Species delimitation based on diagnosis and monophyly, and its importance for advancing mammalian taxonomy

2018·0.27 MB·

by  Gutiérrez, Eliécer E

ZOOLOGICAL RESEARCH
Species delimitation based on diagnosis and monophyly,
and its importance for advancing mammalian taxonomy
EliécerE.Gutiérrez1,2,*,GuilhermeS.T.Garbino3
1Pós-GraduaçãoemBiodiversidadeAnimal,DepartamentodeEcologiaeEvolução,CentrodeCiênciasNaturaiseExatas,Universidade
FederaldeSantaMaria,SantaMaria,RS97105-900,Brazil
2DivisionofMammals,NationalMuseumofNaturalHistory,SmithsonianInstitution,WashingtonDC20013-7012,USA
3Pós-graduação,DepartamentodeZoologia,InstitutodeCiênciasBiológicas,UniversidadeFederaldeMinasGerais,BeloHorizonte,Minas
Gerais31270-901,Brazil
ABSTRACT INTRODUCTION
A recently proposed taxonomic classification for extant
Arecentlyproposedtaxonomicclassificationofextant
ungulates (Groves & Grubb, 2011) sparked a series of
ungulates sparked a series of publications that publications criticizing the species concept upon which the
criticize the Phylogenetic Species Concept (PSC) classification was based, i.e., Phylogenetic Species Concept
claiming it to be a particularly poor species concept. (PSC) (Heller et al., 2013; Zachos et al., 2013; Zachos,
2013,2015;Zachos&Lovari,2013),albeitpreviouspublished
These opinions reiteratively stated that (1) the two
opinionshadalreadypresentedsomeofthesamearguments
fundamental elements ofthe "PSC", i.e., monophyly
against the PSC (e.g., Frankham et al., 2012; Garnett &
and diagnosability, do not offer objective criteria as
Christidis, 2007; Isaac et al., 2004; Tattersall, 2007). Two
to where the line between species should be drawn; main claims about the PSC have been reiteratively used to
and (2) that extirpation of populations can lead to highlight it as a particularly poor species concept: (1) the
artificial diagnosability and spurious recognitions of two fundamental elements of the PSC, i.e., monophyly and
diagnosability, do not offer objective criteria as to where the
species. This sudden eruption of criticism against
linebetweenspeciesshouldbedrawn;and(2)theextirpation
the PSC is misleading. Problems attributed to
ofpopulationscanleadtoartificialdiagnosabilityandspurious
the PSC are common to most approaches and recognitionsofspecies. Moreover,thesecriticismsportraythe
conceptsthatmodernsystematistsemploytoestablish use of the PSC as detrimental to conservation efforts. We
species boundaries. The controversial taxonomic argue that the problems attributed to the PSC are common
to most methodological approaches to species limits and to
propositionsthatsparkedcriticismagainstthePSCare
themostcommonlyusedspeciesconceptsthathavebeenthe
indeedhighlyproblematic,notbecauseofthespecies
basisforthetaxonomicclassificationsofmammalscurrentlyin
conceptuponwhichtheyarebased,butbecauseno
use. Furthermore, we present evidence that the PSC based
evidence(whatsoever)hasbecomepublictosupport on diagnosability and monophyly as operational criteria has
a substantial portion of the proposed classification. helped to substantially advance mammalian systematics. In
We herein discuss these topics using examples addition, we show that the recent criticism against Groves &
Grubb’s(2011)ungulatetaxonomyismistakenlyfocusedonan
from mammals. Numerous areas of biological
"allegedpoverty"ofthePSC(seeabriefcommentrelevantto
research rest upon taxonomic accuracy (including
thisgeneraltopicbyTsangetal.,2016,p. 529),whereasthe
conservationbiologyandbiomedicalresearch);hence,
realcauseoftaxonomicinflationinthatproposedclassification
itisnecessarytoclarifywhatare (andwhatarenot)
therealsourcesoftaxonomicinaccuracy.
