Abstract
Taxonomy is an often confusing topic, especially to those not directly or actively associated with its use. It.is a scientific discipline largely established. and regulated by academicians, whose primary interest is the classification of living forms. Their efforts have created a framework that illustrates the genetic and evolutionary relationships these forms have to one another. It is this same framework that serves as a basis for both the professional and amateur zoologist in his study or inquiry into the animal kingdom. However, in order for the zoologist to pursue these investigations, it is essential that he have an adequate working knowledge of the principles of taxonomy and its associated nomenclature. It is the intent of this paper, therefore, to present the basic fundamentals of this subject in a manner that hopefully can be clearly interpreted by those not directly involved in this specialty.
Since taxonomy concerns itself with the orderliness of things, it is only fitting that we begin with its historical aspects. Carolus Linnaeus (1707 -1778), a Swedish naturalist, is recognized as the father of modern taxonomy and the originator of binomial nomenclature. He realized that there was confusion in the use of vernacular or common names, especially since they were not governed by strict rules of procedure, and that they differed depending on language and local custom. Consequently, he adopted the use of Latin, a universal language, and published his system in the 1758 edition of Systema Nat· urae Regnum Animale. Linnaeus utilized two Latin words in his binomial arrangement, the first to indicate the general kind of animal (genus), and the second to designate the particular kind (species).
Since that time, the classification of animals has developed into a well structured science. A taxonomic hierarchy composed of categories or taxa (phylum, class, order, etc.) now exists that not only makes it easier to identify animals through natural groupings, but also presents the evolutionary relationships these categories, and more importantly the species, exhibit toward each other. If we were to list these taxonomic categories in their order of descent, we would have the following: phylum, class, order, family , genus, and species. There are also groupings prefixed by "sub" or "super" that are often used for further division. These appear between. the previously mentioned categories. In the case of ducks, geese, and swans, tribes are used to subdivide the family.
Let us take an example, the mallard Anas platyrhynchos, artd trace it through its taxonomical sequence.
Phylum - Chordata Class - Aves
Order - Anseriformes Family - Anatidae Tribe - Anatini Genus - Anas
Species - platyrhynchos
(I choose to use "tribe" but omitted the "sub" and "super" categories here for the sake of simplicity.)
The hierarchy or sequence in which the categories appear is referred to as their phylogenetic order. Phylogeny pertains to the lines of descent for any taxon, based upon origin and evolutionary relationships. In general, it is a comparison of primitive structures versus complex, and appears at all levels of taxonomy from phylum to species. For instance, there are 19 phyla beginning with Protozoa, the primitive unicellular organisms, and ending with Chordata, those advanced animal forms possessing a spinal column. Each subsequent phylum in the sequence is considered to be more advanced than the previous one. There are 27 currently recognized orders of birds, beginning with (depending upon the authority) the ostrich (Struthioniformes). This bird exhibits a number of primitive characteristics, such as a keelless sturnum. The sequence of avian orders ends with the perching birds (Passeriformes), which exhibit a number of characteristics such as an advanced perching foot and the prevalence of song for species recognition. The same rule of sequence applies to the genera within the family, and so on.
As stated previously, taxonomy is a well structured science, particularly with regard to nomenclature, the describing and naming of species. The first important step in this process is the evaluation of the specimen in question. Does it actually qualify for specific status; that is, does it originate from a population of similar organisms which actively or potentially interbreed and are reproductively isolated from all other such groups? Once this has been decided and before the species received its Latin name, it must be described. It then becomes a holotype , the specimen which theoretically exhibits all those characte~istics typical of the new species.
When a taxonomist describes a new species, there are numerous criteria that must be taken into consideration. Besides descriptions of the traditional morphological characters (size, shape, color, etc.), physiology (serology, cytology, chemical analysis, etc.); ethology (behavior); ecology and geography must also be examined. Basically, the taxonomist must clarify what differences are supposed to exist between the specimen in question and other similar species. It should be stated here that there are essentially two types of taxonomists, the Jumpers and the splitters. Splitters classify according to minute differences; lumpers differentiate on the basis of larger detail.
Since the time of Linnaeus, we have learned much about animals, especially their evolution, behavior, etc. Linnaeus assumed that all species had been created simultaneously, that they were unchanging, and that all individuals of a species had descended from an original pair. Darwin's work corrected this theory by illustrating that speciation is a continuous evolutionary process. Some Latin names, therefore, have now become literally meaningless or misleading, although many still remain as convenient designations. Even though Latin names were at one time meant to be descriptive of the animal's appearance, over the years this has broadened to cover its habitat or distribution, to honor a friend or colleague or perhaps to honor the person who collected it. The application of Latin names is not a simple matter, as they must follow the strict guidelines of the International Commission on Zoological Nomenclature established in 190 I. It is within the auspices of the Commission, which obtains its authority from the International Congress of Zoology, to regulate and act upon the International Rules of Zoological Nomenclature (The International Code).