Kevin Balkwill

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• Doctor of Philosophy
• Emeritus Professor at University of the Witwatersrand

In this worldwide revision of Syncolostemon sensu lato (including Hemizygia), 51 species are recognised, with three divided into varieties. Forty-nine species occur on mainland Africa, one on Madagascar and one in India. Descriptions, synonymy, habitat and conservation information are provided for each species and an identification key presented. T...

Climatic, edaphic, and topographic differences between mountains and surrounding lowlands result in mountains acting as terrestrial islands with high levels of endemic biota. Conservation of mountains is thus key to successful biodiversity conservation. The Limpopo–Mpumalanga–Eswatini Escarpment (LMEE) in South Africa and the Kingdom of Eswatini is...

Two new species of Barleria subg. Barleria (Acanthaceae) are described from the Soutpansberg Centre of Plant Endemism in Limpopo Province of South Africa: Barleria soutpansbergensis and B. spinosissima . The habitat requirements, conservation status and taxonomic affinities of each species are discussed. Barleria soutpansbergensis is considered to...

What are the spatio-temporal characteristics of a fire pattern that is allowed to develop over time across a species- rich, predominantly grassy landscape? More than 1 300 fires were documented over 13 years in the 48 000 ha Songimvelo Game Reserve in the Barberton Mountainland, South Africa. Most fires were set by pastoralists and were uncontrolle...

The first published record of Stemodiopsis in South Africa was by Dyer in 1975. Since that time, it has been understood that a single species, S. rivae Engl., occurs in South Africa. An analysis of character variation in Stemodiopsis Engl. throughout Africa has revealed that indumentum and inflorescence morphology are important in distinguishing am...

Specimens of an undescribed species of Ochna were found mixed among specimens of O. pretoriensis and O. holstii. It differs from these two species on the basis of leaf shape and its corky bark. It differs from O. schweinfurthiana, a tropical African species with corky bark, on the basis of leaf shape and by producing its flowers simultaneously and...

This Commentary is a response to a Commentary published in the May/June 2020 issue: Nattrass N. Why are black South African students less likely to consider studying biological sciences? S Afr J Sci. 2020;116(5/6), Art. #7864, 2 pages. https://doi.org/10.17159/sajs.2020/7864 Responses to the Commentary in the May/June 2020 issue have been publish...

In South Africa, Ancylobothrys Pierre was last revised in 1963, although the taxa were maintained within the genus Landolphia P. Beauv. Later authors separated Ancylobothrys from Landolphia citing the tendril-like inflorescence and the softly pubescent fruit of Ancylobothrys as two of the most obvious characters separating these genera. A geoxylic...

Wurmbea burrowsii D. Oosthuizen and K. Balkwill and Wurmbea viridiflora D. Oosthuizen and K. Balkwill from Mpumalanga in South Africa are described. Wurmbea burrowsii is restricted to the Mount Anderson Nature Reserve area where it grows in damp to dry grassland on a sandstone substrate. It has a provisional threat status of Vulnerable D2. Wurmbea...

Anthers containing pollen grains of Barleria obtusa at various stages of development were examined to investigate pollen wall ontogeny. Whole anthers containing pollen grains were viewed with a light microscope, firstly to identify stages of pollen grain development and secondly to assess the state of the tapetum. Developing pollen grains were sect...

The majority of metal hyperaccumulating plants accumulate nickel, yet the molecular basis of Ni hyperaccumulation is not well understood. We chose Senecio coronatus to investigate this phenomenon as this species displays marked variation in shoot Ni content across ultramafic outcrops in the Barberton Greenstone Belt (South Africa), thus allowing an...

A species of Viscum (Santalaceae) was collected in eastern Mpumalanga that did not match V. combreticola, V. anceps or V. shirense. We consider the differences to be sufficient to recognise a new species, Viscum songimveloensis D. Oosthuizen & K. Balkwill. This species has so far only been found on one host, Trichocladus grandiflorus, and in a very...

The variation exhibited within three species of Barleria (B. bechuanensis, B. irritans and B. jubata) was studied to establish whether it was discrete or continuous. Morphological characters were examined and recorded in matrices. Cluster analysis was employed to impose a hierarchical non-overlapping association among operational taxonomic units (O...

