Table Of ContentOdonalologica27(2): 239-248 JuneI. 1998
SHORTCOMMUNICATIONS
TheAmazonianCampinadragonflyassemblage:
patternsin microhabitatuseandbehaviour
ina foraginghabitat(Anisoptera)
P.DeMarco
DepartimentodeBiologiaGeral,Universidade Federal deViçosa,
BR-36571-000 Viçosa,Minas Gerais,Brazil
e-mail: [email protected]
Received March 18, 1997/RevisedandAccepted October4, 1997
TheAmazonian Campinaisawoodland,withemergent treesofabout 10m,found
inpatchesinthe Amazonianrain forest. Itusually has open areaswith awhite sand
soil directlyexposedtosun, andshaded areaswithamoredensevegetation.Isampled
the dragonflyassemblagein this system countingevery dragonflyatpre-determined
points,at5minintervals,between7:00and 18:00h.Erythrodiplaxlativittata, Miathyria
marcella and Erythemisvesiculosa were the most abundant spp. The frequencydata
by pointrevealed anassociation ofE. lativittata(percher)with shadedhabitats,and
M. marcella and E. vesiculosa (fliers) with open habitats. The characteristics of
thermoregulationoffliers andperchers seemto explainthis microhabitat selection.
Due tohighproductivity and density ofsmallinsects, the Campinais probablyan
excellent habitatforforaging.Itissuggestedthat intheseforaginghabitats the spatial
species arrangement is mostly determined bybehavioural-physiologicaltraits,which
may helptoexplainthe communityfaunal composition.
INTRODUCTION
Behaviouris animportant componentoffitness(SCHALL&PIANKA, 1980;
WCISLO, 1989;ALCOCK, 1994) andcan alsoinfluencethe species distribution.
Sexual behaviour (e.g. ALCOCK, 1982, 1987a, 1987b; PARR, 1983) and
thermoregulatory behaviour(MAY, 1977, 1980) havebeen intensively studiedin
odonates.Basedonthermoregulatorybehaviour,CORBET(1962) classifiedodonate
species intofliers, thatstayonthewing alarge proportion oftheactivity time,and
perchers, that remainperched on manykinds ofsubstrata. Perchermalesarecom-
monlyfounddefending territoriesnearwaterbodieswhilefemalesareawayforag-
ing and goto wateronly to mateandoviposit (CORBET, 1962).
240 P.DeMarco
Many recent works suggestthatfliersareendothermicand can warmtheirbod-
iesby wing muscleactivity and coolby thorax-abdomenheat exchange and wing
whirling (HEINRICH & CASEY, 1978; MAY, 1991, 1995). Otherwise, the
ectothermic perchers, can control body temperature by posture adjustments,
microhabitatselectionandactivity time shifts(MAY, 1979).
Adultodonate assemblages are poorly known,although severalbehaviouralor
communitystudieshadbeenperformed nearaquatic habitats(e.g. MOORE, 1964;
ALCOCK, 1987a; JOHNSON & CROWLEY, 1989; POLCYN, 1994). In these
habitats, competition between species forterritory patches and a directcompeti-
tionbetween males for females arereadily acknowledged. Otherwise, far away
fromthewater,whereodonate species are commonly observedforaging, there is
nostudy to myknowledge atthecommunity level.
In the foraging habitats, the differencesin thermoregulatory mechanismsbe-
tween fliersandperchers shoulddeterminetheuseofdifferentmicrohabitats.Ifso,
thespatial arrangementofthesespecies willbe mainly determinedby theirbehav-
ioural-physiological characteristics. As a consequence,ifresource competition is
importantbetween adult dragonflies in foraging habitats, it must be higher be-
tweenspecies belonging tothe samebehaviouralgroup.
