GENETIC DIVERSITY AND GENE FLOW IN THE MORPHOLOGICALLY VARIABLE, RARE ENDEMICS BEGONIA DREGEI AND BEGONIA HOMONYMA (BEGONIACEAE)

Begonia dregei and B. homonyma (Begoniaceae), rare plants endemic to coastal forests of eastern South Africa, are two closely related species with high levels of variation among populations in the shape of leaves. Distribution of genetic variation and genetic relatedness were investigated in 12 populations of B. dregei and seven of B. homonyma using polyacrylamide gel electrophoresis. Twelve of the 15 enzyme loci examined were polymorphic, but only seven loci were polymorphic within at least one population. Genetic diversity measures indicated that the among-population gene differentiation represents >90% of the total genetic component in both species considered individually or combined. This indicated restricted gene flow, consistent with the limited dispersal abilities of Begonia generally and the ancient separation of isolated forest patches. Genetic distances among populations are much higher than usually found within species. Allozyme data provide no support for the recognition of B. dregei and B. homonyma as distinct species.Excellent models for the study of evolutionary pro¬cesses are often provided by taxa that pose the greatest problems in systematics (Wolf, Soltis, and Soltis, 1991). Endemic plants provide a superb tool for studying the dynamic processes of speciation and evolution, particu¬larly island endemic plants (Ito and Ono, 1990; Aradya, Mueller-Dombois, and Ranker, 1991; Barrett, 1996). Ev¬idence of most evolutionary events that formed continen¬tal biota has been lost because such biota are so ancient (Carson, 1987). Complex patterns of variation may blur species boundaries and lead to taxonomic complexity

Taxonomic studies in the tribe Justicieae of the family Acanthaceae.

Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1985.Unable to copy from pdf

Chromosome numbers of South African Acanthaceae

Volume: 52Start Page: 143End Page: 15

Factors Affecting the Success of Conserving Biodiversity in National Parks: A Review of Case Studies from Africa

National Parks are a cornerstone for biodiversity conservation in Africa. Two approaches are commonly used to sustain biodiversity in National Parks. Past and current studies show that both approaches are generally ineffective in conserving biodiversity in National Parks in Africa. However, there are a handful of cases where these approaches have been successful at conserving biodiversity in National Parks. The question this paper attempts to answer is why in some cases these approaches have been successful and in other cases they have failed. A metadata analysis of 123 documents on case studies about conservation of biodiversity in National Parks in Africa was conducted. A series of search engines were used to find papers for review. Results showed that all factors responsible for both the success and failure of conserving biodiversity in National Parks in various contexts were socioeconomic and cultural in nature. The highest percentage in both successful case studies (66%) and unsuccessful cases studies (55%) was associated with the creation and management of the park. These results suggest that future conservation approaches in National Parks in Africa should place more emphasis on the human dimension of biodiversity conservation than purely scientific studies of species and habitats in National Parks

Does Hyperaccumulated Nickel Affect Leaf Decomposition? A Field Test Using \u3ci\u3eSenecio Coronatus\u3c/i\u3e (Asteraceae) in South Africa

Nickel hyperaccumulator plants contain unusually elevated levels of Ni (\u3e1,000 mg Ni kg−1). The high Ni concentration of hyperaccumulator tissues may affect ecosystem processes such as decomposition, but this has yet to be studied under field conditions. We used Senecio coronatus Thunb. (Harv.) from two pairs of serpentine sites: one member of each pair contained a hyperaccumulator population and the other a non-hyperaccumulator population. Our main goal was to determine if leaf Ni status (hyperaccumulator or non-hyperaccumulator) affected leaf decomposition rate on serpentine sites. We also used a non-serpentine site on which leaves from all four S. coronatus populations were placed to compare decomposition at a single location. Dried leaf fragments were put into fine-mesh (0.1 mm) nylon decomposition bags and placed on field sites in mid-summer (early February) 2000. Sets of bags were recovered after 1, 3.5, and 8 months, their contents dried and weighed, and the Ni concentration and total Ni content of high-Ni leaves was measured. For the serpentine sites, there was no significant effect of leaf Ni status or site type on decomposition rates at 1 and 3.5 months. By 8 months, leaf Ni status and site type significantly influenced decomposition on one pair of sites: hyperaccumulator leaves decomposed more slowly than non-hyperaccumulator leaves, and leaves of both types decomposed more slowly on the non-hyperaccumulator site. At the non-serpentine site, the highest-Ni leaves (15,000 mg Ni kg−1) decomposed more slowly than all others, but leaves containing 9,200 mg Ni kg−1 did not decompose more slowly than non-hyperaccumulator leaves. Nickel in decomposing hyperaccumulator leaves was released rapidly: after 1 month 57–68% of biomass was lost and only 9–28% of original Ni content remained. We conclude that very high (\u3e10,000 mg Ni kg−1) leaf Ni concentrations may slow decomposition and that Ni is released at high rates that may impact co-occurring litter- and soil-dwelling organisms

Elemental Patterns in Ni Hyperaccumulating and Non-Hyperaccumulating Ultramafic Soil Populations of \u3ci\u3eSenecio coronatus\u3c/i\u3e

Nickel hyperaccumulation can defend plants against herbivores and pathogens. However, variability in plant tissue elemental concentrations in space and time will influence the effectiveness of this defense. We investigated a South African Ni hyperaccumulator, Senecio coronatus Thunb. (Harv.), for variation in nine elements (Ni plus Ca, Cu, Fe, K, Mg, Mn, P and Zn) between populations and between above-ground and below-ground plant organs (leaves, roots). Plant material was collected from four populations growing on ultramafic soils in the vicinity of Badplaas, Mpumalanga Province, South Africa. Concentrations of Ca, Cu, Fe, K, Mg, Mn, Ni, P and Zn were determined in dry-ashed samples. Two-way analysis of variance of data for each element revealed considerable variation in S. coronatus plant chemistry. Leaf concentrations of all elements except Cu were generally greater than root concentrations. Population-level variation was found for Ca, Fe, Mn, P, Ni and Zn, and of these all but P showed significant two-way interactions as well. Significant positive correlations were found between some pairs of elements: in hyperaccumulator roots (Ni–Ca, K–Mg), non-hyperaccumulator roots (Fe–Mn, Fe–Zn, Fe–Cu, Cu–Zn), hyperaccumulator leaves (P–Mg, P–Fe, P–Mn, Fe–Mg) and non-hyperaccumulator leaves (P–Mn, P–Ca, Ca–Mn). Two populations hyperaccumulated Ni in leaves (means of 12,000 and 8800 μg Ni/g) whereas the others did not (means of 120 and 130 μg Ni/g). Such extreme population-level variation in Ni accumulation ability is unusual among Ni hyperaccumulator species: its physiological basis and possible consequences for plant elemental defense deserve further investigation

Two new species of Barleria (Acanthaceae) from the Soutpansberg of Limpopo Province, South Africa.

Two new species of subg. (Acanthaceae) are described from the Soutpansberg Centre of Plant Endemism in Limpopo Province of South Africa: and . The habitat requirements, conservation status and taxonomic affinities of each species are discussed. is considered to be closely allied to the widespread and frequently cultivated southern African species , whilst is morphologically most similar to which has a restricted distribution in northern South Africa and Zimbabwe. Remarkably, the two new species are postulated to occasionally hybridise within the Soutpansberg. Both species are currently assessed as of Least Concern despite their restricted ranges. is noted to be amongst the most densely spiny species of and, indeed, is a contender as one of the spiniest species of plant in South Africa