Temporal variation of an Odonata species assemblage (Rome, Italy)

2004·0.9 MB·English

by  Carchini, G

Odonatologica33(2):157-168 June 1,2004
Temporalvariationofan Odonata
speciesassemblage(Rome, Italy)
G.Carchin,iT.Pacione,C.Tanzill,iM.DiDomenico andA.Solimini
DipartimentodiBiologia,University“TorVergata”,viadellaRicercaScientifica snc,I-00133,Roma,Italy
e-mail:[email protected]
Received August29,2003/Revised andAcceptedNovember 5,2003
TheCastel Porzianoestateisawell preservedcoastalMediterranean woodland,richin
still bodiesofwater,where odonatologicalstudies havebeen takingplacesince the’50s.
Adult Odon. wererecorded forthe entireestatein 1997 and 1998 (March-Nov.;2checks
eachmonth). 1,838adults (22spp.)weremarked,toassesstheir movements. Theresults
showedthatin 1997-1998 atotalof31spp.werepresent. Thisnumberis veryclosetothe
number(29)recorded upto1976.Variationinspeciesassemblagein 16pondswasobserved
from 1997 to 1998.Althoughthe overallspeciessimilaritywaspreserved,the number of
spp.foreachpondandthenumberofpondsinhabitedby each sp.significantlyincreased
from 1997 to 1998.Inregardtothe adultmovements,251 marked individuals of13spp.
werere-sightedonly atthesamepondswheretheyhadbeen marked and 30individuals of
6spp.weresightedatdifferentponds.Amongthelatter,themajoritymovedwithinarange
ofafewhundredmetres,butsomeindividuals wereabletoflyquitefar,e.g. 2.7km(Coen-
agrionpuella)and 5.8km(Libelluladepressa).Itisconcluded thatthe assemblagevaria-
tionfortheentireestatewassmall,varyingmoreonadecennialthanonanannualscale,but
forasinglepondvariationis wideronbothtimescales. Thequickrecolonization among
ponds,duetothe adult’smovements,appears tobethecauseofgreaterstabilityatmeso-
scaleratherthan atlocal scale.
INTRODUCTION
Thereisanincreasing interestinevaluating thevariationintimeof diversity, inor-
dertounderstandifitis linkedwithageneralmodificationoftheenvironment, dueor
notto humanactivity. However,ifwewant touse diversity variationas abiological
indicatorofenvironmentalvariation, itis necessary to distinguish betweenthevaria-
tionduetointrinsicecological characteristicsofthetaxa andthat,ifany, duetoitsre-
sponses tothechanging environment.Also,itis interesting tounderstandwhatis the
correcttemporal andspatial scalefromwhichtoobserve significant variation.Species
diversityof theOdonata is beginning to be usedas anenvironmentalindicator (e.g.
158 G.Carchini,T. Pacione,C.Tanzilli, M.DiDomenico&A.Solimini
CLARK&SAMWAYS, 1996),butoftenthe speciespresence isassessed fromshort
termobservations, sometimesover aflightseason, rarely overa yearandvery rarely
over alonger timespan. However,itis wellknownthatOdonatahavea differentca-
pacity and a differentpropensity regarding dispersal, so thatsomespecies are classi-
fiedas “wanderer”(SCHMIDT, 1978)orasobligateorfacultativemigrants(CORBET,
1999).Furthermore, they ofteninhabitunstable smallbodiesofwater. Consequently,
theOdonatafaunaofabiotopemaychange fromyearto year,boththrough extinction
and colonizationevents. Thebest way toclarify this problem is by long-term study,
unfortunately very rare inscientificliterature.In fact, MOORE (1991)citedonly six
long-term studiesondragonfly populations inEuropean stillbodiesofwater,ofwhich
somewere newlycreatedsothatthevariationoftheOdonataassemblage was also de-
terminedby theecological succession.
Theaimofthisstudy is toelucidatethevariationsoftheOdonataassemblages both
duringlongandshorttimespansinseveralbiotopes inastableenvironment.Toachieve
thisgoalwe chosethepresidential estateofCastelPorziano, whichretains someofthe
naturalcharacteristicsoncecommoninMediterraneancoastalareas. Herewerecorded
fortwo yearsthespecies presence inseveralponds. Sincetheseponds are hydrologi-
callyisolated,wealsoassessedthepossibilityofadultdisplacement.AtCastelPorziano,
aseriesofodonatological observationshavebeenmadesince theearly fifties, starting
withthepioneerstudiesofO.Castellani, andcontinuing withC.Consiglio’s worksand
thoseofhispupils. So,eveniftherewasnoprearrangedlong-term monitoringprogram,
dataontheOdonataassemblages fromthelastdecadesandfromtworecentyearswere
availableforcomparison.
