This paper argues that typical biological species are natural kinds, on a familiar realist understanding of natural kinds—classes of individuals across which certain properties cluster together, in virtue of the causal workings of the world. But the clustering is far from exceptionless. Virtually no properties, or property-combinations, characterize every last member of a typical species—unless they can also appear outside the species. This motivates some to hold that what ties together the members of a species (...) is the ability to interbreed, others that it is common descent. Yet others hold that species are scattered individuals,of which organisms are parts rather than members. But not one of these views absolves us of the need to posit a typical phenotypic profile. Vagueness is here to stay. Some seek to explain the vagueness by saying species are united by “homeostatic property clusters”; but this view collapses into the more familiar realist picture. (shrink)

The fact that the names of biological species refer independently of identifying descriptions does not support the view of Ghiselin and Hull that species are individuals. Species may be regarded as natural kinds whose members share an essence which distinguishes them from the members of other species and accounts for the fact that they are reproductively isolated from the members of other species. Because evolutionary theory requires that species be spatiotemporally localized their names (...) cannot occur in scientific laws. If natural kind status is denied to species on this ground, it must also be denied to most classes of concrete entities which are now accorded such status. (shrink)

What are biological species? Aristotelians and Lockeans agree that they are natural kinds; but, evolutionary theory shows that neither traditional philosophical approach is truly adequate. Recently, Michael Ghiselin and David Hull have argued that species are individuals. This claim is shown to be against the spirit of much modern biology. It is concluded that species are natural kinds of a sort, and that any 'objectivity' they possess comes from their being at the focus of a consilience (...) of inductions. (shrink)

Stamos squarely confronts the problem of determining what a biological species is, whether species are real, and the nature of their reality. He critically considers the evolution of the major contemporary views of species and also offers his own solution to the species problem.

In the 1970s, the position that species are natural kinds characterized by essences came to be challenged, and was replaced by the view that species are individuals. To date, this remains the dominant position, at least among biologists, despite influential arguments that species can be construed as homeostatic property cluster kinds (employing a revised notion of essence). Recent philosophical discussions have broadened the scope by articulating a neo-Aristotelian essentialism for species, developing a post-essentialist account of human (...) nature, and scrutinizing temporal persistence conditions for species in the light of species de-extinction efforts. Yet most such current discussions concerning species have not relied on the notion of an essence, which also parallels recent accounts of natural kinds in the philosophy of science. (shrink)

Difficulties with the typological concept of species led biologists to reject the "typological" presupposition of an archetype which is manifest in each member of a species. The resulting concept of species, which is here called the phenotypic species concept, is considered as implying that biological species are not real. Modern population thinking has given rise to the concept of a species as a gene-pool. This modern concept is contrasted here with the phenotypic concept (...) in light of some general criteria for evaluating species concepts and is shown to be more satisfactory. Finally, it is held that to ask if a species is real is to ask whether the species grouping arrived at by applying the principles involved in the species concept corresponds with groups of organisms amongst which important biological relationships exist. It is argued that in this sense species, as defined by the gene-pool concept, are certainly real. (shrink)

We defend a realistic attitude towards biological species. We argue that two species are not different species because they differ in intrinsic features, be they phenotypic or genomic, but because they are separated with regard to gene flow. There are no intrinsic species essences. However, there are relational ones. We argue that bearing a gene flow relation to conspecifics may serve as the essence of a species. Our view of the species as a (...) Gene-Flow Community differs from Mayr’s definition of the species as a reproductive community. In a reproductive community, each organism is able to successfully reproduce with each other. However, there are species in which geographically distant organisms lost their ability to successfully reproduce, due to strong genetic adaptations to the respective local environmental conditions. Despite this loss of the ability to mutually reproduce, they are still bound by gene flow via continuous intermediate populations. This replacement of Mayr’s notion of an interbreeding potential as a criterion for species membership has important implications for the treatment of populations in allopatry and sympatry. (shrink)

Although it is possible to regard a species as a set with a special internal structure, it is preferable to regard a species as an individual precisely to emphasize this internal structure. It is necessary to recognize, moreover, that two organisms that are part of a single entity with respect to one process need not be part of a single entity with respect to another process. Furthermore, choosing to regard two entities (with respect to one process) as conspecific (...) is not to deny that there are two entities within this species. Thus, the systematist need not propose formal names for every entity he discovers, but the names he proposes ought to be as faithful to the relationship among the entities as is possible. (shrink)

