Sectional nomenclature in Solanum (Solanaceae)

Michel-F6lix Dunal, in his Histoire Naturelle, Medicale et Economique des Solanum (1813), used twelve names for species groups in the genus Solanum. Two additional names were added in his Solanorum Generumque Affinium Synopsis (1816). D'Arcy (1972) considered all fourteen of these names to be of equal sectional rank. The names from each of Dunal's two works will be considered separately. The 1813 thesis was organized in a rigid hierarchical fashion, with a fixed series of symbols setting off different levels of the hierarchy. The first two divisions of the system are marked by I and II, and subsequent divisions (in descending order) by *, +, ?, > >, lower case letters, and Arabic numerals. The hierarchical system in the 1813 thesis was in the form of a key to groups of Solanum species; the 199 species in the treatment were divided into 28 groups using the above symbols. Dunal (1813) gave names to only twelve of these species groups. The symbols demarcating divisions in the system were not part of these names, but preceded and were part of the hierarchical key leads. All groups designated by the same symbol are apparently of equal, though unspecified, rank. In his introductory remarks on taxonomic procedure, Dunal did not mention any names for taxa between the ranks of genus and species. He was, however, very specific about the taxonomic rules ("principales regles") followed in the work. On page 43 (Dunal, 1813) he referred to Pteroidea as a section ("la section designee sous le nom Pteroidea"). Two references were made to sections using common names (page 48--"section des Morelles," and page 104-"section Melongene"). All other references to names of species groups did not use the word "section," but Dunal referred to them as groups ("groupes"). This indicates that he was not thinking of his "sections" as ranks in the taxonomic sense, but instead as merely species groups with convenient labels. Nevertheless, since Dunal did refer to one of these names as a section (Pteroidea), we must accept at least that name at sectional rank. The word "section" was used only one other time in the introduction to the 1813 work, in reference to S. bonariense ("Le Sol. torvum, le Sol. bonariense et tous ceux de sa section, .. ."). Here Dunal referred to the S. bonariense species group (named Subinermia) as a section. The descriptions of the species groups designated Subinermia and Pteroidea were both preceded in the synopsis by the symbol ?. Therefore, in accordance with Article 35.2 of the Code (Stafleu, 1978), I consider all names preceded by this symbol in Dunal's 1813 work to be validly published at the sectional rank, as it seems that Dunal intended them to be of equivalent rank in his hierarchy. Ten of the twelve names were so designated (see Table 1). One of these, Maurella, becomes section Solanum under Article 22.1 of the Code (Stafleu, 1978), and so is not at issue here. Two other species groups given names were preceded by different symbols (**Polymeris and b.Pachyphylla) and were not of equivalent rank with the other ten names. The names Polymeris and Pachyphylla were first clearly designated as sections in the genus Solanum by Walpers (1844) and D'Arcy (1972) respectively and should be so attributed. Dunal's 1816 Solanorum Synopsis was a hurriedly published summary of a never completed revision of his 1813 thesis (D'Arcy, 1979). By Articles 35.2 and 35.4 of the Code (Stafleu, 1978), any statements designating rank of infrageneric taxa in the 1813 publication must not be applied to the 1816 revision, as they are to be considered as separate works. In 1816 Dunal added two names, Leiodendra and Nycterium, to the twelve previously published. No introductory text accompanies the 1816 synopsis, so we can make no decisions about the rank of any of the infrageneric groups published therein. Leiodendra and Nycterium are thus gradi ambiguii in this work. Nycterium had been published as a genus by Ventenat in 1805, and was clearly designated as a section of Solanum by Walpers in 1844. The name Leiodendra on the other hand, was not attributed sectional rank until 1972 (D'Arcy, 1972), but had a long history of synonymy. The first clearly designated sectional name including the lectotype of Dunal's group Leiodendra, S. nudum HBK ex Dunal (see D'Arcy, 1972 for lectotypification of the sections of Solanum), was Solanum section Geminata (G. Don) Walpers (Walpers, 1844). This then