STUDYAREA
TheCastelPorzianoestaterangesfrom theoutskirtsofRome totheTyrrheniancoast, inatypicalMedi-
terraneanclimaticzone.Theestatearea(60squarekm) iscovered mainlybypristineMediterraneanwood-
land.There aremorethanonehundredsmallbodiesofstillwater(ZARATTINIet al.,1999),whiletherun-
ningwatersarelimitedtotwotinyrivuletsonthenorthernboundary,andastretchofaconcreteditchcom-
ingfrom anearbyurbanized area.Thesewerenotconsidered inourstudy.Nearlyall thepondsarefedonly
by directrainfalls(FRICANOet al„ 1999),butfromspringtoautumnthereisalongdryseason,typicalof
aMediterranean climate.Consequently,thepondsaresubjecttostrongwaterlevel variation,andseveralare
temporary (autumnaltype,sensuWARD, 1992).Almosthalfofthepondsareephemeralandunsuitable for
Odonata.Thestudiedpondsweremoreorlessellipticalandrelativelysmall(meansurfaceanditsS.E.were
1390 and275 squaremetres,respectively).Amorecompletedescriptionofestateandpondfeaturesisgiven
inCARCHIN1et al.(2003).
METHODS
ASSESSINGOFODONATAASSEMBLAGE.—Therecordsarebasedonthepresenceofadults,even
whenonlyasinglespecimenwassighted.During1997,16pondsweresurveyedfrommid-MarchtoOctober.
During 1998thepondswereincreasedto23,and,duetoclimaticvariations,theobservationperiodwasfrom
midApriltolateNovember.Inboth years,theobservationsstartedinspringbeforethe firstsightingofadult
specimens,andlasted untilautumnwhenonlyrareindividualswerestillonwings.Eachpondwaschecked
fortnightlyby two oftheauthors walkingalongthebanks. Thecheckingstarted about 10.30andendedat
TemporalvariationinanOdonataassemblage 159
about16.30,andnochecksweremadewhen therewascloudyorwindyweather. InAugust,becauseofthe
estaterales,entrancewasforbidden forthelastthreeweeks, sothecheckswerelimitedtoonevisitforeach
pond.Althoughwechosethepondsamongthosepresumablypermanent,sevenoutof16driedoutinlate
summerof1997.Ontheotherhand 1998 wasrainierandsixofthepondswhichhaddriedoutin 1997re-
tainedthewaterduringthesummer.ToassesswhethertheoverallOdonataassemblagevariedatshortterm,
wecomparedthespeciesdistributionin 16pondscheckedbothin 1997andin1998.
Thespeciesidentificationsweremadebysightingor,whennecessary, specimenswere collectedandthe
keyofCONCI&NIELSEN(1956)wasused. AtCastel Porzianoboth Chalcolestes v. viridis(VanderL.)
and C.viridisparvidens(Artobolevski)arepresent.AccordingtoCOBOLL1 etal.(1994),these shouldbe
considered separatespecies.Becausetheyarehardtodistinguishinthefield,inourstudyweconsideredonly
theoccurrenceofthegenus.
Thespecies’presence fortheentireestate fromthe 1950sto 1976wastaken from UTZER1etal.(1977).
Thispaperdoesnotreportindicationsastowhichpondthespecimenswere collectedfrom,andconsiders all
Chalcolestes specimensasLestesviridis.
MARKINGANDRE-SIGHTINGOFODONATA. — TheOdonataweremarkedandre-sightedin all
the 16pondscheckedin 1997.Itisnecessary tonotethattheindividuals werenotmarkedwhenteneral,so
maidenflightswereexcludedinourdata.The specimens,caughtwithanentomologicalnet, weremarked
immediatelyontheponds.Oneortwosmallspotswerepaintedwithaveryfinebrash,ontheinferior surface
oftheleftposteriorwingfortheZygoptera,andontherightwingfortheAnisoptera.Thepaintwasacrylic,
withwaterassolvent,but water-resistant afterdryingforafew minutes.The colourcombinations allowed
ustosingleoutthepondwherethespecimenwasmarked.Aprogressivenumberwasalsopaintedontheleft
wingoftheAnisoptera,withanon-toxicpermanentpencil.ThemarkedOdonatawereallowedtoflyaway,
andthosespecimensthatwerenotabletoflywereeliminated.Becauseourgoalwastoassessthepossibil-
ityofdispersalonthewhole estate,andthis istoolargetoallow simultaneouschecks inallponds,weonly
recorded themarkedspecimens duringfortnightlypondchecksdescribed above,usingshort-focusbinocu-
larstocheckspots andnumbers.
