Evolutionary Biology,ofwhichthisisthetwenty-thirdvolume,continues toofferitsreadersawiderangeoforiginalarticles,reviews,andcom- mentariesonevolution,inthebroadestsenseofthatterm. Thetopicsof thereviewsrangefromanthropology,molecularevolution,andpaleo- biologytoprinciplesofsystematics. Inrecentvolumes,abroadspectrumofarticleshaveappearedon suchsubjectsasbiochemicalsystematics,comparativemorphologyand embryology,evolutionaryecology,biogeography,andpaleobiology. We havealsoattemptedtoprovideaforumforconflictingideas. Articlessuch asthese,oftentoolongforstandardjournals,arethematerialfor Evo- lutionary Biology. Theeditorscontinuetosolicitmanuscriptsonaninternationalscale inanefforttoseethateveryoneofthemanyfacetsofbiologicalevolution iscovered. Manuscriptsshouldbesenttoeitherofthefollowing:Max K. Hecht,DepartmentofBiology,QueensCollegeoftheCityUniversity ofNewYork,Flushing,NewYork11367,orBruceWallace,Department ofBiology,VirginiaPolytechnicInstituteandStateUniversity,Blacks- burg,Virginia24061. TheeditorswishtocongratulateDr. GhilleanT. Pranceonhisnew appointmentatKewBotanicalGardensandthankhimforhiscollabo- rativeeffortsineditingthepastninevolumes. TheEditors vII Contents 1. MaintenanceofaHereditaryVirus:TheSigmaVirusin PopulationsofItsHost, Drosophila melanogaster 1 Annie Fleuriet Introduction 1 FrenchPopulationsof Drosophila melanogaster…2 PolymorphismofPopulations 2 CharacteristicsofWildStrainsoftheSigmaVirus 3 EffectsoftheInfectionuponCarriers…7 ExperimentalPopulations…9 MaintenanceoftheVirusinFrenchNaturalPopulations…12 GeographicalVariationofthe Drosophila-SigmaSystem 14 PolymorphismofPopulations 14 ViralCharacteristics…17 TentativeInterpretationoftheGeographicalPatternObserved 18 OtherSystemsofVerticallyTransmittedViruses 22 ExistenceofDifferentSensitivitiestotheVirus 22 CharacteristicsoftheViruses…23 MaintenanceintheVectorPopulation 24 Appendix:TransmissionofStabilizedandNonstabilized Conditions…26 Self-MaintenanceofStabilizedConditionthroughMaternal Lineage…26 NonstabilizedCondition …27 References 28 2. Domestication:EvolutionaryChangeunderStress 31 M. J. Kohane and P. A. Parsons Introduction 31 EnvironmentalChangeandDomestication 33 Ix x Contents EcologicalPhenotypes 33 BehavioralPhenotypes…36 AdaptationtoLaboratoryConditions…37 ACaseStudy:DomesticationinFoxes 41 Discussion…43 Summary…45 References 46 3. RangeExpansionandItsGeneticConsequencesinPopulationsof theGiantToad, Bufo marinus…49 Simon Easteal Introduction 49 TheSpreadof Bufo marinus 50 TheIntroductions…50 TheAustralianRangeExpansion 52 GeneticVariationintheIntroducedPopulations…58 TheData…58 GeneticVariability…58 EffectivePopulationSize 62 Dispersal,GeneFlow,andNeighborhoodSize 63 TheGeneticEffectsofRangeExpansion 64 GeographicalPatternsofVariation 74 Conclusion 81 References 82 4. EvolutionbySocialSelection…85 Shozo Yokoyama Introduction 85 ConceptofSocialSelection…86 EvidenceforSocialSelection;…88 MultipleNeurofibromatosis 88 HuntingtonDisease 89 MentalRetardation…90 Schizophrenia 91 SocialSelectionModels…91 AutosomalGenes…92 Contents xl X-LinkedGenes…103 RandomGeneticDriftandVariableSelectionIntensity…112 MaternalEffects 115 DNAPolymorphismandSocialSelection…117 Discussion…118 Summary…121 References 122 5. TheInfluenceofTaxonomicMethodonthePerceptionofPatterns ofEvolution…-…127 Andrew B. Smith and Colin Patterson Introduction 127 TheNatureofTaxa…129 WhyNonmonophyleticGroupsAreNotRealTaxa 131 ParaphyleticTaxaasNaturalAdaptivelyUnifiedGroups. , 131 NonmonophyleticGroupsasValidSamplesof Species-LevelProcesses…132 TheRedQueenHypothesis 134 TaxonDurationIsProportionaltotheNumberofSpecies IncludedintheTaxon 135 TaxonomicExtinctionsunderConsiderationAreLargely Artefactual 139 TheRedQueenasSystematist:TheProbabilityThata TaxonomistWillSplitaGroupIsInverselyProportional totheNumberofSpeciesinThatGroup 142 DecreaseinExtinctionRatethroughTime 142 PeriodicityofExtinction 143 GenericDataandLagerstatten 147 SpeciesDiversity 148 WhatDoFossilSpeciesSample? 152 AnalysisofGaps 153 Summary…