published_or_final_version / Pharmacology / Master / Master of Philosophy

No abstract available. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2003.

Ph.D. / Recent anatomical and molecular studies have highlighted the importance of the African and Malagasy Apiaceae, many of which have been found to occupy early diverging positions within the subfamilies Apioideae and Saniculoideae. Despite the recent interest in the African contingent however, there remain several anomalous and poorly known African and Malagasy taxa in which generic boundaries remain unclear and which have yet to be incorporated within the emerging tribal classification for the family. Generic circumscriptions and affinities amongst hitherto poorly known African and Malagasy genera are here explored using anatomical, cytological, morphological and molecular sequence data. Substantial rearrangements at almost all infrafamilial levels are formalized in order to incorporate the unique African and Malagasy members for the first time. Generic circumscriptions and phylogenetic relationships of the Cape genera Capnophyllum, Dasispermum, and Sonderina are explored through parsimony and Bayesian inference analyses of nrDNA ITS and cpDNA rps16 intron sequences, morphology, and combined molecular and morphological data. The relationship of these genera with the North African genera Krubera and Stoibrax is also assessed. Analyses of both molecular data sets place Capnophyllum, Dasispermum, Sonderina, and the only southern African species of Stoibrax (S. capense) within the newly recognized Lefebvrea Glade of tribe Tordylieae. Capnophyllum is strongly supported as monophyletic and is distantly related to Krubera. The monotypic genus Dasispermum and Stoibrax capense are embedded within a paraphyletic Sonderina. This complex is distantly related to the North African species of Stoibrax in tribe Apieae, in which the type species, Stoibrax dichotomum, occurs. Consequently, Dasispermum is expanded to include both Sonderina and Stoibrax capense. A taxonomic revision of Dasispermum s.l. is presented which includes keys to the species, complete nomenclature, typifications, descriptions as well as geographical distributions. New combinations are formalized for Dasispermum capense, hispidum, D. humile, and D. tenue. In addition two new species, namely D. grandicarpum and D. perrenans, are described. As a result seven species of Dasispermum s.l. are recognised and can be distinguished from one another by their habit (life history and growth form), leaf morphology (leaf texture, leaf colour and breadth of the ultimate leaflet segments), inflorescence structure (length of the peduncle, presence or absence and division of involucre and involucel bracts), fruit morphology (relative length of the styles, fruit size, rib prominence and relative orientation) and fruit anatomy (shape of the cells external to the vittae).

Thesis (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: There is increasing evidence that the rapid and anomalous changes in climate experienced in the last century have had widespread ecological impacts. Indeed, sub- Antarctic Marion Island has experienced particularly large increases in temperature and declines in rainfall. However, the effects of these changes on the island's extensive fellfield vegetation remain largely unexamined. The aim of this study was to examine the sensitivity of a dominant and keystone fellfield plant species, the cushion-forming Azorella selago Hook. (Apiaceae), to changes in climate. Three complementary approaches (two mensurate, one experimental) were used, and all showed that A. selago is likely to change in response to further changes in climate. First, the unimodal age class distribution of A. selago suggested that the species' establishment is episodic, and therefore reliant on specific (possibly climatic) conditions. Azorella selago growth rate was related to environmental factors, suggesting that both the establishment and growth rate of the species is likely to be sensitive to changes in climate. Second, altitudinal variation in A. selago plant attributes suggested that the species' morphology would be responsive to changes in climate (assuming that a spatial gradient in climate is a suitable analogue for similar changes in climate over time). Plant height, leaf size and trichome density differed most consistently over altitude across the island. The altitudinal range of some epiphyte species, as well as the cover and species richness of epiphytes growing on A. selago, also showed consistent patterns along the altitudinal gradient. These cushion plant and epiphyte attributes appeared to be related to climatic factors, and are therefore predicted to change in response to further shifts in climate. Finally, A. selago showed a rapid vegetative response to short-term experimental reductions in rainfall and increases in temperature and