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1、CommunityEcology ConceptoftheEcologicalNicheDefinitionbyHutchinson 1957 Thetotalrangeofconditionsunderwhichtheindividual orpopulation livesandreplacesitself FundamentalNiche Thefullrangeofconditionsandresourcesinwhichthespeciescanmaintainaviablepopulation Assumestheabsenceofcompetition Niche Continu
2、ed RealizedNiche Thenichethatisactuallyusedbyindividualsorthepopulation AssumesthatcompetitorsarepresenttorestrictspeciesAtoamorerestrictedniche DesertRodentCommunityStructure LookatFigure25 5inyourtextbookDesertshavebeenusedextensivelyasmodelsystemsforworkoncommunitystructureDesertsarerichingranivo
3、rousrodents especiallythoseofthefamilyHeteromyidae DesertRodents Continued Twononexclusivehypothesesattempttoexplainthehighspeciesdiversityofgranivorousrodentsindesertecosystems MicrohabitatSelectionHypothesisAssumesthatcompetitionbetweenindividualsofdifferentspeciesisreducedduetothefactthatpotentia
4、lcompetitorsforageindifferentmicrohabitats Animalsdifferin placeniche DesertRodents Continued FoodParticleSizeSeparationHypothesisThishypothesisproposesthatcoexistenceispossiblebecausedifferentbodysizedspeciesselectseedsthatarecorelatedwiththebodysizeoftheanimal MicrohabitatSelection Dipodomysmerria
5、mi 33g Perognathusbaileyi 27g Perognathuspenicillatus 17g Perognathusamplus 12g Foragingmicrohabitatisconsideredtobearesource MicrohabitatSelection Cont AlargetrappinggridwasestablishedwithfourmicrohabitattypesonthegridLargeopenareasSmallopenareasLargebushesTrees Microhabitat Duringthesummer nospeci
6、eswasequallyactiveinallfourmicrohabitatsD merriamifavoredlargeopenareasP amplusfavoredsmallopenareasP penicillatusandP baileyifavoredlargebushesandtrees Microhabitat InwinterthemicrohabitatselectionchangedD merriamifavoredsmallopenareasP amplusfavoredlargebushesP penicillatusandP baileyiarehibernati
7、ngspeciesthatarenotactiveduringthewintermonths Microhabitat Ifcompetitiveinteractionscurrentlymaintainmicrohabitatspecializations thesespecializationsshoulddiminishwhencompetitorsareremovedConversely specializationsshouldincreasewhenacompetitorisaddedtothesystem Microhabitat ExperimentGridestablishe
8、dDipodomysmerriamiusedascompetitorspeciesForall3Perognathusspeciesalone specializationdiddecreasebutstillremainedheterogeneous notrandomuseofhabitat Microhabitat ExperimentContinuedWhenD merriamiwasaddedtoeachenclosure microhabitatshiftsdidoccur Therewasalowerthresholddensitybelowwhichnosubstantials
9、hiftsoccurred FoodParticleSizeHypothesis ExperimentUsed6speciesofheteromyidrodents smalltolarge8typesofseeds smalltolarge wereofferedtoeachanimalTherewasahighlysignificantcorrelationofaverageseedsizeselectedversusaveragebodysizeofaparticularspecies FoodHypothesis Smallindividualsofaparticularspecies
10、selectedthesamesizedseedsasthelargermembersofthespeciesTherewasatendencyforthelargerspeciestotakeagreaterrangeofseedsizes CompetitionAmongDifferentPhyla RodentsandAntsExperimentalManipulationsAreafencedtokeepoutallrodents thoseinareawereremovedAreafencedtokeepoutlargerodentsonlyAntsremovedfromanarea
11、byinsecticideuseBothrodentsandantsremovedfromanareaSeedsaddedtoanarea RodentsandAnts Results ofantcoloniesincreased71 onplotsfromwhichallrodentswereexcluded largeseededplantswerefavoredforgrowthbecausetheantsfedonthesmallseedsExclusionoflargerodentspeciesledtoanincreaseindensityofsmallrodentspecies
12、FoodSelectionHypothesis ResultsContinued ofindividualrodentsincreased18 onplotswhereantswereremovedPlotsfromwhichbothantsandrodentswereexcludedhad5 5Xgreaterdensityofseedsand2 0Xgreaterdensityofannualgrasses Rodentdensitiesincreasedonplotsthatreceivedaddedseeds BatCommunities FromBrazil 4speciesoffr
13、uiteatingbatsfromthegenusArtibeus FoundwithinafewfeetofoneanotherinroostingcoloniesDifferentsizes 10g 20g 45g and70g BatCommunities SizestructurealsofoundininsectivorousbatspeciesMolossus Tadarida EumopsDifferentsizedfooditemsareapparentlyeatenbydifferentsizedbats UngulateCommunityExample SpeciesdependuponanotherspeciesforuseofhabitatCommunityofungulates Zebra Wildebeast Thompson sgazelleZebraisfirsttomoveintoanarea feedsontall coursegrassesWildebeastmovesinafterZebramovesout feedsinamoreselectivemannerThompson sGazellecomesthird feedsonsmallnutritiousfruitsandforbs lowfibercontent
