Population dynamics of larval stages of Tauriphila risi Martin and Erythemis attala (Selys) in Punta Lara gallery forest, Buenos Aires, Argentina (Anisoptera: Libellulidae)

8 Pages·2000·2.7 MB·English

by  Capítulo, A Rodrigues

Odonatologica29(4):333-340 December 1, 2000
Populationdynamicsof larvalstages of
TauriphilarisiMartinandErythemisattala(Selys)
in PuntaLaragalleryforest, BuenosAires,
Argentina(Anisoptera: Libellulidae)*
A.Rodrigues+Capítulo
InstitutedeLimnología“Raúl A.Ringuelet”,Universidad Nacional deLaPlata,
C.C.712,AR-1900 LaPlata,Argentina.
Received May25, 1998/ RevisedandAcceptedMay 10,2000
Larvalpopulationsofthe 2spp. werestudied in alentic freshwaterenvironment. 13
larval instars wererecognized fromplots ofhead width and length of wing-pads.
Density,populationdynamics,age structure,flyingperiodandwinter quiescencewere
analysed. Both uni- and semivoltine individuals werefound. Microhabitat differences
were found between the 2 spp, T. risipreferring Pistia stratiotes and Hydrocotyle
ranunculoides,whereas E. attalapreferredlemnaceas. Alife tablewasconstructed for
T. risi, whichshowedmortalityratemaximaathatchingand at 10and23 months.
INTRODUCTION
Larvae of Tauriphila risi and Erythemis attala occur in permanentponds
associatedwith theRio delaPlatariverandwhichare dominatedby Pistiastra-
tiotes, Lemnagibba and Hydrocotyle ranunculoides. Other larvae of Odonata
associatedwiththesehydrophytes areAeshnabonariensis, Micrathyriaringuele-
ti,M. hipodidyma, Perithemismooma,Erythrodiplax nigricans, Lestes undulatus,
Acanthagrion lancea, Cyanallagma cheliferum, Oxyagrion terminale, Ischnura
fluviatilis andI. capreolus (RODRIGUESCAPITULO, 1996).
Larval stages of E. attala Selys and T. risi Martin were described by
RODRIGUES CAPITULO(1983, 1996).The abundanceofT risiandE.attala
recordedinPuntaLara,agallery forestneartheRio delaPlatariverwas thought
to deserve a deeper ecological analysis. Preliminary results ofthis study were
communicatedattheFirst Congress ofEntomology ofArgentina (RODRIGUES
CAPITULO & MUZON, 1987). A population of Telebasis willinki Fraser
(Coenagrionidae) was studiedatthesametime(MUZON etal., 1990).
*ILPAScientificcontributionNo 346.
334 A.RodriguesCapitulo
The aim ofthispaper is to assess the dynamics, density, age structure, annual
cycle, emergenceofadults, and demography oflarval instarsofthepredominant
species ofAnisoptera in the lenticenvironmentofPunta Lara marginal forest.
The populations considered represent the southernmost extent of the studied
species.
STUDYSITE
The studywasconducted inatemperate zoneofArgentina,inapermanentpondingalleryforest,
at 34° 47’S, 58° OTW. This site
represents arelict areanearBuenos
Aires and La Plata cities. Itis par-
tially influenced by the tides ofthe
Rio delaPlatariver and coveredby
different speciesofpleustonicvege-
tation, among which Lemnaceae,
Salviniaceae, Araceae and Um-
belliferae are predominant. These
macrophytespeciesareusedbylarvae
of Odonata as support or, insome
cases, as oviposition sites. Water
temperatures and hours ofsunlight
relevant to the study period are
Fig. 1.Temperatureofwatersamplingandnumber ofeffec- shown inFigure 1 (hoursofsunlight
tive hours ofsunlight from June 1984 to May 1985. The were provided by meteorological
values of effective sunlight are based on data from the statistics ofthe Observatory ofLa
Observatory ofLaPlatafrom 1961 to 1970. Plata: 1961-1970).
