Dissertations / Theses: 'Alien Species'

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CHINCHIO, ELEONORA. "DISEASE RISK ASSESSMENT OF INVASIVE ALIEN SPECIES." Doctoral thesis, Università degli Studi di Milano, 2021. http://hdl.handle.net/2434/821735.

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Increased global trade and travel have led to a rise in the number of invasive alien species (IAS), i.e. species introduced by humans in geographic areas where are not naturally found, worldwide. Despite the recognized role of wildlife, as well as of wildlife translocations, in the emergence and re-emergence of infections of public health significance, IAS remain mainly studied for their environmental impacts, and their disease risk towards humans and animals is still largely neglected by health professionals. The main aim of this thesis is therefore to cover this gap by setting the ground for a new “invasion epidemiology” field, and this has been done through two main steps: the review and analysis of both the mechanisms underlying IAS disease risk and the information available in literature on IAS pathogens, and the development of a standardized qualitative disease risk assessment method, applicable to different geographic contexts, to assess the risk of mammal IAS to impact on human and animal health. First, I reviewed the existing biological and ecological literature on IAS to identify the main mechanisms by which animal IAS may affect disease risk in their area of release. IAS resulted to potentially affect disease risk both directly, by acting as hosts of infectious agents, thus possibly leading to the introduction of new pathogens, and/or the amplification of endemic ones, or indirectly, by altering the ecosystem equilibrium, through competitive and trophic interactions with native host species or the modification of local habitats. This literature review highlighted how IAS may have important health implications, which should be better acknowledged by people working in the human and animal health field, and how the mechanisms underlying the sanitary outcome of a biological invasion, and in particular indirect ones, are extremely complex, being the product of multiple factors. Acknowledging the important limitations of our current ability to predict possible health impacts driven by indirect mechanisms, I decided to address the issue of IAS disease risk by focusing specifically on IAS possible role as infectious agents’ host. As information on IAS pathogens is not systematized, preventing from knowing the amount and quality of available data to inform possible disease risk assessment procedures, I systematically reviewed the literature on the infectious agents of the main mammal species of European Union concern. Current knowledge on the pathogens harbored by mammal IAS was evaluated through different statistical approaches: the identification of the main factors associated with research intensity and the observed pathogen species richness, the estimation of the true helminth species richness, and a meta-analysis of prevalence of the pathogens of public and animal health significance. Results highlighted the existence of strong information gaps and biases in the way research on mammal IAS pathogens is carried out, the current underestimation of the amount of pathogens harbored by these species and high levels of uncertainty in the pooled prevalence of pathogens of public and animal health significance. However, the review confirmed that mammal IAS harbor pathogens of human and animal health significance, and therefore, the need to identify high-risk species. Considering that the existing knowledge gaps would have resulted in strong limitations in informing a risk assessment procedure, I developed a qualitative disease risk assessment methodology informed by expert opinion. This tool is specifically aimed at assessing IAS disease risk towards humans, domestic animal populations, and/or wildlife populations and allows to obtain a list of the pathogens of animal and human health significance that mammal IAS could transmit to a population of interest (directly or through the communities of local hosts), each with the related level of risk and uncertainty. Key features of the tool are its flexibility, being applicable to different contexts and for different purposes, and the high resolution of the mechanisms under assessment, which make possible for risk managers identifying the most critical pathogens and mechanisms involved in disease risk, allowing them to direct targeted actions and surveillance plans. Finally, the need to combine multiple likelihood estimates deriving from several pathways in an overall risk estimate led me to tackle a methodological aspect of qualitative risk assessment procedures, and I proposed a standardized method applicable in such cases, to reduce the subjectivity that relies in the different ways multiple estimates are currently combined.

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Dutrieux, Mariane. "Spatio-temporal species distribution modeling: Application to invasive alien species’ monitoring." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-224319.

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The developments of species distribution modeling techniques have brought new opportunities in the field of biological invasion management. In particular, statistical niche modeling for spatio-temporal predictions of species’ distribution is a widely spread tool that has proved its efficiency. The main purpose of this Master thesis is to study applicability of species distribution modeling to invasive alien species, with the aim of supporting efficient decision-making for their prevention. Some research questions are: how useful can species distribution modeling be for invasives’ prevention? Is distribution modeling technically feasible in the case of invasive species? What types of techniques are recommended to model distributions of IAS? What are the limits of such a tool? The methods employed to answer these questions are literature review and expert advice. I found that species distribution models can provide risk maps which are necessary to enable effective invasive alien species’ prevention. However intrinsic characteristics of invasives introduce uncertainties in the predictions made. Consequently several preliminary analyses should be conducted before applying the distribution model. Finally recommendations were made on the most appropriate distribution modeling technique to use depending on the urgency of the situation and the availability of data.
Utvecklingen av metoder för modelering av artdistribution har medfört nya möjligheter inom området hantering av biologiska invasioner. Statistisk nischmodelering för spatio-temporala förutsägelser av arters distribution är ett väl använt verktyg som har visat sig vara effektivt. Det övergripande målet med det här arbetet har varit att studera hur lämpad artmodelering är vid förebyggande av invasioner av främmande arter. Det har även undersökts huruvida metoden kan bidra till bättre och enklare beslutsfattande när det kommer till att förhindra sådana invasioner. Forskningsfrågorna lyder: hur användbart är fördelningsmodelering för förebyggande av spriding av invasiva arter? Är distributionsmodelering tekniskt genomförbar när det gäller invasiva arter? Vilka olika tekniker rekommenderas för att modelera spridningen av invasiva arter? Vilka begräsningar har modelerna? De metoder som används är litteraturöversikt och expertråd. Resultaten visar att artdistributionsmodelering kan bidra till att sammanställa riskkartor som är nödvändiga för att möjliggöra ett förebyggande arbete. Men speciella egenskaper hos de invasiva arterna som är svåra att förutse skapar osäkerheter i resultatet. Därför kan preliminära analyser med fördel genomföras innan modelering. I slutsatserna återfinns rekommendationer för vilken distributionsmodelteknik man bör använda, beroende av hur brådskande situationen är och om data finns tillgängligt.

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Theile, H. Lenore. "Invasion of contrasting ecosystems by alien plant species /." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18380.pdf.

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Emer, Carine. "Multiple aspects of alien species in pollination networks." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.686826.

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In a rapidly changing world, where many species are declining due to anthropogenic disturbance while others are invading disturbed habitats, understanding how alien species affect ecological processes is crucially important. In this thesis I use ecological networks as a tool to investigate how alien species integrate and affect pollination at the community level. First, I tested whether the invasion of an alien plant (Impatiens glandulifera) affects pollen transfer networks and found no significant change in network structure between invaded and uninvaded habitats. While more alien pollen was recorded on invaded sites only five plant species retained 91% of all balsam pollen on their stigmas. These results point towards the robustness of pollination networks to plant invasion. Second, I investigated intraspecific variability and specialization in pollen transport and pollen transfer networks; strong intraspecific variation was found for both plants and pollinators along with higher specialization found in pollen transport networks. And finally, I asked whether a species role in network structure differs between its native and alien ranges and whether the former can be used to predict the latter; no significant difference in species role between ranges was detected, and degree and closeness were highly predictable from native to alien habitat. These results suggest species roles conservatism in pollination networks, whereby a species role in a network is similar whether it occurs in the native or in the alien range of its distribution. I conclude that a holistic approach encompassing different spatial, temporal and biological scales is needed if the aim is to understand how alien species interact and affect pollination. I also highlight ecological networks as a powerful tool to understand anthropogenic effects at the community level and suggest that merging the expertise from different disciplines is needed if we are to truly understand the invasion process.

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Saul, Amelia Mozelle. "Exploring the “density-benefit” relationships of alien species." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25806.