Received: 14December2017; Accepted: 12February2018; Online:
Keywords: Alpha taxonomy; Phylogenetic Species 08March2018
Concept; Species concepts; Taxonomic inertia; *Correspondingauthor,E-mail:[email protected]
Taxonomicinflation DOI:10.24272/j.issn.2095-8137.2018.037
SciencePress ZoologicalResearch39(5):301–308,2018 301
laysonnumerousempiricalproblems. With regard to the dPSC (sensu Cracraft, 1983; see also
Eldredge & Cracraft, 1980; Nixon & Wheeler, 1990; Wheeler
PHYLOGENETICSPECIESCONCEPT(PSC)
&Meier,2000andreferencestherein),weagreewithprevious
Before we discuss these matters, we must clarify that the criticisms (Heller et al., 2013, 2014; Zachos & Lovari, 2013,
name “Phylogenetic Species Concept” has been associated Zachos, 2016a) in that this concept is prone to promote
to various concepts (e.g., McKitrick & Zink, 1988; Nixon spuriousrecognitionofmeregeographic(includingsubspecies)
& Wheeler, 1990), two of which are central in the or even individual variants of a single species as if such
above-mentioned debate. These concepts can be better variants were each a valid species. This is due to the high
regardedassetsofcriteriaforspeciesdelimitationratherthan degree of subjectivity and arbitrariness implicit in the task
"concepts",asproposedbydeQueiroz(2007);however,herein of judging what characteristics are to be deemed adequate
werefertothesesetsofcriteriaas"concepts"onlytofacilitate to diagnose species and distinguishing such characteristics
communication by using the same terminology employed by fromthosethatwouldsimplyleadtodiagnosesofpopulations,
authors of previous articles. These concepts are as follows or groups thereof, within a single species (but see Wiens
(seesummariesbyGrovesetal.,2017;Zachos,2016a): & Servedio, 2000). Species are not phenotypically and
genotypically homogeneous across geography, therefore it is
Phylogenetic species concept, diagnosis-based alwaysthecasethatvariouspopulationswithinasinglespecies
version (dPSC): “The smallest diagnosable cluster can be diagnosed. These diagnoses by themselves must
of individual organisms within which there is a not be a justification to regard such populations as different
parentalpatternofancestryanddescent”(Cracraft, species. This limitation of the dPSC is exacerbated when
1983, p.170). Subsequently formulated as “... sample sizes are small, as is often the case for medium and
the smallest aggregation of populations (sexual) largemammals.Inthesecases,aresearchermayerroneously
or lineages (asexual) diagnosable by a unique infertheexistenceofphenotypicdiscontinuityandthepresence
combination of character states in comparable of characteristics enabling the diagnosis of a sample—the
individuals (semaphoronts)” (Nixon & Wheeler, latter based on a set of specimens that at the time were
1990). A more recent version states that species perceived as worthy of species-level recognition. However,
are “... the smallest population or aggregation as more samples are obtained, individuals with intermediate
ofpopulationswhichhasfixedheritabledifferences phenotypeswithrespecttotheputativenewspeciesandother
from other such populations or aggregations” geographic samples may be found. This would render the
(Groves&Grubb,2011;seealsoGroves,2017). putative new species, which was previously thought to be
diagnosable, conspecific with an already recognized species
Phylogenetic species concept, monophyly-based (e.g.,Peresetal.,1996).Examplesoftheseplausibleproblems
version (mPSC) “... a geographically constrained are abundant in the proposed classification of ungulates by
groupofindividualswithsomeuniqueapomorphous Groves & Grubb (2011) (see below), but are by no means
character, is the unit of evolutionary significance” exclusive to it (e.g., Díaz et al., 1999, 2002; Fonseca &
(Rosen,1978,p.176). Pinto,2004; Solari,2004; vanRoosmalenetal.,2000,2007);
numerousexamplesexistinearlycontributionstomammalian
Athirdconceptthatmustbeincorporatedinthediscussion taxonomy(e.g.,Miller,1912; Pocock,1941; Robinson&Lyon,
isasfollows(seeGrovesetal.,2017): 1901),andeventhelastdecadehasseenclaimsadvocatingfor
therecognitionofaspeciesmadeonthebasisofphenotypic
Phylogenetic species concept, diagnosis-and- diagnosesofasfewasoneortwospecimens—e.g.,Meijaard
monophyly-based version (dmPSC), defined as et al., 2017 p. 513; see also Mantilla-Meluk (2013) for a
“... the smallest diagnosable cluster of individual monkeysubspeciesnamedonthebasisofmorphometricdata
organismsformingamonophyleticgroupwithinwhich andpelagecolorationfromonlyfourspecimens.Unfortunately,
there is a parental pattern of ancestry and descent” in some cases descriptions of species have been carried out
(Mayden,1997,p.407;McKitrick&Zink,1988). notonlywithunacceptablysmallsamplesizesbutalsomerely
based on images (illustrations, photos, or both) and lacking
DO THESE VERSIONS OF THE PSC OFFER OBJECTIVE preserved type specimens (see Pine & Gutiérrez, 2018 for a
CRITERIA AS TO WHERE THE LINE BETWEEN SPECIES reviewofcasesandproblemsassociatedtothisphenomenon).
