Thesis (MScConEcol)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 144-155.

Thesis (M. Sc. (Zoology & Entomology))--Rhodes University, 2005.

Thèse (de maîtrise)--Université Laval, 2002. / Bibliogr.: f. 32-35. Publié aussi en version électronique.

<p>The introduction of the North American beaver (Castor canadensis) to Tierra del Fuego is a widely known example of a successful biological invasion. Beavers have impacted enormously the biodiversity of the island of Tierra del Fuego, and they are now spreading northward on the continent, prompting the governments of Argentina and Chile to seek methods to control their spread. Beavers first established in forests, where they were initially introduced, but by the 1990s they began to establish in the adjacent steppe. In this dissertation, I study the biology of invasive beavers across the two major habitat types in Patagonia and attempt to develop modeling tools that might be useful to manage their spread.</p><p>In chapter one I studied the history of the beaver introduction in Patagonia and provide evidence that the beaver introduction occurred as a single release event of 20 beavers from northern Manitoba, Canada. This not only clarifies the origin of the invasion, but also suggests that the beaver population of Patagonia descends from a smaller number of individuals than previously assumed.</p><p>In chapter two I studied the demography of invasive North American beavers in the two contrasting habitat types of the island of Tierra del Fuego, forest and steppe. Habitat differences can affect vital rates which may in turn impact the speed of the invasion, but this has been rarely addressed when managing the spread of invaders. I use repeated observations, mark-resight methods, telemetry and camera traps to estimate colony size and vital rates of beavers in the two habitats. Colony size and the number of offspring (“kits”) produced per colony per year were higher in the steppe, contrary to the belief that forest is better habitat. Here I suggest this may be the result of the longer time since invasion in the forests of Tierra del Fuego and that the forest subpopulation is showing density dependent regulation. Beaver survival was high in all age classes and was higher than survival rates recorded in North America. My work shows that beaver plasticity and predator release have likely facilitated the invasion in Patagonia. </p><p>In chapter three, I investigated the more recent invasion of beavers in an area of the Patagonian steppe. I utilized repeated high resolution satellite images to identify beaver ponds, and used them to study changes in beaver abundance and habitat use over time. The number of beaver ponds increased 85 % between 2005 and 2014. During this period, beavers changed their habitat selection pattern, presumably as a response to increased density. Beavers established on small watercourses in canyons first, but as more canyons became occupied over time, beavers moved to less preferred watercourses in plains and U-shaped valleys. Potential new beaver colonies established close to existing beaver ponds, suggesting proximity to a beaver pond is an important determinant of beaver colonization. Identifying habitat preferred by beavers in the steppe could help to increase early detection of the invader at the invasion front. This work highlights the importance of the use of high resolution remote sensing technologies to better understand and monitor biological invasions. </p><p>Finally, in chapter four, I built a spatially explicit individual-based model parameterized with data I collected in the field and use it to make management recommendations. Specifically I assessed the efficacy of a potential management strategy in which a “fire-break” (a zone beyond the current population front in which beavers are removed) perpendicular to the population front is instituted to attempt to prevent further northward spread of the beaver in continental Patagonia. I found that even a 100 km wide firebreak is insufficient to contain the spread of beavers, long dispersal events being the major cause of this failure. Further, I found that increasing the fraction of beavers culled within the firebreak does not decrease either the arrival time or the number of beavers that cross the firebreak. Counterintuitively, my model indicates that moderate levels of culling within the firebreak (rather than high) may be a more effective method to manage the invasion, likely as a result of inversely density dependent dispersal.</p> / Dissertation