Summary The common view has been that Darwin regarded species as artificial and arbitrary constructions of taxonomists, not as distinct natural units. However, in his transmutation notebooks he clearly subscribed to the reality of species, on the basis of the criterion of non-interbreeding. A consequence of this biological species concept was his identification of the acquisition of reproductive isolation as the mark of the completion of speciation. He developed in the notebooks a theory of geographic speciation (...) on the grounds of (a) an empirical correlation between barriers and the geographical distributions of allied species, (b) the analogy of artificial isolation in the formation of new domesticated varieties, and (c) the logical consequence of blending inheritance. A brief discussion of Darwin's species concept in later writings concludes the paper. (shrink)

Biological type specimens are a particular kind of voucher specimen stored in natural history collections. Their special status and practical use are discussed in relation to the description and naming of taxonomic zoological diversity. Our current system, known as Linnaean nomenclature, is governed by the International Code of Zoological Nomenclature. The name of a species is fixed by its name-bearing type specimen, linking the scientific name of a species to the type specimen first designated for that (...) class='Hi'>species. The name-bearing type specimen is not necessarily a typical example of the species, while establishment of the boundaries of a species requires empirical taxonomic studies. The International Code of Zoological Nomenclature allows for the naming of new species in the absence of preserved specimens. However, photos and DNA sequences should not function as primary type material, while new species should not be described and named without deposition of at least one type specimen in a collection. Philosophically, species are individuals, spatiotemporally restricted entities. Therefore, Linnaean species names are proper names, which do not define the taxon but serve as a label, providing an ostensive definition of a species. Paratypes have no name-bearing function but, nevertheless, are highly valued specimens in natural history collections. Paratypes should be restricted to those specimens originating from the same sample as the holotype. Diagnosis of a species taxon involves establishment of a connection between a Linnaean name and determination of the boundaries of the species. A first step in this process is the choice of an appropriate species concept. It is not the examination of holotypes and paratypes that necessarily provides the best estimate of the taxonomic boundaries of a species, but this is facilitated by a set of voucher specimens known as the hypodigm. Dissatisfaction with the present nomenclatural code led some researchers to propose emendations. Other taxonomists suggested abandoning Linnaean nomenclature and proposed the alternative PhyloCode, albeit that it relegates the naming of species taxa to the traditional nomenclatural codes. (shrink)

Some philosophers of biology state that the metaphysical status of biological species is context determined by the use different branches of biology make of their corresponding proper names, so that one and the same biological species can be both an individual and a natural kind. In this paper, I aim to undermine the idea, often associated with the present thesis, according to which the debate about the metaphysical status of biological species should be deflated, (...) since it would be possible to translate every sentence from natural-kind talk to individual-talk and vice versa. I offer a charitable interpretation of the principle grounding such an idea and show how it is in tension with independent theoretical biological notions. (shrink)

The entry of time and history into biological systems of classification is perhaps the single most significant development in the history of biological systematics in the modern era. Darwin's claiming that descent is ‘… the hidden bond of connexion which naturalists have been seeking under the term of the natural system’, rather than seeing the answer in the multitude of previous attempts to resolve the problem in terms of morphological affinities, analogies, and complex relations of resemblance, marked the (...) turning point in a long search into the meaning of biological taxonomy, and allowed the development of Darwin's insights by Haeckel, Plate and others into modern phylogenetic systematics. (shrink)

This chapter contains sections titled: Introduction Early Species Concepts—Linnaeus Biological Species Concepts Phylogenetic Species Concepts Species Concepts and Speciation Conclusions Postscript: Counterpoint References.

The heart of this book is the reciprocal relationship between philosophical theories of mind and empirical studies of animal cognition.

Are species real categories or just conventions? Are species natural kinds? Are teleological statements a distinctive feature of biology? Can life sciences escape from teleology? These are common issues in philosophy of biology. This paper aims to show that in order to answer to each of these questions it is inevitable to take a position respecting the others. Therefore, there is a historical relation between the concept of species and teleological issues. In order to analyse such relation, (...) I will take a historical perspective.After making such historical reconstruction focused on the Aristotle, Linnaeus, Buffon and Lamarck thoughts, I will analyse the Darwinian peculiar view respect teleology and his ideas about species. Although Darwin set out the collapse of teleological essentialisms in biology, there are important vestiges of teleology in his theory. (shrink)