TheAmazonianCampina is aforestvegetation foundin patches inside thefull-
grown tropical rain forest in Brazil (ANDERSON et al., 1975; SANTOS &
RIBEIRO, 1975).Ithasonestratum withcanopyatabout7-10mandawhitesand
soil.Thisinterruption oftheforestcanopycreates anexcellentopportunity tostudy
theassemblage offorest-dwelling odonates.Many species observedtherearealso
present in the canopy whereecological and behavioural studies are not easy to
perform. In theseareas thetemperature canrise to 38°C (RIBEIRO&SANTOS,
1975)andpossibly represent athreatto dragonfly activity.
Inthis paper,I searchedfor patterns inthe odonateassemblage oftheAmazo-
nianCampinatestingfortherelationbetweenbehaviourandthemicrohabitatpref-
erences. Fromthisstanding point, Ialsodiscuss howbehaviouraldifferencesaffect
community organization inforaging habitats.
METHODS
The studyarea wastheSuframa-INPA reserveatthe ManausCaracarai roadkm 62.this areawas
studied byANDERSON et al.(1975)who classifiedthe vegetationaltype asopen Campina,shaded
Campina,andCampinarana.The open Campinahas alow shrubvegetation(upto 2 m)and asparse
coveroftrees,mainlySandemaniahoehnei(Cogn.)Wurdack(Melastomataceae)upto5m. Thereare
largeareasofwhite sand dominated by Cladonia lichens. The shaded Campinaareclusters oftrees,
mainlyAldina heterophyllaSpr.(Leguminosae)andGlycoxyloninophyllum(Mart.)Ducke(Sapotaceae),
withacoveroflitteronthe sandfloor.The trees have heightsupto 10m. TheCampinaranahas trees
often higherthan 10m,is denserthanthe shadedCampinabut withsimilarspeciescomposition.
All observations reportedhere were madeinthe shadedandopenCampinaandinthe boundary
between shadedCampinaand Campinarana.A point-samplemethod was designedto determine the
spatialvariation inodonatespeciesrelative abundanceandbehaviour.Iestablishedpointsand counted
Amazonian Campinadragonflyassemblage 241
everydragonflywithadistanceof5in fromtheobserver,at5 min intervalson 5 days.All observa-
tionswerebetween7:00and 12:00andbetween 14:00and 18:00suntimeinAugust 1993.There were
atotalof36hours offield observations, discountedthemoments ofheavyrains andmovementfrom
outside ofthe study areatocapture individuals forspecies determinations. Ateach pointIrecorded
eachspecies,itsabundance,thebehaviour ofeach individual,andestimateheightbycomparisonwith
ameasuredobjectneartheobserved dragonflyordragonfly group.Someindividualswerecollected
andI measuredthe distance fromthe base tothe tip ofthe right anterior wing.Inthe study areaI
sampledatotalof57points,39inopenand 18in shadedCampina.Thepointswerescatteredwithno
clearpatterninthearea.Imoved amongthepointsinasystematic mannertodistributethesampling
efforttoeachpointequallyatalltimesofthe day.
I classified the species as fliers orperchersaccording toCORBET (1962). The behaviour was
classifiedasfollows:
(1) normal perching;
(2) droop-wingedperching: thewing-tipsareheld belowthebody and/orthe wingsshadethethorax;
(3) patrolling:flyingbackandforththroughanarea;
(4) transition flight:passing throughanareawithoutpatrolling;
(5) agonistic interaction: chasing anotherindividual.
RESULTS
Iobserved 16odonatespecies (15Libellulidaeand 1Corduliidae)intheCampina,
with 14in openand9in shadedmicrohabitats(Tab. I). Erythrodiplax lativittata.