L'espace mosellan est foncièrement germanique, considéré comme une émanation directe des Grandes Invasions d'où serait issue une Lorraine coupée en deux, germanique - donc franque - d'un côté et romane de l'autre, ayant conservé les traditions du Bas-Empire, le tout séparé par une frontière linguistique. Cette image, directement issue de l'historiographie d'outre-Rhin du XIXe siècle, a toujours force de loi, en Lorraine comme ailleurs, en dépit des progrès de la recherche. Le but de ma thèse est de démontrer que ces théories, forgées en fait sur des critères essentiellement toponymiques, ne reposent sur aucun fondement scientifique réel et ne peuvent résister aux avancées de la recherche moderne, notamment archéologiques. Elle s'articule en trois parties : 1 : Adapter l'espace mosellan au panorama général de l'historiographie moderne. Etudier cet ensemble de l'intérieur, non plus en fonction de pseudo-invasions extérieures mais comme une entité propre. Aborder la frontière linguistique sur des critères objectifs et non plus théoriques. Abandonner le mythe « franc » au profit de la réalité de l'ethnogenèse. Appréhender la réalité archéologique de la Gaule Belgique au Bas-Empire. 2 : Passer du mythe historiographique à la réalite du terrain. Par l'étude de l'occupation du sol au haut Moyen Âge sur des critères archéologiques : implantation des nécropoles mérovingiennes, données les plus récentes quant à la langue « francique » et la toponymie mosellane. Il en résulte une inadéquation totale entre les théories classiques et la réalité, où la romanité s'avère omniprésente. 3 : Redonner à l'espace mosellan une cohérence historique. Dans un tel contexte de pérennité antique, l'organisation du territoire n'a pu que se maintenir: par l'intermédiaire des cadastres et du système fiscal, automatiquement relayés par la toponymie. Elle-même n'a pu qu'être profondément remaniée par les réformes territoriales du Bas-Empire. L?ensemble était encore lisible dans le paysage régional jusqu'à la Révolution, par le biais des structures du diocèse de Metz, héritier direct de la cité des Médiomatriques, dont la frontière linguistique n'a fait que reprendre fidèlement le tracé. On découvre un espace bilingue, au sein duquel la toponymie régionale apparaît clairement comme un héritage de l'administration gallo-romaine et non pas comme la conséquence d'invasions ; elle a été organisée en secteurs germaniques et romans, bien avant les bouleversements du Ve siècle. La combinaison archéologie-toponymie confirme l'existence de centres de romanisation autour desquels se groupent des implantations secondaires, reflet d'une germanité ancestrale intégrée à un cadre administratif gallo-romain, auquel le haut Moyen Âge ne modifiera quasiment rien, comme le confirme l'implantation des nécropoles mérovingiennes. Se dessine alors un paysage ancestral avec la pérennité d'un germanisme endémique, sans rapport avec de prétendues invasions extérieures. L'espace mosellan retrouve enfin une individualité historique et une spécificité culturelle. / The Moselle area is mainly Germanic, seen as taking its roots in the Great Invasions which originated a Lorraine divided into two parts, a Germanic one -so to say Frankish- on one hand and a Roman one on the other, both parts having kept their traditions since the Late Antiquity, the whole being separated by a linguistic frontier. This picture is the product of the XXth century German historiography and is still commonly taken for granted, in Lorraine and everywhere else in spite of the improvements of research. The purpose of my thesis is to show that these theories, based almost essentially on toponymic criteria, have no real scientific grounds and cannot resist in front of the modern research, especially in archaeology. It hinges on three points: 1: to adapt the Moselle area to the general panorama of modern historiography. To study the area from the inside, as a whole entity, no longer depending on pseudo-invasions. To approach the linguistic frontier on unbiased and non-theoretical criteria. To let down the ?Frankish? myth for the benefit of the ethnogenesis reality. To survey the archaeology of Gallia Belgica in Low Antiquity; 2: to give up traditional historiography for the benefit of archaeological reality. To study the settlements in the Early Middle Ages based on Merovingian cemeteries; to examine the latest discoveries about the languages of the Franks and about the Moselle country toponymy. We then discover a total inadequacy between the classical theories and the reality imbued with romanity; 3: to give back an historical coherence to the Moselle area. In such a context of antique duration, the organization of the territory could do nothing but live on thanks to the cadastres and the fiscal system automatically taken over by toponymy which was deeply reorganized by the territorial reforms of the Late Antiquity. This could still be seen in the regional landscape until the Revolution through the structures of the Metz diocese, the direct heir of the Mediomatric city, whose layout was exactly the same A bilingual area reveals itself and the regional toponymy clearly appears as the heritage of the Gallo-Roman administration and can no more be considered as a consequence of migrations. It was set up into German and Roman sectors long before the disruptions of the Vth century. Putting together archaeology and toponymy lead to confirm the existence of a lot of romanized centres surrounded by more little settlements; all this is a mirror of an ancient Germanity, which was included in a Gallo-Roman administrative structure . The Early Middle Ages hardly changed anything as can be shown by the implantation of the Merovingian cemeteries. Then we can rediscover an ancestral landscape with a continuity of an endemic germanism, without any connection with the so-called external invasions. At last the Moselle area recovers its historical individuality and its specific culture.

