From diversity and traditional knowledge to chemicals and microbes With over 100 000 known species, South Africa is the third most biodiverse country in the world, only after Brazil and Indonesia. It comprises approximately 21 000 species of , accounting for 10% of the world’s plant species. The botanical diversity is characterised by high levels of endemism, with 65% of the plant population endemic to the country. In addition, it is the only country in the world to harbour an entire floral kingdom, namely; The Cape Floristic Region. In its simplest definition is the naming and describing, identification and classification of living organisms, where each organism is given a two-word name, i.e. and species. This lecture takes a brief look at plant taxonomy and its importance in the proper documentation of biodiversity. One of the mandates for the South African National Biodiversity Institute (SANBI) is “the co-ordination and promotion of taxonomy in South Africa”, and also to facilitate access to biodiversity data, among other responsibilities. One of the ways in which SANBI provide access to data is the publication of national and regional floras as well as checklists. Our research as taxonomists contributes directly to SANBI’s efforts to meet its mandate.

My PhD project on the taxonomic revision of the legume genus Melolobium, was to shape my research career in the subfamily Papilionoideae of the pea and bean family Fabaceae, which spans almost twenty years. Taxonomic revisions of a number of genera in the tribe Phaseoleae have been undertaken (Canavalia, Dolichos, Neorautanenia, Otoptera, Ophrestia, and Rhynchosia), however only selected genera are here presented. The genus Sphenostylis, represented in southern Africa by only two species which occur in South Africa and Swaziland, can be distinguished from other related genera by its dorsiventrally flattened style, from which it gets its name. The two species can be easily separated by the shape of their leaflets. The genus Canavalia is a relatively large genus and some of the species have agronomic, economic, ethnobotanical, medicinal and nutritional value. In South Africa, it is represented by only five species, with the most important diagnostic characters being the colour of the seeds and length of the hilum. The relatively large genus Rhynchosia, comprising over 240 species, has a pantropical distribution and is distributed mainly across Africa, Madagascar, the Americas, Asia and Australia. Taxonomic studies in the genus have focused at sectional level mainly due to its large size and wide distribution. In South Africa the genus was last revised almost 100 years ago, wherein the species were placed in five sections. However, preliminary molecular phylogenetic studies have shown that this sectional classification is not supported, furthermore one of the sections is not represented in Africa. Studies in the four traditionally recognised sections have been completed and our efforts are currently focussed on the type section, R. sect. Rhynchosia. Taxonomic complexities in two of the most complicated groups, i.e. the Rhynchosia mimina complex and the R. totta complex have been resolved. The most important characters were found to be growth habit, leaf structure, and type and distribution of vestiture. The type section can be divided into two clear groups: erect/sub-erect and climbers/twinners/creepers.

The genus Trifolium, so called because of its trifoliolate leaves, belongs to the tribe Triflieae, in the family Fabaceae. It is a relatively large genus comprising about 300 species distributed in temperate and subtropical regions of both hemispheres. In southern Africa it is represented by 5 indigenous + 15 naturalised or exotic species and for this reason SANBI anticipate that the latter group may have an invasive potential. Studies are ongoing but it appears that the serration and shape of leaflets, type of hairs, as well as inflorescence type are important distinguishing characters in the southern African species. Other ongoing taxonomic studies include revisions of the genera Cynoglossum (Boraginaceae) and Clutia (). Both these genera have been listed by SANBI as priority genera in need of taxonomic revisions. Cynoglossum, so called because of the texture and shape of the leaves, which resemble a dog’s tongue, has a wide distribution in temperate and warm regions of the world. It comprises about 75 species and is represented in southern Africa by eight species. Fruit and floral morphology, trichome type and distribution are of diagnostic importance in distinguishing the southern African species. The genus Clutia is native to sub-Saharan Africa, especially the Cape region, and western Asia. Our studies have so far focussed on the problem species occurring in the KwaZulu- Natal Province, in particular the Clutia abyssinica complex. For example, specimens of C. abyssinica var. usambarica from KZN are morphologically different from those of East Africa, suggesting a different variety.