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The disastrous impacts of invasive alien species are well-documented. However, there is growing evidence that some alien species can also have positive effects in their new environments, adding complexity to their management. Classic density-damage relationships are used to determine cost effective densities at which to control alien populations and limit their adverse effects. In this thesis I proposed that the ecological benefits of alien species are also related to population density, and I hypothesised the different types of relationships that may exist. I then investigated the "density-benefit" relationships of three common alien species through a series of manipulative field experiments. Firstly, I examined the effect of population density on the pollination behaviour of alien black rats, Rattus rattus, that provide a pollination function for an Australian native plant. I found black rats at high densities behave in a way that may reduce their pollinator efficacy. I next investigated the effect of density upon an alien plant, Lantana camara, providing refuge for small native reptiles. I found that the abundance of reptiles was related to L. camara density in a U-shape, showing a benefit at high densities only. Then I conducted a simulation experiment to compare the digging activities of native marsupials and alien European rabbits (Oryctolagus cuniculus) at different densities. Digging density was significantly related to the germination and survival of seedlings. However, I detected a difference in the quality of the ecological function provided by these analogous alien and native species. Together, these results suggest that “density-benefit” relationships need to be integrated into the management of alien species densities. This work will advance the current understanding of alien species ecology, guide the management of alien species with complex impacts and ensure that significant ecological benefits provided by alien species are not lost unnecessarily.

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CHATZIDIMITRIOU, EVANGELIA. "Alien Invasive Species in Europe: Three Case Studies." Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3427137.

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The incidental introduction of alien phytophagous insects and mites has become quite a common event in the world owing to intensive commercial exchanges of plants and goods and ever-increasing tourist traffic. There is evidence that this phenomenon is increasing, in spite of the control measures of the EU phytosanitary system in order to minimize unintentional introductions. The introduction of an alien species in a new ecosystem and the interaction between an alien species and the autochthonous species usually has many disadvantages. The alien species can dominate the invaded ecosystems and eventually become an invasive species due also to the absence or paucity of natural enemies. These invasions can affect the native species that become less common or threatened with extinction. Apart from the environmental impacts alien species are known for their economic and health impacts. In this study were investigated mostly 3 recently introduced alien species in Italy, namely Tuberocephalus (Trichosiphoniella) tianmushanensis Zang (Hemiptera Aphididae), Cydalima perspectalis (=Glyphodes) (Walker, 1859) (Lepidoptera Crambideae), the box caterpillar and Phenacoccus defectus Ferris (Rhynchota Pseudococcidae). The first chapter is a background of invasive ecology and presents with graphs the high number of alien species introduced in Europe the last years.. The second chapter is dealing with Tuberocephalus (Trichosiphoniella) tianmushanensis Zang, an Asiatic heteroecious species so far not recorded in Italy. This species was collected in the University Botanical Garden of Padova in spring 2012. On May 30, 2012 reddish-pink galls, with aphids inside, were observed on the leaves of two Prunus subhirtella cv. pendula trees (Rosaceae) (Weeping Higan Cherry), about 40 years old. Once mounted on slides the aphids were identified as Tuberocephalus (Trichosiphoniella) tianmushanensis Zang. The purposes of this study were to collect data on species distribution over the territory, by monitoring ornamental cherry trees in the Veneto region, to observe the phenology and biology of the Asiatic aphid, to study the life-cycle in screen houses and outdoors, to verify if its secondary host plant was an Artemisia sp., as reported in bibliography. Another aspect of the work was to provide an overview of the species belonging to the genus Tuberocephalus so far described, by consulting the available literature. It was made an effort to gather all the currently available information for each species, its distribution and information on their biology mainly regarding the first and secondary host plants. Results showed that Tuberocephalus (T.) tianmushanensis, is now considered acclimatized in our environment. The aphid is closely related to the presence of its primary host Prunus subhirtella v. pendula with pink flowers. The aphid can carry on two generations on Prunus and can induce two types of leaf galls. The gall A is induced by the fundatrix, while the gall B is induced by the fundatrigeniae. The trial of colonization on Artemisia vulgaris, failed for the second successive year so possibly Artemisia vulgaris is not the secondary host plant of the aphid, as reported in literature. The third chapter concers Cydalima perspectalis (Lepidoptera, Crambiidae) (Walker, 1859), an asiatic pest of Buxus. It was reported for the first time in Europe in Germany in 2007. In Italy it was detected in 2011, in Lombardy, Como province. In a very short time it invaded the other northern regions and was recorded in Veneto in 2012. The larvae feed on leaves and shoots of the box trees and the infestations lead to defoliation of the plants. The objective of this study was to investigate the phenology of C. perspectalis. More precisely we examined the biological cycle of life, the number of molts and the overwintering stage. In addition host plants were monitored by regular samplings, from late winter to late fall to collect data on species distribution over the territory. The life-cycle was studied in screen houses and in the field, to investigate the role of potential predators and parasitoids. Additionally experiments were conducted with pheromones traps with the purpose of checking, monitoring and collecting data on species distribution over the territory, finding any possible differences based on climate, checking the potential differences between types of traps. According to the results of 2014 and 2015 in the Veneto Region C. perspectalis develops three generations / year. In 2014 the overwintering larvae started their activity early in February until mid-April while in 2015 one month later until end of April probably due to different climate conditions between these years. C. perspectalis overwinters in a silk cocoon in-between the leaves as a larva of 2nd instar and the number of larval instar is 5. The number of captures from the sex pheromones traps was low. No differences were observed between the two types of pheromones. C. perspectalis has spread quickly in our environment proving that it has acclimatized. So far, it seems there has been no adaptation by indigenous natural enemies (parasitoids) to C. persectalis. The next chapter is focued on the difficulty to separate the Phenacoccus solani Ferris and P. defectus Ferris (Hemiptera: Pseudococcidae). They are morphologically similar and the microscopic morphological characters of the adult female alone are not enough. In order to resolve their identity, a canonical variates morphological analysis of 199 specimens from different geographical origins and host plants and a molecular analysis of the CO1 and 28S genes were performed. The morphological analysis supported synonymy of the two species, as although the type specimens of the "species" are widely separated from each other in the canonical variates plot, they are all part of a continuous range of variation. The molecular analysis showed that P. solani and P. defectus are grouped in the same clade. On the basis of the morphological and molecular analyses, P. defectus is synonymized under the senior name P. solani, syn. n. Finally a zoogeographic analysis of the Greek scale insects fauna (Hemiptera, Coccoidea) was carried out with the aim to highlight how many alien scale insects species are so far present in the Greek territory. According to the last data, the scale insect fauna of whole Greek territory comprehends 207 species; a total of 187 species are recorded in mainland Greece and minor islands, whereas only 87 scale species are known so far in the island of Crete. The most numerous families are the Diaspididae, with 86 species in total, followed by Coccidae, with 35 species and by Pseudococcidae, with 34 species. The results of a first zoogeographical analysis of scale insect fauna of mainland Greece and the island of Crete is also presented. Five scale species, respectively four in mainland Greece and one in Crete, are considered as endemic. This analysis demonstrated that alien scale insects, introduced and acclimatized a long time ago or recent invaders, make up 30% of the Greek scale insects fauna.
Tra le specie di Phenacoccus neartiche, P. defectus Ferris, P. solani Ferris è P. solenopsis Tinsley condividono l’insolito carattere morfologico dell’assenza di pori pentaoculari è sono morfologicamente simili da rendere difficile l’ identificazione. Il problema della loro identificazione è stato evidenziato da diversi autori (McKenzie, 1967; Williams & Granara de Willink, 1992; Culik & Gullan, 2005; Pellizzari & Porcelli, 2013), benché sia generalmente riconosciuto che P. solenopsis possieda un maggior numero di pori multiloculari e un circulus di maggiori dimensioni rispetto alle altre due specie; inoltre quest’ultima è una specie bisessuale mentre le altre due si riproducono per partenogenesi. Le tre specie di cocciniglie condividono diverse piante ospite. In accordo con Hodgson et al. (2008) ci sono elementi che supportano l’ipotesi che si tratti di varianti di una singola specie. Per definire meglio il loro status tassonomico, abbiamo amplificato mediante PCR e sequenziato il frammento di DNA ‘barcode’ di P. solani, P. solenopsis, e P. defectus.

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Lopezaraiza, Mikel Martha Elena. "The impact of alien species on native pollination systems." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427906.

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Robinson, Tamara Bridgett. "Marine alien species of South Africa : threats and opportunities." Doctoral thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/6705.