The external pollen morphology of Justicia is diverse and offers a wealth of characters currently used for classifying species. The pollen morphology of 12 species of Justicia and six species from five closely related genera was investigated using a focused ion beam-scanning electron microscope (FIB-SEM). This method allows for three dimensional ex...

Species of Gnetum L. are used for a number of purposes, the most important of which is to make a soup or stew, which is called ‘eru’ in Cameroon. Material is heavily harvested for use in Cameroon, export to Nigeria and to Europe and America. Gnetum has been extirpated in some areas and is becoming rare in others because levels of harvesting are uns...

Taxonomy provides a universal method to classify biodiversity at different scales locally and globally. Currently, existing taxonomic treatments are scattered, limiting their accessibility and utility. The Convention on Biological Diversity has responded to this challenge by setting the goal of compiling a World Flora Online (Global Strategy for Pl...

The taxonomy of the white-flowered species of Isoglossa Oerst. in southern Africa is reviewed. Morphology and indumentum of bracts and calyces, micromorphology of pollen and seeds, flowering times and distribution are documented. Several names are subsumed: Isoglossa densa N.E.Br. and Isoglossa sylvatica C.B.Clarke under Isoglossa ciliata (Nees) Li...

The economically important gymnosperm Gnetum L. is distributed in humid tropical forests of Africa. Its leaves are used as commercialized vegetables and greatly alleviate poverty for local people. Previously, the number of species recognized in Africa was uncertain, and Gnetum africanum Welw. and G. buchholzianum Engl. had been variously, and erron...

External pollen grain morphology has been widely used in the taxonomy and systematics of flowering plants, especially the Acanthaceae which are noted for pollen diversity. However internal pollen wall features have received far less attention due to the difficulty of examining the wall structure. Advancing technology in the field of microscopy has...

This paper aims to characterise and describe the species composition of serpentine sites of the Barberton Greenstone Belt as compared to surrounding non-serpentine areas. A floristic analysis of seven serpentine (serpentinite) outcrops of the Barberton Greenstone Belt, in the eastern part of South Africa, recorded 744 species and subspecies, 319 ge...

Material of a common and widespread species of Isoglossa Oerst. in southern Africa keys to I. stipitata C. B. Clarke in Clarke's 1901 taxonomic account in Flora Capensis. However, this material does not match either the type or the description of that species. Thus, a new species, I. glandulosissima K. Balkwill, is described for the Acanthaceae, Ru...

Gnetum L. is a genus of economic importance distributed in the humid rainforests of Central Africa. The African species of Gnetum are dioecious climbers and only two species (Gnetum africanum Welw. and G. buchholzianum Engl.) have been described previously. The names G. africanum and G. buchholzianum have been applied interchangeably to similar mor...

The leaves of three African species of Gnetum (G. africanum; G. buchholzianum and G. latispicum) are an important source of food and income to the people where this forest gymnosperm grows. Sustainable utilization strategies are required to improve its production, method and extent of harvesting in the wild. This study investigates i) variation in...

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Morphological variation within the Oliniaceae is discussed with reference to diagnostic characters used to delimit species and infraspecific taxa. The Oliniaceae is hereby considered to comprise a single genus, Olinia Thunb. with ten species assigned to two sections: sect. Olinia, and sect. Rochetiana. The two sections are distinguishable on the ba...

Calibration and verification techniques are discussed in the context of numerical phenetic analysis. Calibration is introduced to evaluate the character set, decide on the type of phenetic algorithm to be used, and determine the level at which to recognize taxonomic entities. Clusters are verified by analyzing sub-samples of specimens. This determi...

Pollen grain morphology has been widely used in the classification of the Acanthaceae, where external pollen wall features have proved useful in determining relationships between taxa. Although detailed information has been accumulated using light microscopy, transmission electron microscopy and scanning electron microscopy (SEM) techniques, intern...

While current investments in school improvement occur in the context of the worldwide economic downturn, in the South African context, there is in addition widespread disparity in education provision and attainment related to pre-democracy race-based patterns. Despite the education sector receiving the largest national annual budget allocation (at...

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 b...

Copy of full article available on request. Theoretical frameworks play a vital role in research , spelling out the constructs important in the research area, and the relationships between the constructs. An understanding of the theoretical constructs which underpin the research provides researchers with a framework, which enables them to understand...

Identity and typification of Carex cognata and status of C. drakensbergensis.

