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.

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Species’ seasonal behaviour is of paramount importance in understanding community functioning and dynamics. Recently, plant phenology has further gained significance as a reliable indicator of climate change impacts. Despite the importance of understanding plant dynamics, there are relatively few plant phenological records for the sub-Antarctic region, and where records exist they are often not extensive. Sub-Antarctic Marion Island, typical of Southern Ocean Islands, offers a useful setting for addressing these knowledge gaps. This study documented the vegetative and reproductive phenologies (or aggregate phenological patterns) of twelve indigenous and three alien vascular plant species on the island. The phenological differences among the species and distinct seasonal groupings (e.g. early, intermediate and late species) were examined. I also investigated the phenological differences among the indigenous and alien plant species. Furthermore, the onset of selected reproductive phenophases from the current records was compared with historical records for determining the extent of climate change-related alterations in phenology. Phenological data were collected fortnightly on five, 5 m x 5 m permanent plots per species (except for a few species) for a full growing season. Thus the sample size is n = 5 for all plant species except for Crassula moschata (n = 4), Juncus effusus (n=4) and Rumex acetosella (n=1). Sites of the same species were separated by at least 500 m except for the alien plant, Juncus effusus, where all four known populations were selected despite two of these populations being < 500 m apart. This study indicated that Marion Island plants grow throughout the year with no major peaks except in Azorella selago and Acaena magellanica which showed winter dormancy. However, reproduction in most plant species predominately occurred in spring and summer months. Pringlea antiscorbutica and Poa cookii were the first two species to set flower buds in September while most species dispersed their seeds in summer except for Agrostis magellanica and Crassula moschata which dispersed in early autumn. Distinct from most temperate systems, the reproductive seasonality displayed by Marion Island plant species is explained more by daylength than by temperature, perhaps due to the region’s typical thermal aseasonality. Interestingly, many cooccurring species and/or clades across the Falkland, Kerguelen, Macquarie and South Georgia Islands also showed similar flowering onset date to the Marion Island plants, further confirming their daylength sensitivity. However, other external factors seem to come into play at later events of reproduction. Consequently, fruit maturation time of similar species across the sub-Antarctic islands varied substantially despite the plants having flowered in the same month. Although plant species showed similar reproductive seasonality, there were significant differences among species phenologies i.e. phenophase timing, duration and peak occurrence dates. However, using 95% confidence intervals of Generalized Linear Models weighted means, and/or one-way ANOVA (Tukey post hoc test), three homogenous sets of species (early, late, or intermediate onsets) were identified based on flower bud, flowering and seed dispersal phenophase onset dates. The homogenous species groupings observed for flower buds also remained unchanged during flowering onset except for Cotula plumosa and Callitriche antarctica which switched groups. As for the seed dispersal timing, the pattern was not consistent with that of the flower bud and flowering onset homogenous groupings, except for Acaena magellanica and Agrostis magellanica which remained in the early and late groups, respectively. Conversely, in the case of the timing of other phenophases (pollen release, fruit set and fruit ripening), entire phenophase durations, and peak occurrence dates, species overlapped greatly, resulting in an unbroken progression or continuum of phenology among species. Similarly, the three alien plant species investigated here (Cerastium fontanum, Juncus effusus and Rumex acetosella) showed no consistent phenological differences from the rest of the species. However, a widespread alien plant species on Marion Island, C. fontanum, reproduced for most of the year, although its reproduction peak was in summer months as was the case for the rest of the species. This study also indicated that indigenous plant species have altered their reproductive phenologies since 1965. Although the response was species-specific, the majority of plant species significantly delayed the onset of reproductive activities in 2007 by comparison with 1965. However, it is not clear if the observed species response was caused by the now drier and warmer Marion Island climate or by discrepancies in reporting in the earlier studies and/or sampling differences between the recent and historical records. Therefore, these results should be taken with caution. In conclusion, this research provided a detailed phenological dynamics record for vascular plant