Effects of varying sampling effort on the observed diversity of carabid (Coleoptera: Carabidae) assemblages in the Danglobe Project, Denmark

2006·0.13 MB·

by  Maria Sapia

©EntomologicaFennica.11October2006
Effects of varying sampling effort on the observed diversity
of carabid (Coleoptera: Carabidae) assemblages
in the Danglobe Project, Denmark
MariaSapia,GáborL.Lövei*&ZoltánElek
Sapia,M.,Lövei,G.L.&Elek,Z.2006:Effectsofvaryingsamplingeffortonthe
observeddiversityofcarabid(Coleoptera:Carabidae)assemblagesintheDan-
globeProject,Denmark.—Entomol.Fennica17:345–350.
Diversityrelationsamongthreestagesofanurbanisationgradientwerestudied,
usingtheRényiscalablediversityindexfamilyandtheRightTailSum(RTS)di-
versity.Theruralareaswerelessdiversethaneithertheurbanorthesuburban
ones.Theurbanareasweremorediverseconsideringthedominantspecies,while
thesuburbanareasweremorediverseconsideringtherarespecies.Next,weex-
aminedtheimpactofdifferentsamplingregimesonthesediversityrelations.A
pulsatingsamplingmethod(samplingfor2weekseverymonth)gavethesame
diversityorderingascontinuoussampling.Furtherreductioninsamplingperiod
alteredthediversityrelations.
M.Sapia,DepartmentofIntegratedPestManagement,DanishInstituteofAgri-
culturalSciences,FlakkebjergResearchCentre,DK-4200Slagelse,Denmark&
DepartmentofEcology,UniversityofCalabria,87036Rende(CS),Italy
G.L.Lövei,DepartmentofIntegratedPestManagement,DanishInstituteofAg-
riculturalSciences,FlakkebjergResearchCentre,DK-4200Slagelse,Denmark;
*correspondingauthor’se-mail:[email protected]
Z.Elek,DepartmentofIntegratedPestManagement,DanishInstituteofAgricul-
turalSciences,FlakkebjergResearchCentre,DK-4200Slagelse,Denmark.Per-
manentaddress:DepartmentofEcology,Szt.IstvánUniversity,H-1400Buda-
pest,P.O.Box4,Hungary
Received31December2005,accepted25March2006
1.Introduction (Ishitanietal.2003),Belgium(Gaublommeetal.
2005),andHungary(Maguraetal.2004,2005)
Globenet,aninternationalresearchproject,aims indicateaconsiderableeffectofurbanisationon
at assessing changes in biodiversity caused by forest carabids, although this effect is not uni-
anthropogenicmodificationoflandscapesindif- form.FirstresultsfromDenmark(Elek&Lövei
ferent countries, using a common sampling 2005)indicatethattheeffectsinthiscountryare
method(pitfalltrapping)andreferencegroup(ca- closertothoseinCentralthanNorthernEurope
rabidbeetles,Coleoptera:Carabidae)(Niemeläet (Maguraetal.2004vs.Vennetal.2003).
al.2000).ResultsfromFinland(Alaruikkaetal. OneoftheaimsoftheGlobenetProjectisto
2002;Vennetal.2003),Canada(Niemeläetal. monitor the effects of urbanisation on ground
2002), Bulgaria (Niemelä et al. 2002), Japan beetles.Theoriginalset-upcallsforseason-long,
346 Sapiaetal. (cid:127) ENTOMOL.FENNICAVol.17
continuoussampling(Niemelaetal.2000).How- ofAprilandmid-October,2004.Forfurtherde-
ever,inanymonitoringscheme,thereisacontin- tails,seeElekandLövei(2005).
uousdrive(oftenbytheendusers)tosimplifythe We compared the diversity extracted from
methodsandevaluation. Thisisalegitimatere- continuous trapping material from 2004 with
quirement, given the frequent lack of logistical threeother“imaginarysamplingregimes”asfol-
supportandtrainedpersonnel. lows: (1) considering only every second fort-
In this respect, the standard literature on nightly sample (= pulsating sampling), (2) con-
groundbeetleshaslittletooffer.Publishedstud- sideringthecatchforthree,equallyspacedfort-
ieshaveexaminedtheimpactofthetrapmaterial nightly intervals during the sampling period (at
and size (Work et al. 2002), trap arrangement the beginning, middle and end of the growing
(Wardetal.2001,Hansen&New2005)andpre- season),and(3)evaluatingonlymaterialtrapped
servative(Thiele1977)onthecatch,butthestan- during two fortnights, during the peak of the
dard recommendation is still the use of season- carabidactivityperiod.Thesedatawerethussub-
longsampling(Woodcock2005).Acomparison setsofthedatafromcontinuoustrapping.
between continuous pitfall trapping and combi- Weanalysedthediversityofthegroundbeetle
nationsofearlyandlateseasonsamplingperiods assemblages using the Renyi diversity profiles.
