Species Concepts in Biology: Historical Development, Theoretical Foundations and Practical Relevance PDF
Preview Species Concepts in Biology: Historical Development, Theoretical Foundations and Practical Relevance
Frank E. Zachos Species Concepts in Biology Historical Development, Theoretical Foundations and Practical Relevance Species Concepts in Biology Frank E. Zachos Species Concepts in Biology Historical Development, Theoretical Foundations and Practical Relevance FrankE.Zachos MammalCollection NaturalHistoryMuseumVienna Vienna Wien,Austria ISBN978-3-319-44964-7 ISBN978-3-319-44966-1 (eBook) DOI10.1007/978-3-319-44966-1 LibraryofCongressControlNumber:2016950888 ©SpringerInternationalPublishingSwitzerland2016 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilarmethodologynowknownorhereafterdeveloped. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexempt fromtherelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. Thepublisher,theauthorsandtheeditorsaresafetoassumethattheadviceandinformationinthis book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained hereinorforanyerrorsoromissionsthatmayhavebeenmade. Printedonacid-freepaper ThisSpringerimprintispublishedbySpringerNature TheregisteredcompanyisSpringerInternationalPublishingAGSwitzerland To my parents, with love and gratitude Preface Thespeciesproblem hastriggeredthepublicationofanalmostinfinitenumberof theoretical and practical studies, including quite a number of books. I should, therefore, perhaps briefly justify the publication of yet another one. In a nutshell, I hope to have written the kind of book that I would have liked to read as an extended review on the various aspects of species concepts in biology when I startedtoseriouslyandsystematicallythinkaboutspecies.Ireadbooksandreview articles,manyofthemverygood,butIfelttherewasalackofacomprehensivebut accessibletextforbiologistswhoareinterestednotonlyinthebiologicaldimension ofspeciesbutalsointhebiggerpictureandthephilosophicalunderpinningofthe topic.Then,acoupleofyearslater,Ihesitantlydecidedtowritesuchabookmyself. There are books by philosophers (e.g., Ereshefsky 2001; Stamos 2003; Wilkins 2009a, b; Richards 2010) which are primarily theoretical and historical in scope, and there are booksby biologists which usuallydo notcover muchphilosophyor history(e.g.,Kunz2012).Ihaveread,andbenefitedfrom,allofthem,andIhave triedtocombinethesedifferentapproachesintoasinglevolume.AlthoughIhave some formal training in philosophy and the history of science, I am primarily a biologist, and while I have always had a deep interest in the historical and philosophical dimensions of the species problem, my main perspective is that from the viewpoint of evolutionary biology, systematics, and taxonomy. This book,therefore,isaimedprimarilyatpracticingbiologists.Consequently, thereis a much stronger focus on practical biological issues than in the philosophical monographs by, for example, Richards, Stamos, and Wilkins. Their books are based on a sound biological background, but it is mostly theoretical evolutionary concepts that they draw from, which is only fair, since philosophers are not occupied with actual taxonomy based on a real set of specimens in a drawer in front of them or with quantifying biodiversity in a comparative context to make informeddecisionsonwhichareadeservesmoreprotectionthanothers.Tobiolo- gists, the species problem, however, is most real in exactly such cases. Being a biologistmyself,itisofcoursemucheasierformetowriteabookforbiologists,but it also makes sense for a different reason. While the species problem is both a vii viii Preface philosophical and a biological issue, philosophers do not by default need to care aboutspecies.Onecanworkinphilosophy(eveninthephilosophyofscience)fora lifetime without ever dealing with biological species and the problems of their definitionanddelimitation.This,however,doesnotholdforbiologists.Speciesin biologyareinescapable,inbothbiologicaltheoryandpractice!Thatsaid,whilethe topicisaddressedinanoverwhelmingnumberofbiologicalpublicationsandalso features prominently in textbooks of systematics or phylogenetics (e.g., Minelli 1993;Wheeler2012),itissometimesastonishinghowsuperficiallyitistreatedby some. To give just one example: In a recent German textbook of more than 300 pages on evolutionary biology, species concepts are given a mere one-and-a- half pages, and only the morphological and the biological species concepts