Th.--Pharm.--Paris, 1880?

Delairea odorata Lem., an asteraceous perennial vine indigenous to southern Africa, has become naturalised and invasive in many subtropical regions including California, South Australia and Hawaii. Biological control offers a potential long term solution to the management of this species in exotic locations. This study analysed aspects of the biology of D. odorata in its native environment to determine its suitability to classical biological control. To this end an examination of the reproductive biology and natural enemies of D. odorata was made. A study of the pyrrolizidine alkaloid profile was also conducted. Reproductive biology: Delairea odorata reproduces both sexually by seeds and asexually by stolons. The flowering season occurs over the autumn months from April to June. Results of the pollination trials indicate that D. odorata is a cross compatible species and an obligate outbreeder. There is no specialised pollination system and the predominant pollinators belong to the families Apidae, Syrphidae and Calliphoridae. Following pollination, numerous small achenes are produced. Laboratory trials indicate that these achenes germinate readily between 10 and 25 °C and, although germination occurs in both the light and dark, light clearly stimulates seed germination. Greenhouse trials conducted to determine the effect of light on growth and reproduction indicate that D. odorata is a shade tolerant species which shows plasticity in terms of growth form and deployment of biomass in response to changes in light intensity. Growth rate and allocation of biomass to vegetative and sexual reproduction are highest at an intermediate light level. However, greatest allocation of biomass is to stem growth regardless of light level. Natural enemies: Surveys for potential biological control agents against Delairea odorata were conducted in KwaZulu-Natal and several phytophagous species were associated with the plant. However, only one potentially suitable control agent was identified, a stem galling tephritid fly, Parafreutreta regalis Munro. Preliminary studies indicate this species to be fairly host-specific, a valuable asset if it is to be considered as a control agent. Furthermore, as D. odorata proliferates extensively by means of stem regeneration and elongation, galling of these growing points by P. regalis may limit stolon spread in exotic locations. Two species of parasitic wasp (Braconidae) were found to parasitise P. regalis pupae. If P. regalis is to be used as a control agent the likelihood of parasitisation in the new environment must be determined. Pyrrolizidine alkaloids: Host-specificity in insects is often dependent on host-plant chemistry (e.g. alkaloids or essential oils). Thus prior to any biological control programme it is important to determine if there are ecotypes of the host plant present. An investigation to determine the specificity of the pyrrolizidine alkaloid profile of D. odorata, occurring across KwaZulu-Natal, was made. The results indicate the presence of nine retronecine based pyrrolizidine alkaloids which occur in similar proportions in locally distributed plants. However, these alkaloid profiles differ considerably from those published for D. odorata occurring in California. This is an interesting and important result which indicates that chemotypes of D. odorata may exist, a factor which must be considered in the initiation of any biocontrol. If chemotypes of D. odorata are present this may affect the behaviour of natural control agents on the exotic plant populations. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

