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AxiomathesWhere Science Meets Philosophy ISSN 1122-1151Volume 25Number 3 Axiomathes (2015) 25:239-251DOI 10.1007/s10516-014-9244-9

Biodiversity Surgery: Some EpistemologicalChallenges in Facing Extinction

Elena Casetta & Jorge Marques da Silva

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ORIGINAL PAPER

Biodiversity Surgery: Some Epistemological Challengesin Facing Extinction

Elena Casetta • Jorge Marques da Silva

Received: 14 May 2014 / Accepted: 6 August 2014 / Published online: 21 August 2014

� Springer Science+Business Media Dordrecht 2014

Abstract Biological conservation has a long story, but what distinguishes Con-

servation Biology from previous conservation fields is its multidisciplinary scope

and its character as a mission-oriented crisis discipline. These characteristics sug-

gested the introduction of the metaphor of biological conservation as a sort of

surgery. This paper is about the initial stages of such surgery. Firstly, some data

about the so-called ‘‘Big Sixth’’—the disease—will be presented together with some

information about Conservation Biology—the surgeon. Then epistemic and epis-

temological difficulties in extinction assessment and conservation prioritization, and

triage in particular, will be pointed out. It will be argued that, while data deficiency

arising from empirical and practical constraints can in principle be overcome, a

different order of difficulties stems from the competition among several species

concepts. In this case, it will be suggested that the extent of complications is of such

significance to require a thorough re-assessment of the very nature of the patients,

i.e., outside the metaphor, of the concept of species.

Keywords Big Five � Biodiversity � Conservation biology � Extinction � IUCN �Species � Triage

E. Casetta (&)

Centro de Filosofia das Ciencias (CFCUL), Universidade de Lisboa, Lisboa, Portugal

e-mail: elenattesac@gmail.com

J. Marques da Silva

Departamento de Biologia Vegetal e Centro de Biodiversidade, Genetica Integrativa e Funcional,

Faculdade de Ciencias, Universidade de Lisboa, Lisboa, Portugal

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DOI 10.1007/s10516-014-9244-9

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1 The Big Sixth and the Birth of Conservation Biology

Fossil records provide strong evidence that at least five mass extinctions—the so-

called ‘‘Big Five’’—occurred in the history of life on Earth. According to some

studies,1 we could have entered the Sixth mass extinction. In the reconstruction

made by Niles Eldredge (2001), the first phase of the Big Sixth would have started

100,000 years ago, when our species began to disperse out of Africa, and the second

phase would correspond to the starting of agriculture, around 10,000 years ago. The

Millenium Ecosystem Assessment suggests that contemporary extinction rate could

be 1,000 to 10,000 times higher than rates recorded among fossil lineages (Hassan

et al. 2005: 105); and this trend is not expected to change, unless for the worst, in the

near future:

Changes in biodiversity due to human activities were more rapid in the past

50 years than at any time in human history, and the drivers of change that

cause biodiversity loss and lead to changes in ecosystem services are either

steady, show no evidence of declining over time, or are increasing in intensity.

Under the four plausible future scenarios developed by the MA (Millenium

Ecosystem Assessment), these rates of change in biodiversity are projected to

continue, or to accelerate. (Millenium Ecosystem Assessment 2005: VI)

Extinction is a perfectly natural phenomenon (the 99 % of the four billion species

estimated to have evolved on Earth over the last 3.5 billion years are now extinct)2

and, normally, background extinction rate is compensated by speciation rate. In

mass extinctions, things are different: the loss of lineages—usually as a

consequence of some natural catastrophe—is too massive, happens too suddenly

and quickly in geological time, and affects too many ecosystems and biomes for

being balanced by standard speciation. The recovery from mass extinctions usually

proceeds by the spreading of new taxa from surviving taxa by adaptive radiation, an

evolutionary mechanism in which a lineage diversifies extremely rapidly, originat-

ing several new lineages evolving different adaptations. The rapid diversification of

mammals, for instance, constitutes probably an adaptive radiation subsequent to the