shading. Reduced rainfall accelerated autumnal senescence, shortening the species' growing season. Plants were relatively unaffected by the magnitude of warming imposed, although the foliar nutrient concentrations of some elements were higher in warmed plants than in control plants. Experimental shading of A. selago (simulating a predicted indirect effect of climate change: increased cover of the dominant epiphyte species, Agrostis magellanica (Lam.) Vahl (Poaceae)) caused greater stem elongation, and the production of larger, thinner leaves, with lower trichome densities and higher foliar nutrient concentrations of some elements. Given this sensitivity of A. selago to shading, it is possible that changes in epiphyte load could overshadow the direct effects of changes in climate on this species. Ongoing changes in climate are predicted for the next century. Based on the results of this study the following scenarios are proposed. Continued warming and drying of the island will potentially favour the upslope expansion of A. selago (although also shortening its growing season) and decrease the abundance of its dominant epiphyte. Under such a scenario fellfield primary production may decline. In contrast, under warming alone, most epiphyte species could increase in abundance and expand their altitudinal ranges upslope. This would bring about much heavier shading of A. selago plants, leading to a short-term increase in stem growth and leaf nutrient concentrations. However, ultimately a decline in A. selago abundance and production would also be expected if cushion plants experience stem mortality under longer-term shading. Nonetheless, monitoring A. selago leaf size, trichome density and phenology, as well as the altitudinal range of dominant epiphyte species (attributes that this research suggests may be most sensitive to short-term changes in climate), will indicate the biological consequences of these changes in climate. This study, therefore, shows that further climate changes on Marion Island will affect A. selago and its epiphytes, with likely repercussions for fellfield communities. / AFRIKAANSE OPSOMMING: Daar is toemende bewys dat die vinnige en onreëlmatige veranderinge in klimaat oor die laaste half-eeu wye ekologiese gevolge gehad het. Inderdaad, sub-Antarktiese Marion Eiland het 'n ook 'n besondere groot toename in temperature en daling in reënval ervaar. Nogtans is die gevolge van hierdie veranderinge op die eiland se uitgebreide dorveld (fellfield) plantegroei nog nie nagevors nie. Die doel van hierdie studie was om die sensitiwiteit van 'n dominante hoeksteen spesie, die kussingvormige Azorella selago Hook. (Apiaceae), aan veranderinge in klimaat te ondersoek. Drie aanvullende metodes (twee waarnemend, een eksperimenteel) was gebruik, en al drie het aangedui dat A. selago waarskynlik sal reageer op verdere veranderinge in klimaat. Eerstens, die enkelpiek-vormige ouderdomsverspreiding van A. selago dui daarop dat die spesie ongereeld vestig, en is daarom afhanklik van spesifieke (dalk klimatiese) toestande. Verder, was A. selago se groeitempo aan omgewingsfaktore verwant. As gevolg hiervan sal die spesie se vestiging en groeitempo vermoedelik sensitief vir klimaatsveranderinge wees. Tweedens, veranderinge in A. selago eienskappe met 'n toename in hoogte bo seespieël (hoogte) dui daarop dat die spesie se morfologie sal reageer op veranderinge in klimaatstoestande (op voorwaarde dat 'n ruimtelike verandering in klimaat goed ooreenstem met 'n soortgelyke verandering in klimaat oor tyd). Planthoogte, blaaroppervlakte en trigoomdigteid het geleidelik met hoogte verander oor die eiland. Die verspreiding en bedekking van sommige epifitiese spesies, asook epifiet spesie rykheid, was ook aan hoogteverwant. Hierdie verwantskap tussen A. selago (en die epifiete) en hoogte is vermoedelik deur klimatiese faktore veroorsaak, en daarom word voorspel dat dit sal verander soos die klimaat verander. Laastens, het A. selago 'n vinnige vegetatiewe reaksie tot korttermyn eksperimentele vermindering in reënval en toename in temperatuur en beskaduwing gewys. 'n Afname in reënval het blaarveroudering versnel, en dus A. selago se groeiseisoen verkort. Plante het min verander as gevolg van hoër temperature, alhoewel die konsentrasie van sommige plantvoedingstowwe hoër was in blare van verwarmde plante as in die wat gewone temperature ervaar het. Eksperimentele beskaduwing van A. selago (wat 'n verwagde indirek effek van klimaatsverandering naboots, naamlik die toename in bedekking van A. selago deur die dominante epifiet spesie, Agrostis magellanica (Lam.) Vahl (Poaceae)) het stingel groei versnel, en veroorsaak dat groter en dunner blare met laer trigoomdigthede en hoër konsentrasies van sommige plantvoedingstowwe op die plante groei. As gevolg van die sensitiwiteit van A. selago op beskaduwing, is dit moontlik dat die gevolge van veranderinge in die