Effects of constant and fluctuating temperatures on development and reproduction of Megoura crassicauda and Aphis craccivora (Hemiptera: Aphididae)

2018·0.39 MB·

by  Li-Yuan Cheng

©EntomologicaFennica.19March2018
Effects of constant and fluctuating temperatures
on development and reproduction of Megoura crassicauda
and Aphis craccivora (Hemiptera: Aphididae)
Li-YuanCheng,YanZhang,Zhen-ZhenChen&Yong-YuXu*
Cheng,L.-Y.,Zhang,Y.,Chen,Z.-Z.&Yong-YuXu,Y.-Y.2018:Effectsofcon-
stantandfluctuatingtemperaturesondevelopmentandreproductionofMegoura
crassicaudaandAphiscraccivora(Hemiptera:Aphididae).—Entomol.Fennica
29:1–12.
Theinfluenceoffluctuatingtemperaturesonthedevelopmentandfecundityof
twoaphids,MegouracrassicaudaMordvilkoandAphiscraccivoraKoch,were
determinedbycollectinglifetabledataataconstanttemperature(22°C)andtwo
fluctuatingtemperatures(22±3°Cand22±5°C).ThelongevityofM.crassi-
caudadecreasedsignificantlyat22±3°Cand22±5°C,whiletherewasnosig-
nificantdifferenceinthelongevityofA.craccivoraamongthethreetreatments.
Thefecundityandintrinsicrateofincrease(r)ofM.crassicaudadecreasedsig-
nificantlyatbothfluctuatingtemperatures,whileA.craccivorashowedtheop-
positetendency.Theseresultsshowedthatthefluctuatingtemperatureshadneg-
ativeimpactsonthelifehistorytraitsofM.crassicauda,butwerebeneficialfor
A.craccivora.Dataobtainedunderconstanttemperaturesmaynotrevealaccu-
ratelyenoughthebioticresponsesofpestsinthefield.
L.-Y.Cheng,Y.Zhang,Z.-Z.Chen&Y.-Y.Xu,DepartmentofEntomology,The
CollegeofPlantProtection,ShandongAgriculturalUniversity,No.61Daizong
Street,Tai’an,ShandongProvince,271018,China;*Correspondingauthor’se-
mail:[email protected]
Received2December2016,accepted21February2017
1.Introduction ment (Trudgill et al. 2005). Many researchers
conducttheirstudiesunderconstanttemperature
Biological control measures have been increas- conditionsthathavelittle,ifany,variation.Con-
inglyadoptedworldwideasanalternativemeans sequently, their reports on various insect activi-
of pest management. Knowledge of insect and tiesarebasedonobservationsmadeunderunfluc-
miteadaptationsto climaticconditionsplaysan tuatingtemperatureconditions.However,fluctu-
essentialroleinbiologicalcontrol,specificallyin atingtemperaturesaremorerelevantecologically
helpingtopredicttheemergenceofpestsandthe as compared to thetemperatures that organisms
scientificassessmentandapplicationofbiologi- actually experience daily and seasonally in the
cal control agents (Hoelmer & Kirk 2005). As field(Lamb1961,Hagstrum&Hagstrum1970)
ectothermicorganisms,thedevelopmentandfe- and in greenhouses (Tantau 1998, Pollet et al.
cundityofinsectsandmitesarelargelydependent 2009).Infact,manybiologicalcharacteristicsof
onthetemperatureoftheirsurroundingenviron- insect and mite species, including body size
2 Chengetal. (cid:127) ENTOMOL.FENNICAVol.29
(Beck 1983, Bahar et al. 2012), survival rate minetheinfluenceoffluctuatingtemperatureson
(Colinet et al. 2006 & 2007, Carrington et al. thebiologicalparametersofthesetwoaphidspe-
2013, Gotoh et al. 2014), developmental time cies.
