Biological Systematics

History and Theory

Igor Pavlinov

• Publisher: CRC Press
• Year: 2021
• ISBN:
  9781000364316
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Zoology
• Index: Biological Sciences

This volume reviews the historical roots and theoretical foundations of biological systematics in an approachable text. The author outlines the structure and main tasks of systematics. Conceptual history is characterized as a succession of scientific revolutions. The philosophical foundations of systematic research are briefly reviewed as well as the structure and content of taxonomic theories. Most important research programs in systematics are outlined. The book includes analysis of the principal problematic issues as "scientific puzzles" in systematics. This volume is intended for professional taxonomists, biologists of various specialties, students, as well as all those interested in the history and theory of biology and natural sciences.

Key Features

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• Considers the conceptual history of systematics as the framework of evolutionary epistemology

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• Builds a hierarchically organized quasi-axiomatic system of taxonomic theory

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• Contends that more reductionist taxonomic concepts are less objective

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• Supports taxonomic pluralism by non-classic philosophy of science as a normal condition of systematics

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• Documents that "taxonomic puzzles" result from conflict between monistic and pluralistic attitudes

Related Titles

de Queiroz, K. et al., eds. Phylonyms: A Companion to the PhyloCode (ISBN 978-1-1383-3293-5)

Sigwart, J. D. What Species Mean: A User's Guide to the Units of Biodiversity (ISBN 978-1-4987-9937-9)

Rieppel, O. Phylogenetic Systematics: Haeckel to Hennig (ISBN 978-1-4987-5488-0)

Wilkins, J. S. Species: The Evolution of the Idea, 2nd ed. (ISBN 978-1-1380-5574-2)

1

A Brief Introduction to Systematics

Any science is ordering, and if systematics is equivalent to ordering, then systematics is synonymous with science.

George Simpson

If we try to characterize Nature, briefly but at the same time sufficiently profoundly, as a sphere of application of cognitive activity, then perhaps the most appropriate “formula” may be as follows: Nature is an ordered diversity of its phenomena (objects and processes). From a scientific viewpoint, acknowledging the orderliness of Nature as its fundamental feature is of prime importance: cognizable can be only what is ordered. Thus, all scientific disciplines are essentially engaged in the same enterprise: they investigate various manifestations of the diversity of Nature and look for a certain order in this diversity.

Two main analytical approaches are usually distinguished in how the ordered diversity of Nature can be comprehended: parametrizing and classifying [Hempel 1965; Rozov 1995; Subbotin 2001]. In the first approach, the main emphasis is on the order as such: certain parameters (variables, etc.) are fixed and their gradients are linked by a single formula. Illustrative examples are the ratio of mass and energy in physics, the relationship between reaction rate and concentration of substances in chemistry, the relationship between body size and age of a multicellular organisms in biology. All diversity lying outside each such “formula” is ignored as irrelevant to the revealed law-like “nature of things.” The second approach focuses on the diversity as such: the task is to present it as comprehensively and irreducibly as possible in some generalized form. This is usually accomplished by developing classifications that give a certain idea of the ordered structure of the diversity itself. Examples are also well known: classifications of elementary particles in physics, of cosmic bodies in astronomy, of substances and their compounds in chemistry, of organisms in biology.

These two fundamental ways of understanding and describing the ordered diversity of Nature allowed Francis Bacon, 17th-century philosopher, to distinguish between two basic domains of classical natural science, natural philosophy and natural history. The former represents its knowledge in the form of parametric systems (formulas), while the latter does it in the form of classificatory systems (classifications). Accordingly, within the framework of natural philosophy, predominantly parametrizing disciplines emerged (physics, chemistry, astronomy, etc.), and within the framework of natural history, classifying ones began to dominate (biology, geography, geology, etc.). As can be assumed, such a division is not accidental; it reflects a fundamental idea that different aspects of the ordered diversity of Nature can be most adequately represented by different descriptive systems—some by parametric and others by classificatory [Whitehead 1925].

It is of importance to note that there is no contradiction between these two ways of studying and describing the ordered diversity of Nature: in many cases, they complement each other in describing the same phenomenon. A simple illustrative example is the color scale, which can be represented qualitatively as a classification by enumerating traditionally distinguished colors (red, blue, green, etc.), or quantitatively by reference to a continuous scale of wavelength values. Another, not so trivial, example is a thermodynamic system with transitions between quasi-discrete phase spaces under continuous variation of some key parameter: its structure can be described both by an equation expressing that parameter and by a qualitative description of quasi-discrete states. In biology, an example similar to the second one is provided by species diversity: according to the Darwinian model of evolution, a continuous process of speciation yields quasi-discrete diversity of biological species. So, the speciation process is described by a “formula” of continuous transformations of some characters of organisms, while resulted species diversity is described by respective classification.

