species concepts (Re: Eastern/Canadian Tiger Swallowtails)

Doug Yanega dyanega at mono.icb.ufmg.br
Sun Oct 12 18:27:31 EDT 1997


Harry Pavulaan wrote:

><<Ultimately -- what is happening here is a researchers attempt to overturn
>the concept of species and propose a BRAND NEW CONCEPT OF SPECIES based on
>the microscope quite apart from the butterfly's behavior.>>
>
>This is nothing new, Dave.  It is called the Biological Species Concept, and
>has been around for a long time.
[snip]
>What is being found out is that some populations of a species are
>slightly different, genetically, from the main population gene pool.  In
>others, they are more different, in others yet more.  Some of these
>more-different populations show minor differences in appearance and overall
>biology, and though they are not CLEARLY different species, they are unique
>in small ways.
>Linnaean systematics gives you two choices: separate species, or the same
>species.  Black or white.  No in-betweens.  We have gotten around this with
>the concepts of subspecies and "hybrid zones" which are really catch-all
>categories that cover a broad range of possibilities.
>
>The biological species concept allows us to separate organisms down to their
>level of evolutionary development, though nobody has yet come out with a
>refined systematic/taxonomic replacement to the Linnaean system.  Do we call
>these ecotypes, biotypes, sibling species, races, or a variety of other
>designations?  Do we name these organisms?
>
><< There seems to be in this concept that there is a point where after
>counting a number of gene differences, just one more different gene
>constitutes a different
>species. >>
>
>No.  It takes a lot more genes.  But biological differences make a difference
>too.

Actually, Dave was closer to the truth of things than you think, Harry.
Spend a little time and familiarize yourself with the "Phylogenetic Species
Concept" and its proponents like Donoghue and DeQueiroz. People ARE, at
this moment, arguing that (1) species should be defined as any group of
organisms where all sampled members of that group share ANY feature not
possessed by sampled members of any other group of organisms [thus, a
single *base pair* difference that is both consistent and exclusive is
enough, BY ITSELF, to define a species] (2) we should abandon the Linnean
Hierarchy, and admit that only species exist - that all "levels" above
species are artificial and subjective. These are prominent, intelligent,
and influential people making these proposals, and many people are taking
them quite seriously, especially those whose work focuses on molecular
systematics (the majority of the new generation of systematists). It is
entirely possible that a decade or two from now, Mayr's "Biological Species
Concept" will be little more than a historical footnote. Myself, I think
this would likely be a disaster (for various reasons both conceptual and
practical), but if the majority of people who define species adopt this
view, then that's what could happen, whether we like it or not.

Peace,

Doug Yanega    Depto. de Biologia Geral, Instituto de Ciencias Biologicas,
Univ. Fed. de Minas Gerais, Cx.P. 486, 30.161-970 Belo Horizonte, MG   BRAZIL
phone: 031-448-1223, fax: 031-441-5481  (from U.S., prefix 011-55)
                  http://www.icb.ufmg.br/~dyanega/
  "There are some enterprises in which a careful disorderliness
        is the true method" - Herman Melville, Moby Dick, Chap. 82




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