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1、FreshwaterScience,2013,32(4):13671382’2013byTheSocietyforFreshwaterScienceDOI:10.1899/12-203.1Publishedonline:5November2013Aglobalmeta-analysisoftheecologicalimpactsofnonnativecrayfish12LauraA.TwardochlebANDJulianD.OldenSchoolofAquaticandFisherySciences,U
2、niversityofWashington,Seattle,Washington98195USA3EricR.LarsonDepartmentofEcologyandEvolutionaryBiology,UniversityofTennessee,Knoxville,Tennessee37996USAAbstract.Nonnativecrayfishhavebeenwidelyintroducedandareamajorthreattofreshwaterbiodiversityandecosyste
3、mfunctioning.Despitedocumentationoftheecologicaleffectsofnonnativecrayfishfrom.3decadesofcasestudies,nocomprehensivesynthesishasbeendonetotestquantitativelyfortheirgeneralorspecies-specificeffectsonrecipientecosystems.Weprovidethefirstglobalmeta-analysiso
4、ftheecologicaleffectsofnonnativecrayfishunderexperimentalsettingstocompareeffectsamongspeciesandacrosslevelsofecologicalorganization.Ourmeta-analysisrevealedstrong,butvariable,negativeecologicalimpactsofnonnativecrayfishwithstrikinglyconsistenteffectsamon
5、gintroducedspecies.Inexperimentalsettings,nonnativecrayfishgenerallyaffectalllevelsoffreshwaterfoodwebs.Nonnativecrayfishreducetheabundanceofbasalresourceslikeaquaticmacrophytes,preyoninvertebrateslikesnailsandmayflies,andreduceabundancesandgrowthofamphib
6、iansandfish,buttheydonotconsistentlyincreasealgalbiomass.Nonnativecrayfishtendtohavelargerpositiveeffectsongrowthofalgaeandlargernegativeeffectsoninvertebratesandfishthannativecrayfish,buteffectsizesvaryconsiderably.Ourstudysupportstheassessmentofcrayfish
7、asstronginteractorsinfoodwebsthathavesignificanteffectsacrossnativetaxaviapolytrophic,generalistfeedinghabits.Nonnativecrayfishspeciesidentitymaybelessimportantthanextrinsicattributesoftherecipientecosystemsindeterminingeffectsofnonnativecrayfish.Weidenti
8、fysomeunderstudiedandemergingnonnativecrayfishthatshouldbestudiedfurtherandsuggestexpandingresearchtoencompassmorecomparisonsofnativevsnonnativecrayfishanddifferentgeographicregions.Theconsistentandgeneralnegativeef