(Niedereggeretal.2010,Chenetal.2013),sex
ratio(Vangansbekeetal.2013),femalefecundity 2.Materialsandmethods
(Hagstrum & Leach 1973, Carrington et al.
2013), population growth rates (Mironidis & 2.1.Stockcultures
Savopoulou-Soultani 2008, Vangansbeke et al.
2013)andimmunefunction(Karletal.2011)can BothM.crassicaudaandA.craccivorawereob-
differgreatlywhenorganismsarerearedatfluc- tained from the Institute of Plant and Environ-
tuating temperatures compared to constant tem- mentalProtection,BeijingAcademyofAgricul-
peratures.Themechanismsresponsibleforthese ture and Forestry Sciences, Beijing, China in
developmentaldifferencesthatoccuratfluctuat- 2009 and reared on broadbean (var. “Chongli”)
ing versus constant temperatures are not com- plants that were approximately 20 d old. The
pletely known (Worner 1992, Liu et al. 1995, broadbeanplantsweregrownin12cmdiameter
Vangansbekeetal.2015). plasticpotsusingasoilmix(peatmoss:perlite=
Broadbean(ViciafabaL.)isanimportantle- 3:1),andwateredandfertilizedasneeded(Com-
gume crop and its planting area in China from post,COMPOExpertGmbH,Germany).TheM.
1961to2014hasgenerallybeenthewidestinthe crassicauda, A. craccivora cultures, and broad-
world(FAOSTAT,2017).Megouracrassicauda bean plants were kept in a controlled-climate
Mordvilko (= M. japonica Matsumura) and the roomat22±1°C,60±5%RHandthephoto-
cowpeaaphid,AphiscraccivoraKoch(Hemipte- periodof15:9(L:D)h.
ra:Aphididae),arekeypestsofbroadbean,often
causing serious damage (Singh & Van Emden
2.2.Experimentalsetup
1979,Zhouetal.1996,Obopile&Ositile2010).
Megoura crassicauda is an oligophagous aphid ThemeteorologicaldataforthecityofTai’andur-
which feeds selectively on Vicia plants such as ingMayoftheyears2010to2015wereprovided
broadbeanandnarrowleafvetch(Viciaangusti- by the China Meteorological Administration
foliaL.)(Fabaceae).Itsbodylengthofapterous (Fig.1a).Duringthoseyears,theaveragetemper-
adult can reach 3.7 mm. Aphis craccivora is a atureinMaywas21.6°Candtheaveragemaxi-
worldwidekeypestofleguminouscropsandveg- mum and minimum temperatures were 27.7 °C
etables. It has a host range of 200 species of and 15.6 °C, respectively. Before starting our
plants, leguminous and others, and can spread study, we considered several test conditions
more than 50 plant viruses (Stoetzel & Miller foundinliterature,andfoundthatbyHtweetal.
2001).Inbiologicalcontrol,thetwoaphidshave (2013)mostsimilarwiththedailymeteorological
beenusedasnaturalpreyforyear-roundculturing dataofTai’aninMay.
of enemy insects under laboratory conditions Tosimulatetheeffectoftheabovefluctuating
(Gongetal.2006,Chenetal.2013).Understand- fieldtemperaturesonthedevelopmentandfecun-
ingtheeffectsoffluctuatingtemperaturesonthe dityofM.crassicaudaandA.craccivora,acon-
survival, development and reproduction of M. stant temperature (22 °C) and two fluctuating
crassicauda and A. craccivora are crucial for temperatures(22±3°Cand22±5°C)wereused
forecasting, managing and taking advantage of in this study. The amplitudes of the fluctuating
thesetwopests. temperatureswere6°Cand10°C,respectively.
