Fwd: Re: rankless nomenclature

[Philip Cantino]

Doug Yanega wrote:

>I believe you're overlooking how rankless nomenclature works at higher
>levels. We were paid a visit here at UCR a year ago by one proponent and he
>pointed out that names used for higher ranks in traditional nomenclature
>may persist in a rankless taxonomy, but they require explicit definition.
>Once defined, they may not be REdefined - this, he said, gives greater
>stability compared to the Linnaean approach.

This is incorrect.  Under phylogenetic nomenclature, taxon names may
be redefined through a conservation process comparable to that used
under the ICBN and ICZN (see the draft PhyloCode Note 13.1.2).


>          Under a rankless system, we were told, we would permanently DEFINE
>"Geometroidea" as "the clade consisting of Apoprogonidae + Axiidae +
>Callidulidae + Cyclidiidae + Drepanidae + Epicopeiidae + Epiplemidae +
>Geometridae + Pterothysanidae + Sematuridae + Thyatiridae + Uraniidae" (our
>present classification), and if someone comes along and subsequently
>insists that we shoehorn the Rhopalocera in there (where they belong,
>really), then they have to create a *new* name for the new group thus
>created. Likewise if one of the present constituent taxa is removed.
>Ultimately, in this case, the meaning of the name "Geometroidea" is not
>changed, but the name becomes effectively superfluous and goes out of
>circulation (since the group it describes proves not to be a natural group,
>so no one is likely to ever desire to use it again), while a new name is
>created to take its place, and everyone has to learn the new name. This is
>apparently what rankless advocates (at least the one I encountered)
>consider to be "greater stability". Come again?

This is not how phylogenetic nomenclature will function in practice.
Although one could theoretically define a name in such a way that the
entire membership of the taxon is specified and the name cannot apply
to slightly different memberships (e.g., Geometroidea as defined
above), this will rarely if ever be done.  Instead, Geometroidea
would be defined as the clade CONTAINING species A, species B,
species C, etc., where species A is a representative of
Apoprogonidae, species B is a representative of Axiidae, etc.
"Containing" is very different from "consisting of" in that it does
not imply exclusiveness.  If Geometroidea is defined in this way and
then Rhopalocera is found to be a member of the clade, the name
Geometroidea would NOT change, as Doug asserts.  Rather, the same
name would be used but Rhopalocera would be recognized as a member of
Geometroidea.



>          In what way is the creation of new replacement names
>EVERY TIME a different phylogeny is published more stable than redefining
the old names every time?

I hope it is clear from what I said above that the PhyloCode does NOT
require new replacement names when a new phylogeny is published.
This will occasionally occur when someone intentionally writes a very
restrictive definition, but in most cases it will not.  Whoever the
"proponent" of rankless nomenclature was who gave Doug Yanega this
idea either does not understand how the system will work or didn't
communicate it clearly.



>          One final point: even if this is only that one
>person's idea of how rankless taxonomy should work, rankless systems still
>do allow - even encourage, in a way - the application of names to *any*
>node in one's cladogram that one wishes to discuss. Unless my math is off,
>if you have N taxa, they will be supported by N-1 nodes (barring
>polytomies); that means that you can nearly double the number of taxon
>names, if you name each node. Maybe no one would go quite that far, but it
>certainly does nothing to encourage people to be *conservative* about
>creating new groupings, while under the Linnaean system, there aren't
>enough ranks to go around (at least from an entomologist's perspective). I
>can just imagine what would happen to our present insect genera that
>contain 500 or more species, for example. Can you say "open the
>floodgates"?

It is possible that some people will take advantage of rankless
nomenclature to publish excessive numbers of names, but the draft
PhyloCode discourages this in several ways.  First of all, peer
review is a requirement for publication (Art. 4.2); in this respect,
the PhyloCode is more conservative than any of the currently
functioning codes.  Secondly, the PhyloCode contains recommendations
that are intended to discourage people from naming lots and lots of
clades.  For example, Rec. 9B: "Establishment of names for poorly
supported clades should be done with careful consideration of
possible nomenclatural consequences if the phylogenetic hypothesis
turns out to be incorrect.  It may frequently be advisable to use
only informal names for poorly supported clades."  Recommendation 9C:
"Conversion of preexisting names to clade names should be done with a
thorough knowledge of the group concerned, including its taxonomic
and nomenclatural history and previously used diagnostic features.
Wholesale conversion of preexisting names by authors who have not
worked on the systematics of the groups concerned is strongly
discouraged."


I hope the readers of TAXACOM will be cautious about accepting
characterizations of phylogenetic nomenclature offered by its
opponents.  If you will take the trouble to examine the draft
PhyloCode (http://www.ohiou.edu/phylocode/), you will see that most
of the opponents' concerns are either based on misconceptions or are
addressed within the PhyloCode.  Incidentally, this is the case with
Benton's critique, which Ken Kinman referred to in a posting earlier
today.  Harold Bryant and I are currently preparing a response to
Benton's paper.

Phil


Philip D. Cantino
Professor and Chair
Department of Environmental and Plant Biology
Ohio University
Athens, OH 45701-2979
U.S.A.

Phone: (740) 593-1128; 593-1126
Fax: (740) 593-1130
e-mail: cantino at ohio.edu