species on the island. Over time these records may be used as a basis for monitoring and modelling the impact of climate on plant phenology on the island. / AFRIKAANSE OPSOMMING: Spesies se seisoenale gedrag is van die allergrootste belang in die begrip van gemeenskapsfunksionering en dinamika. Meer onlangs het plant fenologie verdere betekenis verwerf as ‘n betroubare indikator vir die impakte van klimaatsverandering. Ondanks die belangrikheid om plant dinamika te verstaan, is daar relatief min plant fenologiese rekords vir die sub-Antarktiese streek en waar rekords wel bestaan is dit dikwels nie omvangryk nie. Sub- Antarktiese Marion Eiland, tipies van Suidelike Oseaan Eilande, bied ‘n nuttige ligging om hierdie kennis gapings aan te spreek. Hierdie studie het die vegetatiewe en voorplantingsfenologieë (of gesamentlike fenologiese patrone) van elf inheemse en drie uitheemse vaatplantspesies op die eiland gedokumenteer. Die fenologiese verskille tussen die spesies en duidelike seisoenale groeperings (bv. vroeë, intermediêre en laat spesies) is ondersoek. Ek het ook die betekenisvolle fenologiese verskille tussen die inheemse en uitheemse plantspesies ondersoek. Voorts, die aanvang van gekose voortplanting feno-fases van huidige rekords is vergelyk met historiese rekords om die mate van klimaatsverandering verbandhoudende veranderings in die fenologie te bepaal. Fenologiese data is twee weekliks ingesamel op vyf, 5 m x 5 m permanente plotte per spesie (behalwe vir ‘n paar spesies) vir ‘n volle groei seisoen. Dus, die insamelings grootte is n = 5 vir al die plantspesies behalwe vir C. moschata (n = 4), Juncus effusus (n=4) en Rumex acetosella (n=1). Persele vir dieselfde spesies is geskei deur ten minste 500 m, behalwe vir die uitheemse plant, Juncus effusus, waar al vier populasies wat bekend is gekies is, ten spyte daarvan dat twee van hierdie populasies < 500 m uitmekaar is. Hierdie studie het aangedui dat Marion Eiland plante regdeur die jaar groei, met geen belangrike spitstye nie, behalwe in Azorella selago en Acaena magellanica wat ‘n winter rusperiode wys. Hoe ookal, voortplanting in meeste van die plantspesies het hoofsaaklik voorgekom tussen die lente en somermaande. Pringlea antiscorbutica en Poa cookii was die eerste twee spesies om blomknoppe uit te stoot in September, terwyl die meeste spesies hulle sade versprei het gedurende die somer, behalwe vir Agrostis magellanica en Crassula moschata wat versprei het in vroeg herfs. Duidelik van meeste gematigde sisteme, word die voortplanting seisoenaliteit, getoon deur die Marion Eiland plantspesies, verduidelik meer deur daglengte as deur temperatuur, moontlik weens die streek se tipiese termiese a-seisoenaliteit. Interessant, baie spesies en/of afstameling-groeperings wat saam aangtref word dwarsoor die Falkland, Kerguelen, Macquarie en Suid Georgia Eilande wys ook soortgelyke bloei aanvangsdatums as die Marion Eiland plante, nog meer bevestigend van hulle dag-lengte sensitieweteit. Hoe ookal, ander eksterne faktore blyk betrokke te raak by latere gebeure van voortplanting. Gevolglik het vrug rypwordingstyd van dieselfde spesies oor die sub-Antarktiek noemenswaardig verskil, ten spyte daarvan dat die plante in dieselfde maand geblom het. Alhoewel plantspesies dieselfde voortplanting seisoenaliteit gewys het, was daar ‘n noemenswaardige veskil tussen spesie fenologieë, m. a. w. feno-fase tydsberekenning, tydsduur en spits voorkomsdatums. Hoe ookal, deur gebruik te maak van 95% betroubaarheid intervalle van Algemene Lineêre Modelle gewigte gemiddelde en/of een rigting ANOVA (Turkey post hoc toets), is drie homogene stelle van spesies (vroeë, laat en intermediêre aanvang) geïdentifiseer gebasseer op blomknop, bloei en saad verspreiding feno-fase aanvangsdatums. Die homogene spesie groeperings waargeneem op blomknoppe het ook onveranderd gebly gedurende bloei aanvang behalwe vir Cotula plumosa en Crassula antarctica wat groepe geruil het. Vir die saadverspreiding tydsberekenning was die patroon nie konstant met die van die blomknop en bloei aanvang homogene groepe nie, behalwe vir Acaena magellanica en Agrostis magellanica wat in die vroeë en laat groepe respektiewelik gebly het. Omgekeerd, in die geval van tydsberekenning van ander feno-fases (stuifmeel vrysetelling, vrugwerp, vrugrypwording), volledige feno-fase tydsduur en spits voorkomsdatums het spesies grootliks oorvleuel, wat ‘n ongebroke vordering of deurlopendheid van fenologie tussen die spesies tot gevolg het. Ooreenkomstig het die drie uitheemse spesies wat hier ondersoek is (Cerastium fontanum, Juncus effusus en Rumex acetosella) geen bestendige fenologiese verskille van die res van die spesies gewys nie. Hoe ookal, ‘n wydverspreide uitheemse spesie op Marion Eiland, Cerastium fontanum, het deur die meeste van die jaar voortgeplant, hoewel met ‘n voorplanting spits in die somer maande soos die res van die spesies. Hierdie studie dui ook aan dat inheemse plantspesies hulle voortplanting fenologieë verander het sedert 1965. Alhoewel die reaksie spesiespesifiek was, het die meerderheid van die plantspesies hulle voortplanting aanvang aansienlik vertraag gedurende 2007 in vergelyking met 1965. Hoe ookal, dis nie duidelik of die waargeneemde spesie reaksie was as gevolg van die nou droër en warmer Marion Eiland klimaat of deur teenstrydighede in verslagewing gedurende die vroëre studies en/of insameling verskille tussen die onlangse en historiese rekords. Daarom moet hierdie resultate met versigtigheid hanteer word. In samevatting, hierdie navorsing voorsien ‘n gedetaileerde fenologiese dinamieka rekord vir vaatplantspesies op die eiland. Oor tyd kan hierdie rekords gebruik word as basis vir monitering en modellering van die impak van klimaat.