DATAANALYSIS. —Thepresence/absenceofeachspeciesforeachpondandfortheentireestatewas
noted.We usedtheWilcoxonMatched PairTestandtheMann-WhitneyUtesttocomparethevariations in
speciesnumberorpondnumber,andtheJaccardindextoevaluatethesimilaritybetweentheassemblagesof
differentpondsordifferentperiods.Totest similaritymatricesweusedtheManteltest,viatheMonteCarlo
iterativemethodbyPC-ORDsoftwarepackage,version3.09(MeCUNE& MEFFORD,1997).Thedataon
markedindividuals werethesiteofmarking,thesiteofre-sightingand,fortheAnisopteraonly,thetimebe-
tweenmarkingandre-sighting.Differencesinre-sightingbetweengroupsweretestedbyPearsonChi-square
statistics.All testsweretwotailedwith acceptancelevelatprobability0.05.
OBSERVATIONS
Thespecies recordedby us fortheentireestateare reported inTableI.Comparing
thelatterwiththeinventory given by UTZERI etal.(1977),thetotalnumberofspecies
increasedfrom29to31(26same,5newand3unrecorded),resultinginaJaccardindex
of0.76.Itwaspossible only forthePIpondtocomparethe 1969-1971species assem-
blage, asreported by CONSIGLIO etal. (1974), withthatof 1997-1998.Thenumber
ofspecies inthispond decreasedfrom19to 12,withonly 11 unvariedspecies, 8 miss-
ing and 1new,resulting inaJaccardindexof0.55.
Thespecies recordedinthesame 16ponds in 1997and 1998arereported inTable
II.Atotalof24species wererecorded,being 21 unvaried, twonew andonemissing,
witha Jaccardindexof0.87.This valueis muchhigherthantheaveragepond value,
0.57,ranging from1 (P5pond)to0.33(T49pond). Insix ponds thenumberofspecies
160 G.Carchini,T.Pacione,C,Tanzilli,M,Di Domenico &A.Solimini
in1998was 1/3 larger(oreven more)thanin1997,withamaximumvariationforthe
pond T49from4to 12species. Infact, thenumberofspecies presentateach pond in-
creasedsignificantly from 1997to 1998(Wilcoxon MatchedPairstest:N= 16,T=23,
Z=2.100,P=0.035).Alsothenumberofponds inhabitedby eachspecies significantly
increasedfrom 1997to 1998(Wilcoxon MatchedPairstest:N=24,T= 19,Z=2.896,
TableI
Listofthe OdonatataxarecordedatCastelPorziano
WWhhoolleeeessttaattee PPIIppoonndd
SSoouurrccee UUTTZZEERR11 TThhiiss CCOONNSSIIGGLLIIOO TThhiiss
eettaal.l.„ ppaappeerr LLIIOOeettaall..,, ppaappeerr
SSppeecciieess 11997777 11997744
PPeerriioodd 11996699--11997766 11999977--11999988 11996699--11997711 11999977--11999988
CCaalloopptteerryyxxhhaaeemmoorrrrhhooiiddaalliiss ((VVaannddeerrLL..)) ++ ++ -_ -_
CCaalloopptteerryyxxsspplleennddeennss((HHaarrrr..)) ++ ++ -- --
CChhaallccoolleesstteesssspp.. ++ ++ ++ ++
LLeesstteessbbaarrbbaarmuss((FFaabbrr..)) ++ ++ ++ --
Lbeesstteessvviirreennss((CChhaarrpp..)) ++ ++ ++ ++
SSyymmppeeccmmaaffuussccaa((VVaannddeerrLL..)) -- ++ -- --
EErryytthhrmommmmaavviirriidduulluumm ((CChhaarrpp..)) ++ ++ ++ --
CCeerriiaaggrriioonntteenneelllluumm((ddeeVViiUll..)) ++ ++ ++ --
IIsscchhnnuurraaeelleeggaannss((VVaannddeerrLL..)) ++ ++ ++ ++
IIsscchhnnuurraappuummiilliioo((CChhaarrpp..)) ++ -- -- --
CCeerrcciioonnlUinnddeennit((SS£elt.)) ++ ++ ++ ++
CCooeennaaggrriioonnppuueellllaa((LL..)) ++ ++ ++ ++
CCooeennaaggrriioonnppuullcchheelllluumm((VVaannddeerrLL..)) -- ++ -- --
CCooeennaaggrriioonnmmeerrccuurriiaallee((CChhaarrpp..)) -- ++ -- --
CCooeennaaggrriioonnsscciittuulluumm((RRaammbb..)) ++ ++ ++ ++
AAnnaaxxiImmppeerraattoorrLLeeaacchh ++ ++ ++ ++
AAnnaaxxppaarrtthheennooppee((Ssadl..)) ++ ++ ++ -
AAeesshhnnaa ccyyaanneeaa ((MMuüllll..)) ++ -- ++ --