Serpentine soils vary in levels of toxicity of the parent material, climate, relief, and biological activity resulting in a range of harsh environments. This harsh environment is likely to result in a unique, usually endemic, flora. However, not all plants growing on serpentine soils are endemic; some plants appear to be indifferent (bodenvag) to t...

The African species of Gnetum L. (Gnetales) are lianas in the humid tropical forests of Central and West Africa. These gymnosperms are nutritionally and economically valuable and contribute greatly to poverty alleviation of the local people as they are widely used as a vegetable (eru). The African species of this genus are however difficult to dist...

A species of Sartidia De Winter, first collected by P.J. Muller in 1972 in the Cythna Letty Nature Reserve in Mpumalanga, does not match existing material of Sartidia, a genus comprising four species. The new species, S. dewinteri J. Munday & L. Fish, is most similar to S. jucunda (Schweick.) De Winter but differs in the leaf sheath colour, lower l...

When geologists first wandered the spectacular ring of hills straddling the Vaal River north of Vredefort nearly 150 years ago, they immediately recognised that the unusually shattered and uptilted rocks bore witness to an exceptionally violent event in the distant past. However, it took more than a century of painstaking work before the accumulate...

The genus Bolandia (Asteraceae, Senecioneae) comprises two known species, B. pedunculosa and B. argillacea, previously included in Cineraria. Distinguishing features of Bolandia include the fusiform shape of the cypselae and strong median rib on the glabrous inner surface of the ray and outer disc cypselae, solitary ecalyculate capitula on long ped...

The biogeography of Cineraria (Asteraceae, Senecioneae) is assessed using a chorological approach in terms of its distribution, centres of diversity and endemism. Rare species are identified and categorised according to Rabinowitz's criteria and causes for rarity in the genus are investigated. The conservation status of the species is assessed acco...

Soil chemistry can play an important role in determining plant diversity. Serpentine soils are usually toxic to many plant taxa, which limits plant diversity compared to that on adjacent non-serpentine soils. The usually high concentrations of toxic metals in serpentine soils are considered to be the edaphic factors that cause low diversity and hig...

Previous circumscriptions of Olinia rochetiana A. Juss. (Oliniaceae) presented a taxonomically variable and widespread species complex in central and tropical East Africa. Results of numerical phenetic analyses of morphological variation within O. rochetiana sensu lato indicate the existence of four taxa which are recognisable at specific rank corr...

Hyperaccumulated elements such as Ni may defend plants against some natural enemies whereas other enemies may circumvent this defense. The Ni hyperaccumulator Berkheya coddii Roessler (Asteraceae) is a host plant species for Chrysolina clathrata (Clark), which suffers no apparent harm by consuming its leaf tissue. Beetle specimens collected from B....

In his appraisal of Isoglossa Oerst., Clarke (1901) placed major emphasis on the sizes of leaves and inflorescences in the key to species, but efforts to sort herbarium material have shown a great deal of variation in leaf size and inflorescence length that is very difficult to interpret. Specimens of a species of Isoglossa were collected from wild...

Background/Question/Methods Hyperaccumulated Ni has been shown to defend plants against a wide array of herbivores. Since Ni is not significantly reabsorbed during leaf senescence, much of the metal-based defense remains intact when leaves abscise. Thus, once metal-enriched leaves are incorporated into vegetation litter, they may also negatively...

Phylogenetic analyses of separate and combined plastid trnL-trnF and nuclear ITS DNA sequences were used to investigate the delimitation of Cineraria with respect to five species previously included in Cineraria, its infrageneric structure, and to contribute to knowledge regarding its relationships in the tribe Senecioneae (Asteraceae). The molecul...

A literature survey has shown that seed surface patterns (seedscapes) are taxonomically valuable in the Acanthaceae. Seed surfaces of 11 southern African species of the genus Thunbergia Retz. were investigated using light and scanning electron microscopy. The aims were to establish whether testa surface patterns are constant within species, are spe...

The Wolkberg Centre of endemism (northeastern Drakensberg escarpment) has a high proportion of species endemic to dolomite- and quartzite-derived soils. The Legalameetse Nature Reserve falls largely within the Chuniespoort Formation, which constitutes the dolomite component of the Wolkberg Centre. A number of species that occur within Legalameetse...

Nickel hyperaccumulator plants contain unusually elevated levels of Ni (>1,000mg 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...

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, M...