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: As the pace of climate change has begun to accelerate so too has it become clear that the direct impacts thereof are likely to have profound consequences for many island systems. Moreover, it has also been suggested that climate change will exacerbate the effects of many invasive species, so further impacting both diversity and ecosystem functioning. Forecasts for such interactions have been most pronounced for the Southern Ocean islands, which are home to a wide variety of endemic species. This thesis is about such interactions and their specific impacts on a key endemic, the black-faced sheathbill (Chionis minor) on the Prince Edward Islands. Of increasing concern is how invasive rodent populations in the Southern Ocean may be responding to global climate change, as ameliorating conditions on these islands are forecast to decrease thermal and resource restrictions on rodents. However, firm evidence for changing rodent populations in response to climate change, and demonstrations of associated impacts on the terrestrial environment, are entirely absent for the region. In Chapter 2 of this thesis, these relationships are explored for invasive house mice (Mus musculus) on Marion Island. Using spatially explicit capture-recapture modeling, it is determined that mouse populations across a range of habitats have increased over time. Owing to an extended breeding season, made possible by ameliorating conditions brought on by climate change, the total number of mice on the island at annual peak density more than doubled over the past decade. It is also demonstrated that mice directly reduce invertebrate densities, with biomass losses up to two orders of magnitude in some habitats. Because of the importance of invertebrates to nutrient cycling on the island, such changes are likely to have significant ecosystem-level impacts. In Chapter 3 the focus expands to examine how increasing mouse impacts and other outcomes of climate change are affecting the ecology of the black-faced sheathbill. It has been established that invasive house mice are capable of suppressing the populations of several seabird species in the Southern Ocean. However, mouse impacts on the region’s few island endemic land-birds remain largely unexplored. Further, a significant effect of climate change may be realized by altering interspecific interactions, specifically food webs. A significant portion of sheathbill diets is derived from rockhopper penguins, a species currently under a climate-change-driven decline, which may have significant effects on sheathbills. The study found that terrestrial invertebrates are no longer a significant prey resource for sheathbills on Marion Island, and that sheathbills have effectively been displaced from a formerly important winter food resource by mice. In response, the number of sheathbills foraging in king penguin colonies increased. Moreover, a reduced rockhopper penguin population lead to significant declines in both the number and proportion of sheathbills foraging in rockhopper penguin colonies. The sum result was a significant decline in the body condition of female sheathbills. Rather than decrease reproductive output, sheathbills responded by decreasing clutch size and producing significantly fewer male nestlings. While population estimates did not detect a reduction in the number of sheathbills, population projections suggest that the population is in decline, with the reproductive population declining faster than the absolute population. There is need for greater study of island species, as for even relatively well-studied taxa such as birds many aspects of ecology remain significantly less studied when compared to species occurring on continents. For example, basal metabolic rate (BMR) is a fundamental characteristic of all endotherms, yet only a handful of island birds have had their BMR measured, and fewer still to a level that allows intraspecific analysis. In Chapter 4 the BMR of black-faced sheathbills on Marion Island was measured to determine whether the unique phylogenetic position and ecology of sheathbills equate to a unique BMR when allometrically compared to other birds. It was found that the BMR of sheathbills is typical for a bird of its size. However, significant intraspecific variation was found to occur, with differences in habitat quality a likely driver. The results of the study show that the combined effects of climate change and invasive species can have significant consequences for terrestrial endemics in the Southern Ocean. Further, the long-term changes observed in