Chromolaena odorata (L.) King and Robinson (Asteraceae) is an invasive weedy shrub native to the Americas that has proven to be a significant economic and ecological burden to many tropical and sub-tropical regions of the world where it impacts negatively on agriculture, biodiversity and livelihoods. A distinct biotype of C. odorata was first recognised as naturalized in KwaZulu-Natal (KZN) province, South Africa, in the 1940s and has since spread to other climatically suitable provinces. Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae: Arctiinae) was released in KZN, South Africa, as a biological control agent against the weed between 2001 and 2009. Although the moth did establish at one out of some 30 release sites, its population level is generally low in the field. This thesis attempts to unravel the reasons for the poor performance of P. insulata in South Africa.Studies of life history traits of P. insulata in the laboratory indicated that the moth possess good biological attributes such as low mortality, high fecundity, egg hatchability and high female mating success. Overall, adult female moths eclosed before their male counterparts suggesting the presence of protogyny. Beyond the contribution of this study to our understanding of the life history traits of erebid moths, it hypothesized that the absence of protandry might have contributed to the low population levels of the moth in the field. To determine if a degree of agent-host plant incompatibility is culpable for the poor performance of P. insulata, insect performance metrics were compared on two distinct C. odorata plants (one from Florida and another from South Africa) in laboratory experiments. Pareuchaetes insulata performance metrics were similar on both plant forms; there were no significant differences in total leaf area consumed, egg and larval development, immature survival rates, feeding index (FI), host suitability index (HSI), growth index (GI), and fecundity between the Floridian and southern African C. odorata plants. In sum, there was no evidence to demonstrate that differences in plant forms in C. odorata are culpable for the poor performance of P. insulata in South Africa.The effects of temperature on the developmental and reproductive life history traits, locomotion performance and thermal tolerance range of P. insulata were studied in order to elucidate the possible role of temperature on the poor performance of the moth. The results showed that at temperatures below 25 °C, mortality increased and development time was prolonged. Fecundity and egg hatchability were negatively affected at a constant temperature of 15 °C. Results futher showed that third instar larvae were unable to initiate movement at 6 °C and locomotor abilities were significantly reduced at 11 °C. In sum, it is hypothesized that both direct and indirect negative impacts of low temperature may partly explain the poor performance of P. insulata in South Africa. Theeffects of seasonal and spatial variations in the leaf characteristics of C. odorata on the performance of P. insulata were investigated. Foliar nitrogen and magnesium concentrations were higher in shaded plants during winter due to low temperatures. Leaves of C. odorata plants growing in the shaded habitat (relative to full sun) and leaves of plants during autumn (relative to winter) were more nutritionally balanced and suitable for herbivore performance. Consequently, P. insulata developed faster, had heavier pupal mass and increased fecundity when reared on shaded leaves (relative to full sun) or when reared on autumn leaves compared to leaves growing in winter. This study demonstrates that low winter temperatures can indirectly affect insect herbivore performance by changing the phytochemistry of host plant and hypothesized that excess nitrogen and possibly magnesium may have detrimental effects on the insect herbivore performance.A cross-feeding experiment was conducted to determine P. insulata response to a change in the diet of offspring due to a shift in plant quality in shaded versus full sun habitats. The results showed that a ‘negative switch’ in herbivore diet (i.e. when progeny from parents reared on shaded leaves were fed on full sun leaves) resulted in high (40%) mortality, prolonged development time and reduced fecundity. Thus full sun foliage is an inferior diet for P. insulata offspring. In laboratory experiments, foliar nitrogen was positively correlated with the performance of P. insulata. From this study, it is demonstrably evident that the poor performance of P. insulata on C. odorata in South Africa is caused by multiple factors such as low temperatures as well as spatio-temporal variations in the leaf characteristic of C. odorata leaves. This study shows the complexity of determining the causes of low populations and apparent low impact of biological control agents and herbivorous insects generally, in the field. The implications of this research to the biological control programme against C. odorata and the direction of future research for the control of C. odorata are discussed.

Abstract viewable in PDF document. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1985.