SHOULDBEDRAWN? Althoughnodataexisttosupportthenotionthatthecollection
of a single individual (for it to properly serve as a preserved
The short answer is “no”, but “no” would also be the answer
holotype) significantly increases the probability of an already
if the question were asked with regard to any other species
endangeredspeciestobecomeextinct,someresearchersmay
concept, including the Biological Species Concept (BSC)
prefer not to carry out such collection (e.g., Donegan, 2008;
whenappliedtoallopatricpopulations(seeGroves,2012and
butseeDubois&Nemésio,2007;Dubois,2009),oritmaybe
references therein). However, the three phylogenetic species
unfeasible due to impediments in obtaining collection permits.
concepts described above differ importantly regarding the
In such cases, a wide survey of museum specimens might
degreeofobjectivitywithwhichtheycanbeapplied.
302 www.zoores.ac.cn
lead to the discovery and subsequent use of specimens in 2003;Nixon&Wheeler,1990;deQueiroz&Donoghue,1988;
taxonomic descriptions. Undertaking comprehensive surveys Zachos,2014b;Zander,2007;seealsoFunk&Omland,2003).
of museum specimens may be disregarded by describers of Discussing these views requires a much more extensive text
new species, but the possible data yielded, which may be andwoulddistractfromtheaimofthisperspectivepiece—i.e.,
coupled with photos of living animals, might ameliorate the clarifying that despite the recent criticisms made against
detrimentaleffectsofextremelysmallsamplesizesandhelpin PSCs,atleastoneoftheseconceptshasservedtopositively
unveilinggeographicandnon-geographic(ontogenetic,sexual) advance mammalian systematics. By requiring monophyly,
variation(e.g.,Garbinoetal.,2016). the application of the dmPSC secures that a phylogenetic
Thesecondconcept,themPSC,underwhichspeciesmust inferenceisconductedtodescribeorrevalidateaspecies,thus
be both monophyletic and geographically restricted, seems decreasingthechancesthatpolyphyleticgroupsofpopulations
indefensible. Within a species there can be large numbers wouldbenamedasaspecies. Thesephylogeneticestimates
ofmonophyleticgroupsthataregeographicallyrestrictedonly alsoprovideframeworksforevaluatingalternativesincasesin
due to recent changes in their environment. An example which the description or recognition of a clade as a species
of this is the populations of brocket deer of the Cordillera wouldrenderanalreadyrecognizedspeciesasparaphyletic.In
de Mérida, Venezuela, which for decades were recognized suchcases,researchersmightsimplynotdescribeorformally
as a valid species, Mazama bricenii. This recognition was recognize that clade at all—which might be acceptable, as
based on no data whatsoever and on the assumption of not every clade in a phylogenetic tree represents a taxon
a plausible differentiation due to its supposed geographic worth naming—or describe it at the subspecies level—with
isolation. However, a recent study that employed ecological paraphyly persisting at a lower taxonomic rank—or describe
niche modeling found that, if these populations were truly itandacceptparaphyleticspeciesasvalid, inwhichcasethe
isolated in modern time, such isolation commenced not long researchercouldnotinvokeanyspeciesconceptthatrequires
ago (Gutiérrez et al., 2015). The study also found that while monophyly (including the dmPSC) upon which to base the
thefocalpopulationformedamonophyletichaplogroup,itwas description. Whichever of these alternatives the researcher
embedded within a larger (yet shallow) clade whose terminal prefers,andattemptstojustify,duetophilosophical,pragmatic,
branches corresponded to Mazama rufina. Results from that or both considerations, the fact that the dmPSC requires a
studyshowedthatwhatwasonceknownasMazamabricenii phylogeneticestimateisanadvantageoverotherconceptsthat
actuallycorrespondstoMazamarufina(Gutiérrezetal.,2015), donot,includingthedPSCandtheBSC.
