Species Concepts in Biology: Historical Development, Theoretical Foundations and Practical Relevance

227 Pages·2016·1.901 MB·English

by  Frank E. Zachos (auth.)

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
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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