HOW TO MANAGE A STABLE NOMENCLATURE FOR NON STABLE TAXA ?
 

Daniel CHICOUENE, 2001 (not published)

The communication of the names of taxa is affected by the double constraint of the stable nomenclature as exposed by McNeill (2000) and of freedom of delimitation of taxa. "Names are defined, but not as taxa" (Jorgensen, 2000). True scientific information is based on a description, communicated through a name.

According to McNeill (1976), names change because "the Rules may not have been followed or may have been applied incorrectly,... changes in the circumscription, position or rank of a taxonomic group". It should also be specified that the observation and the description of the nomenclatural types can evolve, and the rules change somewhat with each edition of the Code.

In addition, the names do not change necessarily whereas the descriptions and delimitations given by the researchers in taxonomy change. As Berendsohn (1997) indicates, "The same name may be applied to different, non congruent concepts of a taxon... This is not accidental, but rather a direct consequence of the rules of botanical nomenclature" ; "the circumscription of a taxon may vary from one author to another".
 

Several references of determination have the same complete name of taxon with different delimitations for several reasons : - the differences in taxonomy, with taxa divided or joined together at different ranks ; - the drift of the name towards a more strict meaning following the description of close taxa of the same rank ; - the drift of the descriptions in terms of the number and states of the characters taken into account with the successive authors ; for example, a more precise description allows a different diagnosis of morphological intermediate individuals within the meaning of Wilson (1992) ; - the nomenclatural type not checked (case of Flora Europaea according to curators of French herbaria), used ill-advisedly, and polemic about the application of a nomenclatural type because the sample is incomplete.

Thus, a single complete name according to the Code can include entities which are overlapping (as Festuca ovina L.) or disjoint (as Oxalis stricta L.) according to researchers in taxonomy or authors of references of determination. Such names may be recognized as ambiguous (rejected within the meaning of article 56) or not, at a given time. A little common sense is sufficient to realize that it is impossible to transmit different conceptions of a taxon by using the same name.
The scientist seeks an univocal communication with one name for one entity ; in other words a name has only one definition according to the principles of Tournefort (1700).

When the delimitation of the entity changes, a different name must be given to prevent confusion. The solution is to provide information about the chosen description. It is more important to specify the description followed than the reference of nomenclature. Apart from taxonomy, for example in applied botany, it is imperative to mention scrupulously the description adopted amongst the literature available (Chicouene, 2000).

The relationship between the nomenclature and the circumscription of taxa must be clearly defined.

Considering that the latin name is independant from "taxonomy", the "diagnosis" should probably be based more on the description of the nomenclatural type (the sample in the herbarium) rather than on the description of a taxon (as specified in article 32.3). Nomenclatural synonymy is normally established from the nomenclatural type, not from the diagnosis. What is the role of the diagnosis ? How does one proceed when typification is not realised ?
If the diagnosis corresponds to the taxon, the Code is deficient in the instructions for use of the name when a circumscription is not the diagnose or the protologue ; in this case, it is evident that one must precise the author and reference of the description followed. The indication of only the latin name and the original author name (articles n° 46 and 47) is not sufficient.
The important problems are how to ascertain whether the determination is based or not on the diagnose or the protologue, how to choose and how to cite the other possible reference used for determination. A proposal such as that of Berendsohn (1995) in the use of "sec." could be generalized each time that a name is used. For the use of this further level of precision, one would also need rules of deontology.
 

The choice of the reference of determination is sometimes difficult. Thus, for Flora Europaea (Tutin & al., 1968-1992) which is a large synthesis for Vascular Plants, a lot of descriptions or keys are inusable for different reasons : - incoherence in text (such as between key and description with Urtica membranacea for petiole in proportion to leaf lenght as mentioned by Chicouene, 2000, this latin name being in a list of legally protected species in France) ; - ambiguity in the construction of keys (as for the distinction between Gramineae and Cyperaceae in the choice n° 73, as exemplified by Chicouene, 1998 a) ; - non application of the description (in the text) to the samples determined with the key (such as mode of tillering and limb width for Poa annua L. as indicated by Chicouene, 1996) ; - failure in the application of keys using some characters with no combination corresponding to the samples (as for the differences between Festuca  and Bromus in the choice n° 159 as mentioned by Chicouene, 1999 b) ; - terminology riddles (as for "auricles" in species of Festuca with probably three different expressions for the same organ and the same term used with two different meanings, as evocated by Chicouene, 1999 a) ; - lack of integration of progress in formal morphology (as for inflorescence types of Gramineae or Cyperaceae in Flora Europaea and in Watson & Dallwitz (1992) which are confused and do not integrate acquisitions from the beginning of the 19th century, as denounced by Chicouene, 1998 b and c). In addition, the "Codex conventionalis terminologiae botanicae" should be specified.

In practice, as for floristic surveys, one must use a reference of circumscription for each taxon. The aim is to have instructions for use of the determination which was followed : could no matter which reference be accepted at a given time ? clearly not ; how is one to manage the application of universal revisions to the regional morphological observations of undetermined samples ?

In analysing the situation, for different aspects and problems in the management of name of non stable taxa, general course for solutions seem evident but practical fixed recommendations lack. A debate on these topics should be interesting at I.A.P.T.

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