AAeesshhnnaammiixxttaa((LLaattrr..)) ++ ++ ++ --
AAeessnnaaaaffffiinniiss((VVaannddeerrLL..)) ++ ++ -- ++
AAeesshhnnaaiissoosscceelleess((MMüullll..)) ++ ++ -- --
BBrraacchhyyttrroonnpprraatteennssee((MMüilllll..)) ++ ++ -- --
LLiibbeelllluullaaddeepprreessssaaLL.. ++ ++ ++ ++
LLiibbeelllluullaaqquuaaddrriimmaaccuullaattaaLL.. ++ -- -- --
OOrrtthheettrruummccaanncceellllaattuumm((LL..)) ++ ++ ++ ++
OOrrtthheettrruummccooeerruulleesscceennss((FFaabbrr..)) ++ ++ -- --
OOrrtthheettrruummbbrruunnnneeuumm((FFoonnsscc..)) ++ ++ -- --
CCrtvoccootthheemmiisseerryytthhrraaeeaa((BBrruüllllet)) ++ ++ ++ ++
TTrriitthheemmiissaannnnuullaattaa((PP.. ddeeBBeeaauuvv)) -- ++ -- --
SSyymmppeettrruummssttrriioollaattuumm((CChhaarrpp..)) ++ ++ ++ ++
SSyymmppeettrruummffoonnssccoolloommbbeeii((SSceli,.)) ++ ++ ++ --
SSyymmppeettrruummssaanngguuiinneeuumm((MMuüllll..)) ++ ++ -- --
SSyymmppeettrruummmmeerriiddiioonnaallee ((SSceli..)) ++ ++ ++ --
SSyymmppeettrruummddeepprreessssiiuussccuulluumm((SS£ell..)) -- ++ -- --
TemporalvariationinanOdonataassemblage 161
P=0.004).However, theManteltestbetweenthe 1997and 1998matricesofallpos-
sible Jaccarddistancesbetweenpairsfromthe 16pondsrejected thenullhypothesisof
independence (Z=0.5,P<0.01). ThismeansthattheOdonataassemblage ofthewhole
setof16ponds was notstrongly alteredbetween 1997and 1998.
Wetestedthedifferencesbetweentheponds driedout ornotin1997inregard tothe
numberofspecies in1997,andin 1998.Notestwas significant(Mann-Whitney Utest:
N = 16foralltests, Z= 1.011, 1.176,P=0.311,0.239,respectively). Comparingthe
numberofspecies in1997and 1998only inthesetofsix ponds thatwere dryin 1997
andwetin 1998wefoundnosignificant differenceseither(Wilcoxon MatchedPairs
test,N=7,T=8, Z= 1.014,P=0.310).
Theresultsofthemarking andre-sightingare showninTableIII.Therewas a clear
positive correlationbetween the numberof markedand re-sighted individuals(linear
correlation:N=25,r=0.791,P<0.001).HoweverCrocothemiserythraeawasanout-
lier, showingahigherre-sighted/marked ratio.Therewasnosignificantdifferenceinthe
percentagesofthere-sightedspecimensbetweenZygopteraandAnisopteraeitherinall
species oronspecies forwhichatleastonespecimen was re-sighted(Mann-Whitney U
test:N=25,U =66.5, P=0.53, andN= 15,U= 16.0,P=0.19respectively). Onthe
contrary, the frequenciesofthere-sighted specimens were significantly lowerforthe
femalesthanformales,forboth theZygoptera (6% versus 14%)and theAnisoptera
(2% versus24%) (Pearsonchi-square testoncounts; x2= 11-65, df= 1,P=0.001 and
X2=35.26,df= 1,P <0.001,respectively). Despite the factthat there-sighting was
doneatseveralponds, allspecies showeda higherfrequencyofre-sighting atthepond
wherethespecimens weremarked,withtheexception ofAeshnaaffinisofwhichonly
two individualswerere-sighted, oneatthemarking pond andtheotheratadifferent
pond.Outofatotalof30specimensre-sighted farfromthemarking pond,thedistance
betweenthemarking pond andthere-sighting pondwas 100m(the smallestdistance
betweentheobservedponds)forthreeCercionlindenioneA.affinis, fiveLibellulade-
pressa, oneOrthetrumcancellationand 14C1 .erythraea; 300mfortwo O.cancellatum
andmuchmoreforafewotherspecimens: 1.5 kmforone O. cancellatum 1.9km for
,
oneC.erythraea, 2.7km foroneCoenagrion puella and5.8km (in only one day!)for
one L. depressa. SomeC. erythraea werere-sighted first inanotherpond andlaterin
thepondwheretheyhavebeenmarked.