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Until recently, marine bioinvasions have received little attention in South Africa, and the status of intertidal marine aliens was last assessed in 1990. I thus investigated the present distribution and status of three intertidal alien species (Mytilus galloprovineialis, Care in us maenas and Careinus aestuarii) and documented the presence and status of a previously unknown invasive, the Japanese oyster, Crassostrea gigas. M galloprovincialis was recorded along the entire west coast of South Africa, with populations extending up to central Namibia, and along the south coast of South Africa to 40 km west of East London. Along South African shores a total stock of 35 403.7 tons (± 7 241.4 SE) was recorded, with the vast majority of the stock occurring on the west coast (31 054.5 tons ± 6 274.1 SE). C. maenas supports a substantial population of 133 568 individuals (95 % confidence range == 97 694 - 166 862) in Table Bay Harbour which appears to be acting as in invasion incubator for surrounding areas. A new population of 9 180 individuals (95 % confidence range 5 870 - 12 003) was recorded in Hout Bay Harbour. This represents a range extension along the Cape Peninsula. The low intertidal abundance of this crab between these localities is thought to reflect the inability of C. maenas to inhabit exposed habitats. C. aestuarii was not recorded during this study despite previous documentation of its presence. In 2003, naturalised populations of C. gigas were documented in the low shore zone of the Breede, Goukou and Knysna Estuaries, but not on the open coast. This may again be indicative of the limiting effect of wave action on species alien to South African shores. As such, the presently undetermined impact of this species may well be focused on estuarine habitats. To quantify the threat posed to intertidal communities by M galloprovincialis, changes in community structure on the rocky shore of Marcus Island and the sandy shore of Langebaan Lagoon were measured. In both habitats, the invasion significantly altered community composition. On Marcus Island the effects were focused within the mid-to-low intertidal zones, where habitat complexity was enhanced and patchiness was decreased, resulting in dramatic changes in invertebrate density, species number, richness and diversity. On sandy shores, M galloprovincialis beds changed available habitat structure, resulting in a concurrent invasion by indigenous rocky shore species. In the sediment below the mussel beds, soft-sediment species were excluded due to anoxia. Following a die-off of the mussel beds the rocky shore species disappeared, but were not replaced by sandy shore organisms as the sediment remained uninhabitable. The subsequent removal of the dead mussel shells appears to have recovered, but community composition is still to return to the preinvasion state. In order to consider the biological viability of a fishery for A1. galloprovincialis in the Northern Cape, a harvesting project operated by two impoverished coastal communities was initiated. Harvesting took place on a rotational basis and twelve sites, nested within four harvesting locations, were each exposed to spectrum of harvesting intensities (F=O, F=30%, F=60% and F=90%). A dynamic biomass-based fisheries model predicted monthly Maximum sustainable yield (MSY) estimates of 1 560 kg per 100 m of shore in March-April and September-October, but two orders of magnitude less (15 kg) during the remaining months. These peaks correspond to spawning periods of this mussel along the South African west coast. Experimental manipulations revealed high recruit densities recorded at low harvesting intensities (2 000 20 000 per 0.01 m exceeding levels required for population maintenance. However, if adult mussel beds are eliminated or significantly reduced (which occurred at F=30% or above), recruitment may limit stock replenishment. Indirect effects on non-target species were also considered. Intertidal communities changed dramatically in response to harvesting, with increased algal dominance and shifts in the distribution of grazers between primary- and secondary-substrates. Community composition did not return to the pre-harvest state after four months of no harvesting, even in areas which were only harvested at an intensity of F=30%. Northern Cape intertidal communities are thus considered to have low resilience and elasticity in response to harvesting of A1. galloprovincialis. It is thus recommended that a harvesting intensity of between 10% and 30% be employed if A1. galloprovincialis stocks in the Northern Cape are to be harvested on a commercial basis. This would protect stock replenishment and minimise effects on intertidal communities. In addition, harvesting should be focused within the two spawning seasons spanning peak MSY estimates so as to maximise yield and aid community recovery between harvests. If implemented, this would represent the first instance in South Africa of a marine invasive species being utilised in a way that employs dynamic fisheries management to achieve socioeconomic goals, while taking into account the effects on other elements of the biotic community.

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Smith, Ross L. "Invasive alien plant species of The Bahamas and biodiversity management." Miami University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=miami1275062320.

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Bailey, John Paul. "Cytology and breeding behaviour of giant alien Polygonum species in Britain." Thesis, University of Leicester, 1989. http://hdl.handle.net/2381/9471.

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An investigation into the cytology and breeding behaviour of the large asiatic Reynoutria species (R. japonica and R.sachalinensis), which were introduced into the British Isles in the last century and are now a significant component of the British Flora. A number of colonies have been examined morphologically and cytologically; hybrids have been identified and artificially re-synthesised in the laboratory. The sex-expression of the Reynoutria taxa has been examined, and has been found to be gynodioecious. R. japonica var. japonica has been found only as male-sterile plants in the British Isles, which has made it particularly susceptible to hybridisation with Fallopia baldschuanica (the commonly grown garden plant Russian Vine). Seed production and viability, and the role of seed production in the colonization of Britain has also been investigated. Chromosome counts and karyotypes have been produced of Reynoutria taxa and of the closely related Fallopia species. 2c DNA amounts have been determined, and Giemsa and fluorescent banding techniques employed. A comprehensive synonomy has been produced, and the relationship between the genera Fallopia and Reynoutria discussed. One conclusion of this research is that the genus Reynoutria should be incorporated into the older genus Fallopia.

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Kühn, Ingolf. "Drivers and impacts of the spread of alien species in Europe." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-179513.

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Slabber, Sarette. "Physiological plasticity in arthropods from Marion Island : indigenous and alien species." Thesis, Stellenbosch : Stellenbosch University, 2005. http://hdl.handle.net/10019.1/50417.