sheathbills make clear the need for improved documentation and study of island species in general, as many of the responses observed in this study are significant but subtle and would not have been evident without detailed knowledge of species ecology and vital rates. Giving greater focus to insular biota is imperative to understanding their current status and ecology as well as establishing a barometer against which further global change can be measured and mitigation measures evaluated. Specific conservation responses for the black-faced sheathbill on Marion Island include the provision of nest boxes at king penguin colonies, and eradication of house mice. The latter would have long-term benefits for the species, invertebrates, ecosystem functioning generally, and likely also for important seabirds such as several species of albatrosses whose chicks are being increasingly preyed on by mice. Eradication would, however, be difficult and expensive, and with substantial potential non-target effects, including on sheathbills, that would have to be carefully managed. In the absence of local mouse eradication, and with ongoing climate change, specific management of the sheathbill population through the provision of supplementary nesting sites seems the most appropriate conservation action. It should therefore be examined in small-scale trials to ascertain the likelihood of unintended consequences. Importantly, the maintenance of Prince Edward Island as largely free of invasive species is key to the conservation of the local black-faced sheathbill subspecies, Chionis minor marionensis, endemic to the Prince Edward Island group. / AFRIKAANSE OPSOMMING: Soos die tempo van klimaatsverandering begin om te versnel, het dit ook duidelik geword dat die direkte impak daarvan waarskynlik ernstige gevolge vir baie eilande gaan hê. Verder word dit is ook voorgestel dat klimaatsverandering die gevolge van baie indringerspesies sal vererger, so ʼn verdere impak het op beide diversiteit en die funksionering van die ekosisteem. Voorspellings vir sulke interaksies is die meeste uitgespreek vir die Suidelike Oseaan-eilande, wat ook die tuiste van 'n wye verskeidenheid van endemiese spesies is. Hierdie tesis is oor sulke interaksies en hul spesifieke impak op 'n sleutel endemiese spesie is, die swart gesig skedebek (Chionis minor) op die Prince Edward-eilande. ʼn Groter bron van bekommernis is hoe uitheemse knaagdier bevolkings in die Suidelike Oseaan kan reageer teenoor globale klimaatsverandering, aangesien toestande op die eilande voorspel word om hitte en hulpbron beperkings vir knaagdiere te verminder. Maar, ferm bewyse vir die verandering van knaagdier bevolkings in reaksie op klimaatsverandering, en demonstrasies van gepaardgaande impakte op die terrestriële omgewing, is heeltemal afwesig vir die streek. In Hoofstuk 2 van hierdie tesis, word hierdie verhoudings ondersoek vir indringende huis muise (Mus musculus) op Marion-eiland. Ruimtelik vang-terugvang modelle word gebruik om vas te stel dat die muis bevolkings oor 'n verskeidenheid van habitatte mettertyd toegeneem het. As gevolg van 'n uitgebreide broeiseisoen as gevolg van die verligting van toestande gebring deur klimaatsverandering, het die totale aantal muise op die eiland by die jaarlikse hoogtepunt digtheid meer as verdubbel oor die afgelope dekade. Dit is ook getoon dat muise die digtheid van ongewerweldes direk verminder het, met biomassa verliese tot twee ordes in sommige habitatte. As gevolg van die belangrikheid van die ongewerweldes vir voedingstof sirkulering op die eiland, behoort sulke veranderinge waarskynlik 'n beduidende ekosisteem-vlak impak te hê. In Hoofstuk 3 word die fokus verbreed om te sien hoe die verhoging van die muis impakte en ander uitkomste van klimaatsverandering die ekologie van die swart gesig skedebek beïnvloed. Daar is vasgestel dat indringende huis muise in staat is om die bevolkings van verskeie spesies seevoëls te onderdruk in die Suidelike Oseaan. Maar die muis impak op die streek se paar eiland endemiese land voëls bly grootliks onverken. Verder kan 'n beduidende uitwerking van klimaatsverandering verwesenlik word deur die wysiging van interspesifieke interaksies, veral voedselwebbe. 'n Beduidende gedeelte van skedebek dieet word gekry van Geelkuifpikkewyne, 'n spesie wat tans onder 'n klimaat-veranderinggedrewe agteruitgang is, wat ook 'n beduidende uitwerking het op die skedebek. Die studie het gevind dat terrestriële ongewerweldes nie meer 'n beduidende prooi hulpbron vir die skedebek op Marion-eiland is nie, en dat die skedebek effektief is verplaas uit 'n voorheen belangrike winter kos hulpbron deur muise. In reaksie hierop het die aantal skedebekke wat kos soek in die koning pikkewyn kolonies toegeneem. Verder, 'n verlaagde Geelkuifpikkewyn bevolking lei tot 'n beduidende afname in beide die aantal en persentasie van skedebekke wat kos soek in Geelkuifpikkewyn kolonies. Die gevolg was 'n beduidende afname in die liggaamstoestand van die vroulike skedebekke. Eerder as ʼn afname van reproduksie, het skedebekke gereageer deur 'n vermindering in die aantal eiers en produseer aansienlik minder manlike kuikens. Terwyl bevolking