A dissertation submitted to the Faculty of Science, University of the Witwatersrand"
Johannesburg, for the degree of Doctor of Philosophy
Johannesburg, 1993 / In this dissertation the circumscription and subdivision of Barletta L. (Acanthaceae) is
investigated.
Barlerla is a large, polymorphic genus of herbs and shrubs, the delimitation and
subdivision of which has long been subject to question. Approximately 300 species are
known in fhe genus, occurring mainly in Africa and south-eastern Asia, particularly in
tropical and sub-tropical zones. Previous studies of Barleria have followed two
divergent approaches: those that result in a broad circumscription of the genus (e.g,
Bentham, 1876), and those that recognise numerous,small segregate genera (eg.
Oersted, 1854). The only world-wide accounts of Barleria to date are those of Nees
(1847), Bentham (1876) and Lindau (1895), All more recent accounts have been
undertaken as parts of :floras for particular geographic or florlstic regions. Despite the
publication of seven such accounts between 1895 and 1967 (the most recent), the
problem. of satisfactory subdivislon of the genus, as perceived by-Bentham (1876), still
remained and provided one of the main motivations for embarking on the current
research.
The aims of this research were to: i) re-assess the-clrcumscription and, subdivision of
Barleria;
ii) provide a modern classification of the genus on a global scale, and iii) assess
evolutionary relationships and lineages within the genus. 'The approach adopted was a
multidisciplinary one, combining research in the laboratory, herbarium and field
wherever possible. Careful sampling of a wide range of species was necessary in order
to cover the morphological variability and geographic distribution of the genus as
thoroughly as possible, Approximately 240 of the 300 described species were studied.
Emphasis was placed on various aspects of morphology, anatomy of fruits and
phytogeography, with particular attentlon paid to the accurate determlnation of characters and character-states, assessment of their evolutionary polarity and distribution.within the
genus. In the search for reliable characters, a number of new and previously neglected
characters were found, and the homology of previously misunderstood characters (e.g.
spine systems) was established. A wide range of characters was investigated, but only
ten of these were selected for use in the cladistic analyses. These characters were those for which evolutionary polarity and homology could be determined with a high degree of confidence and included: basic configuration of the corolla lobes; structure of the
stigma; the presence of hollow or solid beaks on tlle capsules; the number of seeds in
the mature capsule; anatomy of the septum (three characters); composition of the
androecium; the nature of the hygroscopic hairs on the seeds and the structure of the fruit wall. Data was analysed using an iterative approach to cladistics in order to establish a sound empirical basis for a new classification, Crabbea Harv. was used as the outgroup in the cladistic analyses. The generic concept adopted here is a phylogenetic one based on monophyly.
[Abbreviated Abstract. Open document to view full version]
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/20448 |
| Date | 08 June 2016 |
| Creators | Balkwill, Mandy-Jane |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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