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Thesis (PhD)--University of Stellenbosch, 2005.
ENGLISH ABSTRACT: Climate sets range limits in many taxa, and as climate changes, the ranges that plants and animals occupy are altered. The responses of species to climate change involve either migration or local adaptation. An investigation of the local physiological adaptation shown by indigenous and alien arthropods to temperature acclimation formed the primary focus of this study. Increased environmental temperatures favour the establishment of alien species on Southern Ocean Islands. The first records of Porce/lio scaber Latreille, 1804 (Isopoda, Porcellionidae) and an Aphidius wasp species from Marion Island were documented here. The alien wasp was discovered in 2003 and had a current known distribution along the east coast of Marion Island. Both isopods and wasps were reproducing successfully on Marion Island. The wasp species is an aphid parasitoid and had been found mummifying the alien aphid Rhopalosiphum padi. These introductions highlighted the ongoing conflict between use and conservation on the Southern Ocean Islands. Despite considerable work on the upper and lower lethal limits of insects, several major taxa have received little attention. Here this issue was addressed and the lower and upper thermal tolerances and cold hardiness strategy of Antarciopsocus jeanneli Badonnel (Psocoptera: Elipsocidae) from sub-Antarctic Marion Island was investigated. A. jeanneli is freeze intolerant, and more specifically, moderately chill tolerant. Field fresh A. jeanne li had a mean supercooling point (SCP) of -11.1oC, whereas LTSO was -7.7°C, indicating pre-freeze mortality. A. jeanneli responded to acclimation: mean SCP increased from -IS.8°C at a treatment temperature ofO°C, to -7.3°C at ISOC. Investigations of the responses to acclimation of upper and lower lethal limits and limits to activity in insects have focussed primarily on Drosophila. Halmaeusa atriceps (Staphylinidae) was examined for thermal tolerance responses to acclimation, and seasonal acclimatization. In summer and winter, lower lethal temperatures of adults and larvae were c. -7.6 ± 0.03 and -11.1 ± 0.06 °C, respectively. Supercooling points (SCPs) were more variable, with winter SCPs of -S.4 ± 0.4 °C in larvae and -6.3 ± 0.8 °C in adults. The species appeared to be chill susceptible in summer and moderately freeze tolerant in winter, thus showing seasonal acclimatization. Critical thermal minima varied between -3.6 ± 0.2 and -0.6 ± 0.2 °C in larvae, and from -4.1 ± 0.1 to -0.8 ± 0.2 °C in adults. These findings were in keeping with the general pattern found in insects, although this species differed in several respects from others found on Marion Island. In this study the differential responses of indigenous and invasive springtails to temperature were explicitly examined in the context of the beneficial acclimation hypothesis (BAH) and its alternatives. In particular, the thermal acclimation responses of desiccation resistance, supercooling ability, lower and upper thermal limits were compared. Invasive springtails (Pogonognathellus jlavescens, Isotomurus palustris and Ceratophysella denticulata) did not display greater phenotypic flexibility than indigenous springtails (Cryptopygus antarcticus and Tullbergia bisetosa), but did perform better under high temperature conditions. Indigenous species, however, performed better under low temperature conditions. In most cases the BAH was not supported, or could not be distinguished from its alternatives. The prediction that invasive species will outperform indigenous species as climates on Southern Ocean Islands warm was supported. Because temperature plays such a large role in the distribution, abundance and physiological tolerances of invertebrates, microhabitat temperatures along an altitudinal gradient (0 to 800 m above sea level (asi)) were investigated over a two-year period on Marion Island. Mean microhabitat temperatures were comparable to those from previous studies for Southern Ocean Islands, and declined with increasing altitude. The 800 m asl site had the most severe microclimate (highest absolute maximum, lowest absolute minimum and the highest frequency of freeze-thaw cycles). Year one was substantially colder than year two, indicating that interannual variation in microclimate conditions could be responsible for substantial mortality amongst. invertebrate populations. Indeed, indigenous species were best able to tolerate the high incidence of low temperatures at high altitudes, whereas alien species appeared to be confined to lower altitudinal sites on Marion Island, possibly as a consequence of extreme low temperatures at higher altitudes.
AFRIKAANSE OPSOMMING: Klimaat is een van die grootste faktore wat die verpreiding en digthede van dier en plantspesies bepaal. Soos wat klimaatsverandering plaasvind, kan spesies migreer om stresvolle klimaatstoestande te vermy, of hulle kan aanpas by plaaslike omstandighede. Dit is die laasgenoemde opsie wat in hierdie tesis ondersoek was. Die opsporing van Porcellio scaber Latreille, 1804 (Isopoda Porcellionidae) en 'n Aphidius wesp van Marion Eiland word hier aangeteken. Die huidige verspreiding van houtluise in die omgewing van die Navorsingstasie dui daarop dat hulle die eiland waarskynlik vanaf Kaapstad in bou-materiaal bereik het. Die wesp is gedurende 2003 ontdek en is tans versprei langs die oostelike kuslyn van Marion Eiland. Beide hierdie spesies plant suksesvol voort op Marion Eiland. Die wesp spesie parasiteer die uitheemse plantluis Rhopalosiphum padi. Uitheemse muise en die inheemse kleinskedebek weier tot dusver om P. scaber te eet. Die ontdekking van twee nuwe uitheemse spesies dui weereens op die konflik tussen bewaring en benutting van die Suidsee Eilande. Ten spyte daarvan dat aansienlike aandag gewy is aan die hoë- en lae temperatuur toleransies van insekte, is daar talle taksa wat selde nagevors word. Dié toleransies is dus nagevors vir die boekluis Antarctopsocus jeanneli Badennel (Psocoptera: Elipsocidae) van Marion Eiland. Die spesie is vries vermydend, en meer spesifiek, matig verkoelingsbestand. Veldvars A. jeanneli het 'n gemiddelde superverkoelingspunt van - 11.1 °C gehad, en letale temperature (LTSO) van -7.7 °C, wat aandui dat individue vrek voordat hulle vnes, Hierdie spesie reageer op akklimasie: gemiddelde superverkoelingspunt het toegeneem van -15.8 °C na akklimasie by 0 °C tot -7.3 °C na akklimasie by 15 oe. Die effek van akklimasie op temperatuur toleransie in insekte het dusver meestalop Drosophila gefokus. Hier vors ons die effek van akklimasie op die temperatuur toleransie van Halmaeusa atriceps (Styphylynidae) na. In die somer en winter was die lae letale temperature van kewers en larwes onderskeidelik -7.6 ± 0.03 en -11.1 ± 0.06 °C. Superverkoelingspunte (SVP) het meer gevarieer, met SVP van -5.4 ± 0.4 °C in larwes en -6.3 ± 0.8 oe in kewers. Die spesie IS verkoelingsvatbaar in die somer en matig vriesbestand in die winter, wat dui op akklimatisasie in hierdie spesie. Kritiese termale minima het tussen -3.6 ± 0.2 en -0.6 ± 0.2 oe in larwes, en tussen -4.1 ± 0.1 tot -0.8 ± 0.2 oe in kewers gewissel. Hierdie spesie blyk dieselfde fisiologiese tendense wat in insekte te vinde is uit te beeld, maar verskil in verskeie opsigte van ander insekte op Marion Eiland. Hierdie studie het ook die verskillende reaksies van inheemse en uitheemse springsterte met betrekking tot temperatuur akklimasie bestudeer. Die voordelige-akklimasie hipotese en sy alternatiewe hipoteses is in terme van akklimasiereaksies tot desikkasie weerstand, superverkoeling en lae- en hoë temperatuur bestandheid in Marion Eiland springsterte getoets. Die uitheemse springsterte (Pogonognathellus jlavescens, Isotomurus cf palustris en Ceratophysella denticulata) het nie beter fenotipiese plastisiteit getoon as die inheemse spesies (Cryptopygus antarcticus en Tullbergia bisetosa) nie. Die inheemse spesies het egter beter gevaar onder lae-temperatuur toestande. Die voordeligeakklimasie hipotese ontvang nie veelondersteuning in die huidige studie nie, maar kon in sommige gevalle nie van die alternatiewe hipoteses onderskei word nie. Klimaatsverandering mag uitheemse spesies bevoordeel. Die rol wat temperatuur in die verspreiding en fisiologiese toleransies van invertebrate speel word lank reeds waardeer. Daarom vors hierdie studie die mikrohabitat temperature teen 'n gradient tussen seespieël en 800 m bo seespieël (m bs) oor 'n tydperk van twee jaar op Marion Eiland na. Gemiddelde temperature is vergelykbaar met die van vorige studies op Marion Eiland, en neem af soos wat hoogte bo seespieël toeneem. Die 800 m bs studie-gebied het die mees stresvolle mikrohabitat-toestande ondervind (die hoogste absolute maksimum, laagste absolute minimum temperature, en die meeste vries-ontdooi siklusse). Inheemse spesies op Marion Eiland toon hoër.toleransies tot lae temperature as uiheemse spesies, laasgenoemde kom slegs voor by laer hoogtes bo seespieël, waar ekstreme ternperatuur-toestande dalk minder volop is. Klimaatsverwarming mag egter tot 'n toename in ekstreme weerstoestande lei op Marion Eiland, wat aansienlike mortaliteit in invertebraat populasies kan veroorsaak.

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13

Kühn, Ingolf. "Drivers and impacts of the spread of alien species in Europe." Diffusion fundamentals 20 (2013) 14, S. 1, 2013. https://ul.qucosa.de/id/qucosa%3A13536.

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14

Lee, Jennifer Elizabeth. "Alien species and propagules in the Antarctic : movements through space and time." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/4508.