The life table is an important tool for deter- Thefluctuatingtemperatureswerechangedevery
miningbiologicalcharacteristicsandpopulation 6hfromeitherthelowervalue(Tlow,22°Cmi-
growthofpestsundercertainenvironmentalcon- nushalfoftheamplitude)ortheuppervalue(T ,
up
ditions(Bellowsetal.1992,Yuetal.2013).In 22°Cplushalfoftheamplitude)to22°C,but,in
thisstudy, wecollectedandcomparedlifetable doing so, the average daily temperature was
dataofM.crassicaudaandA.craccivoraunder maintainedat22°C(Htweetal.2013).Thetem-
constant and fluctuating temperatures to deter- perature was increased or decreased at a rate of
ENTOMOL.FENNICAVol.29 (cid:127) Temperatureeffectsontwoaphidspecies 3
Fig.1.–a.Highestand
lowesttemperaturesin
Tai’anareainMayin
2010–2015.–b.Simu-
latedfluctuatingtem-
peraturesoftempera-
turetransitionregimes
duringtheexperiments;
photoperiodicityisalso
presented.
0.5°C/minandwascompletedin10min.Forex- trolledartificialclimatechambersunderthe15:9
ample, thetemperatureregimein the22 ± 3 °C (L:D)hphotocycle(2,000lux)andthe70±5%
treatmentwas19,22,25and22°Cduring00:00– relative humidity. The life table experiments on
06:00, 06:00–12:00, 12:00–18:00 and 18:00– M. crassicauda and A. craccivora were con-
24:00, respectively (Fig. 1b). The thermal error ductedbyplacinga2–3weekoldstemofthepre-
was0.5°C.Thephotoperiodwas15:9(L:D)h, floweringbroadbeanplant(5cmlength)ineach
daylight hours were programmed for 06:00– Petridish(9.0cmdiameter,3.0cmheight),along
21:00.Therelativehumiditywas60±5%ateach with a moistened cotton ball to keep the
temperatureregime. broadbeanleavesandthestemfresh.Theplants
were replaced with fresh ones when necessary
(2–3 d). Although we used stem segments, the
2.3.Lifetablestudy
abovemeasureswereadequatetokeepthemfresh
Inapreliminarytest,insectswererearedattem- fortherelativeshorttimeof2–3d.Wedonotei-
peraturesof22°C,22±3°Cand22±5°Cincon- ther consider transferring the aphids from plant
4 Chengetal. (cid:127) ENTOMOL.FENNICAVol.29
Table1.Developmentaltimeandfecundity(mean±SE)ofMegouracrassicaudaandAphiscraccivoraatcon-
stantandfluctuatingtemperatures.
Parameter 22°C 22±3°C 22±5°C
Firstinstar(d)
M.crassicauda 1.7±0.1a* 1.7±0.1a* 1.7±0.1a*
A.craccivora 2.0±0.0a* 1.4±0.1b* 1.4±0.1b*
Secondinstar(d)
M.crassicauda 1.6±0.1a* 1.4±0.1b* 1.5±0.1ab
A.craccivora 1.1±0.1b* 1.1±0.1b* 1.4±0.1a
Thirdinstar(d)
M.crassicauda 1.7±0.1a 1.7±0.1a 1.6±0.1a*
A.craccivora 1.8±0.1a 1.5±0.1b 1.3±0.1b*
Fourthinstar(d)
M.crassicauda 2.0±0.0a* 2.1±0.1a* 2.0±0.0a*
A.craccivora 2.3±0.1a* 1.7±0.1b* 1.7±0.1b*
Preadultperiod(d)
M.crassicauda 7.1±0.1a 6.9±0.1ab* 6.8±0.1b*
A.craccivora 7.1±0.1a 5.7±0.2b* 5.8±0.1b*
Adultperiod(d)
M.crassicauda 21.4±1.0a* 15.5±1.1b 11.0±0.8c*
A.craccivora 11.6±1.2b* 14.0±1.2b 18.4±1.4a*
Longevity(d)
M.crassicauda 28.4±0.9a* 21.6±1.2b 17.6±0.8c*
A.craccivora 18.6±1.2a* 18.3±1.3a 21.2±1.6a*
Ovipositionperiod(d)
M.crassicauda 16.4±0.6a* 12.6±0.8b 9.3±0.7c*
A.craccivora 11.0±1.1b* 12.4±1.0b 15.6±1.2a*
Fecundity(nymphs/female)
M.crassicauda 86.8±3.4a* 58.4±4.0b 44.6±3.7c*
A.craccivora 52.7±4.8b* 66.4±5.0a 73.3±5.6a*
Meansforthesamespeciesinthesamerowfollowedbydifferentlettersaresignificantlydifferent;Meansfordifferentspeciesat
thesametemperatureregimefollowedbyanasterisk(*)aresignificantlydifferent.Pairedbootstraptests,P<0.05.