MATERIALANDMETHODS
SAMPLING.- Samplesweretaken every fifteen days overtheperiod June 1984-June 1985 in
order to estimate density.A 900cm2 square screenwith a 1.5mm mesh wasused. The screenwas
replicated4times andthe meanwascalculated. Sampleswereprocessed in the laboratorybyshaking
the vegetationin waterand then placingthe vegetationin“Berlesse” separatorsfor24hours.
Anetand 15cm diametercolanders wereused tocollectqualitativesamples.Twomanhours were
taken asthe unitofeffort.Additional samplesofwaterwerealso taken in ordertolookforfirst-stage
individuals (particularly after egg-layingperiods). Sampleswerefiltered in an Earle concentrator
(SERVICE, 1976).
Odonatematerialwasfixed in 80% alcohol and measured with aReichter binocular microscope
(0.1 mm accuracy).Samplescorrespondingtoinferiorstagesweremeasuredwiththe aid ofamicro-
meter ocularscale. Adultsofthe two speciesthatemergedfromlarvae wereidentified accordingto
RIS(1909-1919)and RODRIGUES CAPITULO(1992).
DATATREATMENT.- Instars weredetermined by plottinghead width againstinner wingpad
length(RODRIGUES CAPITULO, 1983;PICKUPetal., 1984).Kite diagramswereused tosum-
marise the total cycle ofthe twopredominantspecies ofAnisopterastudied (NORLING, 1984a,
1984b).
LIFE TABLES.- Laboratoryexperimentsweresetupwith 172first stagelarvaeofT.risi froma
femalecollected in tandemon8February 1985. Theywerebroughtupinindividual glasscontainers
Populationdynamicsin TauriphilaandErythemislarvae 335
withvegetationfromthesamesamplingsite.Thewatertemperaturewasmaintained between 15-20°C.
Larvaewerefed intheirearlierstageswithmicrocrustacean (CladoceraandCopepoda),andwithchi-
ronomids andoligochaeteworms inadvancedstages; allcollected in thesamplingarea.
Theresults of survival (lx),mortality(qx 1000)and average life expectancy (ex) wereassessed,
togetherwith abundance and duration ofeverypre-imaginalstage. The life table wasconstructed
accordingtoPOOLE (1974)andRABINOVICH(1978).
RESULTS
DENSITY.- Monthly estimatesofdensity (nr2) are showninFigure 2. E.attala
showed maximum density
values in the February-
-March 1985 period,
reaching 230nr2;valuesfor
the rest of the year were
from 50 to 100 m2. T. risi
showed a maximum value
of density in the period
July-August 1984 with a
peak at270 nr2 in July.This
Fig.2.Density ofErythemisattala and Tauriphilarisi larvae
from June 1984toMay 1985. value gradually decreased
to 10-12 m2 by February;
theminimumlevel coinciding with maximumabundanceofE. attala.
LARVAL STAGEDETERMINATION. - Larval stages ofE. attalaand T. risi were
determinedfollowing descriptions ofRODRIGUES CAPITULO (1983, 1996).
Twelve groupswere delimitedforthedifferentlarvalstagesofT.risi (Fig. 3).For
the first six stagesonly maximumhead width was consideredsince wing pads
appearonly after theF-6stage.
Thefollowingisthebest equationfortherelationship betweenwing-padlength
(WP)andheadwidth(HW);
WP=0.032 x HW2*
InWP=-3,427+2,98 X InHW
(n=104,r=0,98)
DEMOGRAPHY.- Dataobtainedfromsamples ofthetwo species over theperiod
18 June 1984to 29 May 1985were organized intheKite diagrams(Fig. 4).The
useofa logarithmic scale forhead width helped to visualise the size rangefor
eachinstarso thateachindividualcouldbeassigned reasonably accurately toits
instar.
E. attala. - In June,the larvalpopulation ofE. attalacomprised seven stages
(F-6 to F), of which F-l and F-4 were the most numerous. This agestructure
remained unchanged until August, when winter quiescence ended. During
September andOctober only individualsfrom stage F-4 to F-l were observed.
