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Thesis (MSc)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Macroecological relationships have rarely been studied at wide spatial scales and across geographic ranges of species in the field in the sub-Antarctic. In this thesis I examined the occupancy, distribution and abundance, and the relationships thereof, of indigenous plants and alien species at broad (island-wide) and fine scales across sub-Antarctic Marion Island. The impacts of alien species and their interactions with indigenous plants were also investigated. I examined the nature of the abundance structure of a cushion-forming, vascular plant, Azorella selago, at the island-wide scale. Moreover, the hypothesis that species reach their highest abundances at the centre of their geographic range and decline in abundance towards the range edges was tested. Azorella selago cushions were counted in 8 m x 8 m quadrats, placed regularly at 1 minute latitude and longitude intervals across Marion Island. Using spatially non-explicit and explicit methods, this study showed that the abundance structure of A. selago had a more complex pattern of high abundance patches and low abundance gaps in its island-wide distribution. Subsequently, the hypothesis of an abundant centre distribution was not supported for A. selago across Marion Island. Rather, there were sharp discontinuities at both the coastal and altitudinal (667 m a.s.l.) limits for the species, between which little pattern in altitudinal abundance structure existed. Mice (Mus musculus) have recently been found to cause extensive structural damage to A. selago. The structural influence of mice on vegetation structure at the landscape scale has largely been overlooked on many sub-Antarctic islands. I mapped the distribution of evidence of mouse damage within the cushions of A. selago across the island using systematic (at 1 minute latitude and longitude intervals) and opportunistic sampling. Approximately 40 % of the systematically sampled sites had evidence of mouse damage to A. selago. Furthermore, a third of cushions in opportunistically sampled sites was damaged. Mouse damage was high in sites of low A. selago abundance, emphasizing that impacts of mice may be greater in low cushion abundance areas. This damage sometimes led to the disintegration of entire cushions. Given that A. selago acts as a nurse plant and supports high abundances of indigenous invertebrates, the impacts of mice on this keystone species may have significant ecological implications. Studies on interactions between alien and indigenous plants are limited within the sub-Antarctic. I examined the fine-scale distributions and co-occurrences of alien plants, Agrostis stolonifera and Sagina procumbens, and the indigenous Acaena magellanica (in 2 m x 2 m plots, subdivided into 0.25 m x 0.25 m quadrats) along rivers on Marion Island. Environmental variables were important for the occurrence of these species. In particular, 42.95 % and 24.82 % of the deviance in the occurrence of A. stolonifera and S. procumbens, respectively, was explained by environmental variables, compared to 17.35 % for A. magellanica. Furthermore, the co-occurrence of A. magellanica with A. stolonifera was significantly influenced by environmental variables. Significant positive spatial associations between A. magellanica and A. stolonifera were found, while the interactions of either species with S. procumbens were either spatially dissociated or random. Therefore, this study highlighted that alien species are responding to different environmental variables and conditions on Marion Island. Sagina procumbens seems to be less sensitive to the island’s environmental conditions and may thus be affecting biodiversity at broader ranges. This thesis provides unparalleled data on the distributions and interactions of indigenous plants and alien species for Marion Island. Alien species are undoubtedly posing significant threats to indigenous plants on the island and this thesis presents insight into interactions of species, specifically plants, an approach underrepresented in the sub-Antarctic to date. / AFRIKAANSE