Before the Darwinian revolution species were thought to be universals. Since then, numerous attempts have been made to propose new definitions. The twentieth-century German philosopher Nicolai Hartmann defined 'species' as an individual system of processes and a process of life of a higher-order. To provide a clear understanding of Hartmann's conception of species, I first present his method of definition. Then I look at Hartmann's Philosophie der Natur (1950) to present his concepts of "organism" and "species." (...) And I end the paper by pointing out two possible systematic inconsistencies. (shrink)

In this paper I explore how the discussion about the existence of laws in biology, more specifically laws about species taxa, bears on the issue of whether species are kinds or individuals. One of the main arguments offered in favor of the view that species are individuals is that it explains the lack of laws about species taxa, since laws cannot refer to individuals. My aim in this paper is to question the premise that there are (...) no laws about species axa and consequently to show that the proposed argument fails. I will argue that even if there are no strict scientific laws about species taxa, still, scientifically interesting, law-like generalizations are made which are used for explaining phenomena and predicting properties of species members. The existence of these law-like generalizations, in turn, suggests that species are, at least prima facie, best conceived of as kinds. (shrink)

Frank E. Zachos offers a comprehensive review of one of today's most important and contentious issues in biology: the species problem. After setting the stage with key background information on the topic, the book provides a brief history of species concepts from antiquity to the Modern Synthesis, followed by a discussion of the ontological status of species with a focus on the individuality thesis and potential means of reconciling it with other philosophical approaches. More than 30 different (...) species concepts found in the literature are presented in an annotated list, and the most important ones, including the Biological, Genetic, Evolutionary and different versions of the Phylogenetic Species Concept, are discussed in more detail. Specific questions addressed include the problem of asexual and prokaryotic species, intraspecific categories like subspecies and Evolutionarily Significant Units, and a potential solution to the species problem based on a hierarchical approach that distinguishes between ontological and operational species concepts. A full chapter is dedicated to the challenge of delimiting species by means of a discrete taxonomy in a continuous world of inherently fuzzy boundaries. Further, the book outlines the practical ramifications for ecology and evolutionary biology of how we define the species category, highlighting the danger of an apples and oranges problem if what we subsume under the same name ("species") is in actuality a variety of different entities. A succinct summary chapter, glossary and annotated list of references round out the coverage, making the book essential reading for all biologists looking for an accessible introduction to the historical, philosophical and practical dimensions of the species problem. (shrink)

The biological species (biospecies) concept applies only to sexually reproducing species, which means that until sexual reproduction evolved, there were no biospecies. On the universal tree of life, biospecies concepts therefore apply only to a relatively small number of clades, notably plants andanimals. I argue that it is useful to treat the various ways of being a species (species modes) as traits of clades. By extension from biospecies to the other concepts intended to capture the (...) natural realities of what keeps taxa distinct, we can treat other modes as traits also, and so come to understand that theplurality of species concepts reflects the biological realities of monophyletic groups.We should expect that specialists in different organisms will tend to favour those concepts that best represent the intrinsic mechanisms that keep taxa distinct in their clades. I will address the question whether modes ofreproduction such as asexual and sexual reproduction are natural classes, given that they are paraphyletic in most clades. (shrink)

Species is one of the most basic concepts for almost all branches of biology, and it is also one of the most controversial concepts. An important aspect of "the species problem" is the question of "what the ontological status of species is". Traditionally, the answer to the issue about "the ontological status of species" is biological essentialism. Biological essentialism claims that species is a "natural kind", which argues that all and only the members (...) of a species have a common essence. Each species is separated from all others by a sharp discontinuity. However, Darwin's evolutionary theory argues that species are gradual, and the boundaries between species are vague. This view conflicts with biological essentialism. With the continuous transmission of Darwin's theories, biological essentialism was gradually abandoned by philosophers and scientists. In recent years, some philosophers try to resurrect biological essentialism by using new biological resources. Their theories are known as New Biological Essentialism, which mainly includes three different approaches: The Barcode Theory of DNA, Relational Essentialism, and HPC Theory. However, there are so many defects in their theories that they don't provide a successful defense for biological essentialism. By analyzing these theories, I try to point out that the dilemma and failure of new biological essentialism dues to the conflict between its ontological presupposition and modern biological practice. The conflict leads to the tension between essentialism and biology. Further, I argue that the best way to eliminate the tension between biology and essentialism is to regard species as “heterogeneous kinds”. This new understanding of species abandons biological essentialism at the ontological level but retains the value of epistemology of regarding the species as “natural kinds”. (shrink)

This chapter contains sections titled: Historical and Current Views of Species Return to a Darwinian View of Species Practical Implications Postscript: Counterpoint References.

