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The intellectual content of taxonomy: a comment on DNA taxonomy

2003; Elsevier BV; Volume: 18; Issue: 2 Linguagem: Inglês

10.1016/s0169-5347(02)00060-5

1872-8383

Diana Lipscomb, Norman I. Platnick, Quentin D. Wheeler,

Chromosomal and Genetic Variations

Tautz et al. [ 1 Tautz D. et al. A plea for DNA taxonomy. Trends Ecol. Evol. 2003; 18 (DOI: 10.1016/S0169-5347(02)00041-1) Abstract Full Text Full Text PDF Scopus (744) Google Scholar ] propose to ‘solve’ the lack of adequate classifications and effective identification tools (the so-called ‘taxonomic impediment’) by replacing existing classifications with a system in which an infinitesimally tiny fraction of an organism's genome is sequenced and used both to classify and identify the organism in question. The rationale for this suggested change, however, is specious and unlikely to produce a progressive research program. Such a system is already in use for unculturable prokaryotes, where the best we can do at present is collect sequence data from the environment, compile data bases of the results, and construct ‘classifications’ that reflect only the degree of similarity displayed by those sequences. This produces what is at best a caricature of real taxonomy, in which sequences that diverge by <5% are considered ‘conspecific’ (never mind that humans and chimpanzees might be far less divergent than that). Microbiologists would be the first to agree that, when the organisms can be cultured and their other attributes studied, we can do far better than this. Why, then, reduce the taxonomy of all other organisms to this impoverished state? The supposed advantages of DNA taxonomy do not stand up to rigorous scrutiny. For example, the claim that a sequence ‘is not influenced by subjective assessments’ ignores the difficulty of aligning sequences of different length, distinguishing paralogs from orthologs, or even selecting appropriate genes for any particular taxonomic study. Similarly, the supposition that DNA identification will lessen the confusion that sometimes results when taxonomic names change is unjustified. The only way that a DNA sequence identification tag could ameliorate confusion would be if the gene sequence used were constant among all members of the species but different in all other species. There is no evidence that most genes meet these criteria, and any diagnostic character that meets these criteria would work – it need not be molecular.