skattings nie 'n afname in die aantal skedebekke kan vind nie, dui bevolking projeksies daarop dat die bevolking besig is om af te neem, met die voortplanting bevolking wat vinniger daal as die absolute bevolking. Daar is 'n behoefte vir 'n groter studie van eiland spesies, omdat selfs vir betreklik goed bestudeerde groepe soos voëls baie aspekte van die ekologie aansienlik minder bestudeer bly in vergelyking met spesies op die vastelande. Byvoorbeeld, basale metaboliese tempo (BMT) is 'n fundamentele kenmerk van alle endotermiese diere, maar net 'n handjievol van die eiland voëls het hul BMT laat meet, en nog minder tot 'n vlak wat dit moontlik maak intraspesifieke analise. In Hoofstuk 4 was die BMT van die swart gesig skedebek op Marion-eiland gemeet om te bepaal of die unieke filogenetiese posisie en ekologie van skedebekke gelyk aan 'n unieke BMT wanneer allometries vergelyk word met ander voëls. Daar is gevind dat die BMT van skedebekke tipies is vir 'n voël van sy grootte. Daar is egter belangrike intraspesifieke variasie gevind, met verskille in habitat kwaliteit as 'n waarskynlike verduideliking. Die resultate van die studie toon dat die gekombineerde effek van klimaatsverandering en indringerspesies beduidende gevolge vir terrestriele inheemse spesies in die Suidelike Oseaan kan hê. Verder maak die lang-termyn veranderinge waargeneem in skedebekke dit duidelik dat die behoefte aan verbeterde dokumentasie en studie van die eiland spesies in die algemeen, omdat baie van die reaksies waargeneem in hierdie studie betekenisvol is, maar subtiel en sou nie gewees het sonder gedetailleerde kennis van die spesies ekologie van die spesie nie. Om ʼn groter fokus op die insulêre biota te plaas is noodsaaklik om hul huidige status en die ekologie te begryp, sowel as om 'n barometer waarteen verdere globale verandering gemeet kan word en versagtende maatreëls geëvalueer. Spesifieke bewaring antwoorde vir die swart gesig skedebek op Marion-eiland sluit in die voorsiening van nes bokse by koning pikkewyne, en die uitwissing van huis muise. Laasgenoemde sou lang-termyn voordele vir die spesie en ongewerweldes hê, asook funksionering van die ekosisteem in die algemeen, en waarskynlik ook vir belangrike seevoëls soos verskeie spesies van albatrosse wie se kuikens toenemend geëet word deur muise. Uitwissing sou egter moeilik en duur wees, en het 'n aansienlike potensiaal vir nieteiken effekte, insluitend op skedebekke, wat sal versigtig moet bestuur word. In die afwesigheid van plaaslike muis uitwissing, en met voortdurende verandering van die klimaat, spesifieke bestuur van die skedebek bevolking deur die voorsiening van aanvullende broeiplekke blyk die mees geskikte bewaringsaksie. Dit moet dus ondersoek word in 'n kleinskaal proewe om die waarskynlikheid van onbedoelde gevolge te bepaal. Wat belangrik is die instandhouding van Prince Edward Eiland as grootliks vry van indringerspesies en is die sleutel tot die bewaring van die plaaslike swart gesig skedebek subspesie, Chionis minor marionensis, endemies aan die Prince Edward Eiland groep.

<p>Marion Island is situated in the South Indian Ocean and belongs to the sub-Antarctic island group, Prince Edward Islands. The islands in the sub-Antarctic have over the past few decades been exposed to a warmer and drier climate trend. The aim of this thesis is to achieve better understanding of the small-scale spatial and temporal variability between Azorella selago andthe surrounding microclimate. Due to the consequences of climate change, the interactions between Azorella selago, landforms and soil processes are important for the future of the terrestrial ecosystems in the sub-Antarctic. The theory part in this thesis describes different processes and features that are essential to understand the context of this thesis. The energy balance and the insolation is shown to be an important aspect when looking at the spatialvariability of the microclimate. The summary of the results in the thesis is based on temperature and moisture measurements within two grids. One on the east and one on the west side of the island</p><p>The most important result from the measurements is that different weather conditions create different situations for the microclimate. The weather condition ‘sunny no wind’ created a high spatial variability in temperature on the ground, which was completely absent during overcast days. Temperature variability is highly dependent on cloud cover according to these results. Moisture changes also seem to be less weather dependent than temperaturechanges.</p><p>The data provide a first confirmation that an increase in sunshine hours gives increased spatial variability in temperature (not moisture) and soil frost. An increase in spatial variability of the microclimate within small areas could give rise to an expansion in the patchiness of soil frost processes in the landscape. The representivity of single point measurements of ground surface temperature should be questioned.