FortheAnisoptera, whichweremarkedindividually, wealsohadsomeinformation
aboutthe longevityof the specimens ofsomespecies: L. depressa mean 10.9days,
maximum36(N =30); C. erythraea mean20.8, maximum44(N=29); O. cancella-
tum mean21.9days, maximum50(N=7); Sympetrumsanguineum 34days (N= 1);
S.meridionale22 days (N= 1).
DISCUSSION
RELIABILITYOFTHEDATA —Themajorconcernaboutthedatais thattheyarefrom thesightings
ofadults. Asimplesightingmaynotenabletheobservertodistinguishbetweenresidentbreedingspecimens
andnonbreedingvisitorspecimens.However, eventheevidenceofadultreproductiveactivitymaynotyield
162 G.Carchini,T.Pacione,C.Tanzilli,M.DiDomenico& A.Solimini
99g8 ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++
TT4499
9977 ++ ++ ++ ++
++
99g8 ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++
TT3355
9977 ++ ++ ++ ++ ++ ++ ++
99g8 ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ +++ ++ ++ ++ +++
TT2222
9977 ++ ++ ++ ++ ++ ++ ++ ++ + ++ ++ ++ + ++
99g8 ++ ++ ++ ++ +++ ++ ++ ++ ++
TT1199
9977 ++ ++ + ++ ++ ++ ++ ++
years
99g8 ++ ++ ++
TT1177bb
subsequent 9977 ++ ++ ++
TT1177aa 99g8 ++ +++ ++ ++ ++ +++ ++ ++ ++ ++ ++
9977 ++ + ++ ++ ++ ++
two
on 99g8 ++ ++ ++ ++ ++ ++ + ++ ++ ++ ++ ++ ++ ++
TT1I
Porziano 99?7 ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++
PPllil 99g8 ++ ++ ++ ++ + ++ + ++ ++ ++ ++ ++ ++ ++ ++ +
++
Castel 99?7 ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ +++
E in PP1100 99g8 ++ +++ ++ ++ ++ ++ + ++ ++ ++ ++ ++ ++ ++ +
Table ponds 99?7 ++ + ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ +
99g8 ++ ++ ++ ++ ++ ++ ++
16
PP99
at 99?7 ++ ++ ++ ++ ++ ++ ++
recorded PP66 99g8 ++ +++ ++ ++ ++ ++ + ++ ++ ++ ++ ++ ++ +++
99?7 ++ ++ + ++ ++ ++ ++ ++ ++ ++ ++ ++ + ++ ++
species 99g8 ++ ++ ++ ++ ++ ++ ++ ++ ++
PP55
99?7 ++ ++ ++ ++ ++ ++ ++ ++ ++
Odonata
99g8 ++ ++ ++ ++ ++ ++ ++ ++ ++
PP44
the 9977 ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++
of 99g8 ++ ++ ++ ++ ++ ++ ++
List PP33
99?7 ++ ++ ++ ++
99g8 ++ + ++ ++ + ++ ++ ++ ++ ++ +
++ ++ ++
PPII
9977 ++ + ++ ++ ++ ++ + ++ ++ ++ ++ +
AA1l 99g8 ++ ++ ++ +++ ++ ++ ++
97 + ++ ++
Years9?
PPoonnddss Years sspp ddeepprreessssiiuussccuulluumm
.S_SppeeCciieeSs CChhaalclcoolleesstteess bbaarrbbaarmuss vviirreennss SS.f.ufussccaa vviirriidduulluumm eelleeggaannsslliinnddeennii ppuueellllaappuullcchheelllulummscsictiutululumm Iimmppeerraattoorrppaarrtthheennooppee mmixixttaa aaffffiinniiss dedperpersessasaccaanncceellllaattiioonn ccooeerruulelesscceennss brburnunnneeuumm eerryytthhrraaeeaa ssttrriioolalatutumm ffoonnssccoolloommbbeeii ssaanngguuiinneeuummmmeerriiddiioonnaallee
LL. LL. EE.. /I.. CC.. CC.. CC.. CC.. AA.. AA.. AA.. AA..LL. O0.. O0.. OO.. CC.. SS.. SS.. SS.. SS.. SS..
TemporalvariationinanOdonataassemblage 163
apopulationabletocompletethelifecycle.Thecollection oflarvaeorexuviaewouldbeabetterway ofas-
sessingthereal presence ofapopulation,butthesedataarealmostnon-existentinthepast,sothatnocom-
parisonwouldhavebeenpossiblewiththepresentstatus.Therefore,weusedthedataofthesimplepresence
oftheadults, supportedalsoby theconsiderationthatourgoalwastomakecomparisonsbetweenpairs of
situations,eachaffectedbythesamebias.