(Niemelä et al. 1990) established that the latter The Renyi diversity index provides a non-point
canbeanadequatesamplingmethodtoaddress description of diversity, overcoming the prob-
severaltypesofecologicalproblems, especially lems with single index descriptions (Magurran
thosethatfocusonindividualspeciesorgroupsof 2003). The samples were analysed by using
locallyabundantspecies. DivOrd 1.70, a computer program for diversity
Tofulfilthisknowledgegap,wehaveexam- ordering (Tóthmérész 1993) which calculates
inedtheeffectofreducedoralteredsamplingef- anddisplaystheRényidiversityprofilesofcom-
fort on the diversity relationships among three munitiesandseveralotherdiversitymeasures.
stages of the urbanisation process: rural, subur- DivOrdisbasedonparametricfamiliesofdi-
ban,andurbanareas. versity indices, and this method involves more
We found that the usual recommendation of calculationsthanasimplediversityindex[forde-
continuous, season-long sampling (e.g., Wood- tails,seeTóthmérész&Magura(2005)].Fordata
cock 2005) was not necessary to arrive at the analysistwoindexfamilieswereused,theRényi
same conclusions as by continuous sampling diversityandtheRightTailSum(RST)diversity
considering diversity relationships among these (Patil&Taillie1979).
threehabitattypes.
3.Results
2.Materialandmethods
3.1.Thediversityrelations
To assess the impact of different sampling ar- ofwhole-seasonsamples
rangements on diversity, we used the material
collectedintheDanglobeProject,inandaround The comparison of the Rényi diversity profiles
the town of Sorø, Denmark, in 2004 (Elek & (Fig. 1) ofthethreecarabid assemblages (rural,
Lövei2005).TheDanglobeProjectfollowedthe suburbanandurban)indicatedthattheruralareas
Globenetprotocol(Niemeläetal.2000).Weused werelessdiversethaneithertheurbanorthesub-
pitfalltraps(plasticcupsof10cmdiameter,with urban areas. The urban and suburban diversity
200ml70%ethyleneglycol+adropofdetergent, profilesintersected,whichmeansthatthediver-
withagalvanisedironcover)ineachofthefour sityrelationshipbetweenthesuburbanandurban
separate(distancebetweenadjacentpatcheswas area was not unequivocal. The urban area was
aminimumof100m)forestedpatchesineachof more diverse considering the dominant species,
thethree(rural,suburbanandurban)areas.The whilethesuburbanareawasmorediverseconsid-
traps (distance between traps within each patch ering the rare species. Using the RTS-diversity
10m)werecheckedfortnightlybetweentheend profiles(Fig.2),thischangeinthediversityor-
ENTOMOL.FENNICAVol.17 (cid:127) Samplingregimeeffectsonobservedcarabiddiversity 347
Fig.2.RightTailSum(RTS)diversityprofilesofthe
Fig.1.Rényidiversityprofilesforcarabidassem- carabidassemblagesatthesuburbanandurbanar-
blagesinrural,suburbanandurbanareasatSorø, easatSorø,Denmark,in2004.
Denmark,in2004.
samplingregimes(Fig.3a).Atthesuburbanar-
deringbetweenurbanandsuburbanareascanbe eas,thedifferencewaslesspronounced,andthe
located(Tóthmérész1995).Theurbanandsubur- profileranveryclosetothoseofthecontinuous
banprofilescrossedeachother betweenthe4th samplingabove(cid:1)>1.3(Fig.3b).Asimilarcourse
and5thmostfrequentspecies(Fig.2).TheRTS wasseenintheurbanarea(Fig.3c),butherethe
diversitycurvesshowedthatthesuburbanareas
couldbeconsideredmorediversethantheurban
areasonlyifthefirstfourmostabundantspecies
wereincludedintheevaluation.
3.2.Diversityrelations
ofreducedsamplingmethods
Thepulsatingsamplingmethod,i.e.samplingfor
twoweekseverymonth,gavethesamediversity
ordering results as continuous sampling. The
Rényidiversityprofilesofrural,suburbanandur-
banareas,whenapplyingthepulsatingsampling
method (weeks 1, 3, 5, 7, 9 and 11), coincided
withthediversityprofilesofthecontinuoussam-
plingmethod(Fig.3).Therewereonlyminordif-
ferencesbetweenthetwoprocedures,usuallyat
thebeginningoftheprofile,indicatingthatsome
rare species were present only in the data from
continuoustrapping.Thisisadirectconsequence
of reduced trapping effort, and does not greatly
changethediversityoftheassemblage.
