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.

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