Different codes (and eudicots)

[Ken Kinman]

Philip, Thomas, David, and others:
      Correct me if this non-botanist is wrong, but isn't it relatively easy
to distinguish a monocot from a dicot using a combination of simple
characters (just one or two characters will usually do, except for some
paleoherbs).  Isn't there a clear diagnostic reason that two classes have
been recognized for so many generations?  This isn't just tradition for the
sake of tradition.  Traditions often have good reasons behind them, not just
historical precedence.
       On the other hand, how easy is it to tell a "eudicot" from other
dicots?  Other than genetic sequences (and perhaps a certain type of
pollen?) are there diagnostic characters that distinguish the eudicots?
       From the perspective of an evolutionary biologist, of course I find
it a wonderful thing that "the eudicot clade" is so extremely well supported
in rRNA gene trees.  But classifications are for everybody, and you have to
take into account a lot of different things---tradition, stability,
diagnosability on various levels, among other things.  As for the argument
that PhyloCode taxa will only be used by phylocoders in their "phylozone", I
just don't buy it (and I am clearly not alone).
      And as Thomas Lammers has said, we can continue to use an informal
name "eudicot", which seems to be working remarkably well.  If it isn't
broke, don't fix it.
      All the rest of this discussion about PEST and subsidiary ranks is not
the main issue.  That is one of the reasons I dispense with subsidiary
(intermediate) ranks and taxa.  You could certainly use additional ranks in
the Kinman System if you want to, but I find the coding so useful that I
find all these extra ranks a nuisance that create more confusion than
they're worth.  Thank you for helping to prove my point.
      Finally, since the devil is always in the details, if eudicots are to
be given a formal name with a cladistic definition, I would be interested to
know what kind of phylogenetic definition one would give.  Presumably
node-based (rather than stem-based), but which two genera (ooooppps, I mean
clades) would be used to anchor this eudicot clade.  I assume one of them
would be Ranunculus or a close relative.  Has a cladistic definition of "the
eudicot clade" been proposed yet?
                 ----Sincerely, Ken Kinman
P.S.  For Thomas, perhaps Campanula could be made the other "anchoring"
subclade for eudicots, but phylogenetic taxa have no single type genus as
far as I know.  Otherwise you wouldn't have the current situation in which
the clade Ornithosuchia excludes the genus Ornithosuchus.  Believe it not,
it is true.  The PhyloCode is supposed to take care of such situations in
the future (hopefully), but even if it does, there are less obvious slip-ups
that will elude the new code until the confusion is already a done deal.
Therefore, I still think genera should be excluded from this "experiment",
and I'm glad to see Rich (in his support of PhyloCode) also agreed that it
would be prudent to do so.
*********************************************************
>From: Philip Cantino <cantino at OHIOU.EDU>
>Reply-To: Philip Cantino <cantino at OHIOU.EDU>
>To: TAXACOM at USOBI.ORG
>Subject: Fwd: Re: Fwd: Re: Different codes - in support of the phylode
>Date: Thu, 19 Oct 2000 15:14:21 -0400
>>
>>At 01:34 PM 10/19/00 -0400, you wrote:
>>>The eudicot clade is one of the most strongly supported major clades
>>>of angiosperms.  Why shouldn't it have a formal scientific name
>>>rather than being designated with a symbol (Ken's preference) or an
>>>informal English name (Tom Lammers' preference)?
>>
>>I'll grant you, this is one clade that does not seem in any danger
>>of collapse in subsequent analyses.  I'd have no problem with naming
>>this one via the ICBN.  Especially if Campanula L. were the type genus!  :
>>- o
>>
>>>I suspect that the only reason why the eudicot clade has never been
>>>formally named is that to do so under the current system would
>>>require giving it a rank, and it isn't clear what rank it should have.
>>
>>Good point.  We like "monocot" and "dicot" to be classes, and
>>Cronquist, Takhtajan, Thorne, and Dahlgren have used subclass and
>>superorder to recognize diversity within these two.  It's hard to
>>come up with a rank between class and subclass ("supersubclass"????)
>
>The problem is even worse if angiosperms are treated as a class, as
>they often are.
>
>>Part of the problem is what to do with the grade at the base.
>>Essentially, what we have in the angiosperms are two major groups,
>>monocots and eudicots, plus a lump of "miscellaneous" at the base.
>>Cladistic thinking won't let us give names of the same rank to
>>non-sister taxa, so really, what rank do we assign to *any* of them?
>>The monocots are not sister to eudicots, so it really isn't right to
>>call either of them each a subclass, from a cladistic perspective.
>
>The problem is not created by a requirement that taxa at the same
>rank be sister taxa (this Hennigian ideal is not always followed,
>even by people who would call themselves cladists).  It is simply a
>function of there not being enough standard ranks to accommodate all
>the well supported clades that could justifiably be named in a large
>and diverse group like the angiosperms.
>
>>And this, I guess, is why cladists favor a rankless nomenclature system.
>>IF you accept that cladistics is the only way to classify, then I
>>guess you must accept rankless nomenclature as the only way to go.
>>
>The issue that the "eudicots" example raises is not whether
>cladistics is the only way to classify but whether the current system
>allows one to give formal scientific names to all of the well supported
>clades that warrant naming.  If the ranks of order, superorder, and
>subclass are already occupied by taxa that are either
>more or less inclusive than the eudicot clade, we must invent another
>category (e.g., supersubclass) if we want to name this clade.  But it gets
>worse:  If the usual convention is followed, once a
>supersubclass is named, every subclass of angiosperms must belong to
>some supersubclass.  (This is what Kevin de Queiroz calls the Principle of
>Exhaustive Subsidiary Taxa, which happens to have the
>memorable acronym, PEST.)  The PEST convention would require that we either
>name at least one other (probably nonmonophyletic) supersubclass to
>accommodate all of the subclasses that don't belong to the eudicot
>supersubclass or that we assign each non-eudicot subclass to its own
>supersubclass.  Whew!  It's no wonder no one wants to name the
>eudicot clade.
>
>With phylogenetic nomenclature, you would simply make up a name
>(since this clade has never been given a formal name under the ICBN)
>and give it a definition that would explicitly link the name to that
>clade.  You wouldn't have to worry about classificatory issues when
>naming it, as you do with rank-based nomenclature.
>
>Phil
>
>Philip D. Cantino
>Professor and Chair
>Department of Environmental and Plant Biology
>Ohio University
>Athens, OH 45701-2979
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