bedekking van epifiete belangriker sal wees as die direkte gevolge van klimaatsverandering. Verdere klimaatsveranderinge word vir die volgende eeu voorspel. Gebasseer op die resultate van hierdie navorsing, word twee moontlike toekomstige omstadighede voorgestel. Toenemende verwarming en verdroging van die eiland sal vermoedelik veroorsaak dat A. selago op hoër hoogtes voorkom (alhoewel die spesie se groeiseisoen ook sal verkort), en dat die volopheid van A. magellanica sal afneem. In so 'n geval sal dorveld se plantproduksie waarskynlik effens verminder. In teenstelling, as die eiland slegs verwarm (sonder 'n verandering in reënval) kan die volopheid en verspreiding van epifiet spesies waarskynlik toeneem. Dit sal vermoedelik tot 'n toename in the verskaduwing van A. selago lei, wat tot 'n kort-termyn verhoging van stingel groeitempo en plantvoedingstof konsentrasies sal lei. Alhoewel, uiteindelik, word 'n vermindering van A. selago volopheid en groei verwag as plantstingels van lang-termyn beskaduwing vrek. Nietemin, as die blaargroote, trigoomdigteid en groeiseisoenlengte van A. selago en die hoogte verspreiding van die dominante epifiet spesie gemonitor word (eienskappe wat deur hierdie studie aangedui is as gevoelig aan kort-termyn veranderinge in klimaat), kan die biologiese gevolge van hierdie klimaatsveranderinge aangewys word. Hierdie navorsing bewys dus dat verdere veranderinge in klimaat op Marion Eiland 'n invloed sal hê op A. selago en geassosieerde epifiete, met moontlike gevolge vir die hele dorveld gemeenskap.

Made available in DSpace on 2014-06-12T16:27:09Z (GMT). No. of bitstreams: 2 arquivo1172_1.pdf: 2079949 bytes, checksum: 939b3a302bb35eb64c2f54f2b04e5768 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2010 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Foeniculum vulgare Mill, família Umbelliferae/Apiaceae, é uma erva aromática bienal, de folhas invaginantes verde-amareladas e com flores amarelas que se reúnem em umbelas. Conhecida pelo nome de funcho, falso anis e erva-doce-brasileira, é nativo na Europa mediterrânea, norte da África e Ásia ocidental, sendo amplamente cultivada em todo o Brasil. Seu uso é difundido na medicina tradicional de muitos países para o tratamento de várias doenças como: desordens digestivas e problemas menstruais, sendo também empregada como: analgésico, diurético, expectorante, lactígeno, antiinflamatório e antiespasmódico. Este trabalho teve como objetivo avaliar a toxicidade aguda, atividade farmacológica (antinociceptiva em roedores), realizar um estudo fitoquímico, bem como identificar a atividade antimicrobiana dos extratos da semente de Foeniculum vulgare Mill. Os ensaios de toxicidade aguda foram realizados por via oral e intraperitoneal, com observações das respectivas alterações comportamentais para cada dose administrada. Os resultados demonstraram pela via intraperitoneal efeitos estimulantes e depressores; e via oral demonstraram baixas reações comportamentais. Os resultados indicaram que a DL50 de Foeniculum vulgare Mill foi 3g/kg via intraperitoneal. Para a avaliação da atividade antimicrobiana, in vitro, usou-se o método de difusão em disco de papel. Os resultados obtidos mostraram que os extratos testados foram ativos apenas frente à bactérias Gram-positivas, não inibindo bactérias Gram-negativas e levedura, apresentando melhores resultados o extrato acetato de etila. O estudo fitoquímico foi realizado em cromatografia de camada delgada e identificou a maioria dos compostos secundários presentes na fração metanólica, foram observados: triterpenos, glicosídeos de flavanóides, terpenos menores (monoterpenóides, sesquiterpenóide e diterpenóides) e açucares redutores. Para a atividade antinociceptiva utilizou-se o modelo de contorções abdominais induzida pelo ácido acético e os resultados demonstraram que apenas a dosagem de 298 mg/Kg comparado ao padrão conseguiu uma redução significativa no número de contorções. O extrato etanólico das sementes de Foeniculum vulgare Mill não indicou evidências da toxicidade oral, porém apresentou moderada toxicidade intraperitoneal. Estudos posteriores devem ser realizados para a identificação e isolamento de alguns compostos secundários, bem como a realização de outros protocolos de analgesia e atividade antimicrobiana

D.Phil. (Biochemistry) / Plants are able to recognise and respond to signals from the environment through a complex array of biochemical pathways, which enables them to deter pathogenic micro-organisms and herbivores. Thousands of different structures of low-molecular weight organic compounds / natural products can be produced through an inducible chemical defence system; that can be manipulated for biotechnological purposes. The importance of natural products in medicine, agriculture and industry has led to numerous studies such as this, to understand the biosynthesis and biological activity of these substances...