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Thesis (PhD (Botany and Zoology))--University of Stellenbosch, 2009.
ENGLISH ABSTRACT: Although the impacts of biological invasions are widely appreciated, a bias exists in research effort to post‐dispersal processes because of the difficulties of measuring propagule pressure and the detecting of newly established species. Here the Antarctic is used as a model system in which to quantify the initial dispersal of alien species and investigate the factors that contribute to the establishment and range dynamics of alien species once they have arrived in the region. Human movements are known to transport alien species into the Antarctic, some of which have successfully established and had wide ranging consequences in recipient ecosystems. Considering terrestrial flora, this research found that over 700 seeds from 99 taxa, including some species known to be invasive, are transported into the Antarctic each year in association with South African National Antarctic Programme (SANAP) passenger luggage and cargo. The first ever assessment of propagule drop‐off indicated that 30‐50% of these propagules will enter the recipient environment. Further results suggested that the construction of the British Antarctic Survey Halley VI station will facilitate the transport of over 5000 seeds from 34 taxa into the region, making this a significant pathway for introductions. Propagule pressure due to SANAP logistics is also considerable for marine species. Fouling assemblages on the external hull surfaces of the SANAP resupply vessel, the SA Agulhas, form only once the vessel’s anti‐fouling paint has been damaged by travel through sea ice and are characterised by low diversity. Ice scour prevents fouling assemblages from being transported to the Antarctic continent, but assemblages remain largely intact when travelling to sub‐Antarctic Islands. In the sea‐chests of the vessel populations of a known invasive, Mytilus galloprovincialis, were found with some individuals having survived transportation to the Antarctic region on multiple occasions. Once species have overcome initial dispersal barriers, they face further ecological and physiological challenges in order to establish in the recipient region. The parasitoid wasp Aphidius matricariae was first recorded on Marion Island in 2001. Surveys around the island show that adult abundance and the frequency of aphid parasitism are highest adjacent to a common anchor point of the SA Agulhas and decline away from this region. Genetic diversity was low, suggesting that the population was established from a single introduction. This highlights that high propagule pressure is not necessary for successful establishment of introduced invertebrates. Another species that has overcome the dispersal barrier is the terrestrial slug Deroceras panormitanum, which was introduced to Marion Island in the 1970’s and has since spread throughout much of the coastal habitat of the island. For this species range limits are set by intolerance of low temperature and salinity, and abundance structure is characterized by patches and gaps which are associated with this species inability to tolerate dry conditions. To prevent further alien introductions in the region, targeted management of high risk pathways is required. In addition, increased vigilance is needed to detect and manage newly established aliens before their ranges expand.
AFRIKAANSE OPSOMMING: Alhoewel die impak van biologiese indringings in die breë waardeer word, bestaan daar vooroordeel in navorsingspogings ten opsigte van na‐verspreidingsprosesse, weens die moeilikhede om verspreidingseenheid druk te meet en in die opsporing van nuut gevestigde spesies. Hier word die Antarktiese streek as ‘n model sisteem gebruik waarin die aanvanklike verspreiding van uitheemse spesies gekwantifiseer kan word en om die faktore wat bydrae tot die vestiging en grens dinamika van uitheemse spesies te ondersoek, wanneer hulle in ’n streek aangekom het. Menslike bewegings is bekend daarvoor om uitheemse spesies na die Antarktiek te vervoer, sommige waarvan suksesvol gevestig het en omvattende gevolge in die ontvanger ekosisteme gehad het. Aangaande terrestriële flora het hierdie navorsing gevind dat oor die 700 sade van 99 taxa, insluitende sommige spesies wat bekend is om indringend te wees, jaarliks na die Antarktiek vervoer word in assosiasie met die Suid Afrikaanse Nasionale Antarktiese Program (SANAP) se bagasie en vrag. Die eerste waardebepaling van verspreidingseenheid afgooi het aangedui dat 30‐50% van hierdie verspreidingseenhede die ontvanger omgewing sal binnedring. Verdere resultate het voorgestel dat die konstruksie van die Britse Antarktiese Opname Halley VI stasie die vervoer van 5000 sade van 34 taxa sal fasiliteer die streek in, wat dit ’n betekenisvolle weg maak vir indringings. Verspreidingseenheid druk is ook, as gevolg van die SANAP logistiek, aanmerklik vir mariene spesies. Vuilgoed versamelings op die eksterne omhullende oppervlaktes van die SANAP her‐voorsieningsvaartuig, die SA Agulhas, vorm wanneer die vaartuig se anti‐vuilgoed verf beskadig is met reis deur see‐ys en word gekenmerk deur lae diversiteit. Ys skuring voorkom dat vuilgoed versamelings vervoer word na die Antarktiese kontinent, maar versamelings bly grootliks vasgeheg wanneer na sub‐Antarktiese eilande gereis word. Populasies van ’n welbekende indringer, Mytilus galloprovincialis, is gevind in die see‐storingsarea van die vaartuig, met sommige individue wat die vervoering na die Antarktiese streek oorleef het op verskeie geleenthede. Wanneer spesies die aanvanklike verspreidingshindernisse oorkom het, staar hulle verdere ekologies en fisiologiese uitdagings in die gesig ten einde in die ontvanger streek te vestig. Die parasitiese wespe Aphidius matricariae is vir die eerste keer op Marion aangeteken in 2001. Opnames om die eiland toon dat volwasse oorvloed en die frekwensie van plantluis parasitisme die hoogste is aangrensend die algemene ankerpunt van die SA Agulhas en afneem weg van die omgewing af. Genetiese diversiteit was laag, wat voorstel dat die populasie gevestig het van ’n enkele bekendstelling. Dit lig uit dat hoë verspreidingseenheid druk nie nodig is vir die suksesvolle vestiging van bekendgestelde invertebrata nie. ‘n Ander spesie wat die verspreidingshindernisse oorkom het is die landslak Deroceras panormitanum wat in die 1970’s op Marion Eiland bekendgestel is en wat sedertdien versprei het oor meeste van die kushabitat van die eiland. Vir hierdie spesie word grens limiete vasgestel deur onverdraagsaamheid vir lae temperature en saliniteit en die oorvloedstruktuur word gekenmerk deur laslappe en gapings wat geassosieer word met die spesie se onvermoë om droë kondisies te hanteer. Om verdere uitheemse bekendstellings in die streek te voorkom, word geteikende bestuur van hoë risiko weë vereis. Toenemende waaksamheid is bykomend nodig vir die opsporing en bestuur van nuutgevestigde uitheemse spesies voordat hulle grense verbreed.

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15

Dyer, E. "A global study of the distribution and richness of alien bird species." Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1475851/.

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Alien species are a major component of human-induced environmental change, yet spatial and temporal variation in the drivers of their introduction, and their subsequent distribution and richness, are poorly understood. Here, I present a global analysis of the drivers of this variation for a major animal group, birds (Class Aves), using the newly-created Global Avian Invasions Atlas (GAVIA) database. GAVIA includes information on introduction successes and failures, enabling me to examine the effect of colonisation pressure (the number of species introduced) on alien bird distributions. A description of the GAVIA database is given in Chapter 2, with details on its scope and sources, data collation and validation, and the production of alien range maps. Chapter 3 focuses on the early stages of the invasion pathway, and shows that historical introductions tend to originate in Europe, were driven by the global movements of British colonialism, and involved species deemed useful. Modern introductions, in contrast, tend to originate in Southeast Asia and Africa, are driven by factors associated with wealth, and involve species found in the pet trade. Chapter 4 identifies colonisation pressure as the principal determinant of alien bird species richness at a global scale. Additional anthropogenic factors (residence time, distance to historic port) and environmental variables (temperature range, precipitation) also influence richness. Chapter 5 analyses the factors influencing alien geographic range size, with species achieving a larger alien range if they have been introduced more often, have a larger native range and a shorter residence time. Chapter 6 examines latitudinal patterns of alien species richness and range size, and the likelihood of failure relative to latitude and native range limits. Overall, I demonstrate that alien bird distributions are primarily driven by anthropogenic influences, and highlight in particular the importance of incorporating a measure of colonisation pressure into studies of invasion.

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16

White, Evelyn M. "Indirect interactions between alien and native Senecio species as mediated by insects." Thesis, Queensland University of Technology, 2008. https://eprints.qut.edu.au/16580/1/Evelyn_White_Thesis.pdf.