End-Cretaceous mass extinction (in which 40 % of genera and 76 % of species were

lost), some 65 million years ago, when mammals began to diversify into the niches

formerly occupied by dinosaurs.3

Compared to the Big Five, the Big Sixth involves our species as its primary

cause; not only by eradicating species directly but also, and mainly, because of

environmental consequences of our activities. These put existing species and

ecosystems under unprecedented ecological pressure: consider that existing

ecosystems evolved primarily in the absence of Homo sapiens and that the

ecological stressors that species are now experiencing because of our activities—

pollution, habitat fragmentation, overfishing and overhunting, introduction of

invasive non-native species, CO2 levels rising—are ‘‘all more extreme … than most

1 See, among others, Eldredge 2001; Wilson 1988.2 Barnosky et al. 2011: 51.3 For a recent study confirming this hypothesis, see O’Leary et al. 2013.

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living species have previously experienced.’’ (Barnosky et al. 2011: 6) Moreover,

since recovery from mass extinctions is estimated to occur on timescales

encompassing millions of years, it is quite likely that human beings won’t be

able to assist to the possible recovery from the Big Sixth.

It is clear that, since our activities are the main cause of the massive and rapid loss

of species that the Earth is experiencing, we are somehow responsible. For instance,

habitat fragmentation—a collateral effect of constructing highways or creating

hydroelectric reservoirs—is affecting the ability of several species to migrate in

response to climate change, putting their survival at serious risk. We are responsible

as causes in the very same way as geological processes, climatic changes, or natural

catastrophes have been causes in the previous mass extinctions. But, unlike geological

processes, besides of being factually responsible, we are also moral agents since we

possess the capacity to evaluate reasons for acting; accordingly, unlike geological

processes, we can take responsibility of facing extinction and conserving biodiversity.

Even though a science of biological conservation is centuries old, a precise

discipline, Conservation Biology, has been recently devoted to ‘‘address the biology

of species, communities, and ecosystems that are perturbed, either directly or

indirectly, by human activities or other agents. Its goal is to provide principles and

tools for preserving biological diversity.’’ (Soule 1985: 727) The birth of

Conservation Biology can be traced back, in Europe, around the end of Sixties

(the British journal ‘‘Biological Conservation’’ has been established in 1968). In the

United States, Conservation Biology arose, as a systematic and organized academic

discipline, in the Eighties, in parallel with the appearance of the term ‘‘biodiver-

sity’’. Conventionally, the year of birth is 1985, at the end of the Second Conference

on Conservation Biology that took place in Michigan, when biologist Michael Soule

was given the task of organizing the ‘‘Society for Conservation Biology’’.

As mentioned, biological conservation—understood as conservation of natural

resources and wildlife management—has a long story, but what distinguishes

Conservation Biology from previous conservation fields is ‘‘its multidisciplinary

scope and its admitted character as a mission-oriented crisis discipline.’’ (Ehrenfeld

1995) These characteristics, and in particular that of being a mission-oriented crisis

discipline, are underlined by Soule in his 1985 article, ‘‘What is Conservation

Biology?’’ in which the metaphor of biological conservation as a sort of surgery is

introduced:

Conservation biology differs from most other biological sciences in one

important way: it is often a crisis discipline. Its relation to biology … is

analogous to that of surgery to physiology and war to political science. In

crisis disciplines, one must act before knowing all the facts. Crisis disciplines

are then a mixture of science and art, and their pursuit requires intuition as

well as information. (Soule 1985: 727)

When environmental conservation is at issue, theoretical and practical matters go

hand in hand, requiring the cooperation of different disciplines, from philosophy of

science and ethics, to political sciences and economics, to, of course, conservation

sciences, ecology, and biology at large. Bearing this in mind, a distinction can

nonetheless be introduced for convenient expository reasons, between two major

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phases in ‘‘biodiversity surgery’’. The first one is more theoretical and has to do with

assessing extinction and establishing priorities of intervention; the second one is

more practical and political, and consists of deciding the best conservation policy

and implementing it. In the first phase, the damage has to be assessed, and the

priority of species’ treatments4 has to be determined based on the severity of their

condition (the so-called ‘‘triage’’). The most important organization devoted to this

twofold end is the International Union for Conservation of Nature (IUCN), the

world’s largest global environmental network, which also provide, with its ‘‘Red

List of Threatened Species’’, a wide and updated inventory of the conservation

status of species.5 In the second phase, the appropriate conservation programs have

to be elaborated and applied, and their results have to be monitored. By

‘‘appropriate’’ we mean, in particular, appropriate to the species at issue and their

habitat, and appropriate to budget constraints. A conservation project based on

translocation, for instance, could be appropriate for one species at a given point but

not for another one, for which, let us say, captive bred program could be a more

effective practice. Moreover, according to the budget at disposal, a certain

procedure can be more optimal than another one, as we will see in a short while.

