Biosystematic Studies in Southern African Species of Strychnos L. (Loganiaceae)
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UNIVERSITY OF KWAZULU-NATAL BIOSYSTEMATIC STUDIES IN SOUTHERN AFRICAN SPECIES OF STRYCHNOS L. (LOGANIACEAE) ADEKUNLE ADEBOWALE BIOSYSTEMATIC STUDIES IN SOUTHERN AFRICAN SPECIES OF STRYCHNOS L. (LOGANIACEAE) by ADEKUNLE ADEBOWALE Submitted in fulfilment of the academic requirements for the degree of Doctor of Philosophy in the School of Life Sciences College of Agriculture, Engineering and Science University of KwaZulu-Natal, Durban NOVEMBER 2014 ii PREFACE The experimental work described in this thesis was carried out in the School of Life Sciences, University of KwaZulu-Natal, Durban from March 2007 to December 2011, under the supervision of Profs Ashley Nicholas, Jenny Lamb and Dr Yogis Naidoo. The studies represent original work by the author and have not otherwise been submitted in any form for any degree or diploma to any tertiary institution. Where use has been made of the work of others it is duly acknowledged in the text. iii DECLARATION BY SUPERVISORS We hereby declare that we acted as Supervisors for this PhD student: Student's Full Name: ADEKUNLE ADEBOWALE Student Number: 205527654 Thesis Title: BIOSYSTEMATIC STUDIES IN SOUTHERN AFRICAN SPECIES OF STRYCHNOS L. (LOGANIACEAE). Regular consultation took place between the student and ourselves throughout the investigation. We advised the student to the best of our ability and approved the final document for submission to the College of Agriculture, Engineering and Science Higher Degrees Office for examination by the University appointed Examiners. SUPERVISOR: PROFESSOR ASHLEY NICHOLAS ---------------------------------------------- CO-SUPERVISOR: PROFESSOR JENNY LAMB ---------------------------------------------- CO-SUPERVISOR: DR YOGIS NAIDOO iv COLLEGE OF AGRICULTURE, ENGINEERING AND SCIENCE DECLARATION 1 – PLAGIARISM I, Adekunle Adebowale, Student Number 205527654 declare that: 1. The research reported in this thesis, except where otherwise indicated, is my original research. 2. This thesis has not been submitted for any degree or examination at any other university. 3. This thesis does not contain other persons’ data, pictures, graphs or other information, unless specifically acknowledged as being sourced from other persons. 4. This thesis does not contain other persons' writing, unless specifically acknowledged as being sourced from other researchers. Where other written sources have been quoted, then: a. Their words have been re-written but the general information attributed to them has been referenced b. Where their exact words have been used, then their writing has been placed in italics and inside quotation marks, and referenced. 5. This thesis does not contain text, graphics or tables copied and pasted from the Internet, unless specifically acknowledged, and the source being detailed in the thesis and in the References sections. Signed ………………………………………………………………………………………………………………………………… v COLLEGE OF AGRICULTURE, ENGINEERING AND SCIENCE DECLARATION 2 - PUBLICATIONS DETAILS OF CONTRIBUTION TO PUBLICATIONS that form part and/or include research presented in this thesis (include publications in preparation, submitted, in press and published and give details of the contributions of each author to the experimental work and writing of each publication) Publication 1 ADEBOWALE A, NICHOLAS A, LAMB J, NAIDOO Y. 2012. Elliptic Fourier analysis of leaf shape in southern African Strychnos section Densiflorae (Loganiaceae). Botanical Journal of the Linnean Society 170: 542 – 553. Publication 2 ADEBOWALE A, NAIDOO Y, LAMB J, Nicholas A. 2014. Comparative foliar epidermal micromorphology of Southern African Strychnos L. (Loganiaceae): taxonomic, ecological and cytological considerations. Plant Systematics and Evolution 300: 127 – 138. I am the senior author for these two publications. All four authors conceived the research ideas. The first author and Prof Nicholas conducted field works in most cases. I collected data, performed all analyses and interpreted the results under the guidance of the three supervisors. I also wrote the draft manuscripts on which my co- authors commented and critiqued prior to submission. I am also the corresponding author for the publications. ----------------------- Signed: A. ADEBOWALE vi ABSTRACT BIOSYSTEMATIC STUDIES IN SOUTHERN AFRICAN SPECIES OF STRYCHNOS L. (LOGANIACEAE) ADEKUNLE ADEBOWALE Ph.D. thesis, University of KwaZulu-Natal, 2014 Strychnos L. is the largest genus of the pantropical or subtropical family Loganiaceae with about 200 species. Their habits range from trees and shrubs in open areas to lianas in rain forests. The genus is well-known as a source of alkaloids such as strychnine and brucine and other allied compounds, all of which have been used