Erythemis vesiculosaandMiathyriamarcelladominatedbothassemblages. Icould
notcaptureallobserved individualsofZenithoptera.As atleastthreespecies occur
Table 1
Mean Anisoptera abundance in open and shadedCampina(standarddeviationsinbrackets). - [The
behavioural classification isaccordingtoCORBET (1962);F-fliers,- P-perchers]
BBeehhaavviioouurraall
SSppeecciieess OOppeennCCaammppiinnaa SShhaaddeeddCCaammppiinnaa
ccllaassssiiffiiccaattiioonn
EErryytthhrrooddiippllaaxxllaattiivviittttaattaa BBoorrrroorr Pp 00..225599 ((00..223399)) 00..555577 ((00..220099))
EErryytthheemmiissvveessiiccuulloossaa((FFaabbrr..)) FF 00,.227744 ((00..226688)) 00..006600((00..110044))
MMiiaatthhyyrriiaammaarrcceellllaa ((SSeell..)) FF 00..222233 ((00..228811)) 00..008888 ((00..220044))
TTrraammeeaaccaallvveerrttii MMuuttttkkoowwsskkii FF 00..003333 ((00..008866)) 00..001122 ((00..005533))
IIddiiaattaapphheesspp.. PP 00..003311 ((00..007766)) 00..000000 (( -- ))
BBrraacchhyymmeessiiaahheerrbbiiddaa ((GGuunnddllaacchh)) FF 00..001144 ((00..004499)) 00..001166 ((00..006688))
EErryytthhrrooddiippllaaxxuummbbrraattaa ((LL..)) PP 00..000099 ((00..003300)) 00..001199((00..005544))
EErryytthheemmiisshhaaeemmaattooggaassttrraa((BBuurrmm..)) PP 00..000000((00..000000)) 00..002233 ((00..007722))
ZZeenniitthhoopptteerraasspppp.. PP 00..001155 ((00..005555)) 00..000000 (( -- ))
TTaauurriipphhiillaasspp.. FF 00..000000 ((00..000000)) 00..001122 ((00..005533))
MMiiccrraatlhhyyrriiaasspp.. PP 00..000088 ((00..003333)) 00..000000 (( -- ))
AAeesscchhnnoossoommaa aauurriippeennnniissGGeeiijjsskkeess FF 00..000077 ((00..004466)) 00..000000 (( -- ))
MMiiaatthhyyrriiaassiimmpplleexx((RRaammbb..)) FF 00..000066 ((00..002255)) 00..000000 (( -- ))
EErryytthhrrooddiippllaaxxsspp.. PP 00..000022 ((00..001100)) 00..000044 ((00..001199))
PPaannttaallaaffllaavveesscceennss((FFaabbrr..)) FF 00..000055 ((00..002211)) 00,,000000 (( -- ))
UUnniiddeennttifiifeieddLLiibbeelllululildidaaee ?? 00..000044 ((00.,002255)) 00..000000 (( -- ))
242 P.DeMarco
inManaus ((.Z.americana, Z. anceps, Z. lanei). SinceIwas unableto distinguish
betweenthemduringobservationalsampling, Itreatedtheobservedindividualsas
Zenithoptera spp.
Sex ratioestimatedfromcaptured individualswas biasedtowardfemales forE.
lativittata(cJ/9=0.047; n=89)andE. umbrata(only 9 captured; n=7).Iobserved
both androchromaticandnormalfemalesandgynochromatic andnormalmalesof
E. lativittata.
Aeschnosomaauripennis (Corduliidae)appeared only onceintheopenCampina
duringsampling, but Icaptured two individualsintheboundary betweenshaded
CampinaandCampinarana. Theseindividualsflewat2-3minpatrollingactivities,
suggesting aflierbehaviour.
Theproportionoffliersandperchers wasnot differentbetweenopenandshaded
habitats(Fisher exacttest,p=1.000) with54.5%(95% confidenceintervalassum-
ingbinomialdistribution:28.1to77.0%)offlierspecies and45.5%(20.7to69.4%
ofpercher species.
The smallest species was Z. americana(21.6 mm front wing) andthe largest,
was Trameacalverti (45.6 mm).The fourlargestspecies werefliers buttherewas
no clearsize discriminationbetweenfliersandperchers; thesmallM. simplex and
M.marcellaarefliersandthemediumsizedE. haematogastra isapercher(Fig. 1).
