Cladistics and "Eclecticism"

[Thomas DiBenedetto]

-----Original Message-----
From: Hubert Turner


           |--A
       |---|X
       |   |--B
    |--|Y
    |  |------C
----|Z
    |---------D

 ...  why say that taxon Z (or Y, or X) now is no longer a species, but
rather a clade?
*****************
It seems rather obvious to me that Z refers to the entire group that
contains the terminals A,B,C, and D. How can Z be considered a species? Is
Primates a species? At one point in time Z was a species level taxon, but
evolution has happened in the interim.
*****************
To me this looks like using the name Z  at the species level first, and
subsequently (after a splitting event took place) at a higher taxonomic
level.
**************
Well, yeah obviously,,,,Is this not what happens in the real world? When a
new taxon comes into existence at a speciation event, the new taxon is a
terminal lineage branch, a species. If it subsequently diverges, it
encompasses more than one species, it is a non-terminal branch, i.e. a
higher level in the hierarchy of life. Is this not obvious?
*************
 To me it makes more sense to speak of the branch between the splitting off
of species D and the splitting off of species C as "species Y", but of the
same branch together with all its descendant branches (C, X, A, and B) as
"clade Y".
******************
Yes of course. I dont see that this is inconsistent with what I said above.
At the beginning of the evolution of this system you had one taxon, species
Z. Then Z diverged (evolved), and became a higher taxon, with two new
terminal branches, D, and Y. At that point in time, both D and Y were
species level taxa. So the branch between the splitting off of D and C was a
species, Y. When C branched off, Y became more complex, a higher taxon, or a
clade as you say.  At first this clade encompassed the branch that had been
species level taxon Y plus the new terminal, C, plus the other terminal, X.
By now the descendants of the original species Y have even further diverged,
so clade Y (higher taxon Y) now encompasses all that you say it does. I dont
see that we disagree, do we?
*****************
After all, the branch was at one time a proper species,
**********
Yes of course.
************
which ended (went 'extinct' >as a species<; of course the lineage itself did
not go extinct) when it split in two.
 ************
Grrrrr. Why oh why do y'all constantly talk about these things ENDING, or
going extinct? What do you mean "ending as a species"? "Species" is just a
rank, at least in systematics. The lineage evolves, the rank changes, thats
all. It seems to me to do nothing but add to confusion to talk about species
ending.....

Tom DiBenedetto