[Taxacom] Descriptive suprafamilial names of plants

[David Campbell]

The challenge for stability in nomenclature is deciding how much of a
change deserves a new name.  On the one hand, it is unhelpful to follow the
practice of some cladistic extremists and make a new name for every
interesting clade that pops up in their latest analysis if it is not
absolutely identical to any previously named group that they are aware of.
Likewise, strictly defining every taxon as the smallest clade that includes
every originally included species would cause havoc with many early-defined
taxa.  Nautilus, for example, would go from being a genus of shelled
cephalopods to including most if not all eukaryotes, depending on the
latest assessment of foraminiferan-animal relationships, and Anomia would
go from a genus of pteriomorphan bivalves to including a good chunk of
Lophotrochozoa since it would include mollusks and brachiopods.  Compared
to these, Testudo going from a tortoise genus to including roughly all
turtles is a small change.  Even today, it's easy to envision one molecular
study placing two prokaryotes in the same genus and a later genomic study
to determine that the similarity was due to lateral transfer.  Having
ranked taxa controls these problems somewhat by saying that a name proposed
at one level should not automatically transfer to another level, and by
limiting the number of levels used.  Rather than naming each clade, we can
say that within superfamily A, families A and B form a clade, with family C
basal.

At the same time, too large a modification of the definition of an existing
name will cause confusion.  If I did a genetic analysis that accidentally
sampled the epibiotic algae off a Magnolia rather than the Magnolia itself,
and concluded that Magnolia was in fact a highly aberrant alga, it would
cause more confusion than stability to use the name Magnoliophyta for
algae, as most taxa traditionally included in the group would no longer be
included.

Finding the balance between retaining existing names and associating those
names with a particular content is going to have an inherent level of
subjectivity.


On Sun, Nov 24, 2013 at 10:53 AM, Jim L. Reveal <jlr326 at cornell.edu> wrote:

> According to Art. 16 of International Code of Nomenclature for algae,
> fungi, and plants (ICN), names above the rank of family may be (a)
> automatically typified or (b) descriptive. Magnoliophyta is an
> automatically typified name, being based on the genus Magnolia which, in
> turn, is typified on a single species (M. virginiana). That epithet is
> typified on a single specimen and this is the only element that must be
> termed M. virginiana, Magnolia, Magnoliaceae, Magnoliales, Magnoliophyta,
> or any other suprageneric name based on the genus Magnolia.
>
> All other element associated with Magnolia virginiana, or any other taxon
> above that rank, including any other specimens, is strictly a taxonomic
> decision.
>
> A descriptive name is not based on a generic name, may be used unchanged
> at different ranks, and may be defined however one may wish. Descriptive
> terms like Angiospermae, Gymnospermae, Coniferae, Centrospermae are
> circumscribe however one may wish and, in fact, have been. Some author
> define Coniferae to include all gymnosperms, but other restrict their
> concept to just the conifers. Centrospermae has been used for groups of
> algae as well as plants. Authorships are impossible to define as the
> addition or subtraction of any taxon alters the circumscription. Thus, such
> names violate Principle IV of ICN, at least in principle, that a taxon have
> "a particular circumscription, position, and rank" and "can bear only one
> correct name."
>
> Arguably, therefore, for a descriptive name to be used as proposed by the
> original author of the name, say Angiospermae, that author must have
> included in that group all possible taxa and no newly discovered entity can
> be added because to do so this would alter the original circumscription.
> Thus, the second author who proposes Angiospermae with a different
> circumscription creates a later homonym because, as required in Principle
> IV, the earliest name must be used.
>
> Now, this is silly, of course, and today one actually applies the rules of
> nomenclature to descriptive names in the most general and purposefully
> vague ways as possible. Fortunately, no one questions any action and we all
> pretend that use of a specific descriptive name has been followed "in
> accordance with the rules."
>
> Given the problems with descriptive name, I strongly urge that one use
> names that can be typified and that descriptive names should be used only
> as informal terms. Thus, Magnoliophyta or angiosperms; Pinophyta or
> gymnosperms. As Principle II states: "The application of names of taxonomic
> groups is determined by means of nomenclatural types."
>
> Jim Reveal
>
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-- 
Dr. David Campbell
Assistant Professor, Geology
Department of Natural Sciences
Box 7270
Gardner-Webb University
Boiling Springs NC 28017