Message 2004-10-0002: Re: Panstems

Thu, 09 Sep 2004 16:05:58 -0400

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Date: Thu, 09 Sep 2004 16:05:58 -0400
From: [unknown]
Subject: Re: Panstems

>My responses to JRW=3D92s comments on restricting the types of defin=
itions =3D
allowed and on panstems.<

In tandem with Mike Keesey's comments, I would like one or more answe=
rs to =3D
a lingering question from the (very successful) Paris meeting:

In response to Dr. Padian''s suggestion that definitional types be =
restricted to node- and stem-based classes, Dr. de Queiroz responded =
(at =3D
least twice) that he felt it was inappropriate to impose restrictions=
 on  =3D
HOW phylogenetic taxa should be defined. Although I believe Dr. Padia=
n's =3D
points were valid, and I would be willing to consider his proposal, I=
 also =3D
very much respect Dr. de Queiroz's position.

>There are several reasons why allowing only one type of phylogenetic=
definition is inappropriate.  First, it goes against the fundamental =
principle of taxonomic freedom.  Taxonomists should be free to name =
whatever t clades they want to name.  Second, allowing this type of =
freedom is important because it=3D92s the only way to achieve a close=
correspondence between the connotations of a name and the properties =
of =3D
the clade to which it refers.  For example, if a person wants to name=
 the =3D
clade of flying dinosaurs (Volodinosauria?) but is forced to use a =
node-based definition, then the name is likely to end up not referrin=
g =3D
even to the closest relevant node.  For example, we might define such=
 a =3D
name as referring to the clade stemming from the =3D93Archaeopteryx n=
ode=3D94 =3D
based on the idea that Archaeopteryx is the most distantly related ta=
xon =3D
to modern birds that is (currently) thought to have been able to fly.=
However, if we later infer either 1) that Archaeopteryx was not able =
to =3D
fly, or 2) that more distantly related taxa were also able to fly, th=
en =3D
name becomes disassociated from the clade to which it was originally =
intended to apply.  Third, even if we were to agree that only one typ=
e of =3D
phylogenetic definition is permissible, we probably couldn=3D92t agre=
e on =3D
which one, given that different people favor different types (and som=
e of =3D
us favor all of them).  I guess JRW actually favors two.  I thought t=
hat =3D
KP advocated only node-based definitions in his general talk (perhaps=
I=3D92m confusing his view with that of BDM), but I noticed that in h=
is =3D
abstract he used both stem- and apomorphy-based.<

>I also want to comment on the idea that we need to make things simpl=
e for =3D
our colleagues so that they don=3D92t screw things up, which was impl=
ied by =3D
several people who argued for allowing only one type of definition.  =
This =3D
is the type of reasoning that is characteristic of the =3D93hardening=
=3D94 of =3D
a movement, to use Gould=3D92s term.  Although simple rules (symptoms=
 of =3D
hardening) are often advantageous in the short term for getting peopl=
e to =3D
jump on the bandwagon and to separate a new movement from its predece=
 they usually turn out to be misguided and to impose unnecessary rest=
ns in the long run.  That was true of the hardened neo-Darwinist posi=
tion =3D
that selection acts only at the level of individual organisms.  It wa=
s =3D
true of the hardened numerical taxonomist position that taxonomy shou=
ld be =3D
based only on observed similarity regardless of its underlying cause.=
  And =3D
it was true of the hardened cladist position that phylogenetic relati=
s should only be inferred using parsimony methods.  Those views all s=
eem =3D
pretty foolish in retrospect, and they have all exerted retarding eff=
ects =3D
on the development of their respective fields.  I think it would be a=
 huge =3D
mistake to shackle phylogenetic nomenclature with an analogous over-s=

However, as evidenced by the vote late in the meeting, several meetin=
g  =3D
participants, including Dr. de Queiroz, are in favor of restricting W=
NAMES can be defined (specifically, by supporting the non-binding  =
resolution that symposium volume authors be REQUIRED to follow the  =
"panstem" convention). I understand the arguments for panstem nomencl=
  and I am sympathetic. What I do not understand is the justification=
 for  =3D
upholding scholarly freedom on one issue, then denying it on another.=
 Was  =3D
this simply an indication that these individuals would PREFER that pa=
nstem =3D
 nomenclature be employed, inflated to the status of a "requirement" =
only  =3D
because the vote was non-binding? Or do these individuals actually su=
pport =3D
 moving from a Phylogenetic Nomenclature with very limited rules on w=
hich  =3D
names should be employed to a Phylogenetic Taxonomy, with a rigid sys=
tem =3D
for choosing and employing appropriate names?

>There is an important difference between taxonomic and nomenclatural=
freedom.  The PhyloCode follows the traditional codes in adopting =
taxonomic freedom as a fundamental principle.  Thus, neither the tank=
 codes nor the PhyloCode prohibits authors from naming any type of gr=
oup =3D
(note that although the PhyloCode is designed for naming clades, it d=
oes =3D
not prohibit the naming of paraphyletic or and polyphyletic groups), =
nor =3D
do the codes place any restrictions on the composition of the groups =
other =3D
those that are necessary for specifying the references of the names (=
i.e., =3D
the necessary inclusion of the type in rank-based nomenclature, the =
necessary inclusion of internal specifiers and exclusion of external =
specifiers in phylogenetic nomenclature).  In contrast, all codes pla=
ce a =3D
number of restrictions on what names are permitted=3D97that is, on no=
ral freedom.  In other words, there is no principle of nomenclatural =
freedom in any of the codes.  Nomenclatural codes are, after all, set=
s of =3D
rules about what is permitted, and what is not permitted, with respec=
t to =3D
names.  Thus both the rank-based codes and the PhyloCode permit only =
the =3D
use of a particular alphabet, and they both prohibit various diacriti=
cal =3D
marks.  Moreover, the rank-based codes require the names associated w=
ith =3D
particular ranks to have particular terminations and for some of them=
 to =3D
be based on the names of included taxa.  Similarly, the PhyloCode con=
tains =3D
a recommendation (10A), which Phil and I are going to propose be modi=
fied =3D
and made into a rule, that places significant restrictions on the =
definitions (conversion) of existing names (e.g., you aren=3D92t allo=
wed to =3D
convert the name Mammalia for a clade of beetles).  If the PhyloCode =
were =3D
to require the names of total clades to be based on the names of thei=
r =3D
corresponding crowns with the addition of a standard prefix, this wou=
ld be =3D
analogous to certain nomenclatural requirements of the rank-based cod=
es.  =3D
Here I should emphasize that one should not confuse the elimination o=
f the =3D
associations of names with ranks, which is fundamental to phylogeneti=
c =3D
nomenclature, with the elimination of standard affixes, which is perf=
ectly =3D
compatible with phylogenetic nomenclature as long as the affixes do n=
ot =3D
signify rank.  In any case, the point is that a rule requiring adopti=
on of =3D
the Pan- convention would not violate the fundamental principle of =
taxonomic freedom, and thus it is not inconsistent with advocating th=
e =3D
freedom to use multiple types of definitions.< =3D20

9 Sep 2004

Kevin de Queiroz
Division of Amphibians & Reptiles
Smithsonian Institution
P.O. Box 37012
NHB, Room W203, MRC 162
Washington, D.C. 20013-7012
Voice:  202.633.0727
FAX:  202.357.3043


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