are mentioned—the last couple of decades of the debate on one of the most central issuesinevolutionarybiologyhavesimplybeenignoredinatextbookonevolution. Every biologist knows (and usually dreads) the heated debates on species conceptsandspeciesdelimitation(“oneortwospecies?”).Attheriskofsounding condescending,inmyexperience(andnotonlymine)itisremarkableonhowlowa level such discussions are often held (not just philosophically but also biologi- cally!). The complexity of the issue cannot explain this, because biologists, like other scientists, are used to dealing with complex matters. What may be more importantisthefactthatevolutionarybiology,andwithinitparticularlythespecies issue,issocentralandintegraltothelifesciencesthateveryonehas(oratleastfeels they should have) an opinion on what makes a species. When asking biologists about, say, physiology or comparative anatomy, one is not unlikely to hear them admittothefactthattheyarenotveryknowledgeableinthesedisciplines—butone will hardly ever get the same answer with respect to evolutionary theory or the speciesproblem.However,thespeciesproblemisnotdifferentinthisregardfrom any other complicated topic—unless we actively occupy ourselves with it, we cannothopetopenetrateitscomplexity.Andhereinliestherub—gettinganything beyondamerelysuperficialoverviewoftheavailableliteratureonspeciesconcepts tomanyseemslikeaSisypheantask.Anditis.ThelastfiveyearsorsoIhavespent readingalmosteverythingonspeciesIcouldgetmyhandson,andyetitwouldbe preposteroustoclaimthatIhavereadmorethanafractionofwhatisavailable.Ido think, however, or at least I hope so, that I have read the most important publica- tionsonthetopicandperhapsagooddealmorethanthat.Andthisiswheretheidea forthisbookcamefrom.IwantedtowriteabookthatImyselfwouldhavelikedto readfiveyearsago.Thisiswhythisbookisnotunlikeanextendedreviewarticle. Exceptforsomeevaluationsandminorthoughts(thatothersmaywellhavehador evenpublishedbeforeme),IdonotclaimnoveltyforwhatIampresenting.Abook like this, being on the interface of science and philosophy, runs the risk of being belittledorlookeddownuponbyphilosophers(“trivial”or“toosimplistic”)while at the same being dismissed by biologists as too theoretical and irrelevant to the practice oftheirscience.Ihavebeenawareofthisduringthewritingprocess,but therewasnothingIcoulddobuttrytodojusticetobothsidesandhopetosucceed eventually. Preface ix While this book is, I hope, a coherent whole dealing with the three issues of history, theory andpractice of species concepts, Ihave tried to write the different chapters in a way that they can be read independently, in line with its review character. As a consequence, there are probably more repetitions and cross- references than there would be in a book that is explicitly meant to be read only fromcovertocover.Ihopethiswillbeexcused. A word on manner of discourse in the scientific community may also be due: whenitcomestocertaintopics,thetoneofthedebateoftengetsveryheated.Infact, thelevelofspiteandcontemptforotherpeople’sviewssometimesbordersoninsult (oractuallycrossesthatboundary).Oneneedonlybrowsethecommentarysection inphylogeneticjournalswherethefoundationsofsystematicsandclassificationare discussedtogetanideaofhowbadthingscanget.Attimesoneisremindedofthe nastykindofreligiousdebateswhereopponentsarefrequentlyaccusedofheresy. Thespeciesdebateisunfortunatelyoftensimilarinthatregardasitdoesnotonly seem to be a scientific and philosophical but also very much an emotional issue. WhileIfeelstronglyaboutthespeciesproblem(andby“feel”Imeananenthusi- asmforthetopicandadeepconvictionthatitisimportant),IdohopethatIhavenot letmyselfgetcarriedawayandthatIhavetreatedeveryone,boththosewithwhom I agree and those with whom I disagree, fairly and with due respect throughout thebook. I would like to express my gratitude toward people who have helped me in various ways in writing this book. Andrea Schlitzberger, Stefanie Dether, and Sabine Schwarz of Springer Publishers have been a great help and a pleasure to work with. My views on this topic have been sharpened by many fruitful discus- sions with too many colleagues to list them here by name—both researchers with whom I agree and with whom I don’t. The latter have probably been even more important in widening my scope. I am grateful for their willingness to share their opinions and insights with me. Finally, I am deeply indebted to my family, particularlyNicole,forconstantsupportandinspiration. Vienna,Austria FrankE.Zachos 04July2016 Contents 1 IntroductiontotheSpeciesProblem. . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 WhatIstheSpeciesProblem?. . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 SpeciesandSpeciation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3 SpeciesHomonymy:OneWord,MultipleMeanings. . . . . . . . . . 5 1.3.1 TheSpeciesCategoryandtheSpeciesTaxon. . . . . . . . . . 5 1.3.2 TaxonomicSpeciesvsEvolutionarySpecies. . . . . . . . . . . 6 1.4 Synchronic(Horizontal)SpeciesvsDiachronic (Vertical)Species. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.5 ImportantSpecies“–isms”:RealismvsNominalismand MonismvsPluralism. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.6 GeneralRemarksonTerminologyandRecurrentArguments. . . . 13 1.7 OverviewoftheRemainingChapters. . . . . . . . . . . . . . . . . . . . . 15 2 ABriefHistoryofSpeciesConceptsandtheSpeciesProblem. . . . . 17 2.1 TheEssentialismStory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.2 SpeciesfromAntiquitytoDarwin. . . . . . . . . . . . . . . . . . . . . . . . 22 2.3 DarwinandtheSpeciesProblem. . . . . . . . . . . . . . . . . . . . . . . . . 33 2.4 FromDarwintotheModernSynthesis.. . . . . . . . .. . . . . . . . .. . 39 3 TheMetaphysics,orOntology,ofSpecies:Classes,NaturalKinds orIndividuals?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 3.1 Classes,NaturalKinds,SetsandIndividuals. . . . . . . . . . . . . . . . 45 3.2 WhateverelseSpeciesMightBe,TheyMustalsoBe Individuals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.3 Tertiumnondatur?SpeciesasClusterKindsandaPotential ReconciliationofKindswithIndividuals. . . . . . . . . . . . . . . . . . . 58 3.4 TheCognitiveCausesoftheSpeciesProblem: AnEpistemologicalHypothesis. . . . . . . . . . . . . . . . . .. . . . . . . . 62 3.5 SpeciesasRelations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 3.6 SpeciesPluralismandSpeciesCategoryNominalism: DenyingtheExistenceofaSingleorofAnySpeciesLevel. . . . . 66 xi xii Contents 3.7 SpeciesOntologyandTypeSpecimensinTaxonomy. . . . . . . . . . 72 3.8 ConcludingRemarks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 4 AnAnnotatedListofSpeciesConcepts. . . . . . . . . . . . . . . . . . . . . . . 77 5 SpeciesConceptsandBeyond:SelectedTopicsRelatingtothe SpeciesProblem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 5.1 Agamospecies:AreSexualandAsexualSpeciestheSame?. . . . . 98 5.2 TheHierarchyofSpeciesConcepts:TheEvolutionary, GeneralLineageandUnifiedSpeciesConcepts. . . . . . . . . . . . . . 101 5.3 TheBiologicalSpeciesConcept. . . . . . . . . . . . . . . . . . . . . . . . . 109 5.4 TheGeneticSpeciesConcept. . . . . . . . . . . . . . . . . . . . . . . . . . . 115 5.5 CladisticallyBasedSpeciesConceptsandtheHennigian Convention. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 5.6 PhylogeneticSpeciesConcepts. . . . . . . . . . . . . . . . . . . . . . . . . . 121 5.6.1 TheMonophylyVersionofthePhylogeneticSpecies Concept(mPSC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 5.6.2 TheDiagnosabilityVersionofthePhylogenetic SpeciesConcept(dPSC). . . . . . . . . . . . . . . . . . . . . . . . . 125 5.7 ProkaryoticSpeciesandSpeciesConcepts. . . . . . . . . . . . . . . . . . 131 5.8 SpeciesasProcessorasPatternEntities?. . . . . . . . . . . . . . . . . . . 135 5.9 Superspecies,SubspeciesandEvolutionarilySignificantUnits. . . 137 6 SpeciesDelimitation:DiscreteNamesinaContinuousWorld withFuzzyBoundaries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 6.1 TheGeneralProblem:DiscreteNamesinaContinuousWorld. . . 145 6.2 TheTokogeny/PhylogenyDivide:Saviourofthe SpeciesRank?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 6.3 “Chronospecies”,RingSpeciesandaDelimitationAnalogy withLanguages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 6.4 SimilarityandAttemptsatStandardizingtheAssignment ofSpeciesStatus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 7 ThePracticalRelevanceofSpeciesConceptsandthe SpeciesProblem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 7.1 ThePowerofNames:“TaxonomyasDestiny”?. . . . . . . . . . . . . . 163 7.2 SpeciesastheCurrencyinBiodiversityResearch andEvolutionaryBiology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 7.3 ConcludingRemarks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 8 ABriefSummaryoftheBook. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
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