rankless nomenclature

[Philip Cantino]

Doug Yanega wrote:

>As Curtis Clark already hinted, "rankless" classification advocates are
>suggesting precisely this sort of thing. Effectively, you *could* have,
>say, "Species 71456812" as your taxon name, and "simply" show or make
>reference to a cladogram to explain where it fits in your classification.
>The name conveys no information, and doesn't need to, by design - that's
>what the cladogram is for. If you find the idea of not being able to place
>a taxon into any frame of reference unless it comes accompanied with a
>cladogram difficult to accept, well, welcome to the club. ;-)
>Yes, I realize that replacing names with numbers is not an idea with many
>(if any) supporters, so people should always have some (archaic) frame of
>reference even if the rankless advocates win out, but in a rankless scheme
>there really is no *effective* difference between a name and a number.
>

I want to comment on two aspects of Doug's message: the replacement
of species names with numbers, and reference to a cladogram to place a
taxon into a frame of reference.

1) By "rankless classification", I assume that Doug means
phylogenetic nomenclature, which will be governed by the PhyloCode
once it is implemented.  Opponents of phylogenetic nomenclature often
cite the replacement of species names with numbers, or the inclusion
of numbers in species names, implying that this sort of name will be
used in phylogenetic nomenclature.  This is misleading because, as
Doug says, replacing names with numbers is not an idea with many
supporters--among proponents of rankless nomenclature as well as in
the taxonomic community as a whole.

The draft PhyloCode (http://www.ohiou.edu/phylocode/) does not cover
species, but it is the intent of those preparing the PhyloCode to
expand it to cover species names in the future.  It is not
clear at this time what form species names will take in the
PhyloCode, but the options that have been considered are summarized
in a 1999 paper in Systematic Biology (48: 790-807).  None of the 13
forms of species names covered in this paper replace names with
numbers, and only 2 of the 13 options include numbers as part of the
name.  I think it unlikely that either of these two will be adopted
in the end because the inclusion of numbers within taxon names is
distasteful to most people.

All names governed by the PhyloCode will have an associated
registration number, but this will not be the name of the taxon.  By
analogy, everyone in the U.S. has both a social security number and a
name, but everyone recognizes that they are entirely different things.

I don't understand what Doug means when he says that "in a rankless
scheme there really is no effective difference between a name and a
number."

2) Doug says: "If you find the idea of not being able to place a
taxon into any frame of reference unless it comes accompanied with a
cladogram difficult to accept, well, welcome to the club."  This,
too, is misleading.  In phylogenetic nomenclature, one does not
generally make reference to a cladogram when citing a taxon (species
or clade) name.  Rather, the name is either cited alone or optionally
(once the registration system is implemented) with its registration
number or optionally with the names of one or more clades that it is
part of.  For example, a clade named Mentha might be written Mentha
(Reg. # xxxxx) to provide easy reference to the literature via the
online registration database, or it might be written
Lamiaceae/Nepetoideae/Mentha to show that it is part of a larger
clade Nepetoideae and a still larger clade Lamiaceae.  The latter
kind of reference is analogous to the common practice in traditional
nomenclature of citing one or more higher ranked taxa to provide a
frame of reference.

Doug's criticism of rankless nomenclature could also be made of
traditional rank-based nomenclature, where one often "cannot place a
taxon into any frame of reference unless it comes accompanied with" a
reference to a higher ranking taxon to which it belongs.  This is not
true of species names, since the frame of reference is included in
the name (Doug's main point), but it is true of the names of genera,
families, orders, etc.

It is true that with phylogenetic nomenclature, whichever form of
species name is adopted in the end, it will not be possible to tell
from the name alone where it fits into the phylogeny.  An optional
reference to a more inclusive clade will serve this function.  Thus,
species names will function like all other taxon names in this
regard, whereas in the traditional system the species name includes
reference information that is not present in higher taxon names.  The
tradeoff will be that species names under phylogenetic nomenclature
will be much more stable than they are in the Linnaean binomial
system.  New information about the phylogenetic relationships of a
group of species will not entail name changes, as new information
about generic boundaries does in the Linnaean system.  This may well
be appealing to the many users of species names (ecologists,
foresters, horticulturalists, etc.) who get fed up with the endless
species name changes under the current system.

Phil




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

Phone: (740) 593-1128; 593-1126
Fax: (740) 593-1130
e-mail: cantino at ohio.edu