O gênero Butia compreende 20 espécies distribuídas, em sua maioria, no sul da América do Sul. Butia odorata (Barb. Rodr.) Noblick é uma palmeira endêmica do bioma Pampa, com alto potencial alimentício e ornamental. Seu diásporo é composto por um pirênio que abriga de uma a três sementes, as quais apresentam germinação irregular e lenta, resultado de dormência. Sabe-se que há relação dessa dormência com o opérculo da semente, e qual sua composição química também é citada como agravante. Através da remoção desta estrutura tem-se alta porcentagem germinativa, em curto período. A relação entre o opérculo e a influência da temperatura no período da germinação ainda é desconhecida para B. odorata, uma vez que a descrição morfoanatômica da espécie é incipiente e sua histoquímica é inexplorada. Este trabalho objetivou caracterizar a morfologia da estrutura de dispersão e descrever aspectos anatômicos e histoquímicos das sementes de B. odorata quando submetidas a tratamento para a superação da dormência. Diásporos de populações naturais foram semeados em caixas gerbox, sobre areia média lavada, esterilizada e umedecida. O material foi disposto em câmara de germinação sem iluminação interna por 20 dias sob temperatura de 40 ºC, seguido de 20 dias a 30 ºC. Após isoladas dos endocarpos, as sementes foram desbastadas e fixadas. Através de amostragens a cada cinco dias, foram caracterizados modificações anatômicas e a mobilização de reservas na semente. As sementes apresentam um envoltório (testa) com presença de estrias e no opérculo há presença de compostos fenólicos e ausência de lignina. O endosperma é homogêneo, branco e brilhante, com as células da região micropilar apresentando paredes espessas em relação ao restante do endosperma, sendo essas metabolizadas ao longo das amostragens. O embrião é pequeno, basal e apresenta a plúmula já diferenciada na primeira amostragem. Ao longo das amostragens e durante a manutenção dos pirênios sob temperatura de 40 ºC foi percebida a formação de uma zona de fragilidade no endosperma micropilar, o que, ao que tudo indica, está relacionado com a germinação. As reservas encontradas, as quais estavam presentes no endosperma e no embrião das sementes, foram: amido, polissacarídeos totais, lipídios totais, proteínas totais e compostos fenólicos na região opercular. A mobilização das reservas ocorreu antes mesmo do opérculo ser rompido. / The Butia genus comprises 20 species distributed mostly in southern South America. Butia odorata (Barb. Rodr.) Noblick is an endemic palm tree from the Pampa biome, with high food and ornamental potential. Its diaspore is composed of a pyrene which houses one to three seeds that have irregular and slow germination as a result of dormancy. It is known that there is a relationship between dormancy and seed operculum and its chemical composition can also be an aggravator. By removing this structure, seeds exhibit high germination percentage in a short period. The relationship between the operculum, as well as the influence of temperature on the germination period, is still unknown to B. odorata, since the morphoanatomical description of the species is incipient and its histochemical characteristics are unexplored. This study aimed to characterize the morphology of the dispersion structure and describe anatomical and histochemical features of B. odorata seeds when undergoing dormancy breaking treatment. Diaspores of natural populations were sown in gerbox on average washed, sterilized and moistened sand. The material was placed in a dark germination chamber for 20 days at 40 °C, followed by 20 days at 30 °C. Following this procedure, endocarps isolated from the seeds were chopped and fixed. By sampling every five days, anatomical changes and the mobilization of reserves in the seed were characterized. The seeds presented stretch marks in the involucre (seed coat or testa) and phenolic compounds with absence of lignin in the operculum. The endosperm is homogeneous, white and shiny, and the micropilar cells present thick walls, in relation to the rest of the endosperm, that were metabolized along the sampling. The embryo is small, basal and has differentiated plumule. While sampling at 40 °C the formation of a fragile zone in the micropilar endosperm was noted, which seems to be germination related. The reserves present in the endosperm and the embryo of seeds were: starch, total polysaccharides, total lipid, protein and phenolic compounds in the opercular region. The mobilization of reserves occurred even before the operculum was broken.

Biological invasions have increased dramatically in the past centuries and are one of the greatest threats to biodiversity today. Invasions occur when organisms are introduced at a location to which they are non-native, and they reproduce and spread, causing damage to the environment. Chromolaena odorata, a herbaceous shrub from the Americas, is one of the most widespread and problematic invasive plant species in the tropics and sub-tropics. The plant is a serious problem in South Africa, where invasive species threaten the nation’s biodiversity and limited water supply. This study combined transect monitoring data of C. odorata with ecological and clearing management data to assess the efficacy of an invasive plant clearing program over its decade of operation in the Hluhluwe-iMfolozi reserve in KwaZulu-Natal, South Africa. Densities and local extent of the C. odorata invasion were significantly reduced during the period of operations of the clearing program. Seasonal effects impacted clearing efficacy, namely a reduction in efficacy during the seed dispersal period. Effort and fire frequency were positively associated with clearing success, and rainfall negatively associated with clearing success. Excluding the northern section of the reserve, where the invasion progressed over the whole landscape, observations of C. odorata were closer to watercourses than randomized points, indicating a water limitation for invasion in most of the park. Management implications drawn from the results include halting clearing during seed-drop months, giving extra attention to areas with more rainfall and other water availability, and incorporating fire with other clearing methods where possible.