segmentstoothersevery2–3dhavingbeenano- Petridishwascheckeddailyandthedevelopment
tablecauseofdisturbancefortheaphids.Thisis andreproductionoftheindividualwasrecorded
because M. crassicauda and A. craccivora are untildeath.Thesamplesizewas62,50,57indi-
relativelyactivespeciesanditwaseasytotrans- viduals(petridishes)forM.crassicaudapopula-
ferthemaftertouchingtheirantennasbyasmall tionand53,50,50individualsforA.craccivora
brush.Wedidnotusepottedplants,becausethe populationinthe22°C,22±3°Cand22±5°C
nutrientlevelsofplantsprobablydifferwiththeir treatment,respectively.
growingstage.Forexample,inapreliminarytest,
wefoundthataphidsfeedingonyoungerplants
grewfasterthanthoseonolderplants.Inaddition, 2.4.Lifetableanalysis
stem segments occupy less space than potted
plants,i.e.theformeronesweremoresuitablefor ThelifehistoryrawdataofM.crassicaudaandA.
ourartificialclimatechambers. craccivoraobtainedattheconstantandthetwo
Arandomapterousaphidfemalewasplaced fluctuatingtemperatureswereanalyzedusingthe
onthebeanplantstemofeachpetridishandal- age-stage,two-sexlifetabletheorydevelopedby
lowedtoproducenymphsovernight.After24h, ChiandLiu(1985)andChi(1988)toallowinclu-
the adult and all but one nymph were removed sionofthevariabledevelopmentalratethatexists
andthesingleremainingfirstinstarnymphwas among individuals in a diverse population. We
allowedtodeveloponthebroadbeanstem.Each hadonlyfemaleaphidsinourpopulation.How-
ENTOMOL.FENNICAVol.29 (cid:127) Temperatureeffectsontwoaphidspecies 5
Fig.2.Age-
stagespe-
cificsurvival
rate(s)of
xj
Megoura
crassicauda
andAphis
craccivora
atconstant
andfluctu-
atingtem-
peratures.
ever, the above approach allows missing males, been used also earlier for one-sex aphid studies
i.e.itdoesnotaffecttheresultsobtainedforfe- bye.g.Akcaetal.(2015),Akköprüetal.(2015)
males.Theage-stage,two-sexlifetablecan(and andSaskaetal.(2016).
should)alsobeappliedforparthenogeneticpopu- The developmental time, age-stage specific
lations, because contrary to the traditional fe- survival rate (s ), age-specific survival rate (l),
xj x
male-basedlifetable,ittakesthepre-adultdevel- age-stagespecificfecundity(f ),age-specificfe-
xj
opmentandmortalityintoaccountandthuspro- cundity(m),age-specificnetfecundity(lm),in-
x x x
videsmoreaccurateestimatesofpopulationpa- trinsicrateofincrease(r),finiterateofincrease
rameters (Saska et al. 2016). The approach has ((cid:1)),netreproductiverate(R)andmeangenera-
0
6 Chengetal. (cid:127) ENTOMOL.FENNICAVol.29
tion time (T) were calculated using the TWO- the22°Ctreatment,whiletheoppositephenome-
SEX-MSChartprogram(Chi2016a)asdescribed nonwasobservedinthe22±5°Ctreatment.
