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Wageningen University (2012)

The genus Gloriosa (Colchicaceae) : ethnobotany, phylogeny and taxonomy

Maroyi, A.

Titre : The genus Gloriosa (Colchicaceae) : ethnobotany, phylogeny and taxonomy

Auteur : Maroyi, A.

Université de soutenance : Wageningen University

Grade : PhD thesis 2012

Résumé
This thesis focuses on the ethnobotany, phylogeny and taxonomy of the genus Gloriosa L. over its distributional range. Some Gloriosa species are known to have economic and commercial value, but the genus is also well known for its complex alpha taxonomy. An appropriate taxonomy for this group is of great importance because it includes widely used species as traditional medicine, horticultural plants and sources of industrial and pharmaceutical chemical colchicine. The seeds and tubers of G. superba are valued as a commercial source of colchicine.The genus Gloriosa has considerable horticultural appeal because of the conspicuous inflorescence of its members and the ease with which taxa are propagated, introduced into new areas and hybridise in cultivation. G. carsonii, G. modesta, G. simplex and G. superba have been taken into cultivation as ornamental plants in several countries, including native countries of these species. The first part of the thesis deals with ethnobotanical studies on G. superba. These studies documented how people throughout the distributional range of G. superba utilise it. Over 45 ethnobotanical applications in 31 subtropical, tropical African and Asian countries were documented, the majority (93%) of which described medicinal uses. One major question that emerged from this analysis is whether G. superba is a remedy or a poison. (Chapter 2). This question was somehow addressed by analysing the pharmacological properties of the species. G. superba was found to have immense potential as a chemotherapeutic agent to prevent or inhibit the growth of tumours or cancers. Chapter 3 focused on vernacular names, folkloristic and economic uses of G. superba over its distributional range. In total 279 vernacular names in 38 countries are documented for G. superba. This long list of names indicates that local people in countries where G. superba occurs, have an active interest in the species. G. superba represents a species complex showing a mosaic of morphological characters (Chapter 4). It also occurs in a wide range of ecological habitats in subtropical and tropical Africa and Asia. The morphological variation in G. superba was found to be complicated and therefore, multivariate and univariate analyses were used to re-evaluate variation and species delimitation in theG. superba complex. It is proposed that four species should be recognised in the G. superba L. complex : G. baudii (Terracc.) Chiov., G. carsonii Baker, G. simplex L. and G. superba L. G. superba is the most widespread taxon, occurring in South Africa, tropical Africa and tropical Asia. G. simplex, G. carsonii and G. baudii are confined to the African continent ; with G. baudii having the most restricted range, the arid regions of northern Kenya, Ethiopia and Somalia. The final part of the thesis (Chapters 5, 6 & 7) describe how phylogenetic studies have changed the taxonomy of the genus Gloriosa. The many taxonomical changes introduced in this investigation are a result of molecular phylogenetic analysis which recommended sinking of the genus Littonia Hook. into Gloriosa. The expanded genus also meant the need for a wider generic circumscription, and a detailed account of species relationships. This section is concluded by providing a monograph of the genus. Twelve species are recognised for the genus Gloriosa : G. baudii (Terracc.) Chiov. ; G.carsonii Baker ; G. flavovirens(Dammer) J.C.Manning & Vinnersten ; “G. katangensis Maroyi nom. nov.” ; G. lindenii (Baker) J.C.Manning & Vinnersten ; G. littonioides (Welw. ex Baker) J.C.Manning & Vinnersten ; G. modesta (Hook.) J.C.Manning & Vinnersten ; G. revoilii (Franch.) J.C.Manning & Vinnersten ; G. rigidifolia (Bredell) J.C.Manning & Vinnersten ; G. sessiliflora Nordal & Bingham ; G. simplex L. and G. superbaL. It is intended that this revisionary account of the genus Gloriosa will enable users to identify different taxa based on morphological relationships. A key to the twelve recognised species is presented, as well as descriptions and distribution maps for each species

Mots clés : gloriosa / taxonomy / phylogeny / ethnobotany / seeds / plant composition / tubers / colchicine / economic botany

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Page publiée le 25 novembre 2013, mise à jour le 14 janvier 2018