principles of systematics and nomenclature general system and phylogeny of insects systematics of Ephemeroptera

The chapter 1 from the book by N. Kluge  


last update 1.III.2004




I.1 Reconstructing phylogeny
I.1.1 Lingering misconceptions
I.1.1.1 Is embryological method reliable?
I.1.1.2 Applicability of paleontological method
I.1.1.3 Structure complication in phylogenesis
I.1.1.4 Oligomerization of homologous organs
I.1.1.5 Lack of specialization in ancestral forms
I.1.1.6 Evolutionary scenario
I.1.2 Cladistic analysis
I.1.2.1 Terms "apomorphy" and "plesiomorphy"
I.1.2.2 Apomorphy-based phylogenetic analysis
I.1.2.3 Identifying character polarity
I.1.2.4 Interdependency of phylogenetic theory and character definition
I.1.2.5 Independently evolving homologous characters
I.1.2.6 Field of application of cladistic analysis
I.1.3 Why do numerical methods fail
I.1.3.1 Inavailability of parsimony principle
I.1.3.2 Fundamental scortcomming of numerical taxonomy

I.2 Principles of classification
I.2.1 Mono-, poly-, para-, and holophyly
I.2.1.1 Background
I.2.1.2 Definitions
I.2.1.3 Holo-, para- and polyphyly: explanation of terms
I.2.2 Taxonomic schools
I.2.2.1 Cladism, of phylogenetic systematics
I.2.2.2 Traditionalism, or evolutionary systematics
I.2.2.3 Gradism
I.2.3 Real systematics
I.2.3.1 Benefit and damage from paraphyletic (ancestral) taxon
I.2.3.2 Plesiomorphons
I.2.3.2 3 Aspiration of classification for the cladistic ideal
I.2.3.3 4 Reasons of disagreements between cladists and traditionalists
I.2.4 Relative and absolute ranks of taxa
I.2.4.1 Strict hierarchy of classification
I.2.4.2 Absolute ranks
I.2.4.3 Inequality of absolute ranks
I.2.4.4 Problem of genus

I.3 Principles of nomenclature of ZOOLOGICAL taxa
I.3.1 General principles of nomenclatures of biological taxa
I.3.1.1 Availability and validity of names
I.3.1.2 Principle of priority
I.3.2 Different types of nomenclatures and names
I.3.3 Rank-based (ranking) nomenclatures
I.3.3.1 Names regulated by the International Code of Zoological Nomencature (ICZN)
I.3.3.2 Rank-based names of higher taxa
I.3.4 Hierarchy-based (hierarchical) nomenclature
I.3.5 Circumscription-based (circumscriptional) nomenclature
I.3.5.1 Circumscription-related terms
I.3.5.2 Criteria of availability for circumscription-based names
I.3.5.3 Circumscription match
I.3.5.4 Validity of circumscription-based names
I.3.6 Name-related misconceptions
I.3.6.1 Customary interpretation of non-typified names
I.3.6.2 Polyphyletic Hexapoda: How a myth was born
I.3.7 Combining circumscription-based and hierarchy-based nomenclature
I.3.7.1 Usage of different nomenclatures
I.3.7.2 Format of species name in non-rank-based nomenclature
I.3.7.3 Sliding binomina and polynomina
I.3.7.4 The layout of a taxonomic paper
I.3.8 Catalogues of zoological names


