The Role of Taxonomy
The primary way basic information about animals and plants is organized and stored is by taxonomic categories (typically species) [another way is by subject, such as vision or food and feeding]. It is important to understand (1) why good taxonomic databases are essential for studying biodiversity, (2) what taxonomy entails, (3) why a hierarchical classification is useful, and (4) why classifications and names change, thereby making it more difficult to accumulate and keep track of information for many purposes from conservation management to inventories, to species entering commerce, etc.
|Taxonomists have two important tasks...||
Taxonomists have two important tasks: to name organisms and to classify them. The system of hierarchical classification and a two-word system for naming species began with Linnaeus in 1758. The system was codified in 1842 (Strickland et al. 1843), and it became the system used by all zoologists worldwide from 1843 to the present, with changes and improvements along the way. (The present ‘Code’ which all zoologists follow is discussed in Appendix A of the Catalog). The two-word name for species consists of a generic name and a specific name. A genus may contain more than one species, and species are placed together in a genus based on perceived genetic affinity (as determined mostly by morphological differences and similarities, although biochemical techniques are providing new, additional information). (Subspecies are sometimes used to define smaller categories within a species). Taxonomists discover or describe species (1) by assembling specimens through fieldwork and/or by borrowing from museum collections, (2) by studying variation, (3) by grouping the specimens into species categories, (4) by comparing these with previously described species, (5) then naming the new species following specific rules (ITZN 1985, 1999) and (6) by publishing the information in scientific journals and books. Monographs contain thorough treatments of all the species in a larger group, such as a genus or family, and monographs represent the latest summary of information for that group.
|Classifications contain information about relationships||
Classifications are useful because they contain information about relationships. For example, when a chemical suitable for a pharmaceutical product is found in one species, biochemists can quickly learn from classifications of the close relatives (e.g., other species in the same genus or the ‘sister-species’) that might contain similar or even better chemicals. All species in the same genus should share many behavioral, biochemical, ecological and biological properties because they are closely related evolutionarily. The effect of pollution on a species at one location should be similar to the effect on a close relative living in a different area. Those in the same family (next primary category up) similarly share many but fewer features. Classifications thereby have predictive value. Since the late 1960s, most taxonomists have used ‘cladistic’ methods of forming classifications (i.e., Henning’s method, see Box 3), basing them on shared advanced (new) features. This approach results in cladograms or trees that reflect ancestry as well as relatedness of individual taxa.
|Names keep changing||
The changing nature of classifications and scientific names (because of changing ideas of relationships and because of technical [nomenclatural] rules changes) makes it almost impossible to know under which species, genus, or even family names one will find pertinent information in the prior literature or in specimen collections. For example, in 1989 both the genus name and specific name of the rainbow trout were changed (see Smith and Stearley 1989). Thousands of publications cite Salmo gairdneri as the name of the rainbow trout; now we call it Oncorhynchus mykiss. The genus name was changed from Salmo to Oncorhynchus partly based on fossil evidence because the Pacific trouts were thought to be more closely related to the Pacific salmon than to the Atlantic salmon [the name carrier or type of Salmo]. Pacific trout and salmon are now classified as Oncorhynchus. The species name gairdneri was changed to mykiss when it was thought that mykiss from Kamchatka, Russia, was the same as gairdneri; since mykiss was described first, that name had priority for use over gairdneri.
Another major activity of taxonomists is to make ‘synonymies’ that summarize prior accumulated knowledge about species. Unfortunately, scientific names change for several reasons, which makes inventory especially difficult since information about a single species may be found under several scientific names. Names change because:
1. One species may have been described more than once (such as from different geographical areas, from different sexes, from atypical specimens, or from a lack of knowledge of earlier descriptions). As these ‘duplicates’ are discovered, the first described name is selected as the valid name, often resulting in a name change, such as for the rainbow trout.
2. Scientists may differ on what species to include in a particular genus, or species are moved to different genera based on perceived relatedness. This results in the first half (generic) of the name changing; sometimes the ending of a scientific name also changes since, if it is an adjective, it must agree (decline) in gender with the genus.
3. Sometimes names are changed for technical reasons.
|Scientific names are frequently misspelled
Number taxa has not worked
Another problem is that scientific names are frequently misspelled in scientific publications, in collection records for museum holdings, and by abstracting services. Often a name is misspelled because the spelling as originally presented was not verified by subsequent workers. Although there are current arguments about how to incorporate fossils into classifications, and especially how to treat them in higher taxa, the present system probably will continue for many years. Numbering taxa has not worked either. Often common names are more stable than scientific names, and they can be useful in some groups.
ITZN. 1985. International Code of Zoological Nomenclature. The International Trust for Zoological Nomenclature, London.
ITZN. 1999. International Code of Zoological Nomenclature. The International Trust for Zoological Nomenclature, London, UK. 306 p.
Smith, G.R. and R.F. Stearley. 1989. The classification and scientific names of rainbow trout and cutthroat trouts. Fisheries 14(1):4-10.
Strickland, H.E., J. Philipps, J. Richardson, R. Owen, L. Jenyns, W.J. Broderip, J.S. Henslow, W.E. Shuckard, G.R. Waterhouse, W. Yarrell, C. Darwin and J.O. Westwood. 1843. Report of a committee appointed "to consider the rules by which the Nomenclature of Zoology may be established on a uniform and permanent basis". Brit. Assoc. Adv. Sci. Rept. 12th Meeting, 1842:105-121.
William N. Eschmeyer