Cladistics and "Eclecticism"

[Thomas DiBenedetto]

-----Original Message-----
From: Richard Jensen
>                         ------B
>                   ---- |
>                         ------A
>                             |
>                              ---C

Since we're getting into improbable, but certainly not impossible, examples,
let's consider this.  In my example above, the isolated population (C) is
the
result of autopolyploidy with a single propagule getting established and
founding the new population.  C has both morphological apomorphies
(polyploidy
often yields these) and is a "good" biological species.  A, as a
species-level
taxon, no longer exists.  So, we now have two species and let's suppose that
for
the next two centuries C and A undergo separate evolutionary fates.
************
You are confusing me here. You said "A, as a species level taxon no longer
exists". And then for the rest of your message you speak of A as a species.
I would say that A is a higher taxon. So lets give the name D to the
persistent sister of C.
************
The
population of C begins to spread locally and some additional genetic
apomorphies
evolve.  On the other hand, during the same time A {D} experiences
stabilizing
selection that results in no apomorphies that could be used to differentiate
extant A  {D} from A of 200 years ago.  Then, the habitat in which C is
surviving
(ANWR?) is destroyed and C becomes extinct.  What is A {D} now that C is
extinct?
With no apomorphies to differemtiate it from its ancestor (pre-C A), it's
still
A.  Would this be a case of extinction (as a taxon) not being forever?
**************
What do you mean "extinction not being for ever"? _Nothing_ went extinct in
the first place!
If C now goes extinct, and we never had or ever will have evidence of its
existence, then we would never have recognized D, and we would always call
the persistent species A. I am sure that there are millions of little
branches in history that have went extinct without a trace, and that we will
never know about.
If we had seen this whole story transpire, as we here laid it out, then I
guess we could continue to recognize D as a descendant of A, and C as an
extinct descendant of A. The lack of character evidence for D, as opposed to
A, would normally not allow us to recognize D, but given our special
knowledge of what actually happened, we could recognize it none the less.
Character evidence is just that - evidence to support an inference of what
actually happened. It is what actually happened that should be the ultimate
criterion.
May I suggest that instead of coming up with ever more complicated scenarios
for me to deal with, that you join the effort? The principle is simple: lets
try to make our naming system conform to the real history of lineages.

Tom DiBenedetto