Dissertation (PhD)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: The spatial distribution of animals and plants at different scales is a central theme in ecology. Knowledge of biodiversity distribution is essential, especially with the current threat of climate change and invasion by alien species. Since the impact of climate change and alien species will be, and has already been pronounced in polar regions, information on the current spatial distributions of biota in these regions is critical to predict the consequences of climate change and alien species on the future survival, distribution and abundance of indigenous biota. This study was conducted on the sub- Antarctic Prince Edward Islands (consisting of Marion Island and Prince Edward Island), which have experienced rapid climate changes over the past 50 years. Additionally, a number of alien plant, vertebrate and invertebrate (also microarthropod) species have been introduced to these islands. Since microarthropods (mites and springtails) play an essential role in decomposition and mineralization of plant material on the islands, the loss of microarthropods from decomposer communities might have disastrous results for ecosystem processes. Therefore it is essential to know the current distributions of microarthropods in order to predict future distributions patterns in reaction to climate change and invasive species. In this study, the spatial distribution of mites and springtails inhabiting the cushion plant Azorella selago Hook, were examined at different scales of observation. Firstly, the microarthropod community was examined at a fine scale. The relationship between microarthropod species richness and abundance and plant size, isolation, within-plant variability, grass cover and microclimate variables were investigated. Thereafter, the spatial variability of microarthropod abundances was examined within stands of plants, with statistical methods using varying degrees of locational information to determine if microarthropod abundance is random, regular or aggregated at this scale. Further, the spatial variability of microarthropod communities in A. selago at different altitudes and on different sides of Marion Island, i.e. island-wide scale, was examined. The last scale of observation was the island-wide scale, in which microarthropod assemblages were compared between Marion Island and Prince Edward Island, as well as in different plant species. Microarthropods showed spatial heterogeneity within A. selago plants (higher abundances in eastern and southern sides of plants), island-wide (lower springtail abundance on the eastern side of the island and at high altitudes) and between islands (more alien species on Marion Island). In contrast, microarthropod abundance was not spatially heterogeneous within a stand of plants, i.e. mostly randomly distributed. The possible mechanisms responsible for these patterns differ between scales, and range from temperature and nutrient availability at the within plant and island wide scale to alien species between islands. Climate change is likely to alter these distribution patterns of microarthropods, either directly (unfavourable climate for indigenous species growth, development and dispersal) or indirectly (favouring alien microarthropod species; increase in grass cover on A. selago plants may alter community structure). The information presented here, is essential for predicting the possible impacts of climate change on microarthropods in fellfield ecosystems on sub-Antarctic islands. / AFRIKAANSE OPSOMMING: Die ruimtelike verspreiding van diere en plante op verskillende skale is ‘n sentrale tema in ekologie. Kennis van die verspreiding van biodiversiteit is belangrik, veral met die huidige bedreiging van klimaatsverandering en indringerspesies. Omdat die impak van klimaatsverandering en indringerspesies in die poolstreke alreeds duidelik is en nog meer so sal word, is inligting oor die huidige ruimtelike verspreiding van biota in hierdie streke noodsaaklik. Hierdie studie is op die sub-Antarktiese Prins Edward-eilande (bestaande uit Marion Eiland en Prins Edward Eiland) uitgevoer, waar die klimaat vinnig verander het oor die afeglope 50 jaar. Bykomend is ‘n aantal indringer plant, vertebraat en invertebraat (ook mikroartropood) spesies op die eilande ingebring. Omdat mikroartropoda (myte en springsterte) ‘n baie belangrike rol in ontbinding en mineralisering van plantmateriaal op hierdie eilande speel, sal die verlies van mikroartropoda uit die ontbindingsgemeenskap rampspoedige gevolge vir die prosesse in die ekosisteem hê. Kennis van die huidige verpreiding van mikroartropoda is dus noodsaaklik om die toekomstige verspreidingspatrone, asook oorlewing en volopheid van inheemse spesies in reaksie op klimaatsveranding en indringerspesies, te voorspel. In hierdie studie is die ruimtelike verspreiding van myte en springsterte wat in die kussingplant Azorella selago Hook voorkom, op verskillende ruimtelike skale ondersoek. Eerstens is die mikroartropood gemeenskap op ‘n