Message 2001-06-0089: Stepping back

Thu, 17 May 2001 13:26:28 -0400

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Date: Thu, 17 May 2001 13:26:28 -0400
From: David Baum <>
Subject: Stepping back

Hi All,

I have been rather dismayed by the discussion over the last month
because it can only have served to confuse people.  In an attempt to
bring the discussion back into focus I have jotted down some of the
reasons that I think rank-free nomenclature is such a good idea and why
it is worth putting some thought into how best to arrive at that aim. 
I have done this fairly quickly so the points listed below reflect my
internal reasoning rather than the formal arguments one might present
if the aim was to convince a skeptic/cynic.  But maybe it is better to
articulate why I am committed to this new brand of nomeclature rather
than trying to convince other people to get on board?  Anyway here it

1) The capacity to formally name any taxon that a systematist sees as
worthy of naming and to regulate subsequent usage of that name is a
necessity to avoid nomenclatural chaos. [i.e., we cannot depend on
informal names and conventions]

2) The traditional systems depend heavily on ranks - but we all know
that ranks (as opposed to clades that have been assigned historically
to a particular rank!) are not real.  Unless you will claim that there
is something inherent in the distinction between, say, a family and an
order, then it is ridiculous to build a system around ranks.

3) Getting rid of ranks is not possible with the current system because
a rank defines the intension of a name.  For example, Malvaceae
<bold>IS</bold> that family containing Malva sylvestris L. 

4) To get rid of ranks one needs new ways to attach names to taxa via
concrete types (or specifiers).  The phylocode allows for three (can we
think of more). 1) Node-based: lists two or more types and refers to
the smallest clade including all these internal types.  2) Stem-based: 
Refer to one internal type (in my view only one internal types should
be listed - but the draft code allows multiple internal types) and one
or more external types and refers to the largest clade including the
internal types but none of the external types. 3) Apomorphy-based
(personally I wish this mechanism were disallowed): Refers to one
internal type plus an apomorphy manifested by that type and reference
to the smallest clade composed of individuals manifesting that

5) While the PhyloCode elegantly gets rid of ranks it represents a big
change from traditional system because the correct application of names
depends upon phylogenetic knowledge (rather than opinions about rank). 
If people define names based on an incorrect tree then the content of
those taxa could change later.  This is a inconvenience but not, to my
mind a big one.  If people are responsible in only naming
well-supported clades then it should not occur too often.  And even
when such a shift does happen, biologists will quickly learn.  6) I
like the rank-free system because provided two biologists agree on a
tree then the correct name of each clade is unambiguous.  So any
arguments about nomenclature are about phylogeny - and I view phylogeny
as a useful thing for biologists to be studying.  In contrast under the
traditional code nomenclatural arguments rarely turn on issues of

7) As a new code, names can be registered from the outset avoiding the
problem of overlooked names being discovered that have priority over
familiar names.

8) The PhyloCode does not need new names whenever familiar names fit
with clades.  For example, Angiospermae turns out to correspond to a
real clade so that name can be retained but given a rigorous

9) Since names can exist simultaneously as both ranked names governed
by the traditional codes and unranked clades governed by the PhyloCode
there needs to be an convention for distinguishing the two.  [We have
proposed a forward slash as a clade mark, thus distinguishing family
Malvaceae from clade /Malvaceae]

10) No hybrid system is possible because ranks are intrinsic to the
traditional codes and incompatible with the PhyloCode.  Thus, any
transition that might occur (as I hope it will) will involve a period
of coexistence.

11) The phylocode must deal with species.  There are several viable
ways in which it could but, due to differences of opinion among the
code's developers, no one approach has been approved.

12) There are other subtle issue within the PhyloCode that warrant
discussion but those can only be got into once there is agreement on
the preceeding points.

I hope that is helpful.


David Baum                                   

Dept. Organismic and Evolutionary Biology	

Harvard University Herbaria			

22 Divinity Avenue				

Cambridge MA 02138			

Tel: (617)496-6744, -8766

Fax: (617)495-9484

After July 15:

Dept. Botany, University of Wisconsin

430 Lincoln Drive, Madison WI 53706


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