byChiandSu(2006),Tuanetal.(2014a,b)and
Chietal.(2016).Thebootstraptechnique(Efron
& Tibshirani 1993) with 100,000 resamplings 3.2.Age-stagesurvivalrates
was used to estimate the standard errors. The
pairedbootstraptestwasusedtocomparediffer- The age-stage specific survival rates (s ) of M.
xj
ences between treatments. The growth of M. crassicauda and A. craccivora at different tem-
crassicaudaandA.craccivorapopulationatcon- peraturesareplottedinFig.2.Theage-stagespe-
stantandfluctuatingtemperatureswereprojected cificsurvivalratewastheprobability ofanew-
based on the life table data using the program bornsurvivingtoagexandstagej.Becausethe
TIMING-MSChart (Chi 2016b) and the ap- age-stage, two-sex life table can take the varia-
proach described in Tuan et al. (2014a, b). The tionsindevelopmentalratesthatoccuramongin-
plotsforsurvivalrate,fecundity,lifeexpectancy, dividualsintoconsideration,significantoverlap-
reproductive value and the population growth pingbetweenstagescouldbeobserved.Theage-
curveswerepreparedusingtheprogramSigma- specific survival rate (l), showing the survival
x
Plot12.0. rate to age x, is a simplified version of the age-
stagespecificsurvivalrateobtainedbycombin-
ing all stages (Fig. 3). These curves clearly
3.Results showedthatfluctuatingtemperatureshadlessin-
fluenceonthepreadultaphids,buthadagreatin-
3.1.Developmentaltimeandfecundity fluenceontheadultsurvivalrateofbothspecies.
Megouracrassicaudaadultshadthelongestlon-
Thedevelopmentaltimesofdifferentlifestages gevity and highest survival rate at 22 °C, fol-
aswellasfecundityoffemalesofM.crassicauda lowedby22±3°Cand22±5°C.Onthecon-
andA.craccivorawereinfluencedbyfluctuating trary,thefluctuatingtemperatures,especiallythe
temperatures(Table1).ThepreadultperiodofM. 22±5°Ctreatment,increasedtheadultsurvival
crassicauda decreased gradually with the order rateofA.craccivora.
of22°C,22±3°Cand22±5°C,andasignifi-
cantdifferencewasfoundbetween22°Cand22
±5°C. Theadultperiod, longevity, oviposition 3.3.Fecundities
period and fecundity of M. crassicauda de-
creasedsignificantlywiththeorderof22°C,22± Theage-specificfecundity(m)andtheage-spe-
x
3°Cand22±5°C. cificnetfecundity(lm)ofM.crassicaudaandA.
x x
ThepreadultperiodofA.craccivorain22°C craccivoraareshowninFig.3.Theage-specific
treatment was significantly longer than those in fecundity (m) curves of M. crassicauda and A.
x
the22±3°Cand22±5°Ctreatments.Theadult craccivorawerecharacterizedbyarapidincrease
period, oviposition period and fecundity of A. tothemaximumvalueatthebeginningofthere-
craccivoraincreasedwiththeorderof22°C,22± productiveperiodandfollowedbyamoregrad-
3°Cand22±5°C,andtheadultperiodandfe- ual decrease with age in all three test tempera-
cundity in the 22 ± 5 °C treatment was signifi- tures.Thecurvesshowedthatfluctuatingtemper-
cantlygreaterthanthoseintwoothertreatments. atures,especiallyat22±5°C,decreasedthemx
ThefecundityofA.craccivorainfluctuatingtem- valueofM.crassicaudabutincreasedthatofA.
