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Much ado about species (and genus) level taxonomy



Hi, folks,

No solutions to add here, but some good references you might want to check
out:

Two recent volumes on the nature of species, species definitions, species
concepts (or rather species criteria, as De Queiroz point out!), and the
species problem in general:

Howard, D.J. & S.H. Berlocher (eds.)  1998.  Endless Forms: Species and
Speciation. Oxford Univ. Press.

Wilson, R.A. (ed.). 1999.  Species: New Interdisciplinary Essays.  MIT
Press.

If you are indeed serious about thinking about species, I highly recommend
that you find both volumes.  I found Kevin De Queiroz's two essays (on in
each volume) very useful for thinking about the matters at the level we
paleontologists operate, but there are a lot of other good stuff to deal
with in these.

In particular, De Queiroz takes the premise that species are a different
kind of entity than clades (granted, he is not the only one with this
position!).  He makes the distinction between lineages (a series of entities
forming a single line of direct ancestry and descent) and clades, clans, and
clones (all paths or lines of descent from a given ancestor).  Clades,
clans, and clones are monophyletic, whereas lineages may be paraphyletic.
In his thinking:
"In short, species are segments of population-level lineages.  This
definition describes a very general conceptualization of the species
category in that it explains the basic nature of species without specifying
either the causal processes responsible for their existence or the
operational criteria used to recognize them in practice.  It is this
deliberate agnosticism with regard to causal processes and operational
criteria that allows the concept of spcies just described to encompass
virtually all modern views on species, and for this reason, I have called it
the _general lineage concept of species_ (de Queiroz 1998)".
[the above quote from p. 53 in the article in the Wilson volume, and the
1998 paper is the one in the Howard & Berlocher volume.]

Again, I highly recommend these books for folk interested in more than a
general level about species.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796