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The studies described in this thesis investigate the role of indirect effects in invasion biology. The Introduction provides a brief overview of indirect effects and an outline of the thesis structure. The role of indirect effects in the context of invasion biology is addressed in an in-depth published literature review that comprises the second chapter, providing a theoretical background for the subsequent empirical studies. Chapters Three to Six are comprised of manuscripts that have been published or are under review or in press, which describe studies that investigate the importance of indirect effects in invasion biology using a model system consisting of the alien Asteraceae Senecio madagascariensis, a closelyrelated native, Senecio pinnatifolius, and the insect species with which they interact. Senecio madagascariensis and S. pinnatifolius occur in a similar geographic range in eastern Australia and these studies were conducted in mixed and pure populations of the two species. The herbivore and floral visitor assemblages of the two Senecio species at seven field sites in South-east Queensland were compared using sweep-net sampling, manual searching and floral visitor observation techniques. The floral visitor assemblages were similar between the two species, comprised largely of species of Syrphidae and the European honeybee, Apis mellifera. Herbivore assemblages, however, were highly variable both between species and between sites, with greater herbivore abundance and diversity recorded on the native S. pinnatifolius than its alien congener. The most commonly recorded herbivores were sap-sucking species such as Myridae. The magpie moth, Nyctemera amica was the most common folivore on both Senecio species and laboratory studies demonstrated a clear preference by ovipositing females and feeding larvae of this species for the native Senecio species, over the alien. Field surveys supported these findings, recording greater leaf damage on the native species than the invader. Herbivory levels were lower, rather than higher, in mixed populations than in pure populations, thus there was no evidence that the presence of one species enhanced herbivory in the other. Field pollination trials were conducted to determine whether competition for pollinators or facilitation of pollination occurred in mixed Senecio populations. The presence of the native S. pinnatifolius affected pollinator visitation rates to the alien Senecio; bee visits to S. madagascariensis were significantly reduced by the presence of S. pinnatifolius, whilst syrphid visits increased. However, altered visitation rates were not reflected in seed set. The presence of the alien species had no impact on pollinator visits to the native. Surprisingly, S. pinnatifolius seed set was higher in mixed populations than in pure populations. This might be due to abiotic factors, lower rates of herbivory at these sites or transfer of pollen between species resulting in the production of hybrid seed (if S. madagascariensis has greater male fitness). Hybridisation in the field was investigated using AFLP techniques. No mature hybrid plants were recorded in mixed populations, but hybrid seeds were produced by both species. Senecio pinnatifolius maternal parents produced higher numbers of hybrid seed than expected based on the relative frequencies of the two species, whilst hybridisation in S. madagascariensis was lower than expected. This may indicate greater male fitness of the invader. A range of complex indirect interactions can occur between invasive and native species, with these interactions having the potential to influence the success or failure of the invader and its impacts on co-occurring natives. The Discussion addresses the findings of the studies described here in the context of invasion biology theory.

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17

White, Evelyn M. "Indirect interactions between alien and native Senecio species as mediated by insects." Queensland University of Technology, 2008. http://eprints.qut.edu.au/16580/.

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Abstract:

The studies described in this thesis investigate the role of indirect effects in invasion biology. The Introduction provides a brief overview of indirect effects and an outline of the thesis structure. The role of indirect effects in the context of invasion biology is addressed in an in-depth published literature review that comprises the second chapter, providing a theoretical background for the subsequent empirical studies. Chapters Three to Six are comprised of manuscripts that have been published or are under review or in press, which describe studies that investigate the importance of indirect effects in invasion biology using a model system consisting of the alien Asteraceae Senecio madagascariensis, a closelyrelated native, Senecio pinnatifolius, and the insect species with which they interact. Senecio madagascariensis and S. pinnatifolius occur in a similar geographic range in eastern Australia and these studies were conducted in mixed and pure populations of the two species. The herbivore and floral visitor assemblages of the two Senecio species at seven field sites in South-east Queensland were compared using sweep-net sampling, manual searching and floral visitor observation techniques. The floral visitor assemblages were similar between the two species, comprised largely of species of Syrphidae and the European honeybee, Apis mellifera. Herbivore assemblages, however, were highly variable both between species and between sites, with greater herbivore abundance and diversity recorded on the native S. pinnatifolius than its alien congener. The most commonly recorded herbivores were sap-sucking species such as Myridae. The magpie moth, Nyctemera amica was the most common folivore on both Senecio species and laboratory studies demonstrated a clear preference by ovipositing females and feeding larvae of this species for the native Senecio species, over the alien. Field surveys supported these findings, recording greater leaf damage on the native species than the invader. Herbivory levels were lower, rather than higher, in mixed populations than in pure populations, thus there was no evidence that the presence of one species enhanced herbivory in the other. Field pollination trials were conducted to determine whether competition for pollinators or facilitation of pollination occurred in mixed Senecio populations. The presence of the native S. pinnatifolius affected pollinator visitation rates to the alien Senecio; bee visits to S. madagascariensis were significantly reduced by the presence of S. pinnatifolius, whilst syrphid visits increased. However, altered visitation rates were not reflected in seed set. The presence of the alien species had no impact on pollinator visits to the native. Surprisingly, S. pinnatifolius seed set was higher in mixed populations than in pure populations. This might be due to abiotic factors, lower rates of herbivory at these sites or transfer of pollen between species resulting in the production of hybrid seed (if S. madagascariensis has greater male fitness). Hybridisation in the field was investigated using AFLP techniques. No mature hybrid plants were recorded in mixed populations, but hybrid seeds were produced by both species. Senecio pinnatifolius maternal parents produced higher numbers of hybrid seed than expected based on the relative frequencies of the two species, whilst hybridisation in S. madagascariensis was lower than expected. This may indicate greater male fitness of the invader. A range of complex indirect interactions can occur between invasive and native species, with these interactions having the potential to influence the success or failure of the invader and its impacts on co-occurring natives. The Discussion addresses the findings of the studies described here in the context of invasion biology theory.

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18

FALASCHI, MATTIA. "INTERACTIVE EFFECTS OF HABITAT MODIFICATION AND INVASIVE ALIEN SPECIES ON AMPHIBIAN BIODIVERSITY." Doctoral thesis, Università degli Studi di Milano, 2021. http://hdl.handle.net/2434/822579.

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The biodiversity of our planet is facing a severe crisis. Habitat alteration, climate change, the spread of alien species, and overexploitation are major drivers of biodiversity loss. These global change drivers often act jointly or even synergistically on population declines. To identify priorities for conservation, it is thus essential to compare the relative impact of different threats on biodiversity. Amphibians are the vertebrates showing both the largest proportion of threatened species and the highest rate of decline. Out of the ~6,800 amphibian species assessed by the IUCN, more than 4,000 species are threatened by at least one stressor, and more than 2,000 by at least two stressors. Habitat modification (alteration and/or destruction) and alien species are the two factors threatening the largest number of amphibian species. For this reason, this thesis investigates the role of habitat modification and invasive alien species in determining the temporal dynamics of amphibian populations. The role of these stressors is examined at different spatial scales and jointly with other factors such as microhabitat, landscape, or climatic variables. The first study (Chapter 2) is a continental-scale analysis, which evaluates the combined effects of alien species, habitat availability, habitat changes, and climate change in determining population trends of European amphibian (and some reptile) species over the last 45 years. The results showed that populations declined more often in areas with a high number of alien species and where climate change has caused a loss of climatic suitability. The effect of habitat availability was not relevant when averaged across species; however, when excluding the two commonest species, habitat loss was the main correlate of negative population trends for the remaining species. Furthermore, I observed a strong interaction between habitat availability and the richness of alien species, which indicated that the negative impact of alien species was particularly strong for populations living in landscapes with less suitable habitat Then, the thesis focuses on a specific system: the invasion of the red swamp crayfish Procambarus clarkii in Italy, and its effect on the population dynamics of amphibians. The second study (Chapter 3) presents the updated distribution of the red swamp crayfish in Italy. Thirty years after its first record in Italy in 1989, the red swamp crayfish has invaded 80% of Italian provinces. The invasion is particularly extensive in central and northern Italy, where this invasive crayfish is present in 100% and 96% of provinces, respectively. Given the strong negative effects that the red swamp crayfish can exert on native amphibians, its widespread distribution raises concern about the future status of conservation of the Italian batrachofauna. Chapter 4 analyses site occupancy data of newts in northern Italy, in an area suffering the introduction of the invasive crayfish, in order to investigate the role of microhabitat, landscape change, and invasive species in determining the decline of two newt species through time. Initial occupancy of newts was negatively affected by landscape alteration (i.e. urban and agricultural cover) and by the presence of fish. Both species suffered a strong decline, with a net loss of site occupancy of 25%‒36% along the study period. After the crayfish invasion, the main drivers of population dynamics sharply shifted, and occupancy changes were not determined by landscape or microhabitat alterations, as the strongest predictor of local extinctions was the colonization of wetlands by invasive crayfish. The last study (Chapter 5) focuses on the effect of habitat characteristics and invasive crayfish in determining the temporal dynamics of the amphibian community in a large number of wetlands in northern Italy. Since connectivity among wetlands is fundamental for the dynamics of spatially structured populations, we considered two measures of connectivity acting on each focal wetland: incidence of the focal species, and incidence of invasive crayfish. Survival and colonization of local populations were jointly determined by factors acting at different scales. Survival probability was positively related to the area and the permanence of wetlands, while it showed a negative relationship with the occurrence of fish. Colonization probability was highest in semi-permanent wetlands and in sites with a high incidence of the focal species in nearby sites. Furthermore, the incidence of invasive crayfish emerged as one of the strongest drivers of colonization probability. In this thesis, I showed that invasive alien species are a major driver of the decline of European amphibians. The negative effect of invasive alien species acted differently across species and spatial scales. While the site-level impact was evident only for a subset of species, the landscape-level effect of invasive crayfish was ubiquitous across the whole amphibian community. Habitat modification showed a less evident effect, but invasive alien species and habitat modification can strongly interact: the negative effect of alien species is exacerbated in highly modified landscapes. It is thus essential to directly prevent and manage the spread of alien species, while simultaneously preserving natural landscapes. This can help in mitigating the negative effects of invasives, even when habitat alteration is not the main threatening factor.

