecies.Althoughthevegeta- (birds and mammals) species is found in
tionmayappeartoapproachamonocul- young(1 to25yr-old)lodgepolepinefor-
tureinthesehabitats,itisevidentthatthe ests (Taylor 1969, 1973, 1974; Taylor and
insectcommunitiesarediverseanddiffer Barmore1980). Unfortunately,thespecies
markedlybetweenstands.Evenifthe20% diversityofvertebratesinthe5yrfollow-
insectcommunitysimilaritybetweenold- ing a fire was not measured by Taylor
growth habitats is somewhat underesti- (1969,1973,1974).However,plantspecies
mated (fora discussionofthis issue, see richness 1 to 3 yr after a bum was 9 to
Arctherespeciesuniquetoburnedorunbur- 23%ofthemaximum,whichoccurred25
ned habitats?), the total insect diversity yearsafteraburn.Birdandmammalspe-
supported in YNP's mature lodgepole cies richness 7 to 13 yraftera burnwas
pineforestsisalmostcertainlyoftheorder 65 to 81% of the maximum richness,
of several thousands of species. In this which also occurred 25 yr after a burn.
contextitisimportanttonotethattheear- Species diversity dropped to 46% of the
lysuccessionalinsectcommunitiesinspa- maximum in forests 57 to 111 yr after a
tiallydisjunctburnedhabitatsweremore burn.
similar to one another than the commu- Our data demonstrate that insect (Hy-
nities in unburned habitats. This finding menoptera)biodiversitymayrecoverata
suggests that early successional commu- rate similar to that of the plant commu-
nitiestendtoberelativelyhomogeneous. nity.Ifweassumethatthebiodiversityof