andillustratehowtheapplicationofthemPSCwouldhaveled The requirement that a candidate species must also be
tomistakenlyrecognizeM.bricenii asifitwereavalidspecies. diagnosable in order to be recognized under the dmPSC is
Such taxonomic recognition would be a mPSC-based artifact indispensable.Aspeciesmusthaveaseriesofgeneticallyfixed
causedby(1)thefactthatsequencesobtainedfromspecimens characteristicsthatarecommontoitsmembersandthatserve
fromtheCordilleradeMérida(wherethepopulationstowhich todistinguishitfromothersuchspecies. However,asalready
the name M. bricenii would apply occur) were recovered in a discussed (see above), diagnosability alone is, in general, an
monophyletic haplogroup; and (2) because those populations inadequateapproachtoestablishspecieslimits.
mightbegeographicallyisolatedinmoderntime. Acknowledging the existence of the dmPSC is important
The third concept, dmPSC, for which species must be becauseitdoesrepresentoneofthemostexplicitmethodsto
both monophyletic and diagnosable, has been useful for inferspecieslimits—contraauthorsthatignoredtheexistence
improving mammalian taxonomy. As previously noted, many of this concept in their arguments against or in favor of
monophyletic groups are found within a single species, and the "PSC" (e.g., Gippoliti et al., 2018; Groves, 2012, 2017;
that monophyly per se does not constitute a criterion to Heller et al., 2013; Zachos & Lovari, 2013; Zachos et
determine where the line between species should be drawn. al., 2013; Zachos, 2013, 2014a, 2015, 2016a). Some
However, it is also true that assessing whether a candidate operationalstepsindelimitingspecieswillalwaysbearbitrary.
species is monophyletic or not provides a fundamental basis In this sense, the advantage of the dmPSC over other
for its potential recognition as a valid species. Recognizing concepts is that its operational criteria for recognition of
a polyphyletic taxon as if it were a valid species would be speciescanbeobjectivelytested. Inotherwords, monophyly
absurd. On the other hand, in some situations (e.g., species and diagnosability are, in general, more easily testable for
originatingfromperipheralisolation)acandidatespeciesmight allopatric populations than reproductive barriers (BSC), and
meetthecriteria(i.e.,monophylyanddiagnosability)forvalidity more objectively demonstrated than the central criteria upon
under the dmPSC, but its recognition renders the species in which other concepts define species, such as “ecological
whichthecandidatehadthusfarbeenincludedasparaphyletic. roles” in the Ecological Species Concept (Van Valen, 1976).
No consensus has been reached as to whether taxonomists When applied based on sufficient geographic and taxonomic
should accept paraphyletic species as valid, or, alternatively, sampling, and, ideally (but not strictly necessary; see
if taxonomists should recognize as valid only those that are below), employing phylogenetic inferences using data from
monophyletic(seeCarteretal.,2015;Crisp&Chandler,1996; independentsources(e.g.,DNAsequencedataobtainedfrom
Dias et al., 2005; Ebach et al., 2006; Freudenstein, 1998; independently inherited genes), the dmPSC has improved
Funk & Omland, 2003; Hörandl, 2006, 2007; Nelson et al., the taxonomic classifications of various groups of mammals,
ZoologicalResearch39(5):301–308,2018 303
some of which remained problematic for decades. Among Dorcatragus megalotis, Eudorcas nasalis, Eudorcas tilonura,
studiesthatexemplifyhowthedmPSChashelpedtoadvance Gazella acaciae, Gazella karamii, Gazella shikarii, Lama
mammalian systematics, even if some of them used this mensalis, Madoqua hararensis, Mazama fuscata, Mazama
species concept without explicitly or correctly invoking it, are jucunda, Mazama trinitatis, and Redunca cottoni; (3) no
thoseondidelphidmarsupials(e.g.,Díaz-Nieto&Voss,2016; published phylogenetic information seems to be the basis of
Giarlaetal.,2010; Gutiérrezetal.,2010; Martínez-Lanfranco mostoftheirtaxonomicpropositions;(4)ingeneral,nodetailed
etal.,2014;Pavanetal.,2017;Vossetal.,2018),rodents(e.g., discussions were presented on whether recognizing a taxon