The taxonomic studies in Melolobium, further inspired my interest in ethnobotanical research in which I also draw from my own experiences growing up in rural village in Lesotho. Ethnobotany, in its simplest definition is the study of the relationship of people and plants. It is an interdisciplinary science which involves anthropology, botany, chemistry and pharmacology. Ethnobotany is studied through ethnobotanical surveys which involve questionnaires or literature surveys. Our ethnobotanical survey in the Ga-Mashashane area in the Limpopo Province, revealed that 45 species are used for various medicinal purposes, with 1 new species, Senecio barbertonicus in South Africa’s material medica and 12 new uses of plants. Of these, 43 were screened for their antimicrobial properties with 28 showing noteworthy to moderate activity. An ethnobotanical survey in the Maseru District in Lesotho showed that 80 species are used in this area, with eight new plant records and 146 new medicinal uses. Furthermore, the plants are mixed with animal products such as milk, animal dung, chicken gizzard, rock rabbit urine, etc. Forty-four species were tested for antimicrobial activity and 22 of them exhibited noteworthy to moderate activity. In both cases many plants were found to contain an array of chemical constituents including alkaloids, flavonoids, saponins, and terpenoids, which are known to have medicinal properties.

The lecture also discusses the concept of ‘Musa-pelo, as well as important plants such as Searsia erosa, Pentanisia prunelloides, Scabiosa columbaria, and Euphorbia clavaroides used for different categories of ethnobotany. Fifteen legume species, all commonly known as Musa-pelo (‘one who turns around the heart) in Sesotho, are traditionally given to people under duress during bereavement in the family. These plants may function either as sedatives, adaptogens, immune stimulants or digestive bitters. Searsia erosa is used for flavouring tobacco, for treatment of gastro-intestinal and respiratory tract infections, as well as tanning of animal hide. Anatomical structure for this species is reported in our studies for the first time. The plants contain essential oils which comprise numerous constituents and the composition is variable between and within populations, making each plant an ecotype. We are also testing several plants (including Helichrysum odoratisissimum, Hermannia depressa, and Pentanisia prunelloides) used for heartburn, for their antacid and acid neutralising properties. The species Scabiosa columbaria, originally used for the treatment of scabies in humans, is used for numerous medicinal purposes, either individually or in combination with other plants. Our studies evaluate the synergistic effects of this species when used in combination with other plants for treatment of skin conditions, STIs, and gastrointestinal problems. Euphorbia clavarioides is used for the treatment of cracked heals, skin rash in children, sores, and wounds. Ongoing studies reveal that this and 344 other species are traditionally used for wound healing. The plants are being tested for their biological activity, i.e. antimicrobial, anti-inflammatory, antioxidant, and wound healing properties. Several plants are used traditionally as soap substitutes, for example Kedrostis capensis, known in Sesotho as sesepa-sa-linoha (‘soap of the snakes). We test the plants for their saponin content, with some promising results, as well as their antimicrobial properties against skin pathogens.

Numerous wild indigenous plants are also used as vegetables and fruits. We tested a number of wild fruits and vegetables for their nutritional properties, i.e. proximate analyses (ash, carbohydrate, fat fibre, moisture, and protein contents), amino acids, energy value, mineral analysis, and vitamins (A and C) content. Some fruits had good nutritional properties, for example, Halleria lucida had the highest phosphorus content (higher than Prunus domestica), carbohydrates, and protein (higher than Psidium guajava). Phoenix reclinata had the highest content of fibre (higher than the apple), the Lowveld milkberry had high vitamin A, while the sour fig had the highest calcium content. Of the wild vegetables, Citrullus lanatus had the highest protein and ash contents, Solanum nigrum the highest crude fat content, while Sonchus dregeanus had the highest moisture and potassium content.

In my concluding remarks, I ask the question “where to?”. In one of their publications, SANBI have highlighted the dire need for the strengthening of human capacity in plant taxonomy, and also provided a priority list of plant genera that requires taxonomic revisions. Despite the low or lack of citations for taxonomic papers, I have continued my taxonomic work in revising priority genera, starting with Alchemilla (Rosaceae) and Sopubia (as well as other unstudied genera such as Millettia), as part of training future taxonomists. The importance of documentation of ethnobotanical information cannot be over-emphasised, therefore this work will continue, especially with the Free State Province in mind as it is understudied. Numerous plants have shown good antimicrobial activity and therefore need to be subjected to further research. There are two projects which have bioprospecting prospects which should be explored. Several wild indigenous fruits and vegetables were found to have good nutritional value, these will be studied further to determine their dietary quality and nutrient availability as well as toxicity levels.