In the remainder of this article, we focus on the first phase, discussing some of

the main theoretical difficulties that have to be taken up in assessing extinction and

in triaging. These difficulties mostly stem, as it will become evident in the course of

the work, from the epistemology of species. It will then be suggested in the

conclusion that their extent is of such significance to require a thorough re-

assessment of the very nature of the patients (i.e., outside the metaphor, of the

concept of species) in the light of the needs and the aims of Conservation Biology.

2 Extinction Assessment

To assess the gravity of the damage caused by the alleged Big Sixth, two metrics

need to be known: extinction rate and magnitude. The extinction rate is the number

of species that have gone extinct divided by the time over which the extinctions

occurred; the magnitude is the percentage of species that have gone extinct. (In mass

extinctions, the extinction rate is significantly higher than the background extinction

rate, and the magnitude amounts to at least 75 % of species.)

One of the main problems in assessing extinction rate and magnitude is data

deficiency. To assess the metrics of the Big Five, fossil evidence has been used.

Based on fossils, extinction is declared when a taxon disappears from the fossil

record. This datum, however, is strongly approximate. On the one hand, it is

affected by the fact that fossil records usually include only species with anatomical

hard parts that fossilize well. Several species just left no trace whatsoever, and their

extinction has not been recorded. On the other hand, by the fact that most

4 Even though biodiversity conservation cannot be reduced to species conservation only, species remain

the primary target and the focus of conservation efforts.5 Notice, however, that the IUCN Red List is strongly biased towards terrestrial species, and towards

animals rather than plants, even though ‘‘steps are underway of rectify these biases’’, as it can be read in

the IUCN Red List Overview (http://www.iucnredlist.org/about/red-list-overview).

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assessments of fossil diversity take place at the level of genus, not of species, and

the species-to-genus ratio of an extinct genus is usually extrapolated from the

species-to-genus ratio of a well-known group.6 Several biases also affect the metrics

of the Big Sixth. First, only a very little fraction of species (and a strongly biased

towards terrestrial species, vertebrates in particular) has been described, 1.9 million,

and only 1.2 million have already been catalogued in a central database. Recent

results suggest that some 86 % of existing species on Earth and 91 % of species in

the ocean still await description.7 Of 1.9 million described species, only a tiny

fraction of species (\2.7 %) have been formally evaluated for extinction status by

the International Union for Conservation of Nature, and even for clades thoroughly

evaluated from IUCN, many species fall into the Data Deficiency category.8

Considered that Conservation Biology is a ‘‘mission-oriented discipline’’, dealing

with data deficiency is somehow constitutive of its very nature: ‘‘In crisis

disciplines—writes Soule—one must act before knowing all the facts.’’ Still, a

distinction should be traced between lack of knowledge caused by data deficiency

and lack of knowledge rooted in the very epistemology of species. In the first case,

data deficiency can in principle be overcome. For instance, data deficiency around

the Big Five can be filled—if not entirely, at least partially—by improving

comparative methods and statistical and extrapolative techniques; and IUCN, as

mentioned, is proceeding towards a more comprehensive species list, less biased

towards terrestrial and animal species. Of course, data collecting is anything but an

easy task to be performed, mostly because of budget and time constraints; for

instance, considered that around 90 % of the species on Earth have yet to be

discovered, it is more than likely that many of them will be extinct before we even

know of their existence. But, in principle, without such time and budget constraints,

they could be discovered.

In the second case, things are different. If asked the question: ‘‘what is a

species?’’ different researchers can answer providing different species concepts.

