Principios de Taxonomia

2.13 It is One Thing to Identify a Species, but Another to Define what a Species isj39
There are two differences that set the species concept of the reproductive
community apart from the concept of the gene-flow community. The organisms
of geographically distant populations are considered to belong to different
species, as defined by the concept of the reproductive community, if they are no
longer able to mate successfully. However, based on the concept of the gene-flow
community, they are considered to belong to one and the same species as long as
all populations of the species are uninterruptedly connected by gene flow.
Secondly, allopatrically separated organisms are considered to be conspecific
according to the concept of the reproductive community in cases in which the
organisms could potentially crossbreed (Chapter 6). However, the concept of the
gene-flow community must evaluate every allopatric separation as a speciation
because every allopatric separation interrupts the gene flow; therefore, allopatric
separation also interrupts any cohesion among the organisms.
The species concept of the gene-flow community possesses two advantages on
which no other species concept relies:
(1) It is the only species concept that is able to define a species solely by its own
criteria, without borrowing criteria from other species concepts (mixed
classification).
(2) The gene-flow community is able to define the species by objective criteria that
are not human-made classification principles. Gene flow is a clearly defined
matter, not a matter of weighting one property more heavily than another. This
concept is not called into question by the fact that the borders between two
gene flow communities are porous.
The only disadvantage of the species concept of the gene-flow community is that
it is restricted to biparental organisms, which necessitates organisms with
bisexual reproduction. Necessarily, the concept of the gene-flow community
must consider all other organisms to be without species identities.
2.13
It is One Thing to Identify a Species, but Another to Define what a Species is
It is important to distinguish the method of identifying a species from the method to
determine what the species is. The diagnostic decision of which species an organism
belongs to, may not be mixed with the decision of what a species is (de Queiroz, 1999;
Hull, 1968). The ontological status of a true species and the teleological approach,
which indicates the criteria (identification traits) by which a species can be recognized,
are two utterly different approaches to nature (Mayden, 1997; Sterelny and
Griffiths, 1999), with two different goals. The biologist who identifies a species
already presupposes its existence and only pursues the epistemic goal of how to best
recognize that species.
Let this fundamental differences be illustrated using the following example:
organisms of a species are identified by fixed identification traits that have been
successfully used since the time the species has been discovered. Suddenly, there are