</p><p>Patterns of areas with low moisture content within the grid correlate with points where measurements were taken on Azorella selago. The Azorella cushion could, according to the results of this thesis, be associated with dry areas within the grid. Azorella selago is thereby suggested to increase the spatial variability of moisture and also contribute to a locally drier microclimate. Moisture variability varies more between the east and west side of the island, than that it is weather dependent.</p><p>Shaded areas show a pattern of lower temperature than for the other variables under sunny conditions. If more shaded areas are created by for example landforms like Azorella selago or solifluction deposits, the temperatures would probably be lower and also create a wider spatial variability.</p><p>This study provides first data on the important interactions between Azorella selago and how it affects through spatial variability in micro-climate, ground frost potential and resulting soil disturbance by frost creep and solifluction.</p>

Marion Island is situated in the South Indian Ocean and belongs to the sub-Antarctic island group, Prince Edward Islands. The islands in the sub-Antarctic have over the past few decades been exposed to a warmer and drier climate trend. The aim of this thesis is to achieve better understanding of the small-scale spatial and temporal variability between Azorella selago andthe surrounding microclimate. Due to the consequences of climate change, the interactions between Azorella selago, landforms and soil processes are important for the future of the terrestrial ecosystems in the sub-Antarctic. The theory part in this thesis describes different processes and features that are essential to understand the context of this thesis. The energy balance and the insolation is shown to be an important aspect when looking at the spatialvariability of the microclimate. The summary of the results in the thesis is based on temperature and moisture measurements within two grids. One on the east and one on the west side of the island The most important result from the measurements is that different weather conditions create different situations for the microclimate. The weather condition ‘sunny no wind’ created a high spatial variability in temperature on the ground, which was completely absent during overcast days. Temperature variability is highly dependent on cloud cover according to these results. Moisture changes also seem to be less weather dependent than temperaturechanges. The data provide a first confirmation that an increase in sunshine hours gives increased spatial variability in temperature (not moisture) and soil frost. An increase in spatial variability of the microclimate within small areas could give rise to an expansion in the patchiness of soil frost processes in the landscape. The representivity of single point measurements of ground surface temperature should be questioned. Patterns of areas with low moisture content within the grid correlate with points where measurements were taken on Azorella selago. The Azorella cushion could, according to the results of this thesis, be associated with dry areas within the grid. Azorella selago is thereby suggested to increase the spatial variability of moisture and also contribute to a locally drier microclimate. Moisture variability varies more between the east and west side of the island, than that it is weather dependent. Shaded areas show a pattern of lower temperature than for the other variables under sunny conditions. If more shaded areas are created by for example landforms like Azorella selago or solifluction deposits, the temperatures would probably be lower and also create a wider spatial variability. This study provides first data on the important interactions between Azorella selago and how it affects through spatial variability in micro-climate, ground frost potential and resulting soil disturbance by frost creep and solifluction.

Thesis (PhD)--University of Pretoria, 1992. / gm2014 / Zoology and Entomology / unrestricted

The demography of two elephant seal populations was examined and compared. This was done to investigate the reasons for the observed decreases in populations at Marion and Macquarie islands. While a well-established demographic programme had been in place at Marion Island since the 1980's (see Pistorius et al. (l999a) for a review) one had to be established at Macquarie Island. A long-term demographic programme was initiated at Macquarie Island in 1993 and hot brands were used to mark seals. Hot-iron branding was a rapid and reliable method of permanently identifying elephant seals that did not prejudice survival and did not appear to cause undue stress (in the short-term). Neither branding nor handling showed any long-term effects as measured by survival after one year. From the inter-island comparison of survivorship, age at first breeding and wean mass I concluded that the observed decreases in elephant seal numbers between the I 950s and 1990s in the Pacific and Indian Ocean sectors were driven by resource limitation in the Southern Ocean. A conglomerate of factors including local predation by killer whales and intra-specific resource competition was postulated as a cause for the inter-island (regional) differences in population trends. Presently it appears that per capita more