klein skaal ondersoek. Die verwantskap tussen mikroartropood spesies rykheid en volopheid en plantgrootte, isolasie, binne-plant variasie, gras bedekking en mikroklimaat faktore is ondersoek. Daarna is die ruimtelike variasie van mikroartropood volopheid binne in ‘n plantstand ondersoek deur gebruik te maak van metodes wat verskillende grade van ligging data gebruik. Dit is gedoen om uit te vind of mikroartropood volopheid lukraak, reëlmatig of versameld verspreid is. Verder is die ruimtelike verspreiding van mikroartropood gemeenskappe in A. selago op verskillende hoogtes bo seespieël en op verskillende kante van Marion Eiland ondersoek. Laastens is die mikroartropood gemeenskap op Marion Eiland en Prins Edward Eiland, asook die gemeenskap in verskillende plant spesies vergelyk. Mikroartropoda is ruimtelik heterogeen verspreid binne-in A. selago (meer individue in die oostelike en suidelike kante van plante), asook regoor Marion Eiland (minder springstert individue aan die ooste kant van die eiland asook minder op hoë hoogtes bo seespieël) en tussen eilande (meer indringerspesies op Marion Eiland). In teenstelling hiermee is mikroartropood volopheid ruimtelik homogeen oor ‘n plantstand, dus meestal lukraak verspreid. Die meganismes wat moontlik vir hierdie patrone verantwoordelik is wissel van temperatuur en voedselbeskikbaarheid op die binne-plant en oor die eiland skaal tot indringerspesies op die tussen-eiland skaal. Klimaatsverandering mag waarskynlik mikroartropood verspreidingspatrone direk (ongunstige klimaat vir inheemse spesies se groei, ontwikkeling en verspreiding), of indirek verander (indringer spesies word begunstig; toename in grasbedekking bo-op A. selago mag die gemeenskapstruktuur van mikroartropoda verander). Hierdie inligting is belangrik vir die voorspelling van die moontlike impak van klimaatsverandering op mikroartropoda in klipveld ekosisteme op sub-Antarktiese eilande.

Thesis (MSc)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: Understanding the responses of species to climate change is a scientific problem that requires urgent attention, especially under current conditions of global climate change. The large and rapid rates of climate change reported for sub-Antarctic Marion Island makes the island highly suitable for studying the biotic consequences of climate change. Furthermore, the extreme environments on the island result in a close coupling of the biotic (e.g. population dynamics) and abiotic (e.g. climate) factors. Therefore, examining the response of the dominant and keystone plant species on the island, Azorella selago Hook. (Apiaceae), to climate-associated environmental change (e.g. temperature) may provide insight into how A. selago and the associated species communities will be affected by climate change. This study described the variability in microclimate temperatures associated with A. selago across altitudinal gradient and between the eastern and western sides of Marion Island. Microclimate temperatures were also compared to the island’s Meteorological data to determine variation between temperatures experienced by A. selago cushion-plants in the field and those recorded at the island’s Meteorological Station. Temperature variation inside and outside A. selago cushions was also examined. Azorella selago cushions were found to have a buffering effect on temperature, such that species occurring epiphytically on A. selago experience more moderate temperatures than the surrounding environment. However, A. selago were found to experience more extreme temperatures than temperatures recorded at the Meteorological Station. Therefore, A. selago may possibly experience greater environmental warming than recorded by the Meteorological Station. While temperatures decline with altitude, temperature conditions on the western side of the island were more temperate than the eastern side. This presents the first record of temperature conditions on the western side of the island. This study also quantified fine-scale (e.g. within-site) and broad-scale (e.g. island-wide) variability patterns of A. selago (morphology, phenology, and epiphyte load) across Marion Island. Altitudinal gradient and climatic exposure at different sides of the island were used to understand the likely effects of climate associated environmental change on this dominant component of the fellfield habitat. Site-specific processes were found to determine the spatial structure of A. selago characteristics at fine-scales. However, broad-scale observations established strong responses of A. selago characteristics to altitudinal gradients and different sides of the island. Azorella selago morphological features (e.g. plant size and leaf size) were found to be more responsive to differences between the eastern and western sides of the island than to altitudinal gradient. Azorella selago micro-morphological features (e.g. leaf trichomes and stomatal densities) were also found to be more responsive to climatic exposure at different sides of the island than to altitudinal