Principios de Taxonomia

10j 2 Why is there a Species Problem?
of multiple evolutionary processes be compatible with taxonomy s objective of
constructing a consistent mode of classification?
Evolution proceeds with varying speeds. There are old and young species.
If evolutionarily old species are widely spread geographically and their members
are therefore distant from one another, then the organisms belonging to a species
have evolved in different directions over time, regardless of the fact that they belong to
the same species (Chapter 6). Geographically distant individuals within a species may
differ substantially from one another both phenotypically and genetically (Garcia-
Ramos and Kirkpatrick, 1997; Varga and Schmitt, 2008; Habel et al., 2009). How can
this be compatible with the use of genetic distance as a criterion for designating
genetically different organisms as different species, which is a practice that forms the
basis of the barcoding approach (Chapter 4)?
This book gets to the bottom of such questions. It explains and illustrates many
biological examples that are associated with taxonomic problems. In doing so, special
emphasis is placed on genetic foundations. However, an attempt is also made to
philosophically substantiate theoretical conclusions. The question of how organisms
are grouped both in our mind and in nature will be addressed. It is shown that a
grouping according to intrinsic traits differs substantially from a grouping according
to relational connections. It is also demonstrated that the formation of a class is
completely different from grouping organisms as historically transient singularities,
as individuals in the philosophical sense (Chapter 3). The philosophical term of the
natural kind is dealt with, together with the question of what is reality in contrast
to a purely mental concept. Special emphasis is repeatedly given to the question of
what is as distinct from the operational principle of what properties does
something have (see below).
In this book, species as objects of biology are often compared to the objects of
chemistry, that is, atoms. In doing so, it is noted that the objects of biology are subject
to evolution; they constantly change. In contrast, atoms are invariant. They would lose
their class membership and thus become members of a new class if they changed in
atomic number. In contrast, no living organism changes its class membership if it
changes in some of its properties. A dipteran fly (the order of insects with two wings)
remains a dipteran fly even if it experiences a mutation that causes it to develop four
wings (the Hox mutation).
2.2
Can Species be Defined and Delimited from one Another?
The issue of biological species is one of the most curious problems of biology. Darwin
once said something to the effect that everybody already seems to know what a species
is: Noonedefinitionhasyetsatisfiedallnaturalists,buteverynaturalistknowsvaguely
what he means when he speaks of a species (Darwin, 1859). Everyone deals with this
concept every day, but hardly anyone knows how to define the word species. What
underlies this discrepancy between spontaneous subjective certainty ( but that s all
obvious! ) and the fact that no one can indisputably say what a species is?