Hawkins et al., 2016; do Prado & Percequillo, 2017; Rogers as a valid species was more appropriate and justifiable than
& González, 2010; Voss et al., 2013), bats (e.g., Baird et al., regarding it as a subspecies, and it seems that the objective
2008; Molinari et al., 2017; Moras et al., 2016; Velazco et of the authors was to merely recognize as valid species as
al., 2010), and medium and large mammals (e.g., Bornholdt manytaxaaspossible,withoutcriticalevaluationofalternatives
etal.,2013; Gutiérrezetal.,2015; Helgenetal.,2009, 2013; (e.g., recognizing subspecies when appropriate); (5) a list
Janecˇka et al., 2008; Koepfli et al., 2008; Miranda et al., of the specimens examined was not provided, and hence it
2017; do Nascimento & Feijó, 2017 (and references therein is difficult for the scientific community to evaluate the authors’
for phylogenetic evidence)). These studies have not only assertionsonspecimenmorphologiesbasedonthesamematerial
unraveled the true-species nature of previously unrecognized withcertainty;(6)nodataweremadeavailablethatwouldenable
species, but in many cases have shown that taxa considered reproductionandtestabilityoftheanalysesthatwerethebasisof
asvalidspeciesfordecadesarenotvalidspeciesatall. thetaxonomicpropositions;(7)althoughtheauthorscitepublished
TheapplicationofanyPSCcanpromoterampanttaxonomic studies for some of the taxonomic changes they proposed, for
inflation when applied without sufficient rigor. In our opinion, otherstheydidnotandnowhereintheirmonographcanbefound
this inflation is caused less by philosophical aspects and results from any quantitative analyses. We cannot understand
properties of the PSCs and more by empirical shortcomings. why Groves & Grubb (2011) failed to publish the results of their
In several studies, geographic and individual variation do not quantitativeanalysesgivencurrentpossibilitiestodoso(seebelow).
appeartobesatisfactorilyaddressed,andnamesareappliedto Unfortunately,thisproblemisnotuniquetotheproposedungulate
what could be intraspecific variants (see examples in Tattersall, taxonomicclassificationofGroves&Grubb. Animportantvolume
2007). Onotheroccasions,monophyleticgroupsrecoveredfrom on mammals of South America (Patton et al., 2015) contained
molecular phylogenies based on sequence data from a single the first modern taxonomic treatments of various rodent groups
locus promptly receive new or revalidated names (e.g., Boubli (e.g.,familySciuridae,generaAepeomys,Oecomys,Rhipidomys,
etal.,2012; Thinhetal.,2010). Nevertheless, itisimportantto Thomasomys), but results from analytical procedures assessing
notethatwhentheestablished,traditionaltaxonomicclassification geographicandnon-geographicvariationofthosegroupshavenot
of a focal group is the result of dogmatic acceptance of expert been published (in the book or elsewhere), and in some cases
opinions (often past-century authorities), without support from it seems unlikely they will ever be published. Luckily, several
data (see Gutiérrez & Helgen, 2013), then even the use of unpublished Ph.D. dissertations that served as the basis for the
limitedevidence—e.g., analysesofsequencedatafromasingle book sections treating those taxa have been privately shared
locus(despitethewell-knownshortcomingsofthisapproach;see among colleagues. Clearly, making these Ph.D. dissertations
Dávalos&Russell,2014; Knowles&Carstens,2007; Maddison, (andotherunpublishedmaterial)digitallyavailabletothescientific
1997),ideallycoupledwithqualitativeand/orquantitativeanalyses communityfreeofchargefromarepositoryontheInternet(e.g.,
of morphological data—can well justify taxonomic changes if Dryad,Figshare,InternetArchive,ResearchGate,Zenodo),iftheir
based on adequate sampling (e.g., Gutiérrez et al., 2010, 2015, authorsgrantauthorization,shouldbeconsideredbytheeditorsof
2017;Vossetal.,2013;contraZachos,2009,2016b). thisbook,andsimilaractionsshouldbeconsideredbyauthorsand
The proposed ungulate taxonomic classification that editorsoffuturemonographsintroducingtaxonomicclassifications.