Species concepts can be seen as theories on the nature of species that tell us, at the

same time, what a species is and how to identify it. But, as it is widely known, more

than twenty (Mayden 1997) species concepts are competing. As of today, the most

important are the following three (or some version of them): the Biological Species

Concept, according to which species are ‘‘groups of interbreeding natural

populations that are reproductively isolated from other such groups’’ (Mayr 1970:

12); the Ecological Species Concept, that describes a species as ‘‘a lineage … which

occupies an adaptive zone minimally different from any other lineage in its range

and which evolves separately from all lineages outside its range’’ (Van Valen 1976:

233); and the Phylogenetic Species Concept, which defines a species as ‘‘the

smallest diagnosable cluster of individual organisms within which there is a parental

pattern of ancestry and descent.’’ (Cracraft 1983: 170) A fourth concept that is

worthy to mention is the Morphological Species Concept, that asserts that ‘‘species

are the smallest groups that are consistently and persistently distinct, and

6 Barnosky et al. 2011.7 Mora et al. 2011.8 Barnosky et al. 2011; http://www.iucnredlist.org/.

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distinguishable by ordinary means.’’ (Mayden 1997: 402) This last concept has been

strongly criticized since the criterion of distinctness, in addition of being highly

subjective, is neither necessary nor sufficient. Morphological distinctness is not

necessary because, for instance, cryptic species are considered to be species as they

are incapable of interbreeding, but they are morphologically indistinguishable. And

it is not sufficient because in several cases species show strong morphological

differences that are surely not species determinative differences, such as sexual

dimorphism or morphological differences in the developmental stages of several

organisms. In spite of its limits, however, the Morphological Species Concept is

widely used because, being based on similarity, is easy to apply (it is the first

concept that taxonomists apply when faced with a new sample), and sometimes is

the only one that can be used in the absence of any information concerning gene

flow and the ecological niche of a species, as it is the case, for instance, with fossils.

According to several authors, the plurality of species concepts is required by, or

follows from, the very nature of biology. For instance, according to Kitcher (1984),

who follows a distinction made by Mayr (1976: 360), biology covers two separate

fields: functional biology and evolutionary biology. Functional biology is primarily

interested in issues of ‘‘proximate causation’’, while evolutionary biology is more

interested in issues of ‘‘ultimate causation’’. The two kinds of investigations—

neither of them is more fundamental than the other—require different concepts of

species: more focused on structure and morphology, the first one; more on

evolutionary history the second. For Ereshefsky (1992: 676), who offers an

ontological argument for species pluralism, ‘‘the forces of evolution segment

th[e] tree [of life] into a number of different types of lineage … includ[ing] lineages

that form interbreeding units, lineages that form ecological units, and lineages that

form monophyletic taxa.’’ The different species concepts would capture these

different types of lineages. If this sort of arguments is persuasive—and we think it

is—difficulties stemming from the presence of several species concepts cannot be

overcome by improving our knowledge as it would be the case for mere data

deficiency. They require something different, be it a choice among equivalent rival

theories, or a way to reconciling them. Let us see now what these difficulties are.

In alpha-taxonomy, organisms are grouped into species, but different species

concepts may result in different and often inconsistent ways of partitioning the very

same samples. This is because different species concepts point at different properties

which are, at the very same title, properties of species. The reason why it is so is quite

simple: speciation is a gradual process, as already Darwin acknowledged. Species

concepts refer to different types of properties to diagnose species, but those

properties—such as morphological distinctiveness, ecological distinction, or repro-

ductive incompatibility—can be found in different moments of the speciation process.

Thus, between the ancestral species—when no new relevant property has been

acquired and there is a unanimous agreement on the existence of just one species—

and the ‘‘new’’ one or ones—when all the distinctive properties have been acquired

and there is no doubt that a new species (or two, depending on the speciation model)

originated—, there will be a ‘‘gray zone’’, in de Queiroz’s words (2007), in which

different species concepts will possibly diagnose a different number of species. The

problem is that we cannot directly witness speciation events, which generally take

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hundreds of thousands of years; all we have are living organisms or, even worse, fossil

organisms, of which we try to reconstruct the evolutionary story. Discrepancy in

counts, which can be easily explained from a diachronic point of view, becomes

inconsistency in counts from a synchronic point of view. And thus, even though the

why-answer is somehow simple, dealing with it is not.9

Since both extinction rate and magnitude depend on species counting, and

species counts can strongly vary according to the species concept used by

identifying species, disagreement on the nature of species causes a severe problem

in assessing extinction. For instance, taxa identified in fossils data are usually

morphospecies, namely groups of organisms detected on the basis of the

Morphological Species Concept. By contrast, in the case of extant organisms,

species are usually identified in terms of Biological Species Concept or even

Phylogenetic Species Concept. This means that, for instance, the number of species

as calculated for the Big Five (i.e. from fossils) is inconsistent with the number of

species as calculated for the alleged Big Sixth.

