spatial heterogenity, evolutionary diversification, mutation and strong dynamics

spatial heterogenity, evolutionary diversification, mutation and strong dynamics Evolution instructuredpopulations: beyond thekinversusgroupdebate Se´ bastien Lion1*, VincentA.A.Jansen1 and TroyDay2 1 School ofBiologicalSciences,RoyalHollowayUniversityofLondon,EghamTW200EX,UnitedKingdom 2 Departments ofMathematics,StatisticsandBiology,JefferyHall,Queen’sUniversity,Kingston,ON,K7L3N6,Canada Much oftheliteratureonsocialevolutionispervadedby the olddebateabouttherelativemeritsofkinandgroup selection. Inthisdebate,thebiologicalinterpretationof processes occurringinrealpopulationsisoftenconflat- ed withthemathematicalmethodologyusedtodescribe these processes.Here,wehighlightthedistinctionbe- tween thetwobyplacingthisdiscussionwithinthe broader contextofevolutioninstructuredpopulations. In thisreviewweshowthatthecurrentdebateoverlooks important aspectsoftheinterplaybetweengeneticand demographic structuring,andarguethatacontinued focus ontherelativemeritsofkinversusgroupselection distracts attentionfrommovingthefieldforward. It’s likewhatLeninsaid. . . you lookfortheperson who willbenefit,and,uh,uh. . . –The Dude Kin versusgroupselection Recentyearshaveseenarevivalofinterestintheevolution of structuredpopulations,withastrongemphasisonthe evolutionofsocialtraitssuchasaltruisticandcooperative behaviours [1–5]. Thishasreignitedthedebateonkin versusgroupselectionandhasgeneratedmuchdiscussion abouttheprocessesunderlyingtheevolutionofsuchtraits, as wellasthemostappropriatemodellingformalism [6–9]. Muchofthisrecentdiscussionhasdivertedattentionfrom importantbiologicalissues,andourgoalhereisthereforeto placethisdebatewithinthebroadercontextofevolutionin structuredpopulations.Insodoingwehighlightthefact thatinastructuredpopulation,virtuallyalltraitscanbe thoughtofassocial,includingdispersal [10], life-history traitssuchasreproductiveeffort,senescenceandsexallo- cation [11], andvirulenceorresistancetraitsinhost–para- siteinteractions [12,13].Withinthisbroaderperspectivewe pointoutpossibleavenuesforfutureresearch. What isthedebateabout? Thecurrentdebateseemstostem,inpart,fromafailure to clearlydistinguishbetween thebiologicalinterpreta- tion ofprocessesoccurringinrealpopulationsand the mathematicalmethodologyusedtodescribethese processes.Thetwoarenecessarilyintertwined,butit cansometimesbeusefultodistinguishbetweenthem. To thisend,weusethetermskinselection(KS)and multilevel selection(MS)todescribetwodifferentbiologi- calinterpretationsoftheevolutionaryprocessesoccurring instructuredpopulations,andthetermsinclusivefitness (IF) methodologyandmultilevelselectionmethodologyto describe themathematicalapproaches typicallyusedwith each. General background Whenever anindividual’sreproductivesuccessisaffected by traitsexpressedbyotherindividuals,weneedtoac- count forthewayinwhichgenotypesaredistributed among individualstopredictevolutionarychange.The IF andMSmethodologiesaredifferentwaysbywhich theoreticians accountforthisgeneticstructure. As anexample,consideracaseinwhichallindividuals in thepopulationprovidesomelevelofhelpto n other individuals, andsupposethatamutantallelearisesthat causes itsbearertoprovideanincreasedlevelofhelpata cost toitself.Todetermineiftheallelewillspread,weneed to calculatetheselectioncoefficient,whichisthedifference between theaveragereproductiveoutputsofindividuals carrying themutantversuswild-typealleles.Theaverage reproductive outputsaredifficulttocalculatebecauseof the spatialstructureofthepopulation.Infact,thisdiffi- culty arisesfortworeasons:(i)whencalculatingtheaver- age reproductiveoutputsforbearersofeitherallele,we need toknowtheprobabilitythatitsneighbourscarrythe same allele;and(ii)theprobabilitythatitsneighbours carry thesameallelewilltypicallydependontheactionof the allele.Forexample,iftheallelecausesahigherlocal level ofreproductiveoutput,thenitsneighboursmightbe very likelytocarrythisalleleaswell.Thesecomplications typically precludeanalyticalprogressunlessfurthersim- plifying assumptionsaremade. IF andMSmethodologies The IFmethodology(Box 1 and online appendix S1) parti- tions theselectioncoefficientintoadirectandanindirect selection component [14–17]. Thedirectselectioncompo- nent accountsfordifferencesinthedirecteffectsofthe allele onitsbearers’reproductivesuccess.Inourexample this isnegativebecausethemutantallelecausesitsbearer to providemorehelpthanthatofthewild-type,atacostto itself. Theindirectselectioncomponentaccountsfordiffer- ences betweenmutantandwild-typeindividualsinthe Review Corresponding authors: Lion, S.([email protected]); Jansen,V.A.A. ([email protected]); Day,T.([email protected]) * Present address:Centred’E´ cologie FonctionnelleetE ´ volutive, UMR5175,CNRS 1919 routedeMende,34293MontpellierCedex5,France TREE-1342; No.ofPages9 0169-5347/$ – see frontmatter  2011 ElsevierLtd.Allrightsreserved.doi:10.1016/j.tree.2011.01.006 Trends inEcologyandEvolutionxx(2011)1–9 1 PLACE THIS ORDER OR A SIMILAR ORDER WITH US TODAY AND GET AN AMAZING DISCOUNT :)