Systematics of Geophytic Othonna (Senecioneae, Othonninae)
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Systematics of geophytic Othonna (Senecioneae, Othonninae) by Simon Luvo Magoswana Dissertation submitted in fulfilment of the requirements for the degree MAGISTER SCIENTIAE in BIODIVERSITY AND CONSERVATION BIOLOGY in the FACULTY OF NATURAL SCIENCE at the UNIVERSITY OF THE WESTERN CAPE SUPERVISOR: PROF. J.S. BOATWRIGHT CO-SUPERVISOR: PROF. J.C. MANNING CO-SUPERVISOR: DR A.R. MAGEE NOVEMBER 2017 i University of the Western Cape Private Bag X17, Bellville 7535, South Africa Telephone: ++27-21- 959 2255/959 2762 Fax: ++27-21- 959 1268/2266 FACULTY OF NATURAL SCIENCE PLAGIARISM DECLARATION TO BE INCLUDED IN ALL ASSIGNMENTS, THESIS PROPOSALS ETC, BE IT FOR MARKS OR NOT: I…..Simon Luvo Magoswana………………….……………………………………………………… Student number……2934742…………………..declare that the attached dissertation entitled…..Systematics of geophytic Othonna (Senecioneae, Othonninae)……is my own work and that all the sources I have quoted have been indicated and acknowledged by means of complete references. Signed this day ……10…………… of ……November…….. 2017….. at ……Bellville…………... --------------------------------- Signature ii TABLE OF CONTENTS SUMMARY................................................................................................................................vi CHAPTER 1 INTRODUCTION.................................................................................................1 1.1 Aims of the study…………………………………………...……………………….6 CHAPTER 2 MATERIAL AND METHODS..............................................................................7 2.1 Herbarium material.................................................................................................7 2.2 Field studies............................................................................................................8 2.3 Gross morphology..................................................................................................8 2.4 Data Capturing........................................................................................................8 2.5 DNA extraction, amplification and sequencing...................................................9 2.6 Sequence alignment and phylogenetic analyses..............................................10 CHAPTER 3 VEGETATIVE AND REPRODUCTIVE MORPHOLOGY…..................................17 3.1 Habit.........................................................................................................................17 3.2 Foliage.....................................................................................................................22 3.3 Inflorescence structure………………………………..….........................................26 3.4 Involucres……….....................................................................................................27 3.5 Florets………….......................................................................................................28 3.6 Pappus morphology...............................................................................................30 3.7 Fruit morphology…….............................................................................................31 iii CHAPTER 4 PHYLOGENETIC RELATIONSHIPS……………………………………………...…32 4.1 Introduction ………………………………………………………………………………32 4.2 Results……………………………………………………………………………………..34 4.3 Discussion………………………………………………………………………………...45 CHAPTER 5 TAXONOMY OF THE ‘O. BULBOSA’ GROUP....................................................49 5.1 The genus Othonna L………………………………………………….........................49 5.2 The Othonna bulbosa-group..................................................................................51 5.3 Infrageneric classification......................................................................................52 5.4 Key to the species of the ‘O. bulbosa’ group.......................................................54 5.5 The species of the ‘O. bulbosa’ group..................................................................58 CHAPTER 6 GENERAL CONCLUSIONS………………………………………………………….139 ACKNOWLEDGEMENTS.........................................................................................................141 REFERENCES..........................................................................................................................143 APPENDICES: PUBLICATIONS 1: Magoswana S.L., Boatwright J.S., Magee A.R., Manning J.C. 2016. A taxonomic revision of Gymnodiscus (Asteraceae: Senecioneae: Othonninae), a Greater Cape Floristic Region endemic. South African Journal of Botany 106, 71-77. 