Biodiversity changes, often resulting from climate change, land transformation, and the transportation of organisms across geographical barriers are among the most important human induced global changes. To optimize the spatial allocation of conservation efforts, and how to best protect indigenous species, requires an understanding of the principal determinants that structure ecological communities and ecosystems. We studied community-level interaction among a diverse assemblage of specialist and generalist browsers in an African savanna. Hluhluwe-iMfolozi Park (HiP), South Africa, hosts a complete assemblage of vertebrate species across all trophic levels and contains a diverse guild of large browsers. Using species abundance distributions (SADs) we graphically illustrate the diversity and abundance of woody species that comprise six structural habitat types within HiP. We calculated the Shannon-Wiener index and Pianka’s niche overlap to characterise the utilization of forage across habitat types among different browser groups. By using individual plant traits we investigated mechanisms of resource partitioning. We specifically investigated the effect of the temporal expansion of an exotic invasive plant (Chromolaena odorata) on the critically endangered black rhino using GIS and statistical analyses. We found that lower lying habitat types were important forage resources for browser species and individual plant traits that are highly correlated with digestibility strongly predicted browser preference. Black rhino used different strategic and metabolic mechanisms to successfully compete within the same forage height range of other, smaller, browsers. C. odorata has negatively impacted forage species utilization and has led to a spatial reorganization of the population of black rhino. This may partly explain the recent decline in the population. The principles within metapopulation management can be used to successfully conserve endangered species. High diversity of browse across three dimensions (diversity, abundance and maximum height) relative to area facilitates a high diversity and abundance of different browsing herbivores. Therefore the spatial configurations of resources ranging from topological attributes to the individual plant traits are essential to maintaining viable populations of many co-occurring species within conservation areas of limited extent. / Thesis (M.Sc.)-University of KwaZulu-Natal, 2009.

The neotropical semi-woody perennial shrub Chromolaena odorata (L.) King and Robinson (Asteraceae: Eupatorieae) has become a serious invasive weed in the sub-tropical regions of southern Africa, resulting in the initiation of an insect biocontrol research programme at Cedara in the KwaZulu-Natal province. The programme has experienced difficulties in growing and maintaining healthy potted C. odorata plants for research, for almost ten years. In an attempt to identify possible causes of mortality, plants were grown on elevated grids in two trials; (winter-spring 2003) and (autumn-winter 2004) in Durban (subtropical region, within the natural range of C. odorata) and Cedara (temperate region, outside its natural range). Plants that established at all sites, in Trials 1 and 2, did not display any visual symptoms associated with mortality; however, results from Trial 1 indicated that plants grown in a tunnel at Cedara were physiologically stressed evidenced by lower transpiration rates despite higher vapour pressure deficits, compared with plants grown in a tunnel in Durban. Environmental stress was further indicated by the chlorophyll fluorescence ratio and a change in allocation of total non-structural carbohydrate (TNC) within Cedara-grown plants compared with Durbangrown plants. An attempt to relate mortality symptoms of unhealthy C. odorata plants with TNC content of the roots was unsuccessful but unhealthy plants had lower levels of N, P and K than healthy plants. Although mortality seem to be exacerbated by pathogenic fungi in saturated soil, infection was reduced by treating the soil with Previcur N and Benlate drench. Morphological adaptations of plants exposed to waterlogged soils include hypertrophied lenticels and new lateral roots; these were observed on the stem base of unhealthy C. odorata plants placed on the ground, that had reached a critical stage of die-back or had died back and re-sprouted. Examination of the root anatomy of C. odorata plants indicated an absence of cortical aerenchyma (interconnected system of air spaces), which may explain plant mortality in waterlogged pots wherein levels of oxygen in the soil may be reduced. C. odorata stock plants at Cedara have been placed on elevated grids since August 2004 and two years later plant mortality has been significantly reduced. Presently, the only feasible option is to grow potted C. odorata plants on elevated grids at Cedara because this allows for adequate drainage, aeration of soil and air-nipping of roots, and spacing plants on the grids also improves penetration of light. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2007.

Thesis (Ph. D.)--Wageningen University, 2006. / Thesis propositions sheet inserted. "Author's publications": p. 194-196. Includes bibliographical references (p. 151-180).

