Message 2004-10-0183: applying widely known names to crown clades

Tue, 19 Oct 2004 08:35:58 -0400

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Date: Tue, 19 Oct 2004 08:35:58 -0400
From: [unknown]
Subject: applying widely known names to crown clades

Jason Anderson wrote:
>Thus, as I asked in my first email and ask again now,
>why are we persisting on keeping Tetrapoda attached to the crown, an=
d use
>Holotetrapoda for the apomorphy-based definition, when using Tetrapo=
da and
>Neotetrapoda (or whatever) is logically just as consistent, but
>additionally, will maintain consistency with the literature, and mor=
>might help to bring more workers onside?

As I wrote to Jason in an email message last spring (and I would like=
to share with the rest of you now), I am less interested in the=20
applications of particular names than I am in developing a system=
whose consistency will (1) help users to understand and remember the=
phylogenetic meanings of names and (2) convey a limited amount of=
phylogenetic information directly in the name (e.g., that Pan-X is=
the total clade corresponding to crown clade X).

There are other conventions that would also offer such advantages.=
For example, widely used names that refer to a character (e.g.,=20
Tetrapoda) could be applied consistently to  apomorphy-based clades,=
with Neo- and Pan- referring to the corresponding crown and total=
groups, respectively.  However, from a practical standpoint, this=
convention would not work as well.  If the apomorphy referred to in a=
name doesn't fossilize (e.g., Embryophyta), there would be many=20
extinct organisms whose membership in the clade could not be=20
determined.  Also, if a widely used name doesn't refer to a character=
(e.g., Plantae), which synapomorphy-based clade should the name apply=
to if the crown clade has more than one synapomorphy?

Another option would be to apply widely known names consistently to=
total groups, with Neo- referring to the corresponding crown, but=
this would present a different problem.  Some character-based names=
would necessarily apply to clades whose basal members lack the=20
character.  For example, the total clade that would be named=20
Spermatophyta under this convention would include extinct plants that=
predated the evolution of seeds.

I agree with Jason that an apomorphy-based application may be most=
consistent with traditional usage of certain well known names, but I=
place higher priority on the advantages of consistency in application=
of widely used names.  Because applying such names consistently to=
crown clades does not have the practical problems that applying them=
consistently to apomorphy-based or total clades would have, I favor=
the former.


Philip D. Cantino
Professor and Associate 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!