To comparethepatternsof
habitatuse Itested dragonfly
frequency at points in open
and shaded Campina only
whenIobserveda species at
leastten times.Threespecies
showedasignificant associa-
tion with open sites: M.
marcella (in 64.1% of the
open sites and 27.8% of
the shaded sites; x2=6.5I8,
P=0.011), E. vesiculosa (in
69.2% ofthe open sites and
27.8 in shaded sites;
X2=8.595,P<0.001)andIdia-
taphe sp. (in 20.5% of the
open sites and absent in
Fig. I.Mean front wingsize inthe Anisopteracapturedin shadedsites; Fisherexacttest,
Amazonian Campina (bars show standard deviations).The p=0.046). T. calverti was
value for Z. americana is from asingle individual captured found in 20.5% ofthe open
neartheCampina.M. simplexand B. herbida alsorepresent
sites, to 5.6% ofthe shaded
individuals captured outside the study area. Idiataphesp.,
Tauriphilasp.,Micrathyriasp.andanunidentifiedLibellulidae areas but this differencewas
werenotmeasured. not statistically significant
Amazonian Campinadragonflyassemblage 243
(X2=2.072, P=0.I50). Only E.
lativittatashowed a significant asso-
ciation with shaded areas (100% in
shadedand 79.6% in openCampina;
Fisherexacttest,PcO.OOl).
Basedonflightorperchheight, there
is a clear distinction between
Erythrodiplax species (E. lativittata
and E. umbrata), usually perched at
about1 m,andtheotherspecies (Fig.
2).Idiataphe sp. perched mainly at5
mandwas observed foraging making
short verticalflightsinopenCampina.
T.calverti, M.marcellaandE. vesicu-
losaflewatabout 3.5-4.5 m(Fig. 2).
Of the species recorded at least 6
timesE. lativittata, E. umbrata, Idia-
taphe sp.andZenithoptera spp.remain Fig. 2. Mean Anisopteraperch orflightheightin
perched for thegreat majority ofthe Amazonian Campina(bars show standard devia-
time; E. vesiculosa, M. marcellaand tions). Specieswithsameletters werenotstatisti-
T calverti patrolled more than they cally different atp=0.05 in ana posteriori Tukey
MSDtest.
perched (Tab. II). Chasing was ob-
served for thethree most abundantspecies (E. lativittata, E. vesiculosaand M.
marcella)andforMicrathyria sp. Nobehaviourthatcouldbeconsideredrelatedto
reproductive activities was observed.
Iobserved M. marcellaandT calvertiin swarms ofupto 10individualsontwo
occasions. IalsoobservedgroupswithM. simplex, M.marcellaandT. calverti.
Inmanymoments ofthe day somespecies takeaperchposture describedhereas
droop-winged perching, when wings are at an obtuse angle to the body line. I
observed thisbehaviour inmany species, butthe TrameinaeIdiataphe sp. andT
calverti, andalso E.umbrata, donot seemtotakethispostureunderthetempera-
ture profiles ofCampina (Tab.II).