LONGTERMVARIATION
TheCastel PorzianoOdonata faunacensuses cover aperiod ofabout50 years. In
fact,theUTZERIetal. (1977) datawere mainlyfromhundredsofcollectionsmadein
the1969-1975period,butdiscussedalsodatafromprevious literature(CASTELLANI,
1951). A detailedanalysis ofthespecies collectedby us orreported by UTZERI etal.
(1977) gives asmallervariationthanthatreported above. Infact, thetwo Calopteryx
species arerestricted torunning water,and atCastelPorziano werealways foundas
single specimens (only oneforeach species inour data)and considered“occasional”
byUTZERIetal.(1977).Only onespecimen was reportedbyUTZERI etal.(1977)for
I.pumilio, A. isoscelesandL.quadrimaculata,while werecordedjustonespecimen of
A.isosceles. Onlytwo B.pratensespecimens werereportedby UTZERIetal.(1977),
andwefoundonlyonespecimen. Only asingle specimen ofT.annulatawas foundby
us, whilenoneby UTZERI etal.(1977). Theseseven species cannot beconsideredas
trulyresidentinCastelPorziano, butonly occasional visitors.
Onthe contrary. C. mercurialeis confinedto two small rivuletsnear the northern
boundaryoftheestate,neglectedbycollectorsuntil1977andconsequently notincluded
intheUTZERIetal.(1977)list.However,C.mercurialehadalreadybeencollectedin
thesurroundingsoftheestatein1946(CASTELLANI, 1950),thereforewecanassume
itspresence ontheestateevenbeforethefirstcollecting after1977.
Excluding theabovementionedseven species as occasional,and including C. mer-
curialeinbothlists, thetotalnumberofspecies was 24until 1977and26inour data,
theunvariedspecies being 23,thenew3 andtheunrecorded 1,resulting ina Jaccard
index of0.88insteadof0.76.
Only threespecies were realadditions tothe localfauna: C. pulchellum, whichis
widespread inItaly, eveniflessabundantincentralandsouthernItaly thaninnorth-
ernItaly; S.fusca, whichis equally widespreadthroughoutItaly, andS. depressiuscu-
lum, knownas migrantandoftenassociatedwithartificialmarshessuch as rice-fields,
whichismoreabundantinnorthernItaly,andoccurs alsoincentralItaly (CARCHINI
etal., 1985),andinsouthernItaly (D’ANTONIO&DeFILIPPO, 1985;D’ANTONIO,
1996).Themissing species, A. cyanea,isknownalloverItaly,although notatsealevel
insouthernItaly (CARCHINI&ROTA, 1986).
Inregard tothecauseof thislong term variation, we canexcludea directmodifica-
tionof theenvironmentby man.Theestate,whichhasbeenmainlywoodlandforcen-
turiesandsince 1872agamereserve oftheItalianheadofstate,is surroundedby ahigh
wallandentry isstrictlyregulated.Thewoodlandsarenotexploited fortimber,andthe
managementoftheestateremainedunchanged overthelastfiftyyears.Thepondshave
164 G.Carchini, T.Pacione,C. Tanzilb,M,DiDomenico&A,Solimini
TableHI been,ingeneral, lefttonatural
Resultofthe markingandre-sighting.For the Lestidae: *=indi- evolution, with the exception
voifdthuealrsempraordkuecdtiavteesmeearsgoenn(cSee;p*t*em=binedr)i.vTidhueaplesrcmeantrakgeedsa,tatphperosxtai-rt ofafew thatwere artificially
matedatthe integer,refertothe markedspecimens deepened or newly excavat-
ed(in our set only the T1and
NNuummbbeerrooffiinnddiivviidduuaalsls C2 ponds respectively, about
SSppeecciieess MMaarrkkeedd RRee--ssiigghhtteeddaatt twenty yearsago) to increase
ssaammeeppoonndd ootthheerrppoonndd
thenumberofwateringplaces
CChhaallccoolleesstteesssspp** 3322 00 00 forgame.MOORE(2001)stat-
CChhaallccoolleesstteesssspp**** A47lb6 5577((1122%%)) 00 edthat theecological succes-
LL.bbaarrbbaarruuss ** 2266 11((44%%)) 00 sioninnewlyexcavatedponds
LL..bbaarrbbaarruuss**** 2233 11((44%%)) 00 couldlead eventotheextinc-
LL.vviirreennss** 3300 11((33%%)) 00
tionofallOdonatapopulations
LL. vviirreennss**** 113388 1166((1122%%)) 00
EE..vviirriidduulluumm 22 00 00 inforty years,mainlybecause
Il..eelleeggaannss 9911 55((55%%)) 00 ofshadeduetogrowthofhigh
CC..Ulinnddeennti 116600 3366((2233%%)) 33((22%%)) scrubs aroundtheponds. The
CC..ppuueellllaa 8899 1177((1199%%)) 11((11%%)) CastelPorzianoponds, usual-
CC..ppuullcchheelllluumm 99 00 00
lymucholderthanfortyyears,
CC..sscciittiudluumm 8833 1100((1122%%)) 00
AA..iImmppeerraattoorr 1177 00 00 really havevery fewscrubson
AA..ppaanrthheennooppee 22 00 00 theedges.Thisisprobably due
AA..mmiixxttaa 1122 00 00 to the presence ofabundant
AA..aqffffiinniiss 1133 11((88%%)) 11((88%%)) populations of Dama dama
LL.ddeepprreessssaa 227766 3300((1111%%)) 66((22%%))
andSus scrofa whichtrample
OO..ccaanncceellllaattuumm 111166 1111((99%%)) 44((33%%))
OO..bhrruunnnneeuumm 11 00 00 onthebanks during watering.