peraturetreatmentswassignificantlygreaterthan craccivora.Theage-specificfecunditycurvesof
thatinconstanttemperaturetreatment.Therewas M.crassicaudapeakedatthe9thday,withmaxi-
nosignificantdifferenceinthelongevityamong mumvaluesof7.0,7.8and7.4nymphsinthe22
thethreetreatments. °C,22±3°Cand22±5°Ctreatments,respec-
The adult period, longevity and oviposition tively.Themaximalm value(11.4nymphs)for
x
period were significantly longer and fecundity A.craccivoraoccurredat22°Catage8d.This
higherinM.crassicaudathaninA.craccivorain valuewassignificantlyhigherthanthoseat22±3
ENTOMOL.FENNICAVol.29 (cid:127) Temperatureeffectsontwoaphidspecies 7
Fig.3.Age-specificsurvivalrate(l),age-specificfecundity(m),andage-specificnetfecundity(lm)of
x x x x
MegouracrassicaudaandAphiscraccivoraatconstantandfluctuatingtemperatures.
°C(7.1nymphsatthe8thday)and22±5°C(6.9 withtheconstanttemperatureof22°C,thelm
x x
nymphsatthe13thday). values of M. crassicauda decreased at the two
Theage-specificnetfecundity(lm)valuesof fluctuatingtemperatures,whereasthevaluesfor
x x
M.crassicaudaandA.craccivoraunderconstant A. craccivora increased. In general, oviposition
andfluctuatingtemperaturesformedcurvessimi- ceased2to6daysbeforedeathinbothaphidspe-
lartotheaboveage-specificfecundity.Compared cies,exceptforA.craccivoraat22°C.
8 Chengetal. (cid:127) ENTOMOL.FENNICAVol.29
Table2.Populationparameters(mean±SE)ofMegouracrassicaudaandAphiscraccivoraatconstantandfluc-
tuatingtemperatures.
Parameter 22°C 22±3°C 22±5°C
Samplesize(n)
M.crassicauda 62 50 57
A.craccivora 53 50 50
Intrinsicrateofincrease(r,d–1)
M.crassicauda 0.3318±0.0039a 0.3093±0.0059b* 0.3108±0.0061b*
A.craccivora 0.3360±0.0049b 0.3827±0.0096a* 0.3691±0.0117a*
Finiterateofincrease((cid:1),d–1)
M.crassicauda 1.3935±0.0054a 1.3623±0.0080b* 1.3646±0.0084b*
A.craccivora 1.3993±0.0069b 1.4663±0.0141a* 1.4466±0.0168a*
Netreproductiverate(R,d–1)
0
M.crassicauda 86.8±3.4a* 56.1±4.1b 43.8±3.7c*
A.craccivora 52.7±4.8a* 59.8±5.8a 62.0±6.3a*
Generationtime(T,d)
M.crassicauda 13.5±0.1a* 13.0±0.2b* 12.2±0.2c*
A.craccivora 11.8±0.2a* 10.7±0.1b* 11.2±0.2b*
Meansforthesamespeciesinthesamerowfollowedbydifferentlettersaresignificantlydifferent;Meansfordifferentspeciesat
thesametemperatureregimefollowedbyanasterisk(*)aresignificantlydifferent.Pairedbootstraptests,P<0.05.
3.4.Populationparameters 3.5.Simulatedpopulationgrowth
ThepopulationparametersofM.crassicaudaand Population growths of M. crassicauda and A.
A. craccivora are listed in Table 2. Megoura craccivora,basedonlifetableparameters,were
crassicauda and A. craccivora had different re- affectedbyfluctuatingtemperatures(Fig.4).Ac-
sponsestothetemperatureregimes.Allpopula- cordingtothesimulation,thepopulationsizeaf-
tionparametersofM. crassicaudaweresignifi- ter50dayswoulddifferbyoneorderofmagni-
cantlyhigherin22°Ctreatmentthaninthe22±3 tudeandwouldreachapproximately 48.21mil-
°Cand22±5°Ctreatments, buttherewereno lionaphidsat22°C,16.15millionat22±3°C,
significantdifferencesintheintrinsicrateofin- 18.29millionat22±5°CforM.crassicaudaand
crease(r)andfiniterateofincrease((cid:1))between 68.60millionat22°C,657.08millionat22±3
22±3°Cand22±5°C. °C,360.60millionat22±5°CforA.craccivora.
