Due to the irreversible nature of biological invasions, prediction has been a key area of emphasis in invasion biology. Specifically, the degree to which species-specific traits may help us predict invasion success is a core issue in the field. My research examined a series of traits and asked whether they were good predictors of invasion success, particularly establishment success. I compared traits among four species of the poeciliid fish Gambusia, two of them highly invasive (G. affinis and G. holbrooki) and two of them non-invasive (G. hispaniolae and G. geiseri).I examined abiotic tolerances, feeding behavior, behavioral responses to novel predation and competition, life histories, and dispersal tendencies. I found the invasive Gambusia species to be more tolerant of low temperatures and to exhibit higher feeding rates and dispersal tendencies than non-invasives. Invasive species were more likely to respond appropriately to novel predation by reducing foraging and activity level and by increasing refuge use, and less likely to show lower foraging success when faced with competitors. Invasives exhibited higher fecundity and juvenile growth rates, and consequently reached maturity sooner than non-invasives. I found no differences in the species' diet breadth or aggressiveness.I then simulated the invasions of simplified pond communities and measured establishment success (with and without novel competitors) and community impact by tracking population trajectories over several months. As predicted from the trait comparisons, I found that in both simulations invasive Gambusia outperformed non-invasives by achieving andvmaintaining larger populations. In the first experiment, only invasive Gambusia were able to successfully establish (non-invasive populations had zero survival). In the second experiment, invasive Gambusia populations were better able to cope with competition and had greater community impact on lower trophic levels than the non-invasives.Overall, species traits were good predictors of establishment success. A species' ability to cope with the abiotic conditions of the invaded community seemed particularly important to whether or not establishment occurred in the study communities. Life history traits and the species' ability to cope with biotic interactions were important to determining the level of establishment species achieved if invaders survived the novel abiotic element.

Thesis (Master of Conservation Science)--Cape Peninsula University of Technology, 2018. / Introduction pathways of fungal pathogens in South Africa are far less quantified in the literature than those for plants, animals and human infectious diseases. Phytopathogens continue to be introduced to South Africa via several pathways at an unprecedented rate. A number of these species pose a significant threat to South African ecosystems and biodiversity. Despite this, fungal pathogens could also be beneficial when they are used as bio-control agents to control alien invasive plant species. Nevertheless, recent studies revealed pathogens are most likely to be studied after they have caused a detrimental impact on the environment. Invasive fungal pathogens, such as Phytophthora cinnamomi (Oomycota) do not only pose a threat to native species of the family Proteaceae but could also potentially be bio-control agents for emerging alien plant invaders. In this thesis, firstly, I review current knowledge of phytopathogenic fungi introduction pathways in South Africa; secondly, I aim to understand the importance of fungi in limiting plant invasions using Banksia as a case study in the Cape Floristic Region. In chapter two I investigate introduction pathways and dispersal vectors that facilitate the spread of fungal pathogens. I compiled comprehensive list of fungal pathogens in South Africa, and evaluated the dispersal vectors and introduction pathways for each species. I found fifty five casual species, three naturalised species, six invasive species and thirty six pathogens for which invasion status was not classified due to insufficient data. Agriculture is responsible for the introduction of most fungal pathogens in South Africa. Wind was identified to be the prominent dispersal vector facilitating the spread of pathogens. I conclude that knowing introduction pathways of pathogens and their dispersal vectors will assist in developing quarantine protocols that could improve bio-security. Lastly, I provide recommendations for the national invasive microbe species list. In chapter three the study investigates the variability in mortality rate of Banksia species in the Cape Floristic. Species abundance was calculated across known Banksia populations in the Cape Floristic Region to determine survival and mortality rates. Soil and leave samples were taken from Banksia plants to evaluate potential microbial pests that were present. Also, acetone leaf extracts of twelve Banksia species were screened for antimicrobial activity against P. cinnamomi (Oomycota). Lastly, a post-border risk assessment was conducted for 14 Banksia species− present in South Africa − using the Australian Weed Risk Assessment protocol, to evaluate potentially invasive species. The results indicated that survival and mortality rate varied across species; I found the two invasive species, B. integrifolia and B. ericifolia to have the highest survival rate. Phytophthora cinnamomi was the most prominent isolated fungal pathogen sampled from Banksia species roots. The detection of antifungal activities in the minimum inhibitory concentration (MIC) bioassay provided evidence that some Banksia species (B. ericifolia, B. integrifolia, B. hookeriana and B. formosa) have antimicrobial chemical constituents that could possibly inhibit infection and colonisation by P. cinnamomi. The weed risk assessments conducted on Banksia species showed five species pose a high risk of invasion while seven species required further evaluation. I conclude that P. cinnamomi could potentially regulate invasive Banksia species such as B. speciosa with minimal antimicrobial activity against the pathogen. I recommend an in-situ and ex-situ inoculation trials of Banksia species against P. cinnamomi to be conducted to evaluate pathogenicity, under different watering regimes since the pathogens proliferation is favoured by soils that are high in moisture. I present the main conclusions from this thesis in chapter four and provide recommendations for management and invasive species legislation.