O Cerrado é o bioma brasileiro que mais perdeu área para o agronegócio em anos recentes, verificando que a expansão da fronteira agrícola sobre o Cerrado provocou a pulverização dos remanescentes em fragmentos cada vez menores, imersos em matrizes de baixa similaridade, causando uma série de impactos negativos sobre o ecossistema natural. A fragmentação de habitats é considerada uma das mais graves ameaças à conservação da biodiversidade, com consequências ecológicas variáveis, intensificadas na faixa de transição entre matriz e fragmento. Os efeitos de borda são decorrentes de mudanças físicas e bióticas nas faixas marginais das ilhas de vegetação natural, que promovem modificações nas características microclimáticas, as quais conduzem a uma série de alterações importantes nas comunidades que compõem os ecossistemas. O objetivo deste estudo foi investigar a existência de efeito de borda e suas consequências sobre a comunidade vegetal do Cerrado stricto sensu. O estudo foi realizado em fragmento de Cerrado com área de 980,8 ha, localizado no município de Iaras, SP, cujo entorno foi ocupado por pastagem durante cerca de um século. Efetuou-se a caracterização estrutural e florística de diferentes estratos da vegetação em diferentes distâncias da borda (0, 10, 20, 40, 80 m) e coletaram-se dados microclimáticos na matriz (a 10 m de distância da borda) e no interior do fragmento, nas diferentes distâncias da borda e em duas estações do ano (seca e chuvosa). Investigou-se a existência de um possível gradiente de estrutura ou composição da vegetação relacionado com a distância da borda e com as variáveis microclimáticas. Os resultados obtidos mostraram não existir variações de microclima e de estrutura e composição do componente arbóreo e herbáceo-arbustivo em relação à distância da borda do fragmento. Embora independente do microclima e, portanto, diferente dos clássicos efeitos de borda, a invasão pela braquiária (Urochloa decumbens) foi detectada como a única consequência da exposição da periferia do Cerrado stricto sensu às pressões da matriz, causando exclusão das gramíneas nativas e inibindo o desenvolvimento de plantas lenhosas de pequeno porte. A ausência de efeito de borda sobre os demais componentes da vegetação sugere, em um primeiro momento, que esta não é uma ameaça importante para a conservação do cerrado. Porém, a invasão biológica pela gramínea africana é relativamente recente (foi introduzida há cerca de três décadas na propriedade) e suas consequências ainda não podem ser avaliadas adequadamente. É possível que seus impactos sobre os estratos superiores da vegetação venham a ser observados no futuro, quando a inibição da regeneração das espécies arbustivas e arbóreas comprometer a dinâmica da comunidade vegetal e a substituição dos adultos nas populações dessas espécies. Além disso, hoje a invasão só causa impactos significativos sobre a faixa de 0 a 20 m de distância da borda, mas não é possível prever se a gramínea invasora vai se expandir rumo ao núcleo do fragmento no futuro. / From the Brazilian biomes, the Cerrado has been the most widely and rapidly converted to agribusiness in recent years. The expansion of agricultural frontier over the Cerrado domain resulted in thousands of small fragments embedded in matrices of low similarity, causing a series of negative impacts on the natural ecosystem. Habitat fragmentation is considered one of the most serious threats to the conservation of biodiversity and ecological consequences vary, being intensified in the range of transition between matrix and fragment. The edge effects are caused by biotic and physical changes in marginal areas of the islands of natural vegetation, promoting changes in microclimatic characteristics, which leads to a series of important changes in the ecosystems. The aim of this study was to investigate the existence of edge effect and their consequences on the plant community of Cerrado sensu stricto. The study was conducted in Cerrado fragment with an area of 980.8 ha, located in the municipality of Iaras, SP, whose surrounding area was occupied by pasture for about a century. Structure and floristic composition of distinct vegetation layers was assessed at different distances from the edge (0, 10, 20, 40 and 80 m). Climatic data were collected in two seasons (dry and wet), at the same distances withing the fragment and also in the matrix (10 m away from the edge). The existence of a gradient of vegetation composition or structure and the microclimatic variables related to distance from the edge was investigated. No changes in microclimate and structure or composition of the wood layers related to distance from the edge was observed. Although independent of the microclimate and therefore different from classic edge effects, invasion by the African grass Urochloa decumbens (braquiária) was detected as the only consequence of exposure of the periphery of the cerrado sensu stricto to the pressures of the matrix, causing the exclusion of native grasses and inhibiting the development of small woody plants. The absence of edge effect on other components of the vegetation suggests, at first, that this is not a major threat to the conservation of the Cerrado. However, the biological invasion by the African grass is relatively recent (it was locally introduced about three decades ago) and its consequences have not been adequately assessed. It is possible that their impacts on the upper strata of the vegetation may be observed in future, when the inhibition of regeneration of shrub and tree species jeopardize the dynamics of plant community and the replacement of adults in the populations of these species. In addition, at present the invasion has significant impacts only over 0-20 m from the edge, but it is impossible to predict whether the invasive grass will expand or not into the core area of the fragment in the future.