Systematics represents such a necessary division of biological science, without which all other divisions would not have prognostic value and would retain to be descriptive disciplines only. Biologist always deals with taxa; as usual when individual properties of selected specimens are examined, this is done only in order to make conclusion about properties of this or that taxon. Knowledge about structure, functions and ontogenesis of living organisms have a prognostic value only in the case if it is attributed to a concrete taxon, but not to some living creatures in general. This is connected with the fact that all properties of living organisms are gotten by then in a result of unique evolutionary processes. Because of this, in contrast to properties of many other natural objects, properties of living organisms are determined not by universal laws, but by historical development of a certain concrete organism. The systematics of living organisms is traditionally built as a reflection of their phylogeny (or a "natural system", as it was called before evolutionary theory was created), thus it is the systematics which allows to explain a presence of this or that properties in this or that living organisms, i.e. to pass from the descriptive step of science (which answers to a question "how?" to the next step discovery of the cause (i.e. to an answer to a question "why?"). This passage is easier made in the cases connected with properties most easy to study. For insects, as wall as for many other groups of animals, the most easy to study are peculiarities of their external morphology. As the examination of morphology usually is not connected with technical difficulties, there is a possibility to progress in these researches farther than in others, and to bring them to the level on which phylogenetic interpretations can be done and used in systematics. Because of this, sometimes an erroneous opinion appears that the systematics is a science about external morphology only, and investigation of other structures lies somewhere outside if systematic interests. Actually investigations in all fields of biology anatomy, histology, cytology, biochemistry, embryology ethology, physiology, et al. can be and should be used in systematics if bring them to the corresponding level.

Total number of species of living organisms remains to be unknown. It is much more than million, and each year dozens of thousands of previously unknown species are described (these are so-called "new species" species nova), most part of which are insects. At the same time the number of species described for the first time permanently grows. Correspondingly to this, number of newly established supra-species taxa also grows. For instance, while during 1890 there were established about 1000 new zoological names of genus-group (i.e. names of genera and subgenera of animals), during 1990 about 4000 new zoological names of generic group were introduced. As during the last centuries the number of newly described species permanently increases, now we are even unable to predict when all or nearly all species will be at least described and we will get more or less complete picture of their diversity. Some people who have only a vague knowledge about evolution and animal systematics, even think that the new species originate in nature with such incredible speed. However, in reality speeds in which the species new for nature originate, can be neglected as in most cases they are too small in comparison with speed of development of human civilization and science. All so-called new species are the species new for science, but not for nature; investigators found out new species not only during field work, but during examination of old collections as well. By an understandable reason, the most completely studied are species distributed in Middle Europe, but even here previously unknown species are found, especially among mountain endemics and in worse studies systematic groups. As for non-European faunas, they are studied much worse; in some regions of the World probability to find an unknown species of insects is comparable with probability to find a known species.

It will be shown below (I.1.2.4) that for clarifying phylogenetic relations between large groups of animals, it is necessary to involve as much as possible information about species diversity; because of this investigation of general phylogeny and description of species are inseparably linked one with another.

The task of systematics, or taxonomy is to create and to ground a system (i.e. a classification) of living organisms. Concrete elements of such system (for instance, a class Insecta or a species Scarabaeus sacer) are called systematic groups or taxa (plural taxa, singular taxon). Abstract categories such as class or species are called ranks of taxa (see I.2.4). Speaking about problems of systematics, it is necessary to discuss separately three principally different categories of taxa: (1) supra-species taxon a set of species connected only by common origin, while recently genofonds of these species don't influence one to another; (2) species a set of specimens connected by a common genofond, but isolated from other genofonds; (3) infra-species taxa, which in contrast to species and supra-species taxa have no reproductive isolation one from another. As in this book in chapters III -IX only classifications of supra-species taxa are discussed, we will observe only the problems of systematics connected with this category of taxa.

Overwhelming majority of modern investigators agree that systematics should reflect phylogeny. I connection with this it is necessary to discuss in which manner the phylogeny can be reconstructed and in which degree we can believe to these or that phylogenetic hypotheses when build a classification on their bases (see I.1). Than we will discuss various points of view on the question how classification should be built on the base of existent phylogenetic hypotheses (see I.2). An important meaning in systematics has a nomenclature a system of names and rules on their usage. As a colossal number of names which we have to use in systematics produces serious difficult, it is necessary to discuss separately problems of nomenclature of zoological taxa (I.3). Questions of phylogeny, systematics and nomenclature are closely connected one with another, but it is necessary to warn against identification of these categories. The classification can reflect phylogeny as exactly as you want, but it never can be identical to the phylogeny, because a reflection can't be identical to an object. Identification of taxa names with taxa themselves leads to misunderstanding, as well as every identification of a name and an object.

I.1 Reconstructing phylogeny

I.2 Principles of classification

I.3 Principles of nomenclature of zoological taxa

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