Principios de Taxonomia

86j 4 What are Traits in Taxonomy?
against reductionism in biological science has supported the view for the whole.
Entire organs are considered to be more than the sum of their parts, and this world
view may have favored the aim to conceive organs and organisms as whole entities
that should not compartmentalized.
4.10
The DNA Barcoding Approach – is Taxonomy Nothing more than Phylogenetic
Distance?
The technique of barcoding refers to the identification of short DNA sequence
sections, mainly a 648-bp region of the cytochrome c oxidase I gene (COI) of
mitochondria, with the intent of determining taxonomic classifications. These
sequences are compared among the organisms. From the extent of sequence
differences, a conclusion as to the species identification of the organisms is drawn.
Undoubtedly, the differences in DNA sequences indicate the differences in the
phylogenetic distances among the respective organisms. However, the genetic
distances between groups of organisms are not the same phenomenon as the species
differences (Chapter 6). Many studies have documented that reproductively wellseparated
species hardly differ genetically, and in turn, there exist species with large
intraspecific genetic heterogeneity. Hence, barcoding does not lead to the same
entities as other species concepts. Because the barcode determines only the genetic
distance among groups of organisms, it inevitably comprises all of the evolutionarily
young species as a single common species, and it subdivides many old species into
separate species.
The method of DNA barcoding has been highly praised. It is advertised as a
renaissance in taxonomy (Miller, 2007) or as taxonomy of the twenty first century
(Steinke and Brede, 2006). Its application to butterflies (Hebert et al., 2004), birds
(Hebert et al., 2004) (www.plosbiology.org) and many other organisms led to the
discovery of many supposedly new species. One of the first publications of Hebert
and colleagues (Hebert et al., 2004) on the Central American Hesperid butterfly
Astraptes fulgerator has the promising title Ten species in one: DNA barcoding
reveals cryptic species in the neotropical skipper butterfly Astraptes fulgerator.
However, the cogent question is whether all of these promises and visions can
withstand a stanch reconsideration of the biological units that are truly identified by
the barcoding method. One year before the barcoding method was introduced, J.
Willem H. Ferguson from the University of Pretoria published a paper in the
Biological Journal of the Linnean Society that was entitled On the use of genetic
divergence for identifying species (Ferguson, 2002). The abstract of this article
begins with the following three sentences:
Degree of genetic divergence is frequently used to infer that two populations
belong to separate species, or that several populations belong to a single
species. I explore the logical framework of this approach, including the
following assumptions: (i) speciation takes place over very long periods of