Theintrinsicrateofincrease(r)andfiniterate The simulated population growth curves (in a
ofincrease((cid:1))ofA.craccivorawerehigherinthe logarithmicscale)approachedlinearityafterap-
22±3°Ctreatmentthaninthe22°Cand22±5 proximately 20 days, which suggests that the
°Ctreatments,buttheydifferedsignificantlyonly aphidpopulationshadapproachedthestableage-
fromthoseofthe22°Ctreatment.Thetempera- stage distribution. The slopes of the regression
tureregimeshadnosignificanteffectonthenet linesthatdescribesuchlinearpopulationincrease
reproductiverate(R)ofA.craccivora.Thegene- areequaltolog((cid:1))foreachcohort(Table2).
0
ration times (T) of A. craccivora were signifi-
cantlyshorterinthe22±3°Cand22±5°Ctreat-
mentsthaninthe22°Ctreatment,buttherewas 4.Discussion
nosignificantdifferencebetweenthe22±3°C
andthe22±5°Ctreatments.Atconstant22°C, Theprimaryobjectiveofthisstudywastounder-
intrinsicrateofincrease(r)andfiniterateofin- stand the impact of fluctuating temperatures on
crease ((cid:1)) did not differ between the two aphid thedevelopmentandreproductionofM.crassi-
species,butA.craccivorapopulationhadsignifi- cauda and A. craccivora. The effect were as-
cantlyhigherrand(cid:1)thanM.crassicaudaatthe sessed by constructing age-stage, two-sex life
twofluctuatingtemperatureregimes. tablesatconstanttemperatureof22°Candsimu-
ENTOMOL.FENNICAVol.29 (cid:127) Temperatureeffectsontwoaphidspecies 9
Fig.4.Comparisonof
simulatedpopulation
growthforMegoura
crassicaudaandAphis
craccivoraatconstant
andfluctuatingtemper-
atures,basedonage-
stage,two-sexlife
table.Regression
equationsdescribelin-
earpopulationgrowth
ofeachcohortfromday
20onwardsaspopula-
tionsapproachedsta-
bleage-stagedistribu-
tion.
latedfluctuatingtemperaturesof22±3°Cand22 manyoftheearlierstudiesonavarietyofarthro-
±5°Cwithalsoaphotoperiodtoobtainacloser pods (e.g., Brakefield & Mazzotta 1995, Miro-
approximation of a natural field environment. nidis&Savopoulou-Soultani2008,Vangansbeke
Ourresultsindicatedthatmanylifetableparame- etal.2013).Forexample,Baharetal.(2012)re-
tersofM.crassicaudaandA.craccivoraatcon- ported that the developmental times of the
stant temperature did deviate from those at the diamondback moth, Plutella xylostella (Linnae-
twofluctuatingtemperatures,buttheextentofthe us), and its larval parasitoid Diadegma insulare
effectsdifferedinthetwoaphidspecies. (Cresson)werebothshortenedatfluctuatingtem-
Inthepresentstudy,fluctuatingtemperatures peratures(0–14,15–29and23–37°C)compared
accelerated the development of M. crassicauda tothesameaveragecorrespondingconstanttem-
and A. craccivora, as their preadult period was peratures(7,22and30°C).Generally,therela-
significantly shortened at fluctuating tempera- tionship between poikilothermic developmental
tures compared to the corresponding constant rates and temperature is nonlinear (Andrews &
temperature. These findings are consistent with Schwarzkopf 2012). Compared to the corre-
10 Chengetal. (cid:127) ENTOMOL.FENNICAVol.29
spondingmeanconstanttemperature,thedevel- ods(totalof16hat30°C)significantlyreduced
opmentalrateofpoikilothermstendstobehigher thefecundityofSitobionavenae(Fabricius)and
atthelowtemperaturerangeoffluctuatingtem- resulted in a reduced population growth rate
peratureregimes,lowerinthehighertemperature (Jeffs&Leather2014).ForM.crassicaudaand
range, andlittletonodifferenceatintermediate A.craccivorainthepresentstudy,therewasno
temperatures(Vangansbekeetal.2015).Thisef- significantdifferencebetweenthespeciesinthe
fecthasbeenreferredtoastheratesummationef- populationgrowthrate(intrinsicrateofincrease)
fect or Kaufmann effect (Ratte 1985, Worner attheconstanttemperature,butthesimulatedA.
