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1、LETTERdoi:10.1038/nature12489Lifehistorytrade-offsatasinglelocusmaintainsexuallyselectedgeneticvariation1,21,32242SusanE.Johnston{,JacobGratten{,CamilloBerenos,JillG.Pilkington,TimH.Clutton-Brock,JosephineM.Pemberton1&JonSlateSexualselection,throughintra-malecompetitionorfemalechoice,On
2、ewildpopulationwherethegeneticarchitectureofasexuallyisassumedtobeasourceofstrongandsustaineddirectionalselec-selectedtraithasbeencharacterizedistheSoaysheepofStKilda(Ovis1,2tioninthewild.Inthepresenceofsuchstrongdirectionalselec-aries),apopulationofprimitivedomesticsheepthathasexistedc
3、om-tion,allelesenhancingaparticulartraitarepredictedtobecomepletelyunmanagedforaround4,000yearsandhasbeenintensivelyfixedwithinapopulation,leadingtoadecreaseintheunderlyingstudiedsince1985.Duringthematingseason(rut),thereisstrong3geneticvariation.However,thereisoftenconsiderablegeneticc
4、ompetitionbetweenmalesforaccesstooestrousfemales.Mostmalesvariationunderlyingsexuallyselectedtraitsinwildpopulations,developnormalhorns,butaround13%developvestigialhorns(scurs)16andconsequently,thisphenomenonhasbecomealong-discussedconferringreducedreproductivesuccess(Fig.1).Thehornsize
5、of1,4,517issueinthefieldofevolutionarybiology.InwildSoaysheep,normal-hornedmalesispositivelycorrelatedwithmatingsuccess,yetlargehornsconferanadvantageinstrongintra-sexualcompeti-thereissubstantialheritablevariationunderlyingthistrait(h250.37)6.tion,yetmalesshowaninheritedpolymorphismfor
6、horntypeandFemalesdevelopmuchsmallerhorns,andareeithernormal-horned6havesubstantialgeneticvariationintheirhornsize.Hereweshow(32%),scurred(40%),or‘polled’(lackinghornsorscurs,28%;Sup-thatmostgeneticvariationinthistraitismaintainedbyatrade-offplementaryFig.1).Recentstudieshaverevealedtha
7、tasinglegene,betweennaturalandsexualselectionatasinglegene,relaxin-likerelaxin-likereceptor2(RXFP2),explainsmostofthegeneticvariation618,19receptor2(RXFP2).WefoundthatanalleleconferringlargerinhornmorphologyinSoaysheepanddomesticsheep.TwoRXFP211P1horns,Ho,isassociatedwithhigher