Inconsistency also affects current counts. Count of lichen species worldwide ranges

from around 13,000 to 30,000 species; count of bird species worldwide ranges from

9,000 to 20,000. (Richards 2010) It has been calculated, for instance, that the fifteen

amphibian species recognized under the Biological Species Concept have ‘‘become’’

140 under the Phylogenetic one (MacLaurin and Sterelny 2008: 28), and Agapow et al.

(2004) quantified the effects of a shift to Phylogenetic Species Concept from other

concepts, finding a general 48 % ‘‘increase’’ of the number of species, and consequently

of endangered species and the amount of resources required for their preservation.

3 Triage

The next stage in biodiversity surgery is the establishment of conservation priorities.

With another medical metaphor, it is the so-called ‘‘triage’’ (from the French word,

‘‘trier’’: to sort). In medicine, triage is the assignment of degrees of urgency—based

on the severity of injury—in order to decide the order of treatment of patients.

Triage is necessary, first of all, because of the insufficient capacity, in terms of

budget or time, or more generally available resources, of treating all patients

properly; and it is based on the fact that different patients require a different degree

of urgency of treatment (some patients are in more critical state than others and will

die if not treated immediately). Another element that is taken into account in triage

is the different extent of the treatment required as well as the probability of recovery

compared to the amount of investment. This last element, in particular, highlights an

important difference between medical triage and conservation triage. In conserva-

tion triage, it is the economic approach that prevails: mathematical models are used

to assess the costs and benefits of conservation plans, and the goal is optimizing the

return on investment. For instance, it has been calculated that in the case of

Sumatran Tiger, a high budget would allow to successfully manage six populations.

9 An additional source of discrepancy in counting species is the cognitive biases of researchers, such as

count creep and lumper/splitter tendencies, as analyzed by Jody Hey (2001).

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But, in a low budget scenario—as it is often the case—trying to monitor and manage

all six populations wouldn’t be the best choice; monitoring three populations only

would be the optimal solution, and trying to save six would result in a waste of

money and resources.10

The IUCN Red List is widely recognized as the most comprehensive approach

for evaluating the conservation status of plant and animal species, it assesses the

severity of species condition, placing them in different categories of risk, just like

triage in emergency department (Figs. 1, 2).

The criteria used by the IUCN to establish when a taxon—usually, but not

always, a species11—is threatened (i.e. when it must be placed in one among the

CR, EN, and VU categories) are ‘‘a range of quantitative criteria; meeting any one

of these criteria qualifies a taxon for listing at that level of threat.’’ (IUCN Red List

2012: 4–5) Summarizing and simplifying a little, these criteria are population size

and its rate of reduction; extent of occurrence in geographic range and/or size of

area of occupancy; probability of extinction in the wild.

Members of the IUCN categories—the patients—are mainly species, evaluated

by means of their populations or segments of populations. Again, as it was the case

for assessing extinction, the plurality of species concepts has serious consequences

also for prioritization. In the following we briefly examine two of them, the first one

tied to the reclassification of species; the second to their value.

3.1 Species Concepts and Reclassification

Consider the following example. Brown Lemur (Eulemur fulvus) is a polytypic

species comprising six subspecies whether diagnosed by means of the Biological

Species Concept. In 1999, Wyner et al. applied the Phylogenetic Species Concept to

it. They used population aggregation analysis coupled with cladistic analysis and

determined that, even though all six subspecies share a common ancestor, two of

them (E.f. collaris and E.f. albocollaris) share a more recent common ancestor,

which split off from the ancestor common to all six subspecies. Accordingly, under

a Phylogenetic Species Concept, Brown Lemur should not be considered as one

species but rather as three species, one composed of E.f. collaris, one of E.f.