Afurther reduction in the time of sampling,
i.e. three 2-week periods over the growing sea-
son,hadclearerimpactonthediversityprofilesin
thethreehabitattypes,comparedtothetwometh-
odsabove.Inallthreeurbanisationstages,itde-
Fig.3.Rényidiversityprofilesofthecarabidassem-
tectedfewerspecies(Fig.3a–c).Intheruralarea,
blagessampledusingvarioussamplingregimesinru-
theprofileindicated amorediverseassemblage ral(a),suburban(b)andurban(c)areasatSorø,
overmostofthescaleparameterthanthefirsttwo Denmark,in2004.
348 Sapiaetal. (cid:127) ENTOMOL.FENNICAVol.17
Fig.4.Rényidiversityprofilesofcarabidassemblages Fig.5.Rényidiversityprofilesofcarabidassemblages
ofrural,suburbanandurbanareas,sampledover ofrural,suburbanandurbanareas,sampledovertwo
threefortnightlyintervalsatSorø,Denmark,duringthe fortnightlyintervalsatpeakcarabidactivityatSorø,
growingseasonin2004. Denmark,duringthegrowingseasonin2004..
twocurvesranclosetoeachotheratonly(cid:1)>1.5. 4.Discussion
Thethreefortnightlyperiodsofsamplingin-
dicated a different relationship among the three In comparative diversity studies, the frequent
urbanisationstages,too(Fig.4).Theforestarea questionis:“whichassemblageismorediverse?”
wasorderedin-betweentheurbanandsuburban (Tóthmérész1995).Theansweroftendependson
atlowvaluesofthescaleparameter,anditslow the choice of the diversity index, which leads
diversity became apparent only at (cid:1) >1.5. The someecologiststodeclarethequestforananswer
suburbanassemblageseemedtobemorediverse futile and the methods nearly useless (Hurlbert
than theurban oneat theinterval 0.7 < (cid:1) < 4.0 1971).Theuseofone-parametricindexfamilies
(Fig.4).Bothoftheseindicationsweredifferent can resolve this paradox (Tóthmérész 1995,
fromtheresultsobtainedfromthefullaswellas Southwood&Henderson2003).
thepulsatingsamplingregimes. Analysingthediversityalonganurbanisation
Restricting the trapping further to two fort- gradientusingRényiscalablediversityindex,we
nights during the peak carabid activity substan- verifiedthatinDenmarkthediversitybetweena
tially alteredthediversity profiles, andallthree rural, forested and urban forest patches area in-
profilesranconsistentlybelowtheothercurves, creased along the urbanisation gradient. This
thusunderestimatingthediversityoftheassem- trend contrasts with findings in several other
blagevirtuallythroughoutthewholerangeofthe countries, for example in Finland (Alaruikka et
scaleparameteralpha(Figs.3a–c). al. 2002), but is similar to the trends found in
Comparingtherelationshipofthedetecteddi- CentralEurope(Maguraetal.2005)andmerits
versity trends among the urbanisation stages, furtherstudy.
samplingonlyduringthetwopeakactivityperi- Our results also showed that it is not neces-
odsalsodistortsthediversity relationships.Un- sarytofollowtheseason-long,continuouspitfall
der this sampling regime, the suburban area trappingrecommendedbyseveralauthors,most
seemed to support the most diverse carabid as- recently by Woodcock (2005), at least for the
semblageformostoftheprofile(Fig.5),except evaluationofdiversity.Withrespecttodiversity,
under the scale parameter values of (cid:1) <0.4, i.e. thedataresultingfromthepulsatingmethodpro-
whentherarespecieshadhighinfluenceonthe duced the same results as did continuous trap-
diversity measure. This sampling method cor- ping,suggestingthatthenumberofthesampling
rectlyindicatedtheurbanareaasbeingthemost occasions can be somewhat reduced. These re-
diverseone,butnotbetween(cid:1)valuesof0.5and sults are encouraging for the development of
2.1 (Fig. 5). The relationship between the rural morebenignandlessarduousmonitoringmeth-
andsuburbanareaswascorrectlyrepresented,ex- ods for carabids. Reducing the sampling effort
cept for very small values of the scale para- withoutsignificantlynegativelyaffectingthede-
meter,(cid:1). tecteddiversityrelationshipsmaybedesirednot
ENTOMOL.FENNICAVol.17 (cid:127) Samplingregimeeffectsonobservedcarabiddiversity 349
only for logistic reasons, but also for biomoni- editorialresponsibilitiesforthispaper.Thisispublication
toringofprotectedorotherareaswheree.g.en- no.5oftheDanglobeProject.
dangered species occur. However, compared to
thepulsatingmethod,theothersamplingregimes
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