The present-day cycads comprise the diverse, modified, remnants of a much larger group of gymnosperms which flourished in the Mezozoic era. The systematic position that the cycads occupy in the botanical hierarchy is significant in that they represent relatively unchanged survivors from prehistory. The present global complement of 182 species occur in tropical and mild temperate regions in both hemispheres. Despite the density of proliferation of species, about one-half of the extant taxa are considered endangered, vulnerable or rare. Apart from characteristic features such as differences in growth forms, variation in reproductive structures and anatomical details, cycads are distinguished from all other plant groups by the unique phytotoxins, azoxyglycosides, which they possess. The toxicity of cycads is well-documented in cases which refer to both man and animals. Cycasin, which together with macrozamin represent the major azoxyglycosides occurring in cycads, has been reported to elicit responses similar to those that have been observed during carcinogenicity, mutagenicity and neurotoxicity assays. It has become apparent that the mechanism by which azoxyglycosides manifest their toxicity involves deglucosylation, by enzyme systems, which releases the aglycone, methylazoxymethanol (MAM), and sugar moieties. Metabolic activation of MAM succeeds deglucosylation to generate methylene carbene units (: CH2) which are capable of methylating macromolecules including DNA, RNA and protein. During this investigation, macrozamin was extracted from seed kernels of Encephalartos transvenosus and cycasin was tentatively identified in seed kernels of Cycas thouarsii . The hexa-acetate derivative of macrozamin was prepared whereas the tetra-acetate derivative of cycasin was not secured in a pure form. The spectroscopic techniques employed for identification include DV-absorption, infra-red and nuclear magnetic resonance spectroscopy, all of which are useful for detecting signals which arise as a result of the azoxy function. A kinetic study was carried out to determine the rate of hydrolysis of macrozamin with 4M sulphuric acid, and to allow calculation of the activation energy for the process. A comparison of the kinetic parameters determined for the above process with those derived for the hydrolysis of cycasin and methylazoxymethanol under similar conditions followed. The rates of hydrolysis increase in the order macrozamin, cycasin, methylazoxymethanol since the molecules contain two, one and zero glycosidic linkages respectively. Additional glycosidic bonds are observed to decrease the rate of reaction. Consequently, activation energies for hydrolysis of the above molecules decrease in the above-stated order. Macrozamin and cycasin were quantified in cycad material by high performance liquid chromatography (HPLC), gas-liquid chromatography (GLC) and by the chromotropic acid assay. The results of the quantitative analysis has highlighted certain limitations of the methods of detection, and has been found to be applicable to a taxonomic evaluation and a proposal for the biosynthesis of the azoxyglycosides. / Thesis (M.Sc.)-University of Natal, Durban, 1990.

M.Sc. / Africa's cycads (66 species and 2 subspecies in two endemic genera: Encephalartos and Stangeria) are extremely endangered with four species extinct in the wild and 80% threatened (CR, EN, or VU) with all included in CITES Appendix 1. Although South Africa has some of the world’s strictest cycad legislation, these plants are still under threat from illegal collection for horticulture and medicine especially where they are seized in an unidentifiable condition. Currently developed legislation demands accurate identification for permit issue. Ex situ conservation of genetic and locality based diversity is paramount. Furthermore, taxonomically many species of unknown origin are difficult to identify especially when diagnostic characters are absent. Species delimitation and numbers are uncertain with field observations often contradicting current understanding. DNA barcoding can assist with all the above-mentioned scenarios. In the current study all proposed DNA barcoding regions (matK, rbcLa, psbA-trnH, and nrITS) along with several additional regions were tested on ~350 samples from which a phylogeny of 63 of the 65 Encephalartos species was also constructed. Results show general good amplification and sequencing success of proposed barcoding regions, although a shift to specialist primers was made in several cases. Genetic variation however was extremely low as is resolution at species level, even when multi-locus barcodes were employed. Results obtained from the phylogenetic analyses show an increase in resolution at both species and higher levels compared to previous work and as such several new groupings are delimitated. Each species grouping is characterised by shared, derived morphological, ecological, and geographic characters and when compared to previous phylogenetic studies are supported to some extent. The current study provides the first step towards a much-needed monograph and revision of the entire genus Encephalartos.