1992),explainingthedifferencesbetweendevel- craccivora population grew significantly faster
opment predicted by nonlinear models under than the M. crassicauda population in the two
constantandvariabletemperatureswiththesame fluctuating temperature treatments. Thus, our
meantemperature. presentresultsmaybeduetothatA.craccivora
Fluctuatingtemperatures(22±3°Cand22± hasmoretoleranceforhightemperaturesthanM.
5°C)reducedtheadultsurvivalrateofM.crassi- crassicauda.Asimilarphenomenonwasfoundat
cauda, but that of A. craccivora was increased. the constant temperatures, since A. craccivora
Consequently,theovipositionperiodandfecun- couldsurviveandreproduceat31°C,whileM.
dityofM.crassicaudadecreasedinbothfluctuat- crassicaudacannotdeveloptoadultatthistem-
ingtemperaturetreatments, butincreasedfor A. perature(Gongetal.2006).
craccivorainthesametreatments. In conclusion, the fluctuating temperatures
Theintrinsicrateofincrease(r)combinesthe hadnegativeimpactonthelifehistorytraitsofM.
effectsofseverallifetableparameters,including crassicauda, but was beneficial for A. cracci-
thefirstreproductiveage,thepeakofreproduc- vora.Thedataobtainedunderconstanttempera-
tion,thelengthofthereproductiveperiod,andthe tures may not accurately reveal the biotic re-
survival rate, on the population growth rate. sponsesofpestsinthefield.Researchersshould
These population parameters are key demo- taketheseaspectsintoaccountwheninterpreting
graphicparametersandarethemostusefulinpre- their laboratory data and making predictions
dicting the growth potential of insect and mite about population growth in natural populations.
populations (Birch 1948, Vangansbeke et al. Inaddition,informationobtainedfromlifetable
2013).Basedonther-values,thefluctuatingtem- studies under daily fluctuating temperatures
peraturesinthepresentstudyhadnegativeeffect mightbeusefulinmassproductionofbiological
on the development and reproduction of M. controlagents.
crassicauda, but they were beneficial for A.
craccivora. Acknowledgements.ThisworkwassupportedbyTheMo-
Previous studies have demonstrated that the dernTeaIndustryTechnologySystemofShandongPro-
impactoffluctuatingtemperaturesoninsectsand vince,China(SDAIT-19–4),PostResearchofShandong
AgriculturalUniversity,theShandongProvincialNatural
mitesdifferedbetweenspecies.Fluctuatingtem-
Science Foundation, China (ZR2014CP018), and The
peraturescanenhancethepopulationgrowthrate
TechnologicalSystemProjectofWheatIndustryofShan-
of some insects, such as Helicoverpa armigera dongProvince,China(SDAIT-01–09).WethankDrHsin
(Hübner) (Mironidis & Savopoulou-Soultani Chiforhisvaluableadviceoftheage-stage,two-sexlife
2008) and Tetranychus urticae Koch (Vangans- tableconcept.
bekeetal.2013).Ontheotherhand,somestudies
havereportedanadverseeffectofthefluctuating
temperature(Siddiqui&Barlow1973),ornosig- References
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