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1、frbiol$470FreshwaterBiology(1996)35,1±10ClonalvariationinthesurvivalandreproductionofDaphniapulicariaunderlow-foodstressGREGORYT.EPPSectionofEcologyandSystematics,CornellUniversity,Ithaca,NY,U.S.A.Addressforcorrespondence:DrGregoryT.Epp,129LincolnAvenue,Lexington,K
2、Y40502,U.S.A.SUMMARY1.SurvivorshipandreproductiveparametersofeightDaphniapulicariacloneswereevaluatedinalife-tableexperimentunderfourdietaryregimesrangingfromfoodlimitationtocompletefooddeprivation.2.D.pulicariaexhibitedbothdiet-independentinterclonaldifferencesand
3、genotype±environmentinteractionsinlife-span.3.Reproductionceasedentirelyornearlysounderthethreetreatmentswithlowestfoodavailability.Underlife-longfoodlimitation,differencesbetweencloneswereevidentinclutchsizesandageat®rstreproduction.Someclonesproducedephippiaatama
4、rkedlyhigherfrequencythanothersunderfood-limitingconditions.4.Formostofthelife-historytraitsevaluated,within-lakevariationamongclonesexceededdifferencesbetweenthetwolakepopulationstheyrepresented.5.Intraspeci®cvariationsinresponsetoperiodsoffooddeprivationandtoexte
5、ndedquantitativeorqualitativefood-limitationcouldaffecttheclonalcompositionofDaphniapopulations.Theyarethereforeofpotentialimportanceindeterminingtheeffectofalteredphytoplanktonassemblagesonzooplanktoncommunities.IntroductionExaminationsofinterspeci®ccompetitionamo
6、ngreports(citedbelow).Mostresearchonintraspeci®cherbivorouszooplanktonhavefocusedondifferencesvariationinlife-historytraitsofzooplanktonhasbeeninthecapabilityofzooplanktonspeciestowithstandconductedatfoodlevelswellabovethefoodthreshold.lowfoodavailability.Theconcep
7、tofafoodthresholdFoodlevelisapotentiallycriticalfactorinthe(Lampert,1977),belowwhichsomaticgrowthcannotexpressionofreproductivedifferencesamongDaphniabesustained,hasbecomeonecentralparadigmofclones.Life-historytrade-offsbecomeevenmoresuchstudies(DeMott,1989;Rothhau
8、pt,1990).Speciesimportantunderconditionsofresource-limitation(butwithlowerthresholdsmayexcludeotherswhenfoodcf.Glazier&Calow,1992).Althoughfood-s