The absenceofindividualsin the finalinstar(F) inthis period canbe attributed
336 A.RodriguesCapitulo
to an early emergence of
adults. However it might
have been caused by sam-
pling error duetotheearlier
low density ofstage F indi-
viduals.Thehighestpropor-
tion of final instar larvae
occurred in November and
December, corresponding to
the beginning ofthe flying
period (Fig. 4A). Younger
larval instars (F-12 to F-7)
were observed from
January. The highest diver-
sity ofstages was observed
inFebruary andMarch.The
summeris aperiod ofrapid
growth and by April the
Fig. 3. The relationship between wingpad lengthand maxi-
mum head width ofT. risi; F toF-12: larval instars. smallest larvae were in
instar F-9. A very small
numberofindividualswere intheF-l instaratthistime.
The data shownin the Kite diagram (Fig. 4A) appear to indicate semivoltine
individualsemerging atthebeginning oftheflying period, andunivoltineindivi-
duals, which emerge immediately afterthe beginning ofthat period. Thus from
February toNovembertwo differentcohorts coexist.
T risi. - Larvae ofthis species showed an age structure similar to thatofE.
attala(Fig. 4B). Theydifferfromthelatterinthatindividualsare atstagesF-7to
F-l, over thewinterperiod, withthose in ages F-3 andF-2 dominant.The final
instarwas recordedovertheperiod November-February, whichis coincidentwith
the flying period ofthe species. Again, the implication from these data is that
semivoltineandunivoltineindividualsoccur.
SURVIVALLIFE TABLEOF T. RISI
ThemajorityoflarvaehatchedinthesecondweekofFebruary 1985.Thedura-
tionofeachlarvalstage(Fig. 5) indicatesa seriesofrapid moultsinitiallyandby
April 1985 most larvae had reachedF-7. The frequency ofmoulting tendedto
decrease afterthis. Thefirst F-I larvae occurring in March 1986andfinalstage
larvaeinOctober 1986.ThefirstemergenceoccurredattheendofJanuary 1987,
i.e. nearly 24 monthsafterthefirst larvaehatched.
Survival (lx) shows an inverse, hyperbolic relationship with time (Type III
curve ofDEEVEY, 1947). Mortality rate (q 1000) varies, withmaxima occur-
x
Populationdynamicsin Tauriphilaand Etylhemislarvae 337
Fig.4. Kite diagramsshowingheadwidth frequencydistributions duringthe samplingperiod.The
areasenclosed bybroken linesshow theprobabledevelopmentof(A)E. attala and(B)T.risicohorts.
ring athatching, andat 10and23months.Average lifeexpectancy(e )increases
x
slightly over the first 12 monthsand thenshows asteady declineover the fol-
lowing 12months(Fig. 6).
338 A. RodriguesCapitulo
Fig. 5.Monthlyabundance and duration ofthepre-imaginalstagesofT.risi.
DISCUSSION
(1) Thebiological cycle ofE. attala and T. risi are similar inour study. The lar-
valpopulation ofthetwo studied species containedsome individualswith an
annualcyclewith onlyonewinterquiescence period; themajority completed
thecycle in two yearswith two winterquiescence periods (first: F-5 to F-2;
second: F-l toF). In the lattercase, the emergenceofthe images tookplace
atthebeginningofthenext flying period. Probablybothspecies havea facul-
tative diapause in order to regulate their larval and adult populations. 13
instars (not including prolarva) were found in both species (RODRIGUES
CAPITULO, 1983). This number is frequent at other latitudes(JOHANS-
-SON & NORLING, 1994).
(2) InitialstagesofT.risi(F-12 to F-8) were not recordedprobably duetothefact
thatthey inhabita differentlayer thantherest ofthepopulation.
