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1、Theevolutionoflife-histories5.1IntroductionThischapterisconcernedwiththeroleofnaturalselectioninmouldingtheformsoflife-histories,asdescribedbytherelationshipsofage-specificsurvivalprobabilityandreproductiontoage.Thisisanaspectofthetheoryofnaturalselectionwhichwas
2、notinvestigatedbyCharlesDarwin,althoughAlfredRusselWallacebrieflydiscussedthetopic(Rose,1991,pp.4-5).ThefirstdetaileddiscussionwasapparentlythatofAugustWeismann(Weismann,1889;Rose,1991,pp.6-7),whowasprimarilyconcernedwiththeevolutionaryexplanationofageing.Intheab
3、senceofawell-developedscienceofpopulationgenetics,theseearlyattemptswerenecessarilyconfused,andlednowhere.Aftertheriseofpopulationgenetics,Fisher(1930,Chapter2)andHaldane(1941,pp.192-4)bothbrieflydiscussedaspectsofselectiononage-specificsurvival,buttheirremarksha
4、dlittleimmediateimpact.ThemodernerawasinitiatedbyMedawar(1946,1952),whowasthefirsttoformulateclearlytheconceptthatthestrengthofselectionongenesaffectingsurvivalorreproductiondependsontheagesatwhichtheyexerttheireffects.Hesuggestedthatsenescencehasevolvedasaresult
5、ofstrongerselectiononeffectsofgeneswhichareexpressedearlyinlifethanoneffectsexpressedlateron.ThisideawaselaboratedinrelationtocomparativedatabyWilliams(1957),andmadequantitativebyHamilton(1966).Itisdiscussedinsection5.2ofthischapter.Alargebodyofworknowexistswhich
6、wasstimulatedbythesebasicideasandwhichprovidesafirmconnectionbetweenpopulationgeneticsmodelsofthekindsdescribedinthelasttwochaptersandbiologicaldataonageing(Rose,1991).Thisisdescribedinsections5.3.1and5.4.3.Therelationofreproductiveactivitytoageisanotheraspectoft
7、helife-historyproblemwhichhasbeenintensivelystudiedinthelasttwentyyears.Thisinvolvessuchquestionsastheeffectsofselectionontheageatreproductivematurity,selectionforiteroparityversussemelparity,therelationsbetweenageandreproductiveeffort,allocationbetweenmaleandfem
8、alereproduction(inhermaphrodites),andoffspringsexratio(whenthereareseparatesexes).ThistopicwasinitiatedbyCole(1954),CambridgeDownloadedfromCambridgeBooksOnline
