Cladistics and "Eclecticism"

Thomas DiBenedetto tdib at OCEANCONSERVANCY.ORG
Thu Feb 7 10:59:37 CST 2002

-----Original Message-----
From: Richard Jensen
I hate to continue this, but how many times do I have to say this:  As a
level taxon, A no longer exists.  It's obsolent, it's invalid, call it what
Maybe this is semantics, but it strikes me as so strange. If a corporal
Jensen is promoted to sargent Jensen, would it ever occur to someone to say
"As a corporal level soldier, Jensen no longer exists. He is obsolent,
invalid". I suppose it is technically correct in a sense, but it doesn't
sound like a very good way to communicate meaning.
...... if you
continue to argue as if what you are doing is not equivalent to
extinction" (choose your own word), then you are simply being obfuscatory.
so be it
After all, you're the one who said that we would now rename A (to D) to
differentiate it from C as well as from the common ancestor (A) of D and C
Maybe this is the root of the misunderstanding. I am not renaming A to D. I
am ADDING the name D to PART of A. The part after the divergence. Just like
we add the taxon name "sapiens" to the taxon name "Homo" when Homo diverges
(this is not a good example, but you get the idea I hope).
As noted above, see your earlier posting.  You have changed the rank of A
indicated it should be renamed) - it is no longer a species rank taxon!
Once agian, A as a taxon has an origin in time. The name refers to a lineage
of organisms through which the process of inheritence takes place. The name
A will ALWAYS apply to this group of organisms and all of their descendants,
for the rest of time. A is never renamed. If the set of descendants of A
become divergent (some isolated from others in terms of inheritence) then we
recognize those two divergent lineages with lower level names in addition to
If we have an evolutionary entity, A, that is recognizable (by whatever
criteria), and it undergoes stabilizing selection for some length of time,
we have at the end is the same thing, no matter how many peripheral
have become isolated.
How can you claim that this is a systematic sense of species, when in
systematics we recognize taxa on the basis of relationships? Relationships
to other groups - those peripheral populations, for example (if they can be
  To claim that it is something else, is to claim that
anytime an individual with a unique genome leaves the lineage, the lineage
If an individual, or several go off to begin a new, isolated lineage branch,
then the group relationships have changed. How can you deny that? Why
wouldnt you want to recognize that in a system that is focused on
recognizing groups based on their relationsihips?
  I don't think anyone wants to be that extreme.  What happens to A as a
lineage is independent of what happens to the new isolated population (C),
Not if you are concerned with its relationships
and the relationship between A and B has not changed: they are still sister
I almost agree with that last sentence. A and B will always be sister taxa,
since they are the two branches that emerged from a single bifurcation
I maintain, as a systematist, that in my scenario there are now three
two of which continue just as they had before C became isolated.  Nothing
prevents us from recognizing the historical relationships among these three
species and no changes in rank are necessary to allow us to have a system of
classification that works.
So lets say that at the divergence of A and B (before C budded off), the A
lineage developed some neat apomorphy like an amnion or something. This is
now a  shared apomorphy of A and C . Can we recognize that somehow? Is there
to be a higher taxon name for the fact that (your)A and C share this
character, to the exclusion of all other life. Wouldnt some systematist
coming across the scene come to the realization that (your)A and C were
sister species, not A and B?
For my system, D and C would be found to have the apomorphy, and they would
be united in a higher taxon A. This seems to me to be an accurate rendition
of what happened.
For your system, you have species A, that shares an apomorphy with species
C, and they are united in,,,,what? Species A agian?
Please explain.

Tom DiBenedetto

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