CC..eerryytthhrraaeeaa 115533 6633((4411%%)) 1155((1100%%)) Actually, a parallel study on
SS..ssttrriioollaattuumm 2244 00 00 the variables influencing the
SS..ffoonnssccoolloommbbeeii 1188 00 00 numberof Odonata species
SS..ssaanngguuiinneeuumm 88 11((1122%%)) 00
inthe CastelPorzianoponds,
SS..mmeerriiddiioonnaallee 2277 11((44%%)) 00
SS..ddeepprreessssiiuussccuulluumm 1111 00 00 showed that the presence of
riparian vegetation was one
ofthevariables positively correlatedwiththe numberofspecies (CARCHINI etal.,
2003). Excluding avariationoftheenvironmentalconditioninsidetheestate,therere-
mainsthe possibility ofregional variation, such as climatic variationtowardswarmer
and dryerconditions,often invokedas thecauseoffaunisticchanges. AtCastel Por-
zianointhelastthirty yearsseveralponds haveshiftedfrompermanen1to temporary,
but somealsofrom temporarytopermanent,so thatitis difficultto establishifthere
hasbeenanoverallmodificationofthe permanenceofthewater ontheestate. Exam-
ining the rangesof thechanged species, the threenew species occur throughout Italy
orevenmoreabundantly intheNorth.TheabsenceofA. cyanea,andL. quadrimacu-
lata,present insouthernItaly only atsomeelevations (CARCHINI&ROTA, 1986),
coupled withtheappearanceofthesouthernT.annulatawhichhas its northernlimitin
Tuscany (TERZANI, 1991),mightbeinterpretedas anorthwardshift, duetowarmer
TemporalvariationinanOdonataassemblage 165
climaticconditions.Therefore,taking also intoconsiderationthatthelattertwo species
wereoccasionalatCastelPorziano, thereislittleevidencethatthefaunisticchanges at
CastelPorziano aredue toasingle environmentalfactor, such as the supposed global
warming withconsequentsubstitutionofnorthernwithsouthernspecies.
In regardtothefaunaofsingle ponds,itwas possible to comparethe 1965-1971as-
semblage with thatof 1997-1998forthePI pondonly. Inthispond thevariationwas
largelydecreasing, indisagreement withtheconclusionforthewholeestate.
SHORTTERMVARIATIONS
Theresultsofthecomparisonbetweenthe16ponds checkedin1997and1998showed
thatthenumberof species increasedinalmostalltheponds. Accordingly, alsothedis-
tributionofthespecies increased,evenifnotas much.Onthetheotherhand,nosignif-
icantdifferencewas foundbetweenodonatefaunaofponds thatdid,ordidnotdry out
in 1997.Itseems, thattheadultswereinsensitivetothe dryingout in1997.Thedrying
outofpondsoccurredinlatesummer, whenmostofthespecies hadalreadypassed then-
reproductive period. Noinformationisavailableonthefateofthelarvalpopulations in
thedriedout ponds. Somespecies canhavea diapause attheeggstage,theeggbeing
abletosurvive thedrying out.Thisisthecase inA.mixta, L.barbarus,L. virens, Chal-
colestes, S. striolatum, S. depressiusculum, S. sanguineum (seeCORBET, 1999,tab.