OPSOMMING: Makro-ekologiese verhoudings is selde bestudeer op wye ruimtelike skale en oor geografiese gebiede van spesies in die veld in die sub-Antarktiek. In hierdie tesis het ek die digtheid, bewoning, verspreiding en die verhoudings daarvan, van inheemse plante en uitheemse spesies ondersoek op breë (eiland-wyd) en smal skale oor sub-Antarktiese Marion Eiland. Die impakte van uitheemse spesies en hul interaksies met inheems plante is ook ondersoek. Ek het die aard van die digtheidstruktuur ondersoek van 'n kussing-vormende, vaatplant, Azorella selago, op die eiland-wydte skaal. Bowenal is die hipotese dat spesies hul hoogste digtheid bereik in die sentrum van hul geografies gebied en afneem in digtheid na die grense van die gebied getoets. Azorella selago kussings is getel in 8 m x 8 m kwadrante, wat eweredig geplaas is op 1 minuut breedte- en lengtegraad intervalle oor Marion Eiland. Deur gebruik te maak van ruimtelik nie-eksplisiete en eksplisiete metodes, het hierdie studie getoon dat die digtheidstruktuur van A. selago ‘n meer komplekse patroon van hoë digtheidslaslappe en lae digtheidsgapings in sy eiland-wyd verspreiding het. Vervolgens is die hipotese van 'n digte sentrum verspreiding nie gesteun vir A. selago oor Marion Eiland nie. Daar was eerder skerp diskontinuïteite by beide die kus- en hoërliggende (667 m bo seespieël) grense vir die spesie, waartussen daar ’n oneweredige patroon in digtheidstruktuur bestaan het. Onlangs is bevind dat muise (Mus musculus) uitgebreide struktuele skade aan A. selago veroorsaak. Die struktuele invloed van muise op plantegroei struktuur op landskapskaal is grootliks oor die hoof gesien op baie sub-Antarktiese eilande. Ek het die verspreiding van die bewyse van muisskade binne die kussings van A. selago oor die eiland gekarteer deur gebruik te maak van sistematiese (tot 1 minuut breedte- en lengtegraad intervalle) en opportunistiese opnames. Ongeveer 40 % van die sistematiese opname kwadrante het bewyse van muis skade aan A. selago vertoon. Verder, ‘n derde van die kussings in die opportunistiese opname kwadrante was beskadig. Muisskade was hoog in plotte met lae A. selago volopheid, wat beklemtoon dat impakte van muise groter mag wees in lae kussing digtheid gebiede. Hierdie skade het partykeer gelei tot die verbrokkeling van hele kussings. Gegewe dat A. selago as 'n verpleegsterplant optree en ’n hoë digtheid van inheemse invertebrata ondersteun, mag die impakte van muise op hierdie hoeksteen spesie beduidende ekologiese implikasies tot gevolg hê. Studies oor interaksies tussen uitheemse- en inheemse plante is beperk in die sub-Antarktiese gebied. Ek het die smal-skaal verspreidings ondersoek en medevoorkoms van uitheemse plante, Agrostis stolonifera en Sagina procumbens, en die inheems Acaena magellanica (in 2 m x 2 m kwadrante, subverdeel in 0. 25 m x 0. 25 m kwadrante) langs riviere op Marion Eiland. Omgewingsveranderlikes was belangrik vir die voorkoms van hierdie spesies. In besonder, 42.95 % en 24.82 % van die afwykings in die voorkoms van A. stolonifera en S. procumbens, onderskeidelik, is verduidelik deur omgewingsveranderlikes, vergeleke met 17.35 % vir A. magellanica. Verder, die medevoorkoms van A. magellanica saam met A. stolonifera is beduidend beinvloed deur omgewingsveranderlikes. Beduidende positiewe ruimtelike assosiasies tussen A. magellanica en A. stolonifera is gevind, terwyl die interaksies van beide spesies met S. procumbens was of ruimtelik nie-geassosieerd of lukraak. Daarom het hierdie studie uitgelig dat uitheemse spesies reageer op verskillende omgewingsveranderlikes op Marion Eiland. Sagina procumbens blyk minder sensitief te wees tot die eiland se omgewingsomstandighede en mag dus moontlik biodiversiteit op breër vlakke beïnvloed. Hierdie tesis voorsien onge-ewenaarde data oor die verspreiding en interaksies van inheems plante en uitheemse spesies vir Marion Eiland. Uitheemse spesies hou ongetwyfeld ’n beduidende bedreiging in vir inheems plante op die eiland, en hierdie tesis bied insig in die interaksies van spesies, spesifiek plante – ’n benadering wat swak verteenwoordig was in die sub-Antarktiese gebied tot op hede.