medicinally and in curare formulation for centuries. While taxonomic circumscription of the genus has never been contentious, there is no consensus about infrageneric affiliations, the latest of which recognises 12 sections based on morphological characters. Recent molecular evaluation of the genus on a global scale with the internal transcribed spacer (ITS) marker suggests that many of the currently recognised sections are not monophyletic. An understanding of regional patterns of evolution, which is relevant for biodiversity conservation, requires an in-depth study of the focus group on a regional scale. Using a multiplicity of approaches from morphological and molecular to biogeographical, this study is an attempt at elucidating diversity patterns at different levels among the southern African species of Strychnos. Various combinations of morphological attributes from branches, leaves, flowers and fruits distinguish seemingly homologous clusters of species, sometimes supported by molecular data. A lack of molecular support for a hypothetical relationship may vii indicate case(s) of convergent evolution in these features across the taxa involved. Molecular phylogenies based on the ITS and chloroplast markers confirm the non- monophyletic nature of all but section Spinosae. Proposals for sectional re- circumscriptions of the genus are provided. Patterns of speciation within Strychnos suggest a Miocene origin in the rain forests along the South America/Guinea-Congolian axis. Within the southern African subcontinent, the evolution of the genus carries a strong ecological signature along either the forest or savanna biome, with many accompanying morphological adaptations for the respective habitats. The non-synonymy of S. gerrardii with S. madagascariensis is demonstrated with multiple sources of data, as a case of integrative taxonomy succeeding where single-source data approaches might have failed. Routes to current distribution of the genus in southern Africa are hypothesised to involve a combination of palaeo-climatic oscillations and allopatric speciation, consistent with the process indicated in many other plant groups for the region. The findings are discussed in the wider context of their implications for taxonomy and biodiversity conservation in the face of climate change, food security and other relevant issues in systematics. viii DEDICATION For the three Ts in my life: Taiwo, `Tunmise and `Tomide, without whose love and very close technological attention, especially by one of the latter two – in the shape of magically vanishing data via the tea-into-laptop route – this work could have been completed much earlier... but I would not have it any other way! ix ACKNOWLEDGEMENTS I would like to thank my promoter Prof Ashley Nicholas for suggesting this topic and providing me with a stimulating platform to research it. I ‘blame’ him for every Strychnos- related idea popping up in the corners of my head. Thanks for all those philosophical debates that helped sharpen my thinking. I also thank my co-promoters Prof Jenny Lamb and Dr Yogis Naidoo for taking me on an intellectual ride that was both challenging and exciting. Their collective financial support and encouragement ensured the successful completion of the undertaking. Jenny deserves extra mention for being more like an auntie who patiently took me by the hand and guided me to a safe molecular systematics haven. Thanks for all those journal club meetings; they certainly helped. Other people and institutions contributed to this work in different ways. I am grateful to Ademola Olaniran [Adex] for facilitating my coming to South Africa in the first place, happily hosting me in my first three weeks and helping me to settle down. His home has been a second home to me whenever I am in town. I thank the Glen family (Hugh, René and Melissa and of course … Danica the cat) for adopting me almost as a son. In particular, I thank Dr Hugh Glen, for allowing me to pick that beautiful botanical brain of his. I am grateful to David Styles for several botanical adventures in the KZN area, many of them heart- stopping on cliff edges, all in my bid to hunt down some obscure Strychnos specimens, while he chased his rare Crassulas. Mrs Marie Jordaan is gratefully acknowledged for helping me, very early in the work, to recognise some of the taxonomic challenges in South Africa Strychnos. Direct access to collections held by the following herbaria [K, PRE, UDW, PRU, NH, NU, GRA, BM, IFE, and BNRH] is also acknowledged. I thank John and Sandra Burrows for their generosity with information and allowing me to take materials for DNA work from their collections. Ezemvelo KZN Wildlife and eThekwini municipality are acknowledged for permission and access to collect material. I appreciate the effort of the Lowveld Botanic Gardens, Nelspruit for allowing