The demand for traditional medicinal plants and products in South Africa has created an extensive cross-border industry involving thousands of harvesters and traders. The market values of individual taxa vary considerably. Pricing structures fluctuate between markets and over time as the cost of harvesting species varies depending on a gatherer's a...

Cineraria lobata is a highly variable species centred in the Western and Eastern Cape Provinces, South Africa, with disjunct populations in Mpumalanga and Limpopo Provinces. Morphological variation was examined in order to delimit the species and to determine whether recognition at infraspecific levels was warranted. Plants from the Ngwenya Hills,...

Balanites maughamii Sprague (Balanitaceae) is a woodland tree used and harvested for bark products in the traditional medicine trade of South Africa. The tree has a distinctively fluted and buttressed stem, especially in mature individuals. This short communication quantifies the relationship between two diameter measurements D1 and D2 that respect...

Cluster analysis and principal coordinates analysis were used to investigate phenetic variation in Cineraria deltoidea, a species that ranges from near sea level in KwaZulu-Natal, South Africa, to 4300 m a.s.l. on the mountains of East Africa and Ethiopia. Earlier taxonomic revisions reduced nine previously recognized species to synonyms of C. delt...

The incorporation of suitable quantitative methods into ethnobotanical studies enhances the value of the research and the interpretation of the results. Prediction of sample species richness and the use of species accumulation functions have been addressed little in applied ethnobotany. In this paper, incidence-based species richness estimators, sp...

Bark is the most popular product harvested for traditional medicine in South Africa. Harvesting is sometimes selective for particular stem size-classes and the effect of bark removal and the sustainability of harvesting practices are species-specific. However, baseline autecological data that would assist conservation and trade monitoring efforts a...

Nymphs of Stenoscepa sp. feed on leaves of the Ni hyperaccumulator Berkheya coddii at serpentine sites in Mpumalanga Province, South Africa. These sites contain Ni hyperaccumulators, Ni accumulators, and plants with Ni concentrations in the normal range. We conducted studies to: (i) determine the whole-body metal concentration of nymphs (including...

Commercial harvesting of perennial herbs and geophytes for the medicinal plant trade has resulted in significant levels of resource depletion for several of the species concerned. One way to quantify the impacts is to estimate the number of bulbs harvested annually. Using records of bulb diameters sold in the Witwatersrand traditional medicinal pla...

The relationships between Hemizygia and Syncolostemon are investigated. Parsimony analyses of morphological data and sequences of the trnL intron, trnL-trnF intergenic spacer and the rps16 intron were carried out separately and in combination. All analyses largely show strong support for the two genera as a monophyletic group; neither genus as curr...

Twenty-nine species endemic to outcrops of serpentine soils of the Barberton Greenstone Belt have been identified. Of these only 11 were previously Red Data Listed, six as Insufficiently Known (K) or Data Deficient (DD). The populations of these endemics are extremely fragmented and many are threatened by afforestation. IUCN criteria were used to r...

A numerical phenetic analysis of data obtained from populations of the Olinia rochetiana A.Juss. complex occurring in South Africa (Mpumalanga and Limpopo Provinces) revealed the existence of two forms: 1, a shrubby form (up to 2.5 m tall), with thick terminal branches, coriaceous leaves with a tinge of red on margins (towards the apices), short in...

Abstract The high levels of some metals in metal hyperaccumulator plants may be transferred to insect associates. We surveyed insects collected from the South African Ni hyperaccumulator Berkheya coddii to document whole-body metal concentrations (Co, Cr, Cu, Mg, Mn, Ni, Pb, Zn). We also documented the concentrations of these metals in leaves, stem...

Two new species of Cineraria L. (Senecioneae) are described: Cineraria glandulosa Cron, endemic to KwaZulu-Natal, and Cineraria dryogeton Cron from the Umtamvuna Nature Reserve on the border of KwaZulu-Natal and the Eastern Cape. Both species are narrow endemics, restricted to specific habitats and geological formations, and are therefore vulnerabl...

The variation and recognition of taxa within the Hemizygia bracteosa complex was examined using multivariate techniques. Morphological characters were sampled on 197 herbarium specimens. Phenetically H. bracteosa and H. welwitschii overlap in many floral characters. However differences in leaf characters and habit maintain their morphological disti...

