Compromise in the air? (was: Boolean games)

Curtis Clark jcclark-lists at EARTHLINK.NET
Sat Mar 12 11:08:17 CST 2005

on 2005-03-12 08:00 Ken Kinman wrote:
> As for
> Archosauria, I did include it as one of my three "subclasses" of
> Reptilia.  Remember?

Indeed, but I will explain below how that was hollow.

> As for the fluidity of strict cladifications, the nesting has
> actually turned into one "house of cards" after another when applied
> to amphibians and reptiles.  That kind of fluidity yields perpetual
> instability!!!

If I understand the mess at the base of the "tetrapods", it's more a
result of no one having a solid clue what went on in the evolution of
those fossil groups. IMO, shoveling them into clades and shoveling them
into grades are equally unproductive. I remember Ed Wiley suggested an
informal grouping, "plesion", to accomodate these paraphyletic messes. I
could actually back a parallel "paraphylocode" to provide
out-of-ICxN-band information about such poorly understood groups. As I
said in my response to Dick Jensen, it's wrong to deny people the tools
to talk about their ideas, and I think it's more productive to take the
paraphyletic groups out-of-band than to do so with the clades, for one
thing because there are so many fewer of them.

> As for intersecting properties, I only intersect
> by using Kinman markers for exgroups (and that is an advantage
> because it allows formal paraphyly without losing sister group
> information).  The Kinman System retains ranks, is minimally
> intersecting (and does so in a cladistic, informative manner).

Ironically, I think the Kinman system would be a real contribution if
you'd just get rid of all those paraphyletic groups. :-)

Traditional clade-grade grouping suffers from the failing that one never
knows for any given taxon the kind of information used to specify it. In
a phylogenetic system, all taxa are specified by synapomorphy, but in a
clade-grade system, both synapomorphy and divergence are used,
*indiscriminately from the standpoint of a user of just the names*, no
matter how much care went into circumscribing the groups.

Your system (as I understand it) is a clear advance on that, because it
specifies which groups are paraphyletic, and which clades they include.
In fact, the specificity is so great that one can (as I have pointed out
so much that even I tire of it) diagnose the paraphyletic groups by
Boolean operations on the clades. So from an information retrieval
standpoint, the paraphyletic groups are superfluous: "non-avian,
non-mammalian amniotes" specifies the same thing as "Reptilia".

I'm guessing you would argue that they are still useful in talking about
things (and I concur), and that they show evolutionary reality by
including anagenesis. With the latter, I solidly disagree, inasmuch as
anagenesis at the broad scale is most often the result of ignorance of
transitional forms, and anagenesis at the narrow scale of species and
species groups is a confused metric, since different clades diverge in
different ways (for example, in some cases molecular divergence is
faster than morphological, and in others the reverse.)

> I
> know I said this before, but I really am tired of arguing with
> Curtis.

I used to think of it as argument, too, but our interchanges have helped
me immensely in formulating my ideas about the subject (viz. my changing
view about the naturalness of paraphyletic groups), and I want to
publicly thank you for that.

> Yikes, Pteridophyta has been reduced to a
> smaller clade as well?  No wonder Tom Lammers is complaining!!  The
> bullies grabbed yet another pile of sand from our sandbox when I
> wasn't looking.  Will the strict cladists please stop hijacking our
> names and changing their meaning.

As I pointed out to Tom, the use of Pteridophyta to refer to the fern
clade predates the wide acceptance of cladistics by botanists, and may
actually date back to the time when Herb Wagner was the only botanical
cladist (the fact that he worked with ferns is perhaps suspicious, but
the change was embraced by many others). The decision to exclude the
lycophytes from Pteridophyta is not a "cladistic hijacking", it is the
natural outcome of accomodating new information. And I'll repeat, I
learned all this as a graduate student in the 1970s, and a lot of it was
old news even then.

Curtis Clark        
Web Coordinator, Cal Poly Pomona                 +1 909 979 6371
Professor, Biological Sciences                   +1 909 869 4062

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