Cryptolepis R.Br. (Apocynaceae, Periplocoideae) was taxonomically revised.
Detailed descriptions of macro and micro-morphology, palynology, geographic
distribution and ecological characteristics were presented. An identification key to the
species was compiled and the nomenclature of all species was revised while all
available type material was studied and lectotypes and neotypes were designated
where necessary. Molecular phylogenetic analyses, based on the gene regions ITS,
trnDâT and trnTâF, of representative species of 28 periplocoid genera and 22
Cryptolepis species were presented and the monophyly of Cryptolepis was
evaluated.
Historically a total of 81 species names and four subspecies names were published
for Cryptolepis. However, a large number of species names were later placed in
synonymy or transferred to other genera, while several new combinations were
published. This resulted in a total of 29 accepted Cryptolepis species at the
commencement of this study. Three new species, C. ibayana, C. thulinii and C.
villosa, resulted from this study and the latter two were described in this thesis. One
species, C. producta, was synonymised with C. oblongifolia. Cryptolepis, therefore,
comprises a total of 31 species at present.
In terms of species diversity, distribution and potential pharmaceutical and economic
value, Cryptolepis is one of the most significant genera in the Periplocoideae.
Cryptolepis grows throughout sub-Saharan Africa, the southern parts of Yemen, the
island archipelago of Socotra, and southern Asia ranging from India to southern
China, Taiwan, the Philippines and Indonesia. Most of the species grow in tropical
forests or savannah, but 13 species are also adapted to arid environments.
The majority of Cryptolepis species are concentrated in four centres of diversity
along the east coast of Africa and on Socotra. These hotspots are associated with
both arid and forest refugia in areas which have been regarded as local centres of
endemism for a number of other plant taxa. The phylogenetic analysis of Cryptolepis
indicates that most of these hotspots were colonized repeatedly by different
Cryptolepis groups. In addition to the influence of climate shifts, edaphic conditions
and also fire had a significant influence on species diversity and distribution in
Cryptolepis. Macro and micro-morphological investigations indicated that numerous characters,
including growth form, leaf shape and size, leaf epidermal characters, venation,
inflorescence structure, floral structure and seed coat surface characters, are of
diagnostic value at species level in Cryptolepis. However, the species can only be
accurately identified by using a combination of these characters.
The molecular phylogenetic analyses revealed that Cryptolepis is paraphyletic and,
in order to establish a monophyletic genus, it was proposed that the circumscription
of the genus be broadened to include Parquetina as a synonym of Cryptolepis.
Several vegetative and reproductive characters showed a high degree of homoplasy,
suggesting a high degree of morphological plasticity. This plasticity was also found at
species level in C. oblongifolia, which showed significant variation in vegetative and
reproductive features. This, together with a high tolerance for disturbance, has
resulted in C. oblongifolia becoming the most widely distributed of all Cryptolepis
species.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-07182013-111631 |
| Date | 18 July 2013 |
| Creators | Joubert, Lize |
| Contributors | Prof HJT Venter, Prof PV Bruyns, Dr AM Venter |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-07182013-111631/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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