A taxonomic study of the type section of the genus Lebeckia Thunb.(Fabaceae, Crotalarieae)

A taxonomic study of the type section of the genus Lebeckia Thunb. (sect. Lebeckia; syn. Eu-Lebeckia Benth., Phyllodiastrum Walp.) is presented. The genus Lebeckia (Fabaceae, Crotalarieae) is endemic to the western parts of southern Africa and the type section is endemic to the Cape Floristic Region. Species delimitations and relationships within the sections of the genus are not clear and are in urgent need of a revision since the genus has not been studied in its entirety for nearly 150 years. Lebeckia section Lebeckia, now consists of 14 species, all with acicular (needle-shaped) leaves. Based on fruit morphology, four informal species groups have here been distinguished within the section. An analysis of morphological characters revealed the existence of four undescribed species, namely “L. brevicarpa” M.M.le Roux and B-E.van Wyk sp. nov. ined., [previously confused with L. sepiaria (L.) Thunb.], “L. brevipes” M.M.le Roux and B-E.van Wyk sp. nov. ined., (hitherto confused with L. longipes Bolus and L. pauciflora Eckl. and Zeyh.), “L. uniflora” B-E.van Wyk and M.M.le Roux [previously confused with L. wrightii Bolus] and “L. zeyheri” M.M.le Roux and B-E.van Wyk [previously considered to be a variety of L. plukenetiana E.Mey.] A key to the 14 species of section Lebeckia is presented. Diagnostic characters, nomenclature, typification and distribution maps of all the species are presented, discussed and illustrated. Morphological data was used in a cladistic analysis and resulted in a partially resolved cladogram, confirming the presence of four (presumably monophyletic) groups within the section. In a molecular systematic study, four DNA sequences were used to explore relationships, but the resolution was low and unsatisfactory and the result only partially supported the hypothesis based on morphological characters. However, the molecular phylogeny agreed with the morphological analysis in providing convincing support for the monophyly of the section.Prof. B.E. van Wy

A taxonomic study of the genus Crotalaria l (Fabaceae, tribe Crotalarieae) and a modified infrageneric classification system

D.Phil.The genus Crotalaria (tribe Crotalarieae, Fabaceae) includes 700 species with its main centre of species diversity in Africa and Madagascar and secondary radiations to other parts of the world (including North and South America, India, South-East Asia and Australia). Molecular systematics has recently provided profound new insights into generic relationships in the Crotalarieae, thereby creating the opportunity to re-evaluate the taxonomic and functional significance of flower and fruit structure in the tribe, with emphasis on the large genus Crotalaria. A representative sample of flowers from 211 species was dissected to record morphological character states and fruit transverse sections of 142 species was cut to record anatomical variation across the tribe. These data were supplemented from the literature to allow for generalizations. Six structural-functional flower types were identified: (1) pump; (2) gullet; (3) hugging; (4) saddle; (5) tunnel; and (6) brush. The saddle and tunnel types are here described for the first time. Crotalaria is the only genus within the tribe that has the brush type; specialized flowers characterized by a rostrate keel, highly dimorphic anthers, stylar trichomes and four types of elaborate callosities on the standard petal: (1) ridge callosities – vertical swellings on the blade and claw; (2) disc callosities – subcircular swellings on the blade; (3) columnar callosities – cylindrical protruding appendages on the blade; and (4) lamelliform callosities – plate-like protruding appendages on the blade. Trends toward specialization are apparent across the phylogeny as a whole suite of specialized floral characters and are homoplastic as a result of convergence

Electronic identification keys for species with cryptic morphological characters: a feasibility study using some Thesium species

The popularity of electronic identification keys for species identification has increased with the rapid technological advancements of the 21st century. Although electronic identification keys have several advantages over conventional textual identification keys and work well for charismatic species with large and clear morphological characters, they appear to be less feasible and less effective for species with cryptic morphology (i.e. small, obscure, variable characters and/or complicated structures associated with terminology that is difficult to interpret). This is largely due to the difficulty in presenting and illustrating cryptic morphological characters unambiguously. When taking into account that enigmatic species with cryptic morphology are often taxonomically problematic and therefore likely exacerbate the taxonomic impediment, it is clear that species groups with cryptic morphology (and all the disciplines dependent on their correct identification) could greatly benefit from a user-friendly identification tool, which clearly illustrates cryptic characters. To this end, the aim of this study was to investigate and develop best practices for the unambiguous presentation of cryptic morphological characters using a pilot interactive photographic identification key for the taxonomically difficult plant genus Thesium (Santalaceae), as well as to determine its feasibility. The project consisted of three stages: (1) software platform selection, (2) key construction and (3) key evaluation. The proposed identification key was produced with Xper3 software and can be accessed at http://www.xper3.fr/xper3GeneratedFiles/publish/identification/1330098581747548637/mkey.html. Methodologies relating to amongst others, character selection and delineation, visual and textual descriptions, key construction, character coding and key evaluation are discussed in detail. Seventeen best practices identified during this study are subsequently suggested for future electronic key compilation of species with cryptic morphology. This study indicates that electronic identification keys can be feasible and effective aids for the identification of species with cryptic morphological characters when the suggested best practices are followed

A Study of Phenolic Compounds and Their Chemophenetic Value in the Genus Thesium (Santalaceae)

Despite the common use of Thesium species as food and medicine and the prevailing systematic (taxonomic) difficulties of the genus, the diversity of phenolic compounds and their chemophenetic value remain largely unknown. As part of ongoing systematic research on Thesium, phenolic compounds and their composition were investigated at four taxonomic ranks: generic, infrageneric, interspecific and infraspecific. Liquid chromatography–mass spectrometry, multivariate analyses, comparisons to DNA data and manual investigations of total ion chromatograms were conducted for 156 samples of 50 Thesium species, as well the two monotypic genera sister to Thesium (Lacomucinea and Osyridicarpos). A wide diversity of phenolic compounds, primarily flavonols, carboxylic acids, phenolic acids and associated derivatives, were observed. Rutin was the most common compound, followed by citric acid, isorhamnetin O-glucoside O-rhamnoside, kaempferol O-rutinoside, quinic acid and cryptochlorogenic acid. Chemophenetic data proved valuable at the generic and interspecific level and, to a lesser degree, at the infraspecific level. On the other hand, no distinct patterns were observed at the infrageneric level, nor did chemophenetic data correlate with infrageneric classifications based on genetic, geographical or morphological data. At the generic level, the patterns of phenolic compounds in Lacomucinea and Osyridicarpos overlapped with those of Thesium species, but no compound or group of compounds were unique to Thesium. At the interspecific level, total ion chromatograms of the species were largely distinct from one another and, with the exception of four species, remarkably consistent. Two related species (T. triflorum and T. scandens) with doubtful species boundaries had similar but distinct chromatograms, providing evidence of their retention as separate species. At the infraspecific level, the data were mostly inconclusive, but variation in samples of T. asterias revealed two morphologically distinct populations, one of which is possibly a species new to science. This study provides valuable preliminary insights into the phenolic diversity and chemophenetic relationships in Thesium, Lacomucinaea and Osyridicarpos and highlights the potential of chemophenetics in taxonomically problematic plant groups