Over the decades, there has been substantial empirical evidence showing that the unity of species cannot be maintained by gene flow. The biological species concept is inconclusive on this point. The suggestion is made that the unity of species is maintained rather by selection constantly spreading new alleles throughout the species, or bygene circulation. There is a lack in conceptual distinction between gene flow and gene circulation which lies at the heart of the problem. The (...) concept of gene circulation also sheds some new light on the problem of typology and on such a broad concept as evolution. A new species definition is proposed. (shrink)

The biological species concept deals both with the meaning of the sexual species as a harmonious gene pool and with its protection against deleterious outbreeding (effected by isolating mechanisms). According to the Darwin-Muller-Mayr theory isolating mechanisms are acquired by incipient species during alloparty. Isolating mechanisms are not the result of ad hoc selection, but of a change of function of properties acquired during the preceding isolation of the incipient species. The role of behavioral properties (recognition) (...) among the isolating mechanisms has long been recognized and described by naturalists but was rejected as basis of a species definition for a number of valid reasons. (shrink)

ArgumentBiological drawings of newly described or revised species are expected to represent the type specimen with greatest possible accuracy. In taxonomic practice, illustrations assume the function of mobile representatives of relatively immobile specimens. In other words, such illustrations serve as “immutable mobiles” in the Latourian sense. However, the significance of drawing in the context of first descriptions goes far beyond that of illustration in the conventional sense. Not only does it synthesize the verbal catalogue of the type's morphological characteristics: (...) it also enables the examination of these traits. The efficacy of drawing is thus closely related to its power to direct and redirect observation; it is inextricably bound up with the act of making a drawing. Although the invariance of the “immutable mobiles” is a key virtue of the logistics of “paperwork,” the recovery of graphic knowledge requires a much stronger dynamic activity – a process of sequential processing that brings out differences by translating the phenomenon under examination into various modes of graphic representation. (shrink)

Various philosophers and evolutionary biologists have recently defended the thesis that species are individuals rather than sets. A decade of debates, however, did not suffice to settle the matter. Conceptual analysis shows that many of the key terms involved are ambiguous. Current disagreements should dissolve once this is recognized. Explication of the concepts involved leads to new programs for philosophical research. It could also help biology by showing how extant controversies concerning evolution may have conceptual rather than factual roots.

Contrary to frequent characterisations, exotic species should not be identified as damaging species, species introduced by humans, or species originating from some other geographical location. Exotics are best characterised ecologically as species that are foreign to an ecological assemblage in the sense that they have not significantly adapted with the biota constituting that assemblage or to the local abiotic conditions. Exotic species become natives when they have ecologically naturalised and when human influence over their (...) presence in an assemblage (if any) has washed away. Although the damaging nature and anthropogenic origin of many exotic species provide good reasons for a negative evaluation of such exotics, even naturally-dispersing, nondamaging exotics warrant opposition. Biological nativists' antagonism toward exotics need not be xenophobic and can be justified as a way of preserving the diversity of ecological assemblages from the homogenising forces of globalisation. Implications for Yellowstone National Park policy are explored. (shrink)

The species concept is one of the oldest and most fundamental in biology. And yet it is almost universally conceded that no satisfactory definition of what constitutes a species has ever been proposed. The present article is devoted to an attempt to review the status of the problem from a methodological point of view. Since the species is one of the many taxonomic categories, the question of the nature of these categories in general needs to be entered (...) into. (shrink)

Biologists and philosophers have long recognized the importance of species, yet species concepts serve two masters, evolutionary theory on the one hand and taxonomy on the other. Much of present-day evolutionary and systematic biology has confounded these two roles primarily through use of the biological species concept. Theories require entities that are real, discrete, irreducible, and comparable. Within the neo-Darwinian synthesis, however, biological species have been treated as real or subjectively delimited entities, discrete or (...) nondiscrete, and they are often capable of being decomposed into other, smaller units. Because of this, biological species are generally not comparable across different groups of organisms, which implies that the ontological structure of evolutionary theory requires modification. Some biologists, including proponents of the biological species concept, have argued that no species concept is universally applicable across all organisms. Such a view means, however, that the history of life cannot be embraced by a common theory of ancestry and descent if that theory uses species as its entities.These ontological and biological difficulties can be alleviated if species are defined in terms of evolutionary units. The latter are irreducible clusters of reproductively cohesive organisms that are diagnosably distinct from other such clusters. Unlike biological species, which can include two or more evolutionary units, these phylogenetic species are discrete entities in space and time and capable of being compared from one group to the next. (shrink)