sparked the recent series of criticism against the PSC
CANEXTIRPATIONOFPOPULATIONSLEADTOARTIFICIAL
is particularly problematic, but not because it was based
DIAGNOSABILITY AND SPURIOUS RECOGNITIONS OF
on the dPSC. Most controversial aspects of this proposed
SPECIESUNDERTHEdmPSC?
classificationarenotatallassociatedtoanyspeciesconcept,
asitmightseemifonereadstherecentdebatebetweenFrank The short answer is "it can", but again the same answer
Zachos and Colin Groves and their co-authors with regard would apply if the question were asked about other species
to the "PSC", but rather to more practical aspects of such a concepts, including the BSC. In their criticism of the "PSC",
monograph, to name just a few (see also Heller et al., 2013; Zachos&Lovari(2013)claimedthatthefactthatextirpationof
Holbrook, 2013; Zachos, 2014a, p. 1): (1) Groves & Grubb populationscanleadtoartifactualdiagnosabilityandmonophyly
(2011)didnotassessgeographicvariationatallformostofthe isoneoftheweaknessesofthePSC that makes this concept
species they recognized; (2) unfortunately, for some species aparticularlypoorone. Theystatedthat“Thereisyetanother
recognized by these authors, the sample size employed was line of argumentation that clearly shows the shortcomings of
not indicated nor any published study cited to support the both diagnosability and monophyly as yardsticks for species
taxonomicproposals,whereasformanyotherallegedspecies delimitationandthatwebelieveisanothercoupdegrâceforthe
the sample sizes were extremely low—e.g., Alcelaphus tora, PSC.Diagnosability (just likereciprocalmonophyly) can and
304 www.zoores.ac.cn
oftendoesoccurasaconsequenceofextinctionofintermediate Let us imagine a species, species A, with wide distribution
forms...”. Unfortunately, Zachos&Lovari(2013)didnotrealize andshowinggeographicvariationbywayofaclineinseveral
thatextirpationofintermediatepopulationsisoneofthenatural qualitativecranialtraitsbelievedtobetaxonomicallyimportant,
causesofspeciation. Theseeventsleadtospeciation,affecting i.e., used by most authors to distinguish species within the
gene flow and ecological adaptation of extreme phenotypes in corresponding genus. We will illustrate these traits as color
populations that previously were genetically connected by the and shape in polygons that represent populations of species
existence of intermediate populations. In fact, it could be said A (Figure 1, panel 1). If recent extirpations of intermediate
thatlivingtaxathatcanbevalidlyrecognizedontheplanetexist populations take place and only those populations occurring
asseparatebiologicalentitiesandastaxonomicallydiagnosable attheoppositeextremesofspeciesA’srangeremainasextant,
units only because of the extinction of intermediate forms. If then these populations will become allopatric and it would be
all intermediate forms that have lived since the beginning of highly likely that they would be considered as members of
life on Earth were still with us, then all living organisms, from differentspeciesundertheBSC(Figure1,panel2). TheBSC
prokaryotes to eukaryotes and from plants to animals, would would fail to regard these populations as conspecific, even
exist as a single morphological and reproductive continuum: employing the approach presented by Tobias et al. (2010;
no distinguishable taxa would exist! Logically, in cases in see also Brooks & Helgen, 2010), which uses the degree of
whichextirpationshavetakenplacefairlyrecently(e.g.,dueto differentiation known to exist between different but sympatric
human-related causes) no speciation may have yet occurred. species (i.e., species A and B in Figure 1) as a standard
In such cases, the extirpation of populations can potentially to assess the taxonomic relevance of differentiation between
leadtoartifactualrecognitionsofspeciesunderthePSCs,but allopatric populations (i.e., populations of species A in North
thisissueisfarfrombeingassociatedonlytothePSCs;rather, andSouthAmericainFigure1)—inorderwords,thisapproach
it is a problem that can potentially affect most, if not all, usestheformerdegreeofdifferentiationasathresholdatwhich
species concepts currently in use. For example, this issue (or above) allopatric populations could be treated as different
can lead to artifactual recognition of species under the BSC. speciesundertheBSC.

