biosystematic studies in southern african species of strychnos l.

319 Pages·2012·6.32 MB·English

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
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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.
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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
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CO-SUPERVISOR: DR YOGIS NAIDOO
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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 …………………………………………………………………………………………………………………………………
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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
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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
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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.
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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!
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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 Strychnosspecimens, 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 me to sample forDNA in their living collections. I thank all my
Conspec lab mates at UKZN for being such fun folks to work with and for always finding
creative ways to troubleshoot PCR. The herbarium staff at UDW (Pravin and Edward) have
been so helpful assisting me on many collection trips. I thank the Museum staff in the School
of AP&ES at University of the Witwatersrand for their support and encouragement. Thanks
to Leslie Deysel who skilfully produced the botanical illustrations in Chapter 7. A big thank
you to Dr Lena Struwe for making her in-press article on Loganiaceae available to me, and
also sending me a number of hard-to-come-by publications.
Finally, I would like to express a more-than-deserved gratitude to my immediate family: my
wife Taiwo, who has had to temporarily suspend a promising career to support me, and my
children, `Tunmise and `Tomide for their love and understanding throughout the duration of
this programme. They have had to put up with my being absent on several occasions.
Thanks a ton guys.
Thanks to my Strychnosplants for being suchwell-behaved, jolly goodchaps !
Above all else, I thank God for keeping me in good health and sound mind, to embark on this
research and complete it too.
This work was financially supported at various stages by the following institutions: University
of KwaZulu-Natal (UKZN) postgraduate tuition bursary, the then Faculty of Science and
Agriculture, UKZN for travel and research grants; NRF-Thuthuka bursary awarded through
Dr Yogis Naidoo; University of the Witwatersrand SPARC funding for lecturer teaching time
buyouts and laptop purchase; School of Animal, Plant and Environmental Sciences, Wits
University research grants for new staff.
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