A Reduction of "Species" Resolves the Species Problem
Jody Hey
Department of Genetics
Rutgers University
Nelson Laboratories
604 Allison Rd
Piscataway, NJ 08854-8082
phone 732-445-5272
fax 732-445-5870
internet
hey@biology.rutgers.edu
www http://lifesci.rutgers.edu/~heylab
January, 1997
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Abstract - The species problem is the persistent biological
and philosophical debate on the meaning of the word "species" and the methods
of species identification. With a meaning of "species" that follows from
a simple model of DNA replication, species are shown to be real and non-arbitrary
groups of organisms, under some circumstances. However, it also follows that
many organisms do not belong to species. The criteria by which a group of
organisms can be considered a species is whether they share in a process
of genetic drift. This simplification is a negative resolution to the problem
cases of species identification; it permits a concise listing of the causes
of diversity and of the reasons why species can be very difficult to identify,
but it does not simplify the process of species identification. For population
biologists, a reduced species concept reveals a research plan for the study
of organismic diversity that focuses on the determinants of structure in
patterns of genetic drift. The finding that species exist, but that some
organisms do not occur in species, reveals the central difficulty of systematic
theories that assume the existence of species.
The diversity of life seems to have a pattern whereby organisms fall into
a limited number of types. Although the existence of these types, or species,
has long been recognized (Mayr, 1982a) , the definition of the word "species"
and the identification of species remain problematic. One advance is the
understanding that the word "species", as often used by biologists, signifies
a distinct kind of biological individuality (akin to "organism" or "cell"),
and does not simply denote a group of similar organisms (Ghiselin, 1966,
1974; Hull, 1976, 1978). However, some biologists reject species as a distinct
kind of individual (Nelson, 1989) , and among those who do not, there persists
a lack of consensus on the defining properties of this kind of individual
(Endler, 1989). Two questions remain much discussed: is it useful to consider
species as individuals?; and if so, what is the defining attribute of this
individuality - the meaning of the word "species" - that applies to the different
species of the world?
The approach taken in this paper does not begin with an assumption that species
either are or are not individuals. Rather the approach has been to assume
the existence of some simple natural phenomena concerning the nature of DNA
replication, and then to consider whether these things will cause species.
It is shown that these relatively modest phenomena will create a kind of
individual that has a close correspondence with other concepts of the meaning
of species.
The concept that is developed (the genetic species) is similar to some elements
of the cohesion species concept (Templeton, 1989, 1994). In particular, both
species concepts rely extensively on the idea of shared genetic drift. However,
the two concepts differ in their motivation and their purpose. Templeton
begins his discussion with the question "What is a species?" and the implicit
assumption that species as individuals exist in nature. The genetic species
concept arises from the basic question of whether organisms actually occur
in groups that are individuals (i.e. species).
This article is copyrighted and published on the world wide web. If you draw
from this article for preparing a publication, please cite it (e.g. Hey,
J. 1997. A reduction of "species" and a resolution of the species problem.
http://lifesci.rutgers.edu/sconcept/introduction.html). If you have
thoughts about the article and would like to pass them on, please do
(click here: hey@biology.rutgers.edu
).
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© 1997 Jody Hey
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