2: Magoswana, S.L., Manning, J.C., Magee, A.R., Boatwright, J.S., 2017, Othonna sonchifolia L. is an earlier name for Senecio cymbalarifolius L. (Asteraceae: Senecioneae), Bothalia 47 (1), 1-4. iv DEDICATION This dissertation is dedicated to the memory of my late dear mother, Lulama Ruth Magoswana who unfortunately passed on to glory during the completion of this project. She was a constant source of inspiration in my life, a fountain of wisdom and my source of strength, a pillar in my life. Although she is not here, I always feel her presence that carried encouragement to strive and achieve my goals in life. Lala ngoxolo Jola, Qengeba, Mphankomo ugqatso ulufezile! Singaka nje ngamandla akho naloThixo wawusoloko usifundisa ngaye. Undizimele ndisabuka kodwa s’thandwa sam! Ndiyathemba uThixo ekubizele kuye nje uyasazi isizathu soko kwaye singaphezulu kunoba sicinga thina. Wonwabe apho, sohlala sikuthanda kwaye sikukhumbula. Elona themba sinalo lelokuba sizakuphinda sibonane. v Systematics of geophytic Othonna (Senecioneae, Othonninae) SUMMARY A member of the Senecioneae subtribe Othonninae, Othonna L. is a genus of some 120 species mainly concentrated in the Greater Cape Floristic Region (GCFR) of South Africa, with a few species extending into southern Namibia, Angola and Zimbabwe. The South African species of Othonna were last revised by Harvey in 1865. Consequently many species, particularly in the winter rainfall-region, remain poorly understood. As a start to ultimately producing a complete revision of this priority genus, this study focussed on a group of some 26 tuberous geophytic species. The geophytic species were subdivided into two species groups: (1) the ‘O. bulbosa’ group with 23 spp., distinguished by a tuberous rootstock and well-developed stem with leaves cauline, and (2) the ‘O. auriculifolia’ group with ca. 3 spp., characterized by a rosulate habit with a short, condensed caudex. A comprehensive taxonomic treatment of the ‘O. bulbosa’ group is presented, including descriptions, complete nomenclature and typification, illustrations and geographical distribution. Twenty-three species are recognised, of which two are newly described (O. lilacina Magoswana and J.C. Manning and O. sinuata Magoswana and J.C. Manning), and 17 names reduced to synonymy. The species were found to differ in habit, foliage shape, number of involucral phyllaries, pappus length, capitulum type (radiate vs. disciform), and myxogenic or non-myxogenic fruits. The species can be segregated vi among four morphologically diagnosable groups based on habit, capitula type and ray colour: the series Bulbosae Magoswana and J.C. Manning, distinguished by radiate capitula and yellow ray florets; series Roseae Magoswana and J.C. Manning, with radiate capitula and pink to magenta ray florets; series Disciformes Magoswana and J.C. Manning, with disciform capitula, and filiform, female-fertile outer florets, and the pappus of the marginal florets enlarging to twice the length of the cypselas; and series Perfoliatae Magoswana and J.C. Manning, with scandent or sometimes erect stems, the leaves strictly cauline and scattered evenly along the stem, sessile and clasping or auriculate The phylogenetic relationships of the geophytic species of Othonna were assessed through parsimony and Bayesian analyses of both nuclear ITS and plastid (rps16, trnL- trnF) regions. Phylogenetic analyses of the nrITS and combined datasets indicate that the ‘O. bulbosa’ group is monophyletic. However, in the plastid dataset, the group was not recovered as monophyletic. The phylogenetic sampling of Othonna is expanded to include 26 species of the genus, nine representing the ‘O. bulbosa’ group. Species belonging to the ‘O. auriculifolia’ group were not recovered with the other geophytic species and also not close to one another. vii CHAPTER 1 INTRODUCTION Senecioneae Cass. are currently recognised as the largest tribe in Asteraceae, comprising ca. 160 genera and ca. 3 000 species (Nordenstam et al., 2009). The tribe has an almost cosmopolitan distribution, with centres of diversity in South America (ca. 1 300 species) and southern Africa (ca. 700 species). Members of the tribe are represented in almost all habitats, from deserts to vernal pools, from seashore to alpine communities, and from arctic regions to the tropics (Bremer, 1994; Pelser et al., 2007). The tribe displays enormous variation in morphology and life-history strategies and is considered to be the most diverse tribe in the Asteraceae (Pelser et al., 2007). Members of the tribe are mostly annual or perennial herbs but some are shrubs, vines, trees or epiphytes (Pelser et al., 2007; Nordenstam et al., 2009). Despite its large size and diversity, members of the Senecioneae are readily circumscribed morphologically by an involucre of uniseriate (rarely biseriate) bracts (sometimes called phyllaries) (Pelser et al., 2007), and chemically by the presence of pyrrolizidine alkaloids and sesquiterpenes of the furanoeremophilane type (Bremer, 1994; Kadereit