albocollaris, and one composed of the other four subspecies. What are the

consequences of this from the point of view of species conservation? Let us imagine

that, before 1999, Brown Lemur were an endangered species, monitored and

managed by a certain conservation strategy. After the reclassification, that very

conservation action would proved to be completely misdirected. In fact, while

before 1999 restoring one population of Brown Lemurs would have been enough for

saving the species (ideally, of course), after 1999, at least three different populations

of animals would need to be saved. On a general stance, reclassifying Brown Lemur

as three distinct units (three phylogenetic species), rather than as one polytypic

10 Stutchbury 2013.11 ‘‘The criteria can be applied to any taxonomic unit at or below the species level’’ (IUCN Red List

2012: 4).

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species composed of six subspecies, would mean the need to conserve three species

rather than one. From an economical point of view, things change a lot.12

A case not so far from the though experiment sketched above actually happened

in the southeastern U.S. with red wolf (Canis rufus).13 The red wolf, considered—

Fig. 1 A triage sign at a mexican emergency room (http://en.wikipedia.org/wiki/Triage)

Fig. 2 List of IUCN’s categories of risk (IUCN Red List 2012: 5)

12 Agapow et al. 2004.13 Zimmer 2008.

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on morphological bases—a separate species, has recently been the subject of a big

conservation effort, including captive breeding and reintroduction in the wild. But,

based on recent genetic studies, Wilson et al. (2000), concluded that Canis rufus and

Canis lupus lycaon have a common evolutionary history that is independent of the

gray wolf. In other words, they are sister taxa and should be considered as

conspecific. If the reclassification is accepted (as it has been, for instance, in a recent

checklist of North American mammals by Baker et al. 2003), the conservation

project devoted to red wolves would be just misdirected, since thousand of animals

of that species are extant in Canada—even though they are called Canis lupus

lycaon.

3.2 Species Concepts and the Value of Species

As the IUCN itself recognizes, the category of threat is not sufficient to determine

priorities for conservation actions. It just provides an assessment of the extinction

risk based on criteria that are as quantitative as possible. But, think of the case of

Sumatran Tiger mentioned before, or the hypothetical case of Brown Lemur just

discussed; what if budget constraints would force us to choice one among the three

Brown Lemur phylogenetic units? And how to decide which populations of

Sumatran Tiger to focus on to the detriment of the other three? Or, more generally,

towards which species (or subspecies, populations, segment of populations) should

conservation efforts be directed, often to the detriment of other species? More

generally, in an ideal world it may be possible save everything, but under actual

conditions triage is necessary, as said, and triage implies that saving one patient

could mean loosing another patient. Merely quantitative criteria are obviously not

enough in order to choose, as the IUCN itself recognize; our values and beliefs enter

into play. This can be seen easily by looking at the general model underlying the

economic approach to prioritization that we mentioned in the previous section. Such

a model can be summarized by mean of a simple equation:14

Score ¼ value of species � benefit to species � probability of successð Þ=cost

While benefit to species, probability of success, and cost are quantitative

variables, the value of species is not. Even though species can be attributed a

monetary value (justified, for instance, by the fact that in order to evaluate the

benefit-costs of a conservation action, the patient should be expressed in the same

metric as the investment), monetary value is just a way to quantify some different

type of values we attribute to them. These values include ‘‘ecological, evolutionary,

social, cultural and economic attributes, with higher value given to charismatic

species… or those features that provide functional support to ecosystems or

people.’’15 Once again, different species concepts, making reference to different

properties to identify species, can emphasize a certain value: making a choice

among species concepts means also choosing among values. For instance, going for

14 Stutchbury 2013; Bottrill et al. 2008.15 Bottrill et al. 2008.

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a Phylogenetic Species Concept will privilege evolutionary value. In this case, the

value of species or lower units will be directly proportional to its evolutionary

uniqueness. An Ecological Species Concept will stress ecological value attributing,

for instance, a higher value to keystone species—namely those species that, even

when rare, play a key role in ecosystems and, accordingly, the removal of one of

them often results in severe loss of biodiversity—, no matter how much

evolutionary unique they can be. Moreover, the consideration of some types of

value—such as charisma, popularity, or cultural significance of species are

completely missing in scientific species concepts, in spite of their relevance for

general public.