Biology is one of the most “classifying” natural sciences. And it is probably not accidental that a special discipline was formed in it, biological systematics, dealing exclusively with the study and description of the ordered “qualitative” diversity of organisms. This specificity of biological science is a really striking fact of its “biography”—as was just stated, all sciences classify their objects in one way or another, but it seems to be just in biology that systematics appeared as a separate area of research. As a matter of fact, almost all of biology, in the early period of its history, emerged as a “classifications creator,” i.e., as systematics, and was, by and large, subsumed by it in many respects. At present, the importance of systematics is not so overwhelming, as modern biology is very diverse, with molecular biology, physiology, and ecology, each exploiting respective parametric systems, being in the first place. But all of them and other biological disciplines cannot do without appealing to classificatory systems provided by systematics, which describe respective diversity in a qualitative manner: such is one of many manifestations of the complementarity principle.

This introductory chapter describes, in the shortest form, what systematics is: what and it studies and how, and why the results of its research are in demand.

1.1What Is the Natural System?

Everything is System, and systems are everywhere: this is what most prominent systemologists say [Bertalanffy 1968; Urmantsev 1988]. This statement is true with respect to both Nature and scientific knowledge about it—to the extent that every system is essentially an ordered diversity.

So, Nature is a system—and if so, then this statement can be tweaked: Nature, in a sense, is the System of Nature. Such a natural-philosophical understanding of Nature has a special reason: it focuses on the integrity and orderly nature of Nature, encourages one to reveal a certain general order in it, and, on this basis, to try to uncover its causes. Since the 17th century (although probably even earlier), this idea has dominated the minds of European thinkers who understood Nature as a “diversity in unity and unity in diversity.” The author of this aphorism, the philosopher and mathematician Gottfried Leibniz, published a short essay in 1695 under an iconic title “A new system of nature…” [Leibniz 1900]. Half a century later, the naturalist Carl Linnaeus published the first version of his “System of Nature…” in 1735, which underwent a dozen increasingly complete reprints (the last within his lifetime was in 1768). Finally, the philosopher Paul-Henri Holbach, an active participant in the Enlightenment, published his work “The System of Nature…” in 1770 (under the pseudonym of M. Mirabeau), in which he summed up the “laws of both the physical world and the spiritual world” under a common systemic denominator [Holbach 1770].

So now, what is the System of Nature? The answer to this question in its most general form can be twofold. On the one hand, it is an ordered Nature as such, a global systemic object (in the sense of Urmantsev). On the other hand, this is a certain law that orders Nature, makes it this very systemic object. Natural philosophers from various times, trying to get to the fundamentals of the Universe and to find out what this “law” is, asked the same question of the most general order: what is the “law” that causes the orderliness of Nature? For religiously minded thinkers (like Leibniz, Linnaeus), the Divine Plan of Creation appears in this capacity as the causal basis of all that exists. For materialistic natural philosophers (like Holbach), Nature is self-sufficient, its cause is in itself (causa sui). Holbach himself, who imagined Nature as a well-construed “mechanism,” looked for the causes of its systemic essence in universal natural laws like those of Newtonian mechanics. Since the end of the 18th century and especially in the 19th century, one of the fundamental causes of the ordered diversity of the System of Nature was thought to be global evolution; this view had a particular impact on understanding the diversity of living nature as a consequence of biological evolution.

By the time that systemic natural philosophy was clearly shaped, systematics had already been developing for almost two centuries. After the release of the first works of Linnaeus, the concept of the System of Nature (Systema Naturae) became a key for comprehension of wildlife. As a result, the very designation of our discipline as biological systematics acquired a special, deep meaning: it is “biological” and it is “systematics” just because it studies the System of Living Nature. This natural-philosophical concept turned into a more operational concept of the Natural System (Systema naturalis)—just like that, with a capital letter to emphasize its special significance—as a kind of integral mental image of the System of Nature. The natural classification (Classificatio naturalis) elaborated by systematicians—in this case with a lowercase letter—was recognized as the best way to represent it.

It should be noted, for the sake of fairness, that the concept of the System of Nature served at that time only as one of two basic forms of representation of the ordered diversity of Nature. Another one was the equally fundamental natural-philosophical idea of the Ladder of Nature (Scala Naturae), which had a strong influence on the minds of natural scientists. The difference between them is that the System of Nature implies a hierarchical ordering of diversity, while the Ladder of Nature is predominantly linear. Nevertheless, in the “ladderists” community, the general conception of the Natural System was as fundamental as it was among the “systemists.”

Thus, since the middle of the 18th century, systematics was aimed to uncover the Natural System of living beings. In different natural philosophical doctrines, this general concept is filled with different content—“systemic” (Linnaeus), “ladder” (Buffon), organismic (Oken), typological (Cuvier, Baer), genealogical (Darwin, Haeckel)—but these peculiarities do not change the main point.