Leptosporangiate ferns, with more than 9000 extant species, are truly exceptional among the non-flowering lineages of vascular plants. However, this rather remarkable diversity was not simply a consequence of being able to "hold on" as flowering plants rose to dominance. Instead, it appears to be the result of an ecological opportunistic response to the establishment of more complex, angiosperm-dominated ecosystems. The proliferation of flowering plants across the landscape undoubtedly resulted in the formation of a plethora of new niches into which leptosporangiate ferns could diversify. Many of these were evidently on shady forest floors, but many others were actually within the new angiosperm-dominated canopies. Today, almost one third of leptosporangiate species grow as epiphytes on angiosperm trees. My dissertation aims to demystify the evolution and diversification of epiphytic ferns in order to more fully understand the leptosporangiate success story. By assembling and analyzing the most inclusive molecular dataset for leptosporangiate ferns to date, I provide unprecedented insight into overall fern relationships and a solid and balanced phylogenetic framework within which the evolution of epiphytism can be examined. By employing this phylogeny and numerous constraints from the fern fossil record, I uncover the timing of epiphytic fern diversification and examine the origin of the modern tropical rain forest biome in which these ferns reside. / Dissertation

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Alpine tundra is notorious for its fragility and slow recovery following disturbance. Tourism is increasing in alpine areas, creating the need to improve our understanding of the impacts of recreation in these ecosystems. This study examined the impacts of hiking and off-highway vehicle use on the vascular flora of dry alpine meadows in the Canadian Rockies by comparing community data, including rare plant distributions, on recreational trails, on intact tundra meadows, and on sparsely vegetated gravel steps formed by frost disturbance. The trails were found to be different from both undisturbed and naturally disturbed tundra in terms of vascular plant cover, diversity, species composition and soil compaction. Rare plants do not seem to be adversely affected by recreational activities. Trampling leads to environmental conditions that will likely make regeneration of abandoned trails an extremely slow process, and it is advisable to limit the extent of trail networks in alpine areas. / Conservation Biology

abstract: This study identifies the flora of the Eagletail Mountain Region, an area covering approximately 100,600 acres, located in west-central Arizona that includes the Eagletail Mountains, Granite Mountains, portions of the Harquahala Valley, and Cemetery Ridge near Clanton Well. The region is located about 129 km (80 mi) west of Phoenix and 24 km (15 mi) south of Interstate 10. Plants were collected over a six-year period, beginning September, 2004 and ending May, 2010, including two wet winters and two wet summers. A total of 702 collections were made covering 292 species that represented 63 families. Additional information on the region included in the thesis are: 1) an analysis of the climate, based on 20 years of rainfall records; 2) a description of the geology and its influence on plant distribution; 3) a prehistory and history identifying archeological sites; 4) an analysis of food plants used by the Native Americans that suggests how they were able to live in the region; 5)a paleo-botanical history based on an evaluation of pack-rat midden collections from mountain ranges around the region; 6) a comparison of the trees, shrubs, and perennials of the Eagletail Mountain Region with those of the Sierra Estrella and Kofa Mountains; and 7) a survey of non-native species. The habitats that the plants occupied based on climate and soils included were: 1) the bottoms and sides of sandy/ gravelly washes, 2) bajada slopes-volcanic soils, 3) bajada slopes-granitic sandy soils, 4) slot canyons/rock outcrops, 5) desert pavement, and 6) open valleys. Each habitat has its own characteristic species composition and distribution. / Dissertation/Thesis / M.S. Biology 2012

It has been suggested that polyploidization affects the ecological niche of a species, possibly ultimately leading to a shift in the distribution of the species, such as in geographical parthenogenesis. The phenomenon describes the wider distribution and shift of asexuals towards higher altitudes, northern latitudes and more extreme habitats when compared with their closely related sexual relatives. Several hypotheses have been proposed to explain such patterns with lacking empirical evidence because investigations rather focused on single hypotheses, which were rather tested several times independently on multiple organisms than vice versa. Therefore, the present study aimed to tackle the phenomenon of geographical parthenogenesis from multiple angles, i.e. testing several hypotheses simultaneously using Hieracium alpinum as a model system. In the arcto-alpine Asteraceae H. alpinum sexually reproducing diploid individuals occur in a small isolated area in the Eastern and Southern Carpathians, while apomictically reproducing, i.e. asexual reproduction via seeds, triploid plants occupy the remaining and much larger part of the range from the Balkans to the arctic parts of Europe. This implies that asexual triploids have had some fitness / colonization advantage(s), leading to a replacement of sexual diploids...

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The effect of moderate rates of nitrogen deposition on ground floor vegetation is poorly predicted by uncontrolled surveys or fertilization experiments using high rates of nitrogen (N) addition. We compared the temporal trends of ground floor vegetation in permanent plots with moderate (7–13 kg ha−1 year−1) and lower bulk N deposition (4–6 kg ha−1 year−1) in southern Sweden during 1982–1998. We examined whether trends differed between growth forms (vascular plants and bryophytes) and vegetation types (three types of coniferous forest, deciduous forest, and bog). Trends of site-standardized cover and richness varied among growth forms, vegetation types, and deposition regions. Cover in spruce forests decreased at the same rate with both moderate and low deposition. In pine forests cover decreased faster with moderate deposition and in bogs cover decreased faster with low deposition. Cover of bryophytes in spruce forests increased at the same rate with both moderate and low deposition. In pine forests cover decreased faster with moderate deposition and in bogs and deciduous forests there was a strong non-linear increase with moderate deposition. The trend of number of vascular plants was constant with moderate and decreased with low deposition. We found no trend in the number of bryophyte species. We propose that the decrease of cover and number with low deposition was related to normal ecosystem development (increased shading), suggesting that N deposition maintained or increased the competitiveness of some species in the moderate-deposition region. Deposition had no consistent negative effect on vegetation suggesting that it is less important than normal successional processes.

The severity of stratospheric ozone depletion in the temperate and polar latitudes has raised concerns about the sensitivity of terrestrial vegetation and ecosystems to solar ultraviolet (UV-B) radiation. This dissertation examined the responses of plants and microbes to solar UV-B for 3 years in Tierra de! Fuego, Argentina (55° S). This region is under the influence of the Antarctic "ozone hole" during the austral spring. Additionally, a quantitative review of the UV-B literature was conducted using a set of statistical techniques known as meta-analysis. For the field studies in Tierra de! Fuego, plots were established in a Sphagnum moss peatland and a Carexsedge fen during the spring of 1996. These plots received either near-ambient solar UV-B (90% of ambient) or reduced UV-B (20% of ambient) using specially designed plastic films. At the end of the first field season, no effects of the solar UV-B treatments were apparent on the growth and pigmentation of the plant species in either community The height growth of the moss Sphagnum mageffanicum was less under near-ambient solar UV-B than reduced UV-B during the second and third growing seasons. In contrast, volumetric density of the moss was greater under nearambient UV-B. The growth of the vascular plants did not respond to the solar UV-B treatments even after 3 years although UV-B-absorbing compounds were greater under near-ambient UV-B in some species. Populations of testate amoebae (i.e., shelled amoebae) inhabiting S. magellanicum had greater numbers under near-ambient UV-B than reduced UV-B throughout the 3 years. This response may be an indirect effect of solar UV-B mediated by the direct effect of UV-Bon S. mageffanicum height growth. Fungi on the leaf surfaces of the tree Nothojagus antarctica appeared to be directly inhibited by solar UV-B. The quantitative literature review of plant field studies simulating stratospheric ozone depletion assessed the effects of elevated UV-B on 10 plant response variables from papers published between 1976 and mid-1999. Modest significant inhibitions of leaf area, aboveground biomass, and plant height were apparent due to increased UV-B using meta-analysis. An increase in UV-B-absorbing compounds appears to be the most robust general response to increased UV-B radiation.