gradient. However, differences in A. selago epiphyte density (e.g. Agrostis magellanica) and phenology resembled microclimate temperatures in that they were more responsive to altitudinal gradient than to side of the island differences. From these results it can therefore be predicted that the A. selago of Marion Island is likely to be morphologically fairly resilient to moderate climatic shifts, although at lower altitudes and on the eastern side of the island, it may be outcompeted by the epiphytic grass, Agrostis magellanica. The results also suggest that the warming climate of Marion Island may result in an early occurrence of phenological processes particularly at lower altitudes and the eastern side. Azorella selago at lower altitudes and on the eastern side of Marion Island are therefore expected to largely show more symptoms of climate change (e.g. warming) on this species. Azorella selago is also predicted to move up altitudinal gradients in response to warming. / AFRIKAANSE OPSOMMING: ’n Begrip van hoe spesies reageer op klimaatsverandering is ’n wetenskaplike vraag wat onmiddellike aandag benodig, veral onder huidige globale klimaatsverandering. Die groot en snelle tempo waarteen klimaatsverandering waargeneem word op sub-Antarktiese Marion Eiland, maak die eiland hoogs geskik om die biotiese gevolge van klimaatsverandering te bestudeer. Verder veroorsaak die uiterste omgewing van die eiland tot ’n nabye koppeling tussen die biotiese (bv. populasie dinamika) en abiotiese (bv. klimaat) faktore. Dus, deur die reaksies van ’n dominante- en sleutel-spesie op die eiland, Azorella selago Hook. (Apiaceae), op klimaat-geassosieerde omgewings verandering (bv. temperatuur) te bestudeer, mag insig verskaf hoe A. selago en geassosieerde spesie gemeenskappe geaffekteer sal word deur klimaatsverandering. Hierdie studie beskryf die wispelturigheid in mikroklimaat temperature geassosieer met A. selago oor ’n hoogte gradiënt asook tussen die oostelike en westelik dele van Marion Eiland. Mikroklimaat temperature was ook vergelyk met die eiland se Meteorologiese data met die doel om die mate van variasie tussen temperature verduur deur A. selago kussing-plante in die natuurlike omgewing met die van die eiland se Meteorologiese stasie te vergelyk. Temperatuur variasie binne en buite A. selago kussing-plante is ook vasgestel. Dit was gevind dat Azorella selago kussing-plante die temperatuur buffer, met die gevolg dat spesies wat epifities op A. selago voorkom, meer gematigde temperature ondervind as die onmiddellike omgewing om die plant. Daar is egter gevind dat A. selago meer uiterste temperature ondervind as temperature gemeet by die Meteorologiese stasie. Dus mag A. selago groter omgewings verwarming ervaar as wat temperature gemeet by die Meteorologiese stasie dui. Terwyl temperatuur afneem met ’n toename in hoogte, was temperatuur aan die westekant van die eiland mere gematig as die oostekant. Dit verskaf die eerste rekord van temperatuur toestande aan die westekant van die eiland. Hierdie studie bepaal ook die fyn-skaal (e.g. binne-terrein) en groot-skaal (e.g. oor die eiland) variasie patrone van A. selago (morfologie, fenologie, en epifiet lading) oor Marion Eiland. Die hoogte gradiënt en klimaat blootstelling aan verskillende kante van die eiland is gebruik om die waarskynlike effekte van klimaats-geassosieerde omgewings verandering op die dominante deel van die felfield habitat te verstaan. Daar is gevind dat terrein spesifieke prosesse die ruimtelike struktuur van A. selago se klein-skaal eienskappe bepaal. Groot-skaalse waarnemings dui egter ’n sterk antwoord van A. selago eienskappe op die hoogte gradiënt en aan verskillende kante van die eiland. Azorella selago morfologiese eienskappe (e.g. plant- en blaar grootte) is gevind om meer te reageer op verskille tussen oostelike en westelike kante van die eiland as op die hoogte gradiënt. Azorella selago mikromorfologiese eienskappe (e.g. blaar trigome en stomata digtheid) is ook gevind om meer te reageer op omgewings blootstelling tussen verskillende kante van die eiland as op die hoogte gradiënt. Verskille in A. selago epifiet digtheid (e.g. Agrostis magellanica) en fenologie het egter mikroklimaat temperature gevolg, in dat beide meer gereageer het op die hoogte gradiënt as eiland-kant verskille. Hierdie resultate voorspel dus dat dit waarskynlik is dat A. selago van Marion Eiland morfologies redelik terugspringend sal wees ten opsigte van matige klimaatsverandering, al mag dit uitgekompeteer word deur die epifitiese gras, Agrostis magellanica by lae hoogtes en aan die oostekant van die eiland. Hierdie resultate dui ook dat verwarming van Marion Eiland se klimaat ’n vervroeging van fenologiese prosesse mag hê, veral by lae hoogtes en aan die oostekant van die eiland. Dus word dit verwag dat Azorella selago by lae hoogtes en aan die oostekant van Marion Eiland om meer simptome van klimaatsverandering (e.g. verwarming) te dui. Dit word ook voorspel dat Azorella selago opwaarts teen die hoogte gradiënt sal beweeg in reaksie tot verwarming.

Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Climate has shown some remarkable changes over the past century, especially at the polar and sub-polar regions. Southern Ocean Islands provide good models for studies related to climate change effects, since effects may be evident in the short term and may also be clearer. Marion Island is an example of such a system with a harsh abiotic environment, and low species richness often vulnerable to change. Climate change is predicted, and also reported, to have biological consequences on plant communities, affecting the phenology, morphology, and the interaction between individuals and species. This study examines the association between the keystone plant species, Azorella selago Hook. (Apiaceace), and its dominant epiphyte Agrostis magellanica Lam. (Poaceae). Two complimentary approaches were used, one observational and the other experimental. The main objective for the observational study was to quantify bioticallyrelevant microclimate temperature, as well as the morphology, epiphyte load and phenology of A. selago at three different altitude sites on Marion Island. This provided information on baseline variation for understanding specific variability in plant response to the experimental part of this study, against which future patterns arising from biological monitoring can be compared. Studying plants at different altitudes provides a possible analogue for temperature-related climate change consequences for the ecology of A. selago, and its interaction with A. magellanica. The microclimate temperature associated with A. selago differed between the three sites examined. This difference was related to local topographic conditions and altitude differences. Cushion size differed distinctively between the three altitude sites, with this difference related to environmental heterogeneity such as differences in age and substrate structure. Azorella selago annual growth rate was estimated through stem length and the number of leaves on both exposed and shaded stems. Within-site variability, as well as epiphyte cover were found to be the contributing factors on A. selago annual growth rate. This highlights the importance of site-specificity when estimating growth rate within and between different altitude sites. Leaf characteristics differed between the sites, with this attributed to local habitat conditions, such as topography, as well as epiphyte cover. As expected, the difference in leaf size between exposed and shaded leaves demonstrated a larger specific leaf area on leaves shaded by A. magellanica. Agrostis magellanica abundance and density were altitudinally related, with A. selago demonstrating facilitation effects on A. magellanica. The trend shown in this study suggests that in spite of general facilitative effect of A. selago on A. magellanica towards higher altitudes, the abiotic environmental threshold for A. magellanica occurs at lower altitudes than it does for A. selago. Phenological differences were also apparent between the three sites. The objectives of the experimental part of this study were to quantify the effect of the dominant epiphyte, A. magellanica on biotically-relevant microclimatic temperatures, as well as on the phenology and physical condition of A. selago. Different treatments were applied to cushions at the three altitude sites to examine the shading effect of epiphytic A. magellanica on cushion plants, as well as the effect of treatment-related disturbance. Azorella selago microclimate temperature showed no significant difference between treatments, suggesting that on average epiphytic A. magellanica cover has no effect on cushion microclimate temperature. The percentage of flower budding and flowering of A. selago was negatively related to epiphyte cover. Cushion vitality was also responsive to epiphyte cover, with higher vitality scores on low grass covered cushions than on high grass cushions. This shows that A. magellanica competes with A. selago, while A. selago facilitates A. magellanica. Heavy epiphyte numbers impose negative effects on A. selago vegetative and reproductive performance, as well as cushion vitality. Therefore, the results of this research show that the vegetative and reproductive performance of A. selago and cushion vitality are likely to be negatively affected under ongoing climate change on Marion Island if this brings about heavier epiphyte loads on this keystone cushion plant species. / AFRIKAANSE OPSOMMING: In die afgelope eeu het die klimaat in die Antarktiese en sub-Antarktiese gebiede merkwaardige