Reproduction de : Thèse de doctorat : Sciences de la vie : option Hydrobiologie animale : Metz : 2003. / Titre provenant de l'écran-titre. Notes bibliographiques.

Thèse de doctorat : Sciences de la vie et de la santé : Tours : 2008. / Titre provenant de l'écran-titre.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2000. / Bibliography: leaves 82-89.

Thesis (M.S.) in Teaching--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaves 108-117).

Thesis (Ph.D.)--University of Wyoming, 2008. / Title from PDF title page (viewed on Mar. 9, 2010). Includes bibliographical references.

Marine bioinvasion has been increasing exponentially due to intensive human activities. To manage the threats posed by marine bioinvasion, it is important to understand the key factors for invasion success. Stress tolerance is thought to play an important role in the invasion process, however, little is known of the nature of this tolerance, particularly whether stress tolerance is species- or population-specific. To determine this, laboratory experiments were conducted to investigate differential tolerance of populations of a cosmopolitan marine invasive mussel, Perna viridis, and whether stress tolerance can be altered through pre-selection of individuals. Comparisons were firstly made between two local P. viridis populations from the intertidal and subtidal zones to test if stress tolerance was population-specific. Individuals from the intertidal population had higher baseline heart rates, lower critical salinity values, Scrit, for cardiac activity and longer survival duration at low salinity than individuals from the subtidal population, supporting the presence of population level differences in stress tolerance. Mortality of P. viridis was also compared at sites in both their introduced range (Hong Kong) and native range (Indonesia) which revealed that individuals from the Hong Kong population were more stress tolerant than their native counterparts in Indonesia. Using the same experimental approach, the effect of pre-selection to stress (a prior pre-selection to hypoxia and a subsequent exposure to heat) showed that stress tolerance can be enhanced by pre-selection. The second part of this study investigated whether invasive mussels, Brachidontes variabilis and P. virdis, were more stress tolerant than the native, non-invasive, Septifer virgatus. Laboratory experiments compared the Scrit as well as critical temperature, Hcrit for cardiac activity. Mortality and byssus thread production were also measured in a factorial design with different combinations of temperature (16, 24 and 32 °C) and salinity (8, 16, 32 p.s.u) for 15 days. The two invasive mussels had a higher Hcrit and lower Scrit, which indicated a higher stress tolerance, than the non-invasive mussel. The mortality rate of P. viridis was faster than in B. variabilis and S. virgatus at 8 p.s.u. whereas S. virgatus was the only mussel that exhibited mortality in the medium hyposalinity (16 p.s.u.) and showed much slower byssus attachment than the invasive mussels, suggesting that the invasive mussels are more stress tolerant to heat and medium hyposalinity than the non-invasive species. Overall, stress tolerance proved to be higher in the invasive than non-invasive species and was also population-specific with higher stress tolerance in the invasive population, which may be attributed to the selection of more tolerant individuals during the invasion process. Such a process may occur when founding individuals successfully pass through an invasion process, which may increase the overall mean population-level of stress tolerance and explain why invasive species are generally more stress tolerant than native species. Thus stress tolerance plays an important role in invasion success and invasive species with high stress tolerance may be favoured by climate change, including ocean warming and increased precipitation, which may extend their current distribution range. / published_or_final_version / Biological Sciences / Master / Master of Philosophy

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Thesis (Ph. D.) -- Lincoln University, 2008. / Includes case study of Argentine ant in New Zealand. Also available via the World Wide Web.