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19

Ibrahim, Mohamed Somo. "Characterization of Common Wheat Translocations Carrying Leaf Rust Resistance Genes from Alien Species." Diss., North Dakota State University, 2016. http://hdl.handle.net/10365/25828.

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Leaf rust caused by Puccinia triticina Erikss may inflict significant yield losses in wheat; however, can be controlled by breeding for increased host resistance. In earlier studies, effective, resistance has been transferred to common wheat from the wild relatives Thinopyrum ponticum (Lr19), Aegilops sharonensis (Lr56), Ae. peregrina (Lr59), and Ae. neglecta (Lr62). Each translocation was subsequently re-engineered by the induction of homoeologous chromosome exchanges with a normal wheat chromosome to remove unneeded alien chromatin. For each gene the 3-8 most promising recombinants that retained the least linkage drag, but could not be differentiated, were identified. This study employed physical and genetic mapping in conjunction with molecular markers and genomic in situ hybridization to identify those recombinants that are best suited for breeding. For each gene, the recombinant with the least alien chromatin that also appeared to be fully compensating was identified and marker loci suitable for marker-assisted selection were suggested.
North Dakota Wheat Commission
Minnesota Wheat Research and Promotion Council

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Jurk, Clova. "Fouled yachts : a vector for marine invasive alien species to South African shores?" Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/11045.

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Biofouling on recreational yachts is an important vector for marine invasive alien species (MIAS) in many countries. There are various characteristics of a vessel that make it more susceptible to hull fouling. Yachts in three Western Cape marinas were surveyed to assess extent of fouling, hull maintenance patterns, travel history and yacht-owner awareness of MIAS issues.

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ULMAN, AYLIN H. "Recreational Boating as a vector of spread of alien species around the Mediterranean." Doctoral thesis, Università degli studi di Pavia, 2018. http://hdl.handle.net/11571/1227789.

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Mentre in passato la distribuzione delle specie marine era limitata da barriere geografiche, l'attuale globalizzazione ha fatto sì che queste vengano infrante, e che quindi siano i fattori climatici a controllare la distribuzione di molte specie. L'aumento globale dei viaggi e commerci marittimi ha facilitato infatti il trasporto di specie aliene per lunghi tragitti. Alcuni elementi chiave, quali il cambiamento climatico, l'aumentata frequenza dei trasporti, la creazione di corridoi artificiali e la mancanza di regolazioni sul biofouling hanno comportato un aumento delle invasioni biologiche marine negli ultimi decenni. È urgente effettuare una valutazione del ruolo della navigazione da diporto nel facilitare le invasioni biologiche, specialmente nel Mediterraneo che da solo ospita circa i 2/3 del traffico da diporto globale, e inoltre è il mare più affetto da invasioni biologiche. La presente tesi affronta questo problema, e rappresenta il primo studio a scala dell'intero bacino Mediterraneo che investiga il ruolo della navigazione ricreativa nel trasferimento di specie non-indigene tramite il vettore biofouling, analizzando sia le marine turistiche, sia le imbarcazioni. Una campagna di campionamento finalizzata a determinare se le marine turistiche rappresentano effettivamente "punti caldi" di introduzione di specie non-indigene è stata condotta in 34 marine, dalla Spagna alla Turchia, focalizzandosi sulle comunità di macroinvertebrati. Contestualmente, circa 600 diportisti sono stati intervistati sulle caratteristiche della loro imbarcazione, le abitudini di pulizia e verniciatura dello scafo, nonché il loro itinerario dell'ultimo anno. Da queste imbarcazioni sono stati inoltre raccolti anche campioni di biofouling, al fine di esplorare la correlazione tra abitudini di utilizzo del natante e presenza di specie non-indigene. I risultati di questa indagine a scala Mediterranea sono stati integrati con risultati di altre ricerche pregresse, condotte con simili modalità in marine turistiche italiane: la base dati che ne è risultata include l'elenco di NIS marine presenti in 50 marine del Mediterraneo. Questi dati sono stati analizzati con approccio statistico multivariato, al fine di identificare i fattori abiotici che contribuiscono maggiormente alla ricchezza in specie aliene nelle marine, e alla similarità nella composizione in NIS tra marine diverse.
Many stressors, such as climate change, overfishing, pollution and biological invasions, are currently devastating marine domain. Despite species being passively transported to new marine ecosystems since the onset of boat travel, invasion biology is relatively new field of science. Recreational boating as a major vector in the transport of non-indigenous species (NIS) has largely been overlooked until very recently, mostly because of the perceived effectiveness of antifouling coatings on boat-hulls. The role of recreational boating in facilitating marine bioinvasions urgently necessitated a proper evaluation, especially in the Mediterranean Sea which hosts 2/3 of global charter boat traffic and is also the global hotspot for alien species. This study addresses this shortfall by completing the first-ever Mediterranean basin-wide study investigating the influence of recreational boats in the transfer of NIS from biofouling both in marinas and from boat-hulls. First, a thorough investigation of NIS was conducted in 34 marinas across the Mediterranean (spanning from Spain to Turkey), targeting benthic macroinvertebrates. All marinas were found to host NIS, ranging from 2 to 27 per marina. This first output of this research provides a massive update of new NIS records and updated species distributions for the Mediterranean, and presents three new species in the Mediterranean basin, 51 new NIS country records and 20 new subregional records, which can now be fed into models and databases to gain a better comprehension of the scale of NIS colonizing marina habitats. Next, boat owners/captains were surveyed on their vessel characteristics including hull-cleaning and painting history along with their recent travel itinerary. Subsequently, biological samples of the biofouling were collected from approximately 600 of the same boat-hulls whose captains had already completed the survey, in order to search for correlations between the findings of the two. After the biofouling samples were identified, it was realized that almost 75% of sampled fouled vessels were found to host at least 1 NIS, while quite a few boats hosted as many as 8 NIS. It was also found that recreational vessels visiting new marinas sometimes carry NIS not yet present neither in that marina nor in the country in which they are visiting, thus providing ample evidence of recreational boating supplying new NIS to marinas. The results of this large-scale Mediterranean marina assessment were combined with other existing data on NIS in Italian marinas for a total sample size of 50 marinas, which were then used to feed multivariate statistical tests aimed at identifying which abiotic factors mainly contribute to NIS presence amongst marinas. The results revealed that NIS distributions in Mediterranean marinas are largely shaped by environmental factors which are found to be associated with the native ranges for species such as temperature, salinity, and biogeographical region and climate type. Proximity to the Suez Canal has a strong influence on NIS distributions, confirming that this particular pathway has a unique and prevailing influence particularly in the Eastern Mediterranean. Rather surprisingly, some factors that we thought to be relevant in determining NIS presence, were not found to be significant contributors affecting NIS similarities between communities. These marina factors included marine area, presence of shipyard presence of and total pontoon length and marina opening size (enclosement ratio). The results presented within this thesis, adding to those surveyed from around the world, form a robust case that recreational boating provides an extremely important pathway in facilitating the primary NIS introduction events and their associated secondary spread to other coastal areas as ‘stepping stone’ habitats. These results indicate that the recreational boating vector requires urgent management to reduce the scale of future invasions.

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Riley, Sophie Law Faculty of Law UNSW. "Invasive alien species and the protection of biodiversity: the role of quarantine laws in resolving inadequacies in the international legal regime." Publisher:University of New South Wales. Law, 2008. http://handle.unsw.edu.au/1959.4/41301.

