domingo, 16 de septiembre de 2007

"Virus Species: A Controversy" (Rebuttal)

When you name and classify, that’s taxonomy in practice. The goal for taxonomy is to name things in order to place them in an intuitive invented classification that can suggest relationships and meaningful associations. In The Linnaenan hierarchy of taxonomic the organism are classified in a ranked hierarchy, starting with domains and then turned (in a simplified way) into phyla, orders, families, genera and species. Groups of organisms at any of these ranks are called taxa. Species taxa are the individual lineages we call ‘species’ (thus Homo sapiens is a species taxa). The species category is a more inclusive entity. The species category is the class of all species taxa. In that way all taxonomic classes are abstract concepts, constructions fabricated by the mind and not real entities as species taxa (as diagnosable lineages) which are located in space and time and that we encounter in our handling of viruses. I empathized this distinction because the virologist see the species mainly as classes [1] and then ascribe some properties to that class as disease clinical presentations [2]. Ascribing properties to species (a polythetic class in the virology field!) and allocating individuals in those not only means to consider species as abstracts classes, in fact it might no reflect natural relationships (like to use the utility or threaten that vertebrates represents to humans to allocate vertebrates in particular species). As virus diseases became recognized, the causative viruses were given names in different languages that often reflected the symptoms of the corresponding diseases as well as the hosts or organs that become infected [1]. The international Committee on Taxonomy of Viruses (ICTV) decided in 1998, to confer the status of official species names to the English common names of viruses and introduced a typography using italics and a capital initial to indicate that these names correspond to species. Names are simply signs or labels that refer to specific species, therefore I do not see a problem in naming species until all available combination of letters and numbers in our vocabulary are exhausted.

The task of defining species is commonly confounded with the task of identifying the member of species. The PSC sensu Wheeler and Platnick define species as the smallest aggregation of lineages diagnosable by a unique combination of character states [3]. The definition says nothing about how to identify particular species. For each one species there is a unique combination of character states (morphological, molecular, etc) that allows us to identify them. The only objective of the PSC is to recognize the lineages that perpetuate more in the nature avoiding the arbitrary in the decisions for their identification because it is based mainly on characters.


References

1.
Van Regenmortel, M.H.V., 2003. Viruses are real, virus species are man-made taxonomic constructions. Arch. Virol. 148, 2481–2488.

2. ICTVdB - The Universal Virus Database, version 4.http//www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/

3. Wheeler, Q. D. and Meier, R. (Editors). 2000. Species Concepts and Phylogenetic Theory: A Debate. New York: Columbia University Press