DISCUSSION
There is a clearpartition betweenflierspecies using openhabitatsandpercher
species in theshaded areas. Air temperaturein open Campina can rise to 38°C
(RIBEIRO& SANTOS, 1975) and thethermoregulation is very important to in-
crease netenergy supply. MAY (1991) suggested thatthermaladaptations might
bereflectedinthecomposition ofentirefaunasand hypothesized thatinthewarm
andrelatively equable tropics theZygoptera andpercherAnisoptera mightbe ata
relative advantage. Ifound7 perchers and 8 fliers in thewholeassemblage. The
244 P.DeMarco
Table II
Frecuencyofbehavioural categories(percentsinbrackets). Ateach pointthe behaviour ofevery drag-
onfly within5moftheobserverwasrecorded during5minperiod.- [Totalsamplerepresent 36hours
offield observations, n=576]
PPeerrcchh FFlliigghhtt
SSppeecciieess NNoorrmmaall DDrroooopp--wwiinnggeedd PPaattrroolllliinngg CChhaassiinngg TTrraannssiittiioonn TToottaall
EErryytthhrrooddiippllaaxxllaattiivviittttaattaa 112266 ((8844..00)) 1100 ((66..77)) 22 ((11..33)) 66 ((44..00)) 66 ((44..00)) 115500
EErryytthheemmiissvveessiiccuulloossaa 44 ((44..00)) 33 ((33..00)) 7766 ((7755..22)) 11 ((11..00)) 1177 ((1166..88)) 110011
MMiiaatthhyyrriiaammaarrcceellllaa 33 ((44,,99)) 11 ((11.66)) 5566 ((9911..88)) 11 ((11.66)) 00 ((00..00)) 6611
IIddiiaattaapphheesspp.. 1122 ((8855..77)) 00 ((00..00)) 00 ((00..00)) 00 ((00..00)) 22 ((1144..33)) 1144
TTrraammeeaaccaallvveerrttii 33 ((2255..00)) 00 ((00..00)) 88 ((6666..77)) 00 ((00..00)) 11 ((88..33)) 1122
ZZeenniitthhoopptteerraasspppp.. 66 ((7755..00)) 22 ((2255..00)) 00 ((00..00)) 00 ((00..00)) 00 ((00..00)) 88
EErryytthhrrooddiippllaaxxuummbbrraattaa 77((110000..00)) 00 ((00..00)) 00 ((00..00)) 00 ((00..00)) 00 ((00..00)) 77
BBrraacchhyymmeessiiaa hheerrbbiiddaa 00 ((00..00)) 00 ((00..00)) 55 ((8833..33)) 00 ((00..00)) 11 ((1166..77)) 66
MMiiccrraatthhyyrriiaasspp.. 22 ((5500..00)) 00 ((00..00)) 11 ((2255..00)) 11 ((2255..00)) 00 ((00..00)) 44
PPaannttaallaaffllaavveesscceennss 22 ((6666..77)) 00 ((00..00)) 00 ((00..00)) 00 ((00..00)) 11 ((3333..33)) 33
MMiiaatthhyyrriiaa ssiimmpplleexx 33((110000..00)) 00 ((00..00)) 00 ((00..00)) 00 ((00..00)) 00 ((00..00)) 33
EErryytthhrrooddiippllaaxxsspp.. 22((110000..00)) 00 ((00..00)) 00 ((00..00)) 00 ((00..00)) 00 ((00..00)) 22
EErryytthheemmiisshhaaeemmaattooggaassltrraa 22((110000..00)) 00 ((00..00)) 00 ((00..00)) 00 ((00..00)) 00 ((00..00)) 22
AAeesscchhnnoossoommaa aauurriippeennnniiss 00((00..00)) 00 ((00..00)) 00 ((00..00)) 00 ((00..00)) 11 ((110000..00)) 11
TTaauurriipphhiillaasspp.. 00((00..00)) 00 ((00..00)) 11 ((110000..00)) 00 ((00..00)) 00 ((00..00)) I1
UUnniiddeennttiiffiieedd LLiibbeelllluulliiddaaee 00((00..00)) 11 ((110000..00)) 00 ((00..00)) 00 ((00..00)) 00 ((00..00)) I1
mostabundantspecies in thishabitatwas thepercher E. lativittata, but theother
three species thatfollowedit inabundance were fliers.It seems thateven ifthey
sufferarelative disadvantage, flierscan copewiththeseproblems andefficiently
use theCampinahabitat.
POLCYN (1994), studying anotherextreme habitatwithrespect to air tempera-
tures, the Mojave desert, did not observe any differencein activity periods or
thermoregulation abilitiesbetween fliers and perchers. Possibly both fliers and
perchers facepotentialproblems athigherair temperaturesthatconstraintheirac-
tivity(POLCYN, 1994).Duetotheobserved microhabitatselection,fliersforaged
under higherair temperatures than theperchers in Campina. Although I did not
regularly measurethetemperatures,someobservations duringnormalactivitiesof
dragonflies in openCampina show valuesranging from25-35°C. Polcyn’s study
wasdoneinabreeding poolwhereonlyreproductive activitieswereobserved while
my observations only refer to foraging activities. Further studies are neededto
understandhow differentactivities influencethermaladaptation in dragonflies.