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The problem of invasive alien species (IAS) is recognized as the second most serious threat to loss of biodiversity after habitat destruction. It is a problem largely created by humans as they transport and introduce species, deliberately and accidentally, from one part of the globe to another. The pressures exerted on biodiversity by international trade are one of the most serious aspects of the IAS problem. Although states are under obligations in international environmental law to prevent the entry of, and control, those alien species that threaten biodiversity, to date state practice has often been found wanting. In particular, quarantine regulation, which can be a state??s first line of defence against IAS, is mainly used by states to protect their farming and agricultural product sectors rather than biodiversity at large. The reasons for this include lack of domestic resources and lack of guidance at the international level. However, even if states were to expand the purview of quarantine, the question arises whether they would be able to use quarantine regulation to protect biodiversity from IAS while simultaneously fulfilling their international trade law obligations. This study seeks to answer this question by examining international environmental law and international trade law in their application to quarantine regulation. In doing so, the study identifies many areas of conflict. The different policies that underpin environmental and trade regimes mean that environmental concepts, such as the precautionary principle and the ecosystem approach, are difficult to apply within the international trade law regime. A way of achieving a more harmonized international response to the problem of IAS is suggested by incorporating environmental considerations into the international standards used by states to design and implement domestic quarantine measures. To facilitate the practical implementation of international standards the study further recommends appropriate financial and institutional capacity building mechanisms.

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Jarošová, Martina. "Rizika vyplývající z chovu a introdukce akvarijních plžů." Master's thesis, Česká zemědělská univerzita v Praze, 2016. http://www.nusl.cz/ntk/nusl-258156.

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Information was gathered regarding all aquarium and already introduced alien snail species (Gastropods), which are being imported to Europe. For the integrity of the research non-native and aquarium clams (Bivalve) were also included. Profiles of species were created based on collected information and the data were subsequently used for creating questionnaires. Questionnaires of each species were processed by FI - ISK, version 1.19 screening tool. Score of invasiveness risk potential was evaluated for each species individually. Surveyed taxa were divided into three groups according to their scores: low risk, medium risk and high risk. Celetaia persculpta was evaluated as aquarium snail (Gastropods) with the lowest risk for native fauna of Czech Republic. According to the results, Pomacea maculata and Pomacea canaliculata are the aquarium snails (Gastropods) with the highest invasiveness risk potential. The riskiest introduced species is Potamopyrgus antipodarum. Scabies crispata and Hyriopsis bialata are clams (Bivalve) with the least risk for the native fauna of Czech Republic. Corbicula fluminea and Dreissena polymorpha were analyzed as clams (Bivalve) with the highest invasiveness risk potential. By comparing aquarium species with species that were already introduced into Czech nature, I conclude that the aquarium snails (clams) do not represent similar risk like the alien species that were introduced without the share of aquarists.

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24

Phillips, Ben Lee. "Evolution and impact of invasive species : cane toads and snakes in Australia." University of Sydney. School of Biological Sciences, 2004. http://hdl.handle.net/2123/611.

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Evolution can occur rapidly, along timescales that are traditionally regarded as 'ecological'. Despite growing acceptance among biologists of rapid evolution, a strong paradigm of contemporary evolution is still absent in many sub-disciplines. Here I apply a contemporary evolution viewpoint to conservation biology. Specifically, I examine the impact of cane toads (Bufo marinus) on Australian snakes. Toads were introduced into Australia in 1935, have spread rapidly and represent a novel, extremely toxic prey item to na�ve Australian predators (including snakes). Based on dietary preferences and geographic distributions I find that 49 species of Australian snake are potentially at risk from the invasion of the toad. Furthermore, examination of physiological resistance to toad toxin in 10 of these �at risk� species strongly suggests that most species of Australian snake are poorly equipped to deal with a likely dose of toad toxin. Even species that are highly resistant to toad toxin (such as the keelback, Tropidonophis mairii) face indirect fitness costs associated with consuming toads. Within a population of snakes however, the impact of toads is unlikely to be random. For example, the examination of several component allometries describing the interaction between snakes and toads revealed that, within a species, smaller snakes are more likely to ingest a fatal dose of toad toxin than are larger snakes. Further consideration of the interaction between snakes and toads suggests that toads will not only be exerting differential impact on snakes based upon morphology, but also exert non-random selection on prey preference and resistance to toad toxin in snake populations. To examine the possibility of a morphological response by snakes to toads, I examined changes in the body size and relative head size of four species of snake as a consequence of time since exposure to toads. Two of the species (green treesnakes and red-bellied blacksnakes) are predicted to face strong impacts from toads. These two species showed an increase in mean body size and a decrease in relative head size as a consequence of time since exposure to toads; both changes in an adaptive direction. In contrast, the other two species (keelbacks and swampsnakes) are predicted to face much lower impact from toads, and these two species showed little or no evidence of morphological change associated with time since exposure to toads. These results indicate an adaptive change in morphology at a rate that is proportional to the predicted level of impact for each species, strongly suggesting an evolved response. Red-bellied blacksnakes (a toad-vulnerable species) were further assessed for evolved responses in prey preference and toxin resistance. Comparisons between toad-exposed and toad-na�ve populations of blacksnakes revealed that snakes from toad-exposed populations exhibited slightly higher resistance to toad toxin and a much-reduced tendency to eat toads, when compared with toad-na�ve snakes. Na�ve snakes exhibited no tendency to learn avoidance of toxic prey, nor were they able to acquire resistance to toxin as a result of several sub-lethal doses, suggesting that the observed differences between populations is evolved rather than acquired. Together, these results strongly suggest that blacksnakes are exhibiting an evolved shift in prey preference and toxin resistance as a consequence of exposure to toads. Thus, it appears that snakes are exhibiting adaptation at multiple traits in response to exposure to toads. Given the high likelihood that these adaptive shifts have an evolved basis, it appears that the impact of toads will decrease with time in many snake populations. But what about toads? Because the outcome of the interaction between a toad and a snake is also mediated by the body size and relative toxicity of toads, it is important to understand how these traits vary in space and time. Exploratory analysis revealed that toads exhibit a decrease in body size and a decrease in relative toxicity as a consequence of time since colonisation, indicating that their impact on native predators decreases with time. Additionally, there appears to be meaningful spatial variation in toad relative toxicity, indicating that some populations of native predators are facing higher impact from toads than others. Overall, these results clearly indicate the importance of assessing the potential for rapid evolutionary response in impacted systems. Doing so may provide evidence that some species are in less trouble than originally thought. Additionally, and as more data accumulate, it may be possible to characterise certain categories of environmental impact by their potential for eliciting adaptive response from �impacted� species. This approach has strong implications for the way conservation priorities are set and the way in which conservation dependent populations are managed.

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Smith, Owen Peter. "Allelopathic potential of the invasive alien Himalayan balsam (Impatiens glandulifera Royle)." Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/1592.

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Investigations were carried out into the allelopathic potential of the invasive alien annual Himalayan Balsam (Impatiens glandulifera Royle) using a series of bioassays, including ones developed or adapted for this study. They were evaluated for their suitability to detect three of the four main modes of allelochemical release, namely leaching, exudation and decomposition. Assays which involved the measurement of lettuce radicles and hypocotyls gave reliable results and allowed a range of different Impatiens material, both living and dead, to be assessed and ranked according to the allelopathic effects demonstrated. Attempts were made to isolate resource competition from allelopathy using separately grown but connected donor and receiver plants and a density dependent design where single I. glandulifera plants were grown in pots with variable numbers of receiver plants. Results proved inconclusive. Initial experiments showed that the allelopathic potential of I. glandulifera varied according to the organ from which the material was derived. Pods, leaves and stems produced the greatest inhibition of lettuce seedlings. Effects on germination were not significant at most of the concentrations tested. Live roots of I. glandulifera plants produced pronounced orange staining of the agar into which they were placed and showed clear evidence of distance dependent inhibition of lettuce radicles. Effects were limited to growth rather than germination of the test plants. Germinating I. glandulifera seeds caused a significant inhibition of lettuce radicle elongation when the two species were grown together in an agar medium. The inhibitory effects increased significantly with increasing exposure time. Increasing I. glandulifera seedling number also produced significant reductions in lettuce radicle length. Dormant seeds, by contrast, stimulated growth. Dead seeds did not produce significant changes to the growth of the test plants. When rhizosphