Species with-out evolutionary assumptions
Erika Jazmín parada Vargas.
The Species concept and its delimitation are old problems in biology and multiple debates have been done since multiple disciplines (Cracraft, 2000). Here is presented The Phylogenetic Species Concept (PSC) (sensu Wheeler and Platnick), and are showed some of its advantages.“Species delimitation, like character-state definition, is a preliminary activity of phylogenetic analysis, and both of these elements, characters and terminals, are the fundamental components of which hypotheses of phylogenetic relationship are constructed” (Davis and Nixon, 1992). This is an important premise because there are concepts (i.e., Biological Species Concept) that rooted the identification of species in presumptions of speciation. The presumption of speciation anchors the concept in the inverted view that understanding speciation is a prerequisite to defining species rather than a product of that delimitation (Goldstein & DeSalle, 2001).
By definition (for PSC) a species is “the smallest aggregation of populations or lineages diagnosable by a unique combination of character states in comparable individuals (Semaphoronts) (Wheeler & Platnick, 2000). It is important to make the distinction between the PSC and the monophyletic species concept (sensu Mishler and Theriot), because the second one is based on the concept of shared derived characters, called synapomorphies (in this case autapomorphies, because they belongs to a single group, and the monophyletic groups are defined by the autapomorphies (Pleijel, 1999)). “If two or more individuals or populations share a derived character then they are assumed to be more closely related than individuals or populations lacking that character” (Goldstein & DeSallle, 2001). But whether or not some individuals within a particular species are more or less closely related to one another than to members of another phylogenetic species is irrelevant to the reconstruction of relationships among species (Goldstein & DeSallle, 2001).