Itis expected thatpercher species thatinhabitshadedtropical forestswillcome
tothetree topsforbasking (e.g. CLAUSNITZER, 1996).Thiswas notthecasefor
thespecies thatpreferred theshaded Campina. Dueto theparticular structure of
thishabitat, it is possible that theair temperaturehere is neartheoptima forthe
activity forthese species and sun basking is not needed.
Amazonian Campinadragonflyassemblage 245
I didnotobserve dragonflies intheobeliskposition, whichiscommonwhenthe
temperatureishigh(MAY, 1977;WILDERMUTH, 1991),presumably becausethe
percher species Iobserved were generally not directlyexposed to sun. Idiataphe
sp. was theonlypercher species exposed forlong periods to sunbecauseitused5
mtrees inopenareas. Thisspecies differsfromtheotherTrameinaethatare fliers,
andfromtheperchers thatusually used lowerstrata.Itis possible thatthepercher
behaviourinthisspecies is aderivedtraitandphysiological characteristicsshared
withotherTrameinaeleadto anintermediary statuswithhigh success.
B.herbidawasclassifiedasaflierinthisstudy despiteapercherbehaviourinthe
reproductive habitats(pers. observ.). In theforaging habitathere studiedI never
observed it perched. In the same way,this species can use urban areas (as it is
commontoP.flavescens) andIobserved manyindividualsforaging insidethecity
ofSantarem,Para, Brazil, usually exhibiting apatrolling behaviour.Furtherstud-
iesareneededtoestablishtowhatextentitsbehaviouralclassificationis afunction
ofthehabitatunderconsideration.
Which factors determinethe species composition in a dragonfly assemblage?
Dragonflies are generalist predators asadultsandlarvae andresource preferences
donot seemtobeanimportant factordetermining species composition. However,
in the larval stage, substrata preferences (including macrophyte association:
WELLBORN &ROBINSON, 1987;LOUNIBOS etal„ 1990),predation by other
dragonflies (BENKE et al„ 1982; ROBINSON & WELLBORN, 1987;
WISSINGER, 1989)andfishpredation(MORIN, 1984a, 1984b)may determineif
aspecies ispresentor not ina givenassemblage.
Here,I discuss whetheradultbehaviourisalso importantin determining species
composition using thepatterns shown intheAmazonianCampina.
This dragonfly assemblage was composed mainly ofopen-habitat long-distant
dispersers such as E. vesiculosa, M. marcella, B. herbida, P.flavescens. These
species havewidedistributionintheNeotropical region orare pantropical (DAVIES
& TOBIN, 1985). They areobservedinplantations, roads andopenhabitatsnear
thestudy area,andtheirabundancesarehigh intheCampina.T. calvertiis themost
widespread species from the ‘cophysa-group’ of Tramea, ranging from southern
United States to Rio de Janeiro, Brazil. Itis considereda migratory species in
CentralAmericaandVenezuela(DEMARMELS &RACENIS, 1982).
Ithas long been consideredthatspecies withwidedistributionsalso havelarge
mean abundances(e.g. DARWIN, 1859). BROWN (1984) suggested that species
withbroad niches will be widespread and abundant.The species offliers found
seemto beabundantand widespread butthey are dependent onthe existenceof
openhabitats.Thesespecies forage inopenCampinabutarelessfrequentinshaded
Campina where they use theemergent trees with directexposure to sun. Open
habitats like grasslands, successional patches or forest edges may alsobe impor-
tanthabitatsfortheseflierspecies. Theycanbe viewednot as habitatgeneralists,
to conformto Brown’stheory, butforagers thatuse a widespread habitat.Inthese
246 P.DeMarco
systemsitiscommontoobserveflierssuchasTrameinaespecies inforagingswarms
likethoseobservedamongM. marcella,M.simplex andT.calvertiinCampina. On
theother hand, E. lativittatawas the mostabundantspecies inCampina andwas
not observed inothernearby habitats.Femalesofthispercher species, andalso E.
umbrata, have a cryptic andsomewhat disruptive coloration in shaded habitats.