A taxonomic revision of the genus Cineraria L. (Asteraceae, Senecioneae) is presented. Thirty-five species are recognised, the majority from southern Africa, with C. deltoidea occurring throughout the highlands of southern and East Africa, C. abyssinica in Ethiopia, Yemen and Saudi Arabia and C. anampoza endemic to Madagascar. Two new species, four...

Two new species and a new variety of Cineraria L. from tropical Africa are described: C. pulchra Cron from the Nyanga and Chimanimani Mountains of Zimbabwe and Mozambique (Mount Gorongoza), C. huilensis Cron from the Serra da Chela in the Huila Province of Angola and C. mazoensis S. Moore var. graniticola Cron from the granite domes of Zimbabwe.

The lack of scientific rigour in analysing ethnobotanical surveys has prompted researchers to investigate ways of quantitatively describing their data, including the use of ecological diversity indices. There are numerous indices and measures available to describe sample diversity. Twenty-two measures of species richness, diversity and evenness wer...

Information on tree stem characteristics and dimensions is sparse, especially information that would enhance conservation and trade monitoring efforts for species where bark is harvested for medicinal use. Several tree stem characteristics were investigated during a study on the relationship between bark thickness and stem diameter, and this paper...

In Tanzania, well-defined land tenure and resource protection apply in forest reserves which account for 30% of forested land, while the remaining 70% (mostly miombo woodlands) are village and general lands with very limited protection. The aim of this study was to determine local peoples ownership rights, knowledge and institutional capacity for s...

Genetic variability in Barleria argillicola and B. greenii, two sympatric and endemic species restricted to Estcourt in KwaZulu-Natal, was compared with B. saxatilis, a closely related widespread species inhabiting dry hot areas in KwaZulu-Natal, Mpumalanga, Limpopo and Swaziland bushveld. Three populations from each species were sampled for electr...

A new species of Ocimum, O. motjaneanum McCallum & K. Balkwill, endemic to serpentine soils in the north-west of Swaziland, is described and compared with O. obovatum, the species it most closely resembles. It has a very localized distribution with an area of occupancy under threat of encroachment by exotic trees and development, which makes it cri...

The literature on African pollination biology is reviewed. It is found that relatively little work has been done on pollination biology in Africa, and a very small proportion of pollination relationships has so far been studied. Much of the research which has been done is of an evolutionary nature. Very little work has been conducted at the communi...

This study compared and contrasted natural regeneration by coppicing of tree species in a forest reserve and more disturbed adjacent public lands in eastern Tanzanian miombo woodlands. Data were collected between August and October 1997 using sixty-four 20m×50m plots. Eighty-three percent of the 30 harvested woody species in the forest reserve resp...

The Dunbar Valley serpentinite outcrop has a flora comprising 254 taxa (species and below) in 172 genera and 63 families. Dunbar Valley has more species than other studied serpentinite sites in the Barberton Greenstone Belt (BGB). The genus Senecio is the most speciose genus in the BGB. The level of species endemism at Dunbar Valley is 2.0%. Most o...

The communities of Tsehlanyane and Bokong depend on subsistence agriculture and harvesting natural resources for a variety of needs, mainly firewood, handcrafts, medicine, food, construction, and socio-cultural amenities. They have done so since time immemorial and are singularly responsible for the good conservation value that the area represents....

Native to South-Africa, species of the Senecio inaequidens complex are presently invasive in Europe, Australia and South-America. Previously, different ploidy levels have been found in these different areas, with only tetraploid individuals reported in Europe, and only diploids in South-Africa and Australia. In the present study chromosome counts a...

Barleria greenii is a rare endemic taxon with an extremely restricted distribution area found only near Estcourt, South Africa. Three of eight known populations of B. greenii, representing a hierarchy from closely spaced to geographically distant sites, were studied by horizontal starch gel electrophoresis to assess the levels of genetic variation...

This paper presents a comprehensive assessment of the contribution of communal resources to households in Bokong and Tsehlanyane in Lesotho. It argues that communal resources are an extremely important element in the livelihoods of people in the study area. It uses households as units of analysis in order to gain an understanding of the role that c...

Barleria L. (Acanthaceae) is a large, polymorphic, widespread genus of herbs and shrubs comprising about 300 species, occurring mainly in Africa and Asia but with one species, Barleria oenotheroides Dum.Cours., extending to the New World tropics. Recent completion of a monographic infra-generic classification of the genus (in which seven sections a...