Principios de Taxonomia

42j 2 Why is there a Species Problem?
populations that would double or triple today s internationally agreed upon number
of approximately 9000 bird species.
The situation is the same with regard to descent relations or kinship. Monophyletic,
apomorphy-based bifurcations can be traced by modern molecular technology
into the minutest branches, and in doing so, these traces can be justified in a
theoretically consistent manner to represent speciation according to the cladistic
species concept. There are always some autapomorphies if two sister individuals are
born by the parents (Chapter 7). In the exploration of the cladistic bifurcations in the
genealogical tree, branching into repeatedly new lateral branches can lead to an
inscrutable chaos of clades. One branch follows the other and the branches are
continually inter-nested (Mishler, 1999). This may increase the species numbers
currently in use by a 100-fold (Cracraft, 1997; Mallet, 1995). Where does one begin to
assign organisms to species, and where does one stop?
A similar situation arises with regard to species as gene-flow communities
(Chapter 6). Tiny, isolated, reproductively separated populations can disaggregate
into hundreds or thousands of groups of organisms that no longer have gene flow
among themselves. These delimited gene-flow communities can be small if the
organisms are not very mobile and if numerous barriers splinter the totality of
organisms into the smallest separated gene-flow communities. Considering each
isolated gene-flow community as a separate species also could increase the species
number currently in use by a 100-fold.
What is the consequence of this dilemma? From this dilemma it follows that there
are, and probably always must be, two different taxonomies (Schmitt, 2004).
Biodiversity can be sorted into manageable units with which humans pursue goals
and achieve results that satisfy practical needs, but nothing more. The second
taxonomy is based on the theory of evolution. Descent and kinship play a role, as
do reproductive communities. This is a taxonomy that does not follow operational
convenience, but it satisfies the human need for consistency in lines of thinking.
The species problem as a never-ending story does not seem to stem from the
disagreement about the more than twenty species concepts currently on the market
(Mayden, 1997), ranging from the phenetic species concept and the concept of the
reproductive community to the ecological species concept. This abundance of species
concepts is usually called species pluralism (Hull, 1999). Instead, the species
problem seems to hearken back to the fundamental difference between the theoretical
concept of and the practical instructions for how to distinguish different
species (Ereshefsky, 1999).
It may be unavoidable to separate both taxonomies from the start. Both
taxonomies pursue different goals. One taxonomy conducts a classification that
is feasible and serves for communication between scientists and laypeople. The
other taxonomy is concerned with the biological unit that plays a role in evolution
and is subject to natural selection for this reason. The question is to what extent
nature has an interest in organizing organisms into cohesive groups that are
maintained as isolated groups without merging into others. This kind of a natural
species is a unit in biodiversity that would be present without human-imposed
principles of order.