O gênero Butia compreende 20 espécies distribuídas, em sua maioria, no sul da América do Sul. Butia odorata (Barb. Rodr.) Noblick é uma palmeira endêmica do bioma Pampa, com alto potencial alimentício e ornamental. Seu diásporo é composto por um pirênio que abriga de uma a três sementes, as quais apresentam germinação irregular e lenta, resultado de dormência. Sabe-se que há relação dessa dormência com o opérculo da semente, e qual sua composição química também é citada como agravante. Através da remoção desta estrutura tem-se alta porcentagem germinativa, em curto período. A relação entre o opérculo e a influência da temperatura no período da germinação ainda é desconhecida para B. odorata, uma vez que a descrição morfoanatômica da espécie é incipiente e sua histoquímica é inexplorada. Este trabalho objetivou caracterizar a morfologia da estrutura de dispersão e descrever aspectos anatômicos e histoquímicos das sementes de B. odorata quando submetidas a tratamento para a superação da dormência. Diásporos de populações naturais foram semeados em caixas gerbox, sobre areia média lavada, esterilizada e umedecida. O material foi disposto em câmara de germinação sem iluminação interna por 20 dias sob temperatura de 40 ºC, seguido de 20 dias a 30 ºC. Após isoladas dos endocarpos, as sementes foram desbastadas e fixadas. Através de amostragens a cada cinco dias, foram caracterizados modificações anatômicas e a mobilização de reservas na semente. As sementes apresentam um envoltório (testa) com presença de estrias e no opérculo há presença de compostos fenólicos e ausência de lignina. O endosperma é homogêneo, branco e brilhante, com as células da região micropilar apresentando paredes espessas em relação ao restante do endosperma, sendo essas metabolizadas ao longo das amostragens. O embrião é pequeno, basal e apresenta a plúmula já diferenciada na primeira amostragem. Ao longo das amostragens e durante a manutenção dos pirênios sob temperatura de 40 ºC foi percebida a formação de uma zona de fragilidade no endosperma micropilar, o que, ao que tudo indica, está relacionado com a germinação. As reservas encontradas, as quais estavam presentes no endosperma e no embrião das sementes, foram: amido, polissacarídeos totais, lipídios totais, proteínas totais e compostos fenólicos na região opercular. A mobilização das reservas ocorreu antes mesmo do opérculo ser rompido. / The Butia genus comprises 20 species distributed mostly in southern South America. Butia odorata (Barb. Rodr.) Noblick is an endemic palm tree from the Pampa biome, with high food and ornamental potential. Its diaspore is composed of a pyrene which houses one to three seeds that have irregular and slow germination as a result of dormancy. It is known that there is a relationship between dormancy and seed operculum and its chemical composition can also be an aggravator. By removing this structure, seeds exhibit high germination percentage in a short period. The relationship between the operculum, as well as the influence of temperature on the germination period, is still unknown to B. odorata, since the morphoanatomical description of the species is incipient and its histochemical characteristics are unexplored. This study aimed to characterize the morphology of the dispersion structure and describe anatomical and histochemical features of B. odorata seeds when undergoing dormancy breaking treatment. Diaspores of natural populations were sown in gerbox on average washed, sterilized and moistened sand. The material was placed in a dark germination chamber for 20 days at 40 °C, followed by 20 days at 30 °C. Following this procedure, endocarps isolated from the seeds were chopped and fixed. By sampling every five days, anatomical changes and the mobilization of reserves in the seed were characterized. The seeds presented stretch marks in the involucre (seed coat or testa) and phenolic compounds with absence of lignin in the operculum. The endosperm is homogeneous, white and shiny, and the micropilar cells present thick walls, in relation to the rest of the endosperm, that were metabolized along the sampling. The embryo is small, basal and has differentiated plumule. While sampling at 40 °C the formation of a fragile zone in the micropilar endosperm was noted, which seems to be germination related. The reserves present in the endosperm and the embryo of seeds were: starch, total polysaccharides, total lipid, protein and phenolic compounds in the opercular region. The mobilization of reserves occurred even before the operculum was broken.