The simultaneous increase in biological invasions and habitat alteration through the building of coastal infrastructure is playing an important role in reshaping the composition and functioning of nearshore marine ecosystems. This thesis examined patterns of marine invasions across anthropogenic and natural habitats and explored some of the processes that influence establishment and spread of invaders. The goals of this thesis were four-fold. First, I examined the habitat distribution of marine nonindigenous species (NIS) spanning several taxonomic groups and geographical regions. Second, I conducted systematic subtidal surveys in anthropogenic and natural habitats and investigated the distribution of nonindigenous ascidians on Southern Vancouver Island, British Columbia, Canada. Third, I tested methods for in-situ larval inoculations and utilized these techniques to manipulate propagule supply and assess post-settlement mortality of ascidians across habitat types. Fourth, I investigated the role of biotic resistance, through predation by native species, on the survival of ascidian colonies in anthropogenic and natural habitats. Results from this research showed that anthropogenic habitats are hubs for marine invasions and may provide beachheads for the infiltration of nearby natural sites. Specifically, a literature review of global scope showed that most NIS are associated with anthropogenic habitats, but this pattern varied by taxonomic group. Most algal and mobile invertebrate NIS were reported from natural habitats, while most sessile NIS were reported from artificial structures. Subtidal field surveys across both anthropogenic and natural habitats showed that nonindigenous ascidians were restricted largely to artificial structures on Southern Vancouver Island and that this pattern is consistent across their global introduced ranges. Field manipulations using the ascidian Botrylloides violaceus as a model organism, showed that post-settlement mortality is high and that large numbers of larvae or frequent introduction events may be needed for successful initial invasion and successful infiltration of natural habitats. Experiments also showed that predation by native species can limit the survival of B. violaceus in anthropogenic and natural habitats. This dissertation contributes knowledge about the patterns and processes associated with habitat invisibility; provides insight into factors affecting colonization; and supplies valuable information for predicting and managing invasions. / Graduate / 0329

Alien invasive species pose a great threat to ecosystems and human communities (Richardson & van Wilgen 2004; Hobbs & Humphries 1995). On private lands, there is a need to find institutional, administrative and scientific responses to the alien plant problem that operate beyond the scale imposed by property boundaries (Slocombe 1998; Grumbine 1994). One such response is the development and support of institutions, such as the St Francis Conservancy, that foster cross-boundary management of landscapes (Hurley et al. 2002). This study seeks to promote collective decision-making and collaborative management by private landowners through the development of a resource allocation system for the control of alien invasive plants on the St Francis Conservancy. The conservancy is located in the south-eastern lowlands of the Cape Floristic Region, between the villages of Cape St Francis and Oyster Bay, and is comprised of the properties of multiple landowners. Mutliple Criteria Decision Analysis (MCDA) and Geographical Information Systems (GIS) techniques were integrated to provide a spatially explicit resource allocation system that considered environmental, social and economic concerns. The MCDA technique selected for use was the Analytical Hierarchy Process (AHP). This technique has a record of providing robust, defensible decisions and enabled the resource allocation decision-problem to be decomposed into a hierarchy of objectives, criteria and indicators. Stakeholders participated in the development of the resource allocation system, especially through providing input into the determination of the relative importance of criteria and indicators through the assignment of weights. Various weighting scenarios were presented and these were interpreted into an ii implementation plan. The costs and effort required to clear alien plants were estimated, and obstacles facing the implementation of the plan were identified.

The fire-prone mountain fynbos of the southwestern Cape Province of South Africa has been severely invaded by introduced trees and shrubs. These invasions have transformed fynbos shrublands to dense thickets of trees and shrubs in many parts of the region, thus disrupting various natural ecosystem processes. The ecology of invasions by species of Pinus and Hakea (the most successful genera) was studied using a series of natural experiments in conjunction with autecological studies. The study was divided into main four parts: (i) case studies to elucidate major patterns and processes of invasion; (ii) studies of the life history and population ecology of selected invaders; (iii) studies of the determinants of invasibility; and (iv) assessments of the consequences of invasion and of control programmes. Bibliography: pages 235-272.