Erika Jazmín Parada Vargas
The transference of the knowledge is part of any activity, and the basic research in biology is not the exception. As the species are the basic units which different biological programs work with, (and not all the researchers are experts in the groups) a feasible way to communicate its necessary. That system or classification needs to reflect the history of the group, in which the species are contained.
Although the delimitation of the species is related to the classification, they are not the same. The inference about the history of the groups is an after activity to its delimitation (Davis & Nixon, 1992). The PSC (sensu Wheeler & Platnick, 2000), has the advantage that is not worried about the evolutionary mechanisms that have caused the species, but the way how could we distinguish them. The way we could distinguish among species is the unique combination of character states.
As the species are not external, and our knowledge about the organisms is not immaculate, we need a concept not based on abstract or unpractical characteristics (i.e., niche, reproductive isolation, percentage rules). But on observational features, the unique combination of character states of the PSC gives us a testable hypothesis. (Wheeler & Platnick, 2000).
Davis, J. I. & Nixon, K. C. Populations, Genetic Variation, and the Delimitation of Phylogenetic Species Systematic Biology, 1992, 41, 421-435
Wheeler, Q. D. and Meier, R. (Editors). 2000. Species Concepts and Phylogenetic Theory: A Debate. New York: Columbia University Press