Defining Taxonomic Ranks
“Well, in our country,” said Alice, still panting a little, “you’d generally get to somewhere else—if you ran very fast for a long time, as we’ve been doing.”
- PDF / 527,185 Bytes
- 29 Pages / 539 x 751 pts Page_size
- 20 Downloads / 197 Views
CHAPTER 1.3 gn i nfieD
c imonoxaT
sknaR
Defining Taxonomic Ranks ERKO STACKEBRANDT
Systematics and Classification “Well, in our country,” said Alice, still panting a little, “you’d generally get to somewhere else—if you ran very fast for a long time, as we’ve been doing.” “A slow sort of country!” said the Queen, “Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!” —Lewis Carroll, Through the Looking Glass, (1872) Those who have chosen systematics, classification, and taxonomy as research topics have learned to consider the complexities as exciting and important. For others, these topics are mainly boring and through changes in names of microbial taxa, may cause confusion. Indeed, the problem of changing names of taxa is inherent. Classification is motivated by the desire of taxonomists to provide the user with a system that in their opinion optimally reflects the natural relatedness between the taxa. Now finally, the determination of phylogenetic relationships is achievable (Stackebrandt, 1992). Looking back in the history of microbiology, the lack of interest in classification can be traced to the enormous difficulty of past generations of systematists to put in order the phenotypic and genotypic properties of the steadily growing numbers of bacterial strains. The user of taxonomy was confronted with constantly changing classification concepts and systems, taxonomic rearrangements, and synonymy of names. Problems also arose from the terminology: while some regard systematics and taxonomy as synonymous, others define taxonomy as the theory and practice of classifying organisms and systematics as broader, including the evolutionary and phylogenetic components. For many researchers, nomenclature is their only contact with taxonomy, and the contact occurs only when they are confronted with name changes. However, systematics includes more than naming of organisms (Stackebrandt et al., 1999).
Classification is done by generating as much data on the properties of novel isolates as possible and by the process of identification, e.g., comparing the data with the database of previously classified organisms and by affiliating the isolate with a previously described or a new species. Classification includes the theory and process of ordering the characterized organisms into one or more systems. Nomenclature is the naming of the appropriate taxon within a classification system, and it includes subjective changes that occur whenever novel insights alter the taxonomic weight of characters, and thereby the rank of taxa. As outlined (Stackebrandt et al., 1992), several classification systems exist in parallel and no classification system can claim predominance. No two systems of clustering need to match. As long as a system succeeds in doing what it sets out to do, it cannot be described as wrong or in error. There are systems that group microorganisms on the basis of their increasing degrees of risk to humans, anim
Data Loading...