A.3.5)andprobably also inS.meridionale.Fortheremaining species weshouldexpect
thedeathofthelarvae,butrecentobservationssuggestthatsomenon-diapausing species
mightbeabletosurvive thedrought, as eggsorlarvae, forsomeweeks: viz.I.elegans
(MOORE, 1991),andL. depressa(citedby severalauthors),andperhaps C.puella(see
CORBET,1999,tab.A.6.5andp. 191).Inanycase, the drought shouldhavecauseda
decreaseinthenumberofspecies inthefollowingyear.However,in1998thiswasnot
thecase. Wecanconclude,therefore,thattherewereseveralre-colonizationevents,in
agreementwiththeobservedspecies increaseintheponds studied,andthatthemajor-
ityoftheCastelPorzianospecies atadultstageare unabletoassess whetherapondhad
driedout intheprevious year,orthey are unawareofthefact.
ADULTDISPLACEMENTANDLONGEVITY
There-sightings showgreatdifferencesamongthespecies,butingeneralthere-sight-
ing frequencies are lowerthanthosereportedby UTZERI et al.(1976, 1984,1988) for
CastelPorzianopopulations ofL.barbarusandL.virens,andbyCONRAD etal.(1999)
forseveralZygopteraandAnisoptera species.Anescapereaction, duetomarkingstress,
whichmighthaveinducedsomeindividualstoflyoutoftheestate,cannotbeexcluded.
This mightbethecase intheAeshnidae,ofwhichonly twoA.affinis werere-sighted
outof44marked specimensoffourspecies. Themarked aeshnidspecimens quickly
flewintothesky,outofsight,immediately afterrelease.Anotherfactorreducingthere-
sightingmaybethecheckroutine.Eachmarkingpondwas checkedaftertwoweeks,so
166 G.Carchini,T.Pacione,C.Tanzilli,M.DiDomenico&A.Solimini
thatthemarkedspecimens weresubjecttoacertainmortalityratebeforethenext check
inthesamepond. Since,basedonourevidenceandonliteraturedata(CONRAD etal.,
1999),itseems thatthemostinidividualsdidnot move fromthemarking pond, these
two factorsreducedthe numberofre-sighted specimens, especially ifcompared with
thestudiesinwhichalsothemarkingpondswerecheckedcontinuously afterthemark-
ing.Thisfact shouldbeparticularly important intheCoenagrionidae, whoseindividual
reproductive periodlastsaboutoneweekonaverage(seeCORBET,1999,tab. 8.12).It
isalsoprobable thatourdispersal rateswouldhavebeenlargerifwehadalsobeenable
toassess themaidenflightorthepre-reproductive period movements. CONRADetal.
(1999)showedsimilardispersal ratesbetweenteneralandmature individuals.
Themajority ofthe specimens re-sighted outofthe marking pond werere-sighted
inponds whichwereabout100maway. This distanceis withintherangeofthecom-
mutingmovementofseveralspecies. However,theOdonataappeartobeabletoreturn
tothesamespot, ifthey “want” (seetheexamples inCORBET, 1999).Consequently,
theobserveddisplacements shouldbeconsideredmigrationflightsevenwherethedis-
tancescoveredwereshort.Ahigh dispersal atsmalldistancesis inagreement withan
exponential negative correlationbetween distance and dispersal rate,as reported by
CONRAD etal. (1999). However,ourdatashowlonger displacements thanthosere-
portedinthatpaper(max. 1.2km inS.sangineum) eveninC.puellaforwhichthepre-
viousrecordwas 800m(BANKS& THOMPSON, 1985).Inallspecies, weobserved
aloweroverallre-sighting ratioin thefemales, whichwouldbeinagreementwitha
higher femaledispersal tendency. Unfortunately, thenumberof specimens re-sighted
outofthemarkingpondwas sosmallthatatestonthedifferencesbetweenmale/female
frequencies was not possible.
The philopatry oftheLestidae, highlighted already by UTZERI etal. (1976, 1984,
1988),appearsconfirmedbyourdata.Thisapplies alsotoChalcolestes, whichwasnot
studiedpreviously.
Finally, ourdataon theAnisopteralongevity inthefieldappeartoexceed themean
value (11.5 days) reported by CORBET (1999, tab. 8.12), with the exception of C.
erythraeawhichhadanalmostidenticalvalue.
CONCLUSIONS
OurobservationsindicatethattheOdonataassemblages variationintimedependson
thespatialscalefromwhichitwas investigated. Onthescaleoftheentireestate,which
canbedefinedasthemesoscale, variationover ashortterm(year) was very low,both
forthenumberofchanging species (as shownby Jaccard values)andfortheiroverall
distributionamongtheponds(as shownby Manteltest). Alsooveralong term(several
decades)thevariationwas small, although higher thanover ashortterm.Onthescale
ofasingle pond, whichcanbedefinedas thelocalscale,thevariationwas muchhigher
bothover long periods (as shownby thecomparison ofthePI assemblages), andover
shortperiods (as shownbythe Jaccardvaluesandbythesignificant increaseofspecies