verandering getoon. Die Suidelike See Eilande dien as goeie modelle vir studies verwant aan die gevolge van klimaatsverandering, aangesien die kort termyn effekte in die gebiede duideliker mag wees in die toekoms. Marion Eiland is ‘n voorbeeld van so ‘n sisteem, met ‘n ruwe abiotiese omgewing en lae spesies rykheid, wat vatbaar is vir verandering. Daar word voorspel, en is reeds bevind dat klimaatsverandering biologiese gevolge op plant gemeenskappe het, in terme van morfologie, fenologie en die interaksie tussen individue en spesies. Hierdie studie ondersoek die assosiasie tussen die hoeksteen plant spesie, Azorella selago (Apiaceace), en sy dominante epifietiese gras, Agrostis magellanica Lam. (Poaceae). Die studie is op twee komplimentêre maniere benader, naamlik deur waarneming en eksperiment. Die hoof doel van die studie was om die biotiese belang van mikroklimaat temperatuur te kwantifiseer, en die hoeveelheid epifiete, die morfologie en die fenologie van A. selago te bepaal by drie verskillende hoogtes op Marion Eiland. Laasgenoemde het inligting verskaf oor die variasie in die reaksie van plante tot die eksperimentele aspek van die studie, waarteen patrone vanaf toekomstige biologiese beheer vergelyk kon word. Deur plante te bestudeer by verskillende hoogtes bo seespieël word ‘n moontlike analoog vir die gevolge van temperatuur-verwante klimaatverandering in terme van die ekologie van A. selago, en laasgenoemde se interaksie met A. magellanica verskaf. Die mikroklimaat temperatuur geassosieer met A. selago verskil tussen dié drie liggings. Die versil was verwant aan die plaaslike topografiese toestande en die verskillende hoogtes bo seespieël. Die grootte van die kussingplante het duidelik versil tussen die drie liggings, met die verskille verwant aan die omgewing se heterogeneïteit, byvoorbeeld die verskille in ouderdom en substraat struktuur. Azorella selago se jaarlikse groeitempo was bepaal deur die stingel lengte en die aantal blare, op beide die wat oorskadu is deur die gras, en die was nie oorskadu is nie. Daar is gevind dat die faktore wat bygedra het tot die jaarlikse groeitempo van A. selago, varieër binne die verskillende liggings, en bedekking deur epifiete. Dit beklemtoon die belang van spesifisiteit van ligging wanneer groeitempo in en tussen die liggings van verskillende hoogtes bepaal word. Die blaar eienskappe het verskil tussen verskillende liggings, as gevolg van plaaslike habitat toestande, soos topografie en bedekking deur epifiete. Soos verwag, het die blare wat oorskadu was deur A. magellanica ‘n groter spesifieke blaar area getoon as blare wat blootgestel was. Die hoeveelheid en digtheid van Agrosits magellanica was verwant aan hoogte bo seespieël, met A. selago wat fasiliterende effekte toon op A. magellanica. Die tendens waargeneem in hierdie studie is dat ten spyte van die algemene fasiliterende effek van A. selago op A. magellanica, die abiotiese omgewingsdrempel op ‘n laer hoogte is vir A. magellanica as vir A. selago. Fenologiese verskille was ook duidelik tussen die drie liggings. Die doel van die eksperimentele deel van die studie was om die effek van die dominante epifiet, A. magellanica, te bepaal op bioties relevante mikroklimaat temperature, asook op die fenologie en fiesiese toestand van A. selago. Verskeie behandelings is aangewend op die kussingplante by die drie liggings om die effek van skaduwee van die epifietiese A. magellanica op die plante te bepaal, asook die effek van versteurings versoorsaak deur die behandelings. Azorella selago se mikroklimaat temperatuur het geen betekenisvolle verskille tussen behandelings getoon nie, wat voorstel dat epifitiese A. magellanica oor die algemeen geen effek op die kussingplante se mikroklimaat temperatuur het nie. Daar was ‘n negatiewe verwantskap tussen die hoeveelheid epifiete op A. selago en die persentasie blomme en blomknoppe op die kussingplante. Die plante se vitaliteit was ook afhanklik van epifiet bedekking, met ‘n hoër vitaliteit telling vir kussingplante bedek met lae gras as die bedek met hoë gras. Dit toon dat A. magellanica met A. selago wedywer, terwyl A. selago vir A. magellanica fasiliteer. Hoë epifiet getalle het negatiewe effekte op A. selago se vegetatiewe en reproproduktiewe nakoming, asook die kussingplante se vitaliteit. Die resultate van hierdie studie toon dus dat die vegetatiewe en reproduktiewe nakoming van A. selago en kussingplant vitaliteit heel moontlik negatief geaffekteer sal word indien klimaatsverandering op Marion Eiland hoër epifiet getalle op die sleutel kussingplant spesie tot gevolg sal hê.