4 Concluding Remarks: Rethinking the Concept of Species?

It has been suggested (e.g. Mishler 2010) that the concept of species should

simply be dismissed as inevitably flawed. However, this would seem a bad move,

and probably not a feasible one. In fact, even though the data in our possess

cover just a small part of the variety of life on Earth, and even though they are

strongly biased and approximate, they are mostly framed in terms of species: we

already possess good—although not complete or fully coherent—species

inventories, such as species collections in natural museums, or species online

databases, as well as some fairly reliable ways to recognize species in practice,

by means of both traditional taxonomic tools and molecular techniques such as

the DNA barcoding (Hebert et al. 2003). Moreover, species are well entrenched

in the framework of evolutionary biology, as well as being a familiar concept to

the general public.

The presence of several species concepts is not a problem in itself; on the

contrary it seems to be required by the nature of biological explanations and, as

said, it would mirror the way in which evolution itself works in producing new

lineages. Yet the extent of the difficulties stemming from the usage of several

species concepts is of such import as to require a rethinking of the concept of

species itself, at least in the scope and for the purpose of Conservation Biology.

Our suggestion is that a solution could be to proceed from the plurality of species

concepts towards a pluralistic species concept. Here follow some possible

directions for this reassessment, assuming as a departure point the difficulties

stressed in Sects. 2 and 3.

First, as for extinction assessment (Sect. 2), the question is: how to overcome the

inconsistency and discrepancy in species counts arising from the use of different

species concepts? In order to handle with the inconsistency between species counts

regarding the Big Five and the Big Sixth, it has been suggested to proceed towards a

comparative technique that ‘‘would aggregate modern phylogenetic species into

morphospecies or genera before comparing with the fossil record’’.16 We would like

to suggest that an analogous move could be done to deal with the possible

inconsistency between species counts when extant organisms are at issue. In

16 Barnosky et al. 2011.

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particular, the following could be a possible path to explore. A certain agreement

has been reached on a general definition or characterization of species as a lineage

or a segment of a lineage. For instance, LaPorte (2007), defines a general concept of

species as ‘‘the least inclusive salient and stable lineage to which an organism

belongs,’’ and de Queiroz (2007) talks of species as ‘‘separately evolving

metapopulation lineages.’’ But a general concept of this sort is of course too broad

to be implemented. It should then be provided with diverse and explicit criteria of

application specifically designed for Conservation Biology. The resulting concept

would be monistic in recognizing species as lineages, and pluralistic in being

provided with a multiplicity of criteria of application.

Second, from the analysis of conservation prioritization (triage, Sect. 3), two

different points emerge. One is that a more fine-grained concept of species than the

biological or the morphological species concepts would lead to greater surgical

precision in prioritization. Such precision is desirable and even required, consid-

ering that economical resources are limited and that, for some species, there remain

only a very small number of exemplars. Shouldn’t we just go for the Phylogenetic

Species Concept, whose application typically results in more fine-grained species

(think of the nested reclassification of Brown Lemur)? There are several reasons

why the answer should be in the negative. First, the Phylogenetic Species Concept

has been criticized as being strongly arbitrary (in particular, both the level of

divergence necessary for a lineage to qualify as a different species and the trees that

can be constructed from the very same data would involve a high degree of

arbitrariness). Second it would require an enormous effort in revising the data in our

possession, which are mostly framed in terms of biological species or morphospe-

cies. Third, electing evolutionary uniqueness as privileged value seems to be a too

theory-dependent choice, and it would neglect completely other values whose

significance cannot be reduced to evolutionary history. Here, again, proceeding

towards a pluralistic species concept could be a more feasible path. And such a

concept, provided with the adequate application criteria, could also go into the right

direction for handling the second critical point that emerges from the analysis of

triage. Something seems missing in our concepts of species when conservation

prioritization is at issue, namely some criteria that help us to decide beyond the

mainly quantitative assessment of risk. As said, electing one species concept among

the several on the market would result in missing values that are taken into account

by the others, and that cannot be reduced to the chosen one. If this sounds

reasonable, proceeding towards a pluralistic species concept, whose criteria of

application take into account the needs and the goals of Conservation Biology could

be a path to explore.

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