Figure1Illustrationofhowpopulationextirpationscanpromoteartifactualrecognitionofpopulationsofasinglespeciesasifthey

weredifferentspeciesundertheBiologicalSpeciesConcept(andmanyotherconcepts)
Figure 1 Illustration of how population extirpations can promote artifactual recognition of
SpeciesA,whichisrepresentedbyquadrilaterals(rectangleandrectangle-likepolygons),possessesawidedistributionandgeographicvariationbywayofaclinein
severalqualitativecranialtraitscopnospiduelraetidontasx oofn ao msiincgallely sipmepcoiersta anst ;ifh ethreeyin wtheerse editrfafeitrsenatr espilelucsietrsa utenddears tchoel oBrioalnodgsichaal pSepoecfitehse polygons(panel1).SpeciesB,which
isrepresentedbycircles,isrestrictedtoNorthAmerica,whereitoccursinsympatrywithsomeNorthAmericanpopulationsofspeciesA(panel1).Ifextirpationof
Concept (and many other concepts)
populationsofspeciesAtakesplaceandonlythosepopulationsoccurringattheoppositeextremesofspeciesA’srangeremainasextant,thenthesepopulationswill
Species A, which is represented by quadrilaterals (rectangle and rectangle-like polygons),
becomeallopatric(panel2).Inthatscenario,itwouldbehighlylikelythattheremainingextantpopulationswouldbeconsideredasmembersofadifferentspecies
undertheBSC(panel2).TheBSpCoswseosusleds faa iwltiodere dgiastrrdibtuhteisoen panodp uglaeotiognraspahsicc voanrsiapteiocnifi cb,ye wveany eomf ap lcolyinineg inth seevaeprparlo qaucahliptaretisveen tedbyTobiasetal.(2010;seealso
Brooks&Helgen,2010),whichusesthedegreeofdifferentiationknowntoexistbetweendifferentbutsympatricspecies(i.e.,speciesAandB)asastandardto
cranial traits considered taxonomically important; herein these traits are illustrated as color and
assessthetaxonomicrelevanceofdifferentiationbetweenallopatricpopulations(i.e.,populationsofspeciesAinNorthandSouthAmerica).
shape of the polygons (panel 1). Species B, which is represented by circles, is restricted to North
CONCLUSIONS America, where it occurs in sympatry with some Noruths eAsmebriocatnh podpiualgatnioonss iosf sapencdies mA onophyly (dmPSC) to delimit
species has been, and will continue to be, important for
(panel 1). If extirpation of populations of species A takes place and only those populations
Major differences exist among the different concepts labeled positively advancing mammalian taxonomy. Our preceding
as the "Phylogenetic SpeocciceusrrinCgo ant tcheep otp"p,osaitne dexttrhemeeso onfe spethciaest A's randgeis rceumsasinio ans esxthaontu, ltdhenre thcetsifey pompuislautniodnes rstandings that could arise
will become allopatric (panel 2). In that scenario, it would be highly likely that the remaining
extant populations would be considered as members of a different speciesZ uonodloerg tihcea BlRSCe s(epaanreclh 39(5):301–308,2018 305
2). The BSC would fail to regard these populations as conspecific, even employing the approach
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COMPETINGINTERESTS
do Nascimento FO, Feijó A. 2017. Taxonomic revision of the tigrina
Theauthorsdeclarethattheyhavenocompetinginterests. Leopardus tigrinus (Schreber, 1775) species group (Carnivora, Felidae).
PapéisAvulsosdeZoologia(SãoPaulo),57(19):231–264.
AUTHORS’CONTRIBUTIONS
do Prado JR, Percequillo AR. 2017. Systematic studies of the genus
ThewritingofafirstdraftofthemanuscriptwasledbyE.E.G.Bothauthors Aegialomys Weksler et al., 2006 (Rodentia: Cricetidae: Sigmodontinae):
substantiallycontributedtoallaspectsofthispublication. geographic variation, species delimitation, and biogeography. Journal of
MammalianEvolution,doi:10.1007/s10914-016-9360-y.
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DoneganTM.2008.Newspeciesandsubspeciesdescriptionsdonotand
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