PhD (Botany) / Department of Botany / Cycads are regarded as the oldest living seed plants on earth and they have existed for about 300 million years. Ever since the awareness of the existence of this plant group, they have been facing high extinction risk. Currently they are referred to as the most threatened plant group in the world. Many ecological and anthropological forces are promoting extinction crisis of this taxonomic group. Africa is one of the centres of diversity of this plant group with 70% of the total number of the taxa in this group in Africa found in South Africa. Also South Africa is one of the global hotspots for cycads and it contains the third largest number of cycads after Australia and Mexico. Studies have revealed that there have been high threats and extinction risks among the cycad taxa in South Africa. The Soutpansberg Mountain is a major biodiversity hotspot in Limpopo Province in South Africa with high level of flora and fauna taxa. About 3000 vascular plants species are represented on this mountain. Biodiversity on this mountain has been under threat in recent times and there is need to investigate how cycads are facing risk on this mountain. The main focus of this study is to look at the extinction pattern in South African cycads and cycads endemic to Soupandberg Mountain in Limpopo Province in South Africa. v The first objective evaluated all African cycads over a decade using IUCN red list. Data from IUCN 2014 version was used to calculate the percentages of African cycads in each IUCN categories. The results were compared with those presented by Donaldson 2003. They showed that there have been significant decline and increase in extinction of African cycads over this period. It was also discovered that majority of this extinction crisis were trending in South Africa. The second objective used the IUCN red list to evaluate extinction pattern in South African cycads. The percentages of IUCN threat categories of South African cycads was calculated using IUCN red list. ArcGIS was used to construct distribution map for threatened and extinct South African cycads. The study revealed that the proportion of historically Extinct and Critically Endangered cycads is higher in Limpopo, KwaZulu-Natal and Mpumalanga than the rest of the provinces in South Africa. The third objective of this research investigated extinction pattern of Encephalartos transvenosus Stapf & Burtt Davy (Modjadji cycad) on Soutpansberg Mountain. Indigenous knowledge and population ecology approaches were used to determine current threats Modjadji cycads are facing on Soutpansberg Mountain. The results showed that anthropogenic activities have caused a substantial decline of one important unprotected population of this species on Soutpansberg Mountain. / NRF

Cycads first appeared about 300 million years ago and historical data indicates that they survived fluctuations of global temperature and carbon dioxide concentrations and reached peak abundance during periods where temperature and carbon dioxide concentrations were much higher than the present conditions as well as the predicted increased levels. With Africa being one of the most vulnerable regions to climate change and in the absence of an evaluation of predicted impacts of climate change on cycads, this study aims to contribute to our understanding of responses of Encephalartos longifolius to increased temperature. Encephalartos longifolius (Jacq.) Lehm is an Eastern Cape endemic and like most cycads has been around for millions of years with very little change to its basic structure. Photosynthetic rates showed E.longifolius seedlings have C3 photosynthesis and even under stress they do not switch over to CAM photosynthesis. The photosynthetic rates of seedlings showed a typical C3 -plant type response under elevated carbon dioxide levels. Increased temperatures could be detrimental to the species but coupled with elevated carbon dioxide levels the growth of Encephalartos longifolius are postulated to outweigh the negative impacts of increased temperatures. Whilst climatic conditions in the Eastern Cape might not impact the abundance of Encephalartos longifolius, the species however is declining rapidly to the present near-threatened status. Demographic studies revealed a high percentage of juvenile numbers in the wild; however juvenile plants are impacted on by animals thereby jeopardizing their survival. Adult plants are heavily impacted on by animals; this reduces the probability of new offspring being produced. Cycads are also very slow - growing which is the primary cause of their ruin in the wild. Encephalartos longifolius grows at just over approximately 1 cm per year with growth being more rapid in the juvenile plants. Once juvenile plants reach approximately 60 cm they stop growing in diameter but only get taller. Seed germination is also a very slow process with an optimum temperature of 28°C and a growth medium of at least 50 percent moisture. Regardless of the Eastern Cape predicted to become the hottest province in South Africa as a result of climate change, cycads will be able to adapt to the changing environment and conservation plans should focus on animal and human impacts that are the major force causing decreasing abundance of Encephalartos longifolius in the wild.

In addition to habitat loss and fragmentation, habitat degradation can have important consequences for biodiversity and population persistence, including effects on ecological and genetic processes beyond decreased demographic viability and the loss of genetic variation. Particularly interesting is the potential for evolutionary changes and adaptation to degraded habitats, that can affect population viability even in the short-term. Here, I explore how environmental changes after habitat degradation affect the evolutionary dynamics of populations of the rainforest cycad Zamia fairchildiana, specifically how habitat degradation affects gene dispersal, inbreeding, directional selection, and genotype-by-environment interactions, and the potential for genetic differentiation between populations. Colonies of Z. fairchildiana showed little genetic differentiation in neutral molecular markers across study sites, thus can be considered as subpopulations. Subpopulations in the disturbed habitat are experiencing different environmental conditions when compared to subpopulation in their native habitat. Disturbed-habitat subpopulations showed a faster life-history. This faster life history is associated with a weaker spatial genetic structure and higher levels of inbreeding in the disturbed-habitat subpopulations. In addition, higher light availability in the disturbed habitat seems to be a major agent of selection on traits like leaf production that have the potential to respond to selection in these subpopulations. Different traits were under selection in the native-habitat subpopulations, suggesting the potential for genetic differentiation between native and disturbed-habitat subpopulations. Genotype by environment interactions in seed germination and seedling survival, in response to light and water availability, further suggested that subpopulations can adaptively diverge between habitats, but the relative role of genetic and environmental factors, particularly maternal effects, on the magnitude and rate of genetic differentiation between subpopulations remains to be evaluated. These results suggest that habitat degradation can have important consequences for the evolutionary dynamics of populations of this cycad, not necessarily typical of habitat loss and fragmentation. This study identified factors and processes important for population persistence in degraded habitats, but population responses to habitat degradation are complex. Thus further studies and long-term experiments are required for better understanding the effects of habitat degradation on population viability.