Bothspecies were commonlyobserved onshrubs atabout1 minshadedCampina
but E. lativittatawas moreofahabitatspecialist having a closeassociation with
shaded areas. Its colorationand behaviourseems to lead to a higher success in
thesehabitats.
Usually odonatefemalesspendmostoftheirtimeinforaginghabitats(CORBET,
1957;ANHOLT, 1992). The excess offemalesof E. lativittataand E. umbrata
suggest that the shaded habitatis usedfor foraging by femalesandpossibly by
recently emerged malesthatstay therebeforethey search forabreeding territory
nearwater bodies.Thegynochromatic colorationinrecently emergedmaleswould
increase thesuccess oftheseindividualshereas suggested by CORBET(1962).
Foraging habitatsare usually neglected incommunity andpopulation studiesof
dragonflies, inspiteoftheirobviousimportanceinpersistence andcomposition of
communities.Intheory, afemalethatusesahighly productive habitatwillproduce
moreeggs, mature fasterand visitthereproductive habitatmorefrequently. Inthe
sameway,itisassumedthatafteremergencemany dragonfly malesgotoforaging
habitats forafew days (CORBET, 1957, 1980).A moreproductive habitatshould
increase therate ofmaleweight gain andthen increasetheirability to maintaina
territory or go more quickly to thereproductive habitats.With highersolar inci-
dence, theCampina couldbemoreproductive, maintainarich shrubfloraattrac-
tive toinsects, andthenanexcellentforaging habitatforthese dragonflies.
The argument above suggests that natural selection on adult dragonflies will
favorbetterforaging habitatselectionandmechanismsthat increaseefficiency in
thesehabitats.ThecolorationoftheErythrodiplax femalesfromCampinasuggests
that predation couldbe an important selective factor in these foraging habitats.
But, inamore general view, behaviouraladaptations associatedwithmicrohabitat
selectionare the moreimpressive characteristicofthisassemblage.
PIMM (1991) writes: “A community is consideredto have structure or to be
patterned ifthe species it contains are a nonrandom subset ofthose that could
occur init”. Ecological communitiesare commonly viewed as asetof“compat-
ible”species sampledfromaspecies poolby theircompetitiveabilities(DIAMOND,
1975;CASE, 1990;DRAKE, 1990)orasetofspecies thatco-occur by theirnested
spatial distributiondeterminedby thetolerancesandefficiency to a given abiotic
gradient (GLEASON, 1926;ANDREWARTHA &BIRCH, 1954).The ‘sampling’
process thatproduced theAmazonianCampina dragonfly assemblage seems tobe
conveniently describedby behavioural-physiological characteristicsthatareasso-
ciatedwith microhabitatpreferences. In this generalist predator assemblage one
mightexpectthat resource-partitioning shouldbeachievedby spatial organization
Amazonian Campinadragonflyassemblage 247
due to territorialdisputes or microhabitatselection.Disputes forforaging space
werearareeventamongthefliers(E. vesiculosaandM.marcella)andthepercher
E. lativittata.Theseobservationssuggestthatthisassemblage offoraging organ-
ismsshouldbeconsideredanon-interactivesystemwithoutresource monopoliza-
tionor strongcompetitive interactions.
ACKNOWLEDGEMENTS
This work was doneduringthefirst courseofthe “Ecology ofAmazonian Forest” organizedby
Universidade Estadual de Campinas (UNICAMP), Institute de Pesquisas da Amazonia (INPA-
-MANAUS),OrganizationforTropicalStudies(OTS) andtheSmithsonianInstitute.Iam gratefulto
WOODYBENSON andBRUCEWILLIAMSON,who encouragedmetodevelopthis work. Iamalso
greatlyindebted toA.B.M.MACHADO, J.H.SCHOEREDER, E.F.MORATOand M.A.MELO,who
readanearlydraftofthemanuscript.
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