This main point is as follows. Wildlife is part of the general System of Nature and can be thought of as an ordered diversity of organisms. This orderliness is manifested in law-like interrelationships, either hierarchical or linear, between organisms and their attributes. A fundamental property of these interrelationships is that their hierarchy is quite evident while some linear “parameterized” ordering is but weakly manifested. All this taken together—both diversity, and its orderliness, and the latter’s non-linearity—is what systematics should uncover and present in a form of the Natural System of organisms—or, less pretentiously, in a form of the natural classification.

The Natural System, being a product of cognitive activity, is not identical to the System of Nature as such, but should be isomorphic to it, i.e., reflect it as precisely as possible. In this capacity, the Natural System may be thought of as a kind of “absolute truth,” an ideal towards which systematics should strive. However, it is obvious that this ideal, like any other one, is in principle unattainable. Therefore, the concept of the Natural System serves for systematics as a kind of “lighthouse” that directs taxonomic research in a certain direction. This direction does not represent a single main path; as mentioned above, both the System of Nature itself and the Natural System representing it can be understood in different ways, so that the “lighthouse” is not a monolithic illuminator, but rather something composite with its pieces highlighting different aspects of the System of Nature. In the language of modern systematics, these “pieces” are treated as different research programs: they develop classifications filled with different content. Each such classification can be considered natural to an extent that it approximates a particular aspect of the Natural System.

1.2What Is Biological Systematics?

It is customary to define scientific disciplines through their subject areas by indicating what exactly they study: physics, chemistry, biology, geography, linguistics, etc. Within each of these domains of knowledge, sub-areas are distinguished on a similar basis: microphysics and cosmology, economical and physical geography, histology and embryology, etc. It can be reasonably assumed that this general principle is true for biological systematics.

As can be seen from the previous section, systematics, if considered natural-philosophically, is associated with exploration of the System of Living Nature, with its ultimate end being elaboration of the Natural System or, more correctly, natural classification representing it in some way. From a quite empirical standpoint, systematics is defined as a branch of biology studying diversity of organisms (biological diversity, aka biodiversity) in all and any of its manifestations, representing the results of the study in the form of some “omnispective” classifications as a kind of reference system [Blackwelder 1967]. Both treatments, despite a significant difference in their backgrounds, are too broad: it turns out that systematics is the science of biological diversity “in general” and, accordingly, should be rightfully called biosystematics (in fact it is sometimes defined and called this way). In this case, what about ecology or biogeography also dealing with the same biodiversity, though in their own manner? On the other hand, there are significantly narrower definitions of systematics, based on their particular backgrounds: for example, it is defined sometimes as a “science of species” [Mayr 1969; Wheeler 2009]. In this case, a question arises: what about the supraspecific taxa? Does not and should not systematics study them?

From this, it becomes clear that the definition of systematics as a scientific discipline through the definition of its subject area is not an easy task. To say that it studies the System of Living Nature “in general” or biodiversity “in general” is too vague. But it is too narrow to associate it with some particular task (as in the case of the study of species). Systematics is actually a branch of biology studying the diversity of organisms and elaborating classifications to represent it in one way or another—but what kind of biodiversity does it actually deal with?

Taking all the above considerations into account and not going more deeply into this issue, it seems correct enough, from a theoretical perspective, to treat systematics as a branch of biology that develops:

•specific ways of understanding the System of Living Nature (typological, phylogenetic, organismic, etc.) as particular manifestations (aspects) of the ordered diversity of organisms

•the methods and criteria by which specific classifications can be elaborated within the contexts of those particular understandings

•the classifications that might be treated as natural with respect to those particular understandings.

1.2.1The Structure of Systematics

A well-thought-out “stratification” of systematics as a scientific discipline should, first of all, provide for the delineation of its main divisions. What exactly and how exactly should be reflected in classifications, how they should be elaborated, by which criteria they could be considered natural—these fundamental questions are posed and answers sought for by the theoretical division of systematics. Various kinds of theoretical propositions are implemented in specific classifications by its practical division. Finally, methods of bringing such classifications into the forms suitable for use by other disciplines are being developed by the applied division of systematics.

Theoretical systematics was denoted as taxonomy by the botanist Augustin Pyramus de Candolle at the beginning of the 18th century [de Candolle 1819]; another recent designation is taxonology [Zuev 2015]. This understanding of taxonomy is most widely accepted in contemporary literature, but there are other interpretations of it. Some authors identify taxonomy with the entire systematics [Mayr 1942; Rogers 1958; Griffiths 1974a,b; Zuev 2015]. Others call taxonomy the practical issues dealing with the identification of particular taxa [Blackwelder and Boyden 1952; Black...