(3) The flying and egg-laying periods are the same in both species. Although
images ofT. risi were recordedby theend ofSeptember, thesewould have
been inmigrants from other populations, since at that sampling time there
were no specimens in the last larval stage. There are no other studies of
Anisoptera ofSouthAmericato comparedifferencesin life cycles. MUZON
etal.(1990) describedalarval population ofTelebasis willinkiand observed
anannualcycle, a high rateofsynchronisation andunivoltinespecimens.
(4) Asimilarmicrodistributiontothatobserved inthispaperhasalsobeenfound
Populationdynamicsin TauriphilaandErythemislarvae 339
Fig. 6. Life table curves ofthe experimentalpopulation ofT.risi; survivorship(lx), average life
expectancy (ex) and mortality(qx1000).
in Chascomus pond (province ofBuenosAires, Argentina) where E. attala
was found inlemnaceas while T. risi was found particularly in Ceratophyl-
lum demersumRODRIQUES CAPITULO (1983). Probably the differences
are theresult ofcompetitive interactionsand permit the coexistence ofthe
two species inthesame area.
ACKNOWLEDGEMENTS
IamgratefultoDrG.JURZITZA,DrA.MARTENS andDrE.POLLARD forvaluable comments
onearlydraftsonthis article. Ithank DrJ.MUZ6Nforassistance in the field.
REFERENCES
DEEVEY,E.S., 1947.Life tables fornaturalpopulationsofanimals. Q. Rev. Biol. 22(4):283-314.
JOHANSSON, F.&U.NORLING, 1994.Afive yearstudyon thelarvallifehistoryofCoenagrion
hastulatum (Charpentier) and C. armatum (Charpentier) in northern Sweden (Zygoptera:
Coenagrionidae).Odonatologica23(4): 355-364.
MUZON, J„ A. RODRIGUES CAPITULO & G. JURZITZA, 1990, Populationsdynamik von
Telebasis willinkiFraser, 1948 im Galerie-Wald des Rio de la Plata bei Punta Lara,
Argentinien(Odonata:Coenagrionidae).Opusc.zool.flumin.53: 1-10.
NORLING, U., 1984a.Lifehistory patternsinthe northernexpansionofdragonflies.Adv. Odonatol.
2: 127-156.
NORLING, U., 1984b. The lifecycle and larvalphotoperiodicresponses ofCoenagrionhastulatum
(Charpentier)intwoclimatically differentareas(Zygoptera;Coenagrionidae).Odonatologica
13(3):429-449.
POOLE, R.W.,1974.Anintroduction toquantitativeecology. McGraw-Hill-Kogakusha,Tokyo.
340 A.RodriguesCapitulo
PICKUP, J., D.J. THOMPSON & J.H. LAWTON, 1984. The life history of Lestes sponsa
(Hansemann):larval growth(Zygoptera;Lestidae).Odonatologica13(3):451-459.
RABINOVICH, J.E., 1978. Ecologiadepoblacionesanimates. Org.Am.States,Washington,D.C.
RIS,F., 1909-1919. Libellulinen monographischbearbeitet. Colins zool. deSelysLongchamps9/16:
1-1278,pis 1-8excl.
RODRIGUES CAPITULO,A., 1983. DescriptiondelosestadiospreimaginalesdeErythemisattala
Selys(Odonata: Libellulidae).Limnobios, 2(7);533-548.
RODRIGUES CAP1TULO,A., 1992. LosOdonatadela RepublicaArgentina(Insecta).Fauna Agua
duke Argent. 34(1):1-91.
RODRIGUES CAPITULO,A., 1996. Descriptionofthe larvaofTauriphilarisi Martin (Anisoptera:
Libellulidae).Odonatologica25(4):391-395.
RODRIGUES CAPITULO,A.& J.MUZ6N, 1987. Dinamica poblacionalde etadios preimaginales
deOdonata enambientes lenticos de la selva marginal dePuntaLara (Prov.Buenos Aires).
Resum. Congr. arg. Ent.,Tucuman,p. 55.
SERVICE,M.W., 1976.Mosquitoecologyfieldsamplingmethods. Appl.Sci. Publishers,USA.