resources are available to the Marion Island population than are available to the Macquarie Island population. The vital rates that had the greatest impact (elasticity) on fitness (population growth) for all populations i.e. Marion Island, Macquarie Island and South Georgia, were, in order of importance: (I) juvenile survival, (2) adult survival, (3) adult fecundity and (4) juvenile fecundity. At Marion Island juvenile and adult survival contributed equally to the fitness of the population while at Macquarie Island and at South Georgia Island juvenile survival was more important than adult survival in determining population fitness. The global population of elephant seals in 200 I was estimated at approximately 738 772 which represents an increase of I I % from the last world estimate (664 000). It seems clear from the evidence presented and reviewed here that the present changes in seal populations, unlike the period of direct exploitation in the 19th and 20th centuries, are neither a consequence of direct human interactions nor present-day commercial activities. While the significance of inter-specific competition between elephant seals and other Antarctic predators remain largely unknown or quantified, it would seem prudent that these relationships be studied. This is because resource competitors (toothed whales) have been increasing in number since the cessation of commercial whaling. Even though elephant seals are considered the most studied of all pinnipeds (Ling&Bryden, 1992) much remains to be learnt. Foremost are to gain a clear understanding of the in situ, diet of elephant seals and to assess the role pathogens play in the regulation of seal populations. In addition to these studies it is also important that the current long-term monitoring programmes at Marion and Macquarie islands continue, as they provide valuable base line information on the fate of elephant seal populations. / Thesis (PhD (Zoology))--University of Pretoria, 2005. / Zoology and Entomology / unrestricted

The aim of this study was to identify the algal genera found in the different freshwater bodies on Marion Island, to relate the presence or absence of the genera to the chemistry of the water bodies and to group the genera according to their limno-chemical preferences. The Island's freshwater algal genera were also compared with genera found on other Southern Ocean islands. The major factors influencing the chemical composition of the freshwaters of the island are the surrounding ocean and the manuring of seals and seabirds. The Western and Southern lakelets and wallows had higher mean conductivity values than most of the other water bodies. Eastern Inland lakelets, crater lakes and glacial lakes had low ion and nutrient concentrations, since they are mainly situated inland, away from bird or seal colonies. The chemical composition of wallows was influenced by manuring of seals and seabirds. The freshwaters are acidic and lakelets tend to be more acidic than glacial lakes. The lentic waters were more acidic than the stream. In total, 106 genera, mainly belonging to Chlorophyta (60 genera; 56% of total) and Cyanophyta (29 genera; 27% of total), were found in the freshwaters on the island. Other algal divisions found were Chrysophyta (7 genera), Euglenophyta (4 genera), Pyrrophyta (2 genera) and Xanthophyta (4 genera). Mean number of genera per sample ranged from 8 (in wallows) to 16 (in Eastern Inland lakelets). Filamentous algae were present in all the samples. Abundant green algae were Cosmarium, Klebsormidium, Mougeotia and Oedogonium. The most common cyanobacteria were Lyngbya and Chroococcus. The filamentous yellow-green alga, Tribonema, was also common. There were distinct differences in the algal composition between the southern, western and northern lakelets and the lakelets on the eastern side of the island. Sixty percent of the algal genera were present in waters with low conductivity values. Trichodesmium, Sphaerocystis and Tolypothrix occurred in freshwater bodies with higher conductivity values. Variance analysis showed that 87 of the 106 genera were less likely to occur in nitrogen and phosphate containing waters. Chlamydomonas, Prasiola, Spirogyra Trachelomonas, Tribonema, Ulothrix and Xanthidium were among the genera commonly found in nitrogen and phosphate containing waters. Diversity (number of genera per sample) was negatively correlated with conductivity, PO4-P, NH4-N and NO3-N. Diversity declined significantly with increasing salinity and eutrophication. Genera likely to occur in acidic waters include Binuclearia, Chlamydomonas, Chroococcus, Cosmarium, Klebsormidium, Microspora, Oedogonium, Oocystis, Prasiola, Scenedesmus, Staurastrum, Stigeoclonium, Tetrastrum, Ulothrix, Lyngbya, Synura and Tribonema. Marion Island’s algal flora shows a high affinity with that of Îles Kerguelen and Crozet, both located in the same biogeographical province (South Indian Ocean Province) of the sub-Antarctic than Marion Island, and a lesser affinity with islands in other sub-Antarctic provinces. Algal genera were grouped according to their limno-chemistry preferences. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2012.

The aim of this study was to identify the algal genera found in the different freshwater bodies on Marion Island, to relate the presence or absence of the genera to the chemistry of the water bodies and to group the genera according to their limno-chemical preferences. The Island's freshwater algal genera were also compared with genera found on other Southern Ocean islands. The major factors influencing the chemical composition of the freshwaters of the island are the surrounding ocean and the manuring of seals and seabirds. The Western and Southern lakelets and wallows had higher mean conductivity values than most of the other water bodies. Eastern Inland lakelets, crater lakes and glacial lakes had low ion and nutrient concentrations, since they are mainly situated inland, away from bird or seal colonies. The chemical composition of wallows was influenced by manuring of seals and seabirds. The freshwaters are acidic and lakelets tend to be more acidic than glacial lakes. The lentic waters were more acidic than the stream. In total, 106 genera, mainly belonging to Chlorophyta (60 genera; 56% of total) and Cyanophyta (29 genera; 27% of total), were found in the freshwaters on the island. Other algal divisions found were Chrysophyta (7 genera), Euglenophyta (4 genera), Pyrrophyta (2 genera) and Xanthophyta (4 genera). Mean number of genera per sample ranged from 8 (in wallows) to 16 (in Eastern Inland lakelets). Filamentous algae were present in all the samples. Abundant green algae were Cosmarium, Klebsormidium, Mougeotia and Oedogonium. The most common cyanobacteria were Lyngbya and Chroococcus. The filamentous yellow-green alga, Tribonema, was also common. There were distinct differences in the algal composition between the southern, western and northern lakelets and the lakelets on the eastern side of the island. Sixty percent of the algal genera were present in waters with low conductivity values. Trichodesmium, Sphaerocystis and Tolypothrix occurred in freshwater bodies with higher conductivity values. Variance analysis showed that 87 of the 106 genera were less likely to occur in nitrogen and phosphate containing waters. Chlamydomonas, Prasiola, Spirogyra Trachelomonas, Tribonema, Ulothrix and Xanthidium were among the genera commonly found in nitrogen and phosphate containing waters. Diversity (number of genera per sample) was negatively correlated with conductivity, PO4-P, NH4-N and NO3-N. Diversity declined significantly with increasing salinity and eutrophication. Genera likely to occur in acidic waters include Binuclearia, Chlamydomonas, Chroococcus, Cosmarium, Klebsormidium, Microspora, Oedogonium, Oocystis, Prasiola, Scenedesmus, Staurastrum, Stigeoclonium, Tetrastrum, Ulothrix, Lyngbya, Synura and Tribonema. Marion Island’s algal flora shows a high affinity with that of Îles Kerguelen and Crozet, both located in the same biogeographical province (South Indian Ocean Province) of the sub-Antarctic than Marion Island, and a lesser affinity with islands in other sub-Antarctic provinces. Algal genera were grouped according to their limno-chemistry preferences. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2012.

Craniometrics is a very reliable and effective tool for studying the difference in animal morphology. Previously, traditional craniometrics were conducted with the aid of calipers in two dimensional format (2D). Such discounting of actual three-dimensional 3D form may result in loss of some relevant and critical information leading to compromised and unreliable results for studies such as population variation analysis of morphology. The employment of 3D photogrammetry allows a close to complete representation of the physical dimensions of a specimen. The use of photogrammetry in mammalogy concentrated on measuring of body size/mass, but little has been done on animal skull delineation through photogrammetry. This dissertation describes advances in morphometrics and 3D photogrammetry application in craniometrics, investigates the craniometric variation between closely related species (Arctocephalus gazella and A. tropicalis), and A. tropicalis interpopulation craniometrics between two geographically distinct populations, at Marion Island and Gough Island, using Photomodeler Scanner® (PMSc®) three-dimensional (3D) modelling software to produce accurate, high resolution 3D skull models. A total of 117 3D models were created from adult male fur seal crania, and 16 traditional measurements recorded, using specimens archived at the Port Elizabeth Museum, Bayworld, South Africa. Sixteen linear measurements, (8 caliper recordings and 8 3D recordings) were used for PMSc® methodology testing, 16 (A. gazella n= 8 and A. tropicalis n= 8) used for species cranial comparison and 85 (Marion Island n= 54 and Gough Island n= 31) used for interpopulation variation. The craniometric variations were analysed using the Statistica® v11 software package, StatSoft, Inc. The comparison between linear traditional caliper cranial measurements and 3D measurements produced significantly similar results, attesting to the accuracy of the PMSc® 3D model production. Photomodeler Scanner® therefore produces accurate and high resolution 3D models of skulls which allow 3D measurements. I predicted that PMSc® would detect the existing significant differences between the skulls of adult male A. gazella and A. tropicalis and modelled and compared their 3D models, and I further predicted that PMSc® would detect any existing differences between the skulls of A. tropicalis from Gough and Marion islands by comparison of their 3D models. The Gough Island and Marion Island A. tropicalis populations could not be discriminated based on linear 3D cranial I conclude that PMSc® is a reliable and effective tool for accurate and high resolution 3D modelling. The present study confirms previous findings and contributes additional evidence that suggests that adult A. tropicalis males from Gough Island and Marion Island cannot be discriminated based on linear measurements of craniometrics, and deviates from the Bergmanian rule as applied to large mammals. The present study, however, makes several noteworthy contributions to the use of PMSc® and 3D modelling in morphometrics. Taken together, these findings suggest a role for PMSc® 3D modelling in promoting accurate digitization of museum specimens and creation of online museum libraries. This research will serve as a baseline for future studies and usefulness of PMSc® in 3D morpho-volumetric measurements. / Dissertation (MSc (Zoology))--University of Pretoria, 2014. / Zoology and Entomology / MSc (Zoology) / Unrestricted