describing new spp in tabular form

[Mike Dallwitz]

                                                              5 January 1998

> From: Buz Wilson <buz at MAIL.USYD.EDU.AU>
> To: Taxacom

> I recently submitted my first description of a freshwater crustacean that
> was generated by a DELTA database, and was a bit disturbed by its length
> (we have 530+ characters). Because it was the description of a new genus,
> I let it go and (so far...) the editor has not complained about the
> verbosity. For a larger monographic work, the length of each description
> will have to be reduced considerably.

There was recently some discussion about a similar subject on the IOPI ISC
mailing list. Here is a copy of my contribution.

> Subject: Completeness vs. brevity in printed descriptions

> From: Dick Brummitt
>    (communicated by "W. Berendsohn" <wgb at zedat.fu-berlin.de>)

> ... there could be difficulties with "every character used on a taxonomic
> level must be recorded for all taxa on that level". In small genera what
> you ask for would probably be automatically done, but in a large genus it
> might well result in very long and indigestible descriptions. If every
> Solanum species has a unique attribute and the absence of that has to be
> recorded for every other species, we could be well over the prescribed
> limit for the species description.

In order to set a sensible standard for preparing written descriptions, we
need to know their purpose. Descriptions written by conventional methods are
seldom properly comparative (e.g. L. Watson (1971), Basic taxonomic data:
the need for organisation over presentation and accumulation, Taxon 20:
131-136), and with the best will in the world, it is very difficult to make
them so. The best way to achieve high-quality descriptions is to generate
them from a database. And if such a database is available, why would you
want to extract comparative information from written descriptions?

The purpose best served by a written description is to paint a word-picture
of a taxon, so that the reader can get a feel for the taxon. And for that
purpose, the descriptions don't need to be comparative at all. In the most
extreme case, each description could consist of a unique attribute of the
taxon, and the corresponding character need not be mentioned at all in the
descriptions of the other taxa. Of course, in this simple case the
descriptions are effectively comparative, as you can infer that the other
taxa have the negatives of the distinctive attributes. However, if a
diagnostic description (which separates a taxon from the others) contains
two or more attributes, it is not possible to infer the (individual)
attributes of the other taxa.

A decision would still need to be made about what data are essential to
record in the underlying database. Naturally, you want as much comparative
data as possible, but resources for gathering data are limited. When people
are preparing DELTA databases, I strongly recommend that they frequently run
the Diagnose option in Intkey, with a suitable value of DiagLevel. This
identifies groups of taxa that are poorly separated by the data. The
taxonomist can then add characters to separate these taxa. The question then
arises, should these characters also be recorded for the other taxa? The
answer will often be `no'; doing so might involve re-examining large numbers
of specimens, and this effort might be better spent elsewhere.

However, some (probably most) characters should be recorded as completely as
possible. Confor provides a MANDATORY CHARACTERS directive to check that a
specified set of characters is recorded for every taxon.

The DELTA directive IMPLICIT VALUES specifies character values which apply
to every taxon unless values are explicitly recorded for individual taxa.
Values which are _not_ explicitly recorded do not appear in natural-language
descriptions. (This directive should be used carefully. It should not be
regarded as an easy way to avoid gathering data. You need to be sure that
the implicit values really do apply to those taxa for which they are not
recorded.)

Diagnostic descriptions can be generated by Intkey at any desired level of
robustness (set by the DiagLevel parameter), and the results used for
generating natural-language descriptions in various ways. The descriptions
may consist _only_ of the diagnostic parts, or the diagnostic parts may be
highlighted in complete descriptions. It is also possible to generate
descriptions which include a specified subset of the characters for every
taxon, plus the different automatically generated diagnostic characters for
individual taxa, plus any other manually selected characters for individual
taxa.

Several sets of descriptions generated in HTML format from DELTA databases
are available at http://biodiversity.uno.edu/delta/. Some include lists of
implicit values and highlighted diagnostic descriptions, e.g.:

   Festuca of North America
   Flowering plants (angiosperms) - families
   Grass genera of the world
   Grasses of the Canadian Arctic Archipelago
   Pooideae (Poaceae) in Australia

Mike Dallwitz                                  Email md at ento.csiro.au
CSIRO Division of Entomology                   Fax +61 2 6246 4000
GPO Box 1700, Canberra ACT 2601, Australia     Phone +61 2 6246 4075