Message 2001-02-0048: Fwd:

Fri, 09 Feb 2001 14:24:06 -0500

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Date: Fri, 09 Feb 2001 14:24:06 -0500
From: Philip Cantino <>
Subject: Fwd:

I would like to add to the several messages that have already been
posted in answer John Janovec's questions.

John wrote:

>I hate to be a pessimist, but I observe very little to no discussion of the
>groups for which no to few phylogenies are available.  How will the Pcode be
>applied to the many groups of organisms which are not represented by
>phylogenies?  Insects come to mind.  Many tropical plants at the subfamilial
>level come to mind.  I hear plenty of arguments for application of the Pcode
>with regard to vertebrates and perhaps even higher levels in the plant
>world, but how in the hell can we expect to apply a Pcode classification and
>nomenclature to understudied and very diverse groups?

The PhyloCode is designed to govern the naming of clades (and,
eventually, species).  In a poorly studied group, the PhyloCode will
still facilitate naming clades to the extent that they have been
discovered.  In some groups, only a few clades have been found, and
these can be named using the PhyloCode.  If one wants to name other
phenetically-defined assemblages of species, then the current codes
are available to do so.  The PhyloCode may or may not ever replace
the rank-based system, but it certainly won't replace it in the near
future.  Some magazine articles have emphasized the abandonment of
"Linnaean" nomenclature (after all, journalists love controversy),
but it is clear to me that the two systems will operate in parallel
for long while.  Thus, the rank-based system will remain available
for those who want to delimit and name phenetic groupings, and the
PhyloCode will be available for those who wish to discover and name
clades.  People whose study groups are poorly known phylogenetically
may want to use both systems in the taxonomy of a single group.  If
so, symbols can be used used to indicate which names are governed by
which code.

>If we freeze names of clades based on current phylogenetic understanding (or
>misunderstanding), then what happens when the phylogenies change?  The names
>remain the same but get placed in different clades.  What will this do to
>the (utilitarian) system of communication?  Confusion? Chaos?  Disorder?
>And what do we tell the general consumers of taxonomic information-- the
>agrarians, the foresters, the high school teachers, or even local indigenes
>in the Neotropics being trained to recognize local plants as assistants in
>biodiversity surveys.

As Jonathan Wagner pointed out, changes in our understanding of
phylogeny will change the content of clades named under both systems.
Moreover, the rank-based system is plagued by an additional source of
instability that is not found in phylogenetic nomenclature: clade
names may change due solely to shifts in rank, without any change in
our knowledge of phylogeny.  This has been pointed out repeatedly in
many different papers, so I won't belabor it here.

>Is the Pcode really a communication and recognition

It is a device for communication (of information about phylogeny) but
not for recognition (i.e., identification).  This is equally true of
the current system of nomenclature, in which taxon names are
operationally defined in terms of ranks and types.  For example, in
the traditional system, Asteraceae is the taxon of family rank that
contains the type of Aster.  From this information alone, you could
not recognize a member of Asteraceae.  Identification requires
descriptions and keys, and these should be provided no matter which
system of nomenclature is used.

>Is the Pcode truly rank-free?
>Won't there always be a ranked hierarchy in nature, regardless of the
>classification system applied?

Of course nature has a hierarchy because the evolutionary process
creates a hierarchy of relationships.  Clades contain clades contain
clades, regardless what system you use to name them.  However,
phylogenetic nomenclature is rank-free in the sense that ranked
categories (e.g., genus, family) are not mandatory.  You can still
use them if you want to, but they have no bearing on the spelling or
application of names.

>Don't we have a great deal of basic biodiversity survey work to do before we
>can just drop the current system and convert to a new system?

As explained above, I don't think anyone is suggesting that we "just
drop the current system and convert to a new system."  We are
introducing a new system that we feel works better for naming clades
and species.  It will function in parallel with the traditional
system for a while (probably a long while).  If it works well, the
community of biologists MAY (or may not) eventually decide that the
old rank-based system is no longer needed.  Whether or not this ever
occurs, the PhyloCode will be extremely useful in the short term by
making it far easier to name clades than it is currently.  At a time
when clades are being discovered at an unprecedented rate, this in
itself is an important contribution.


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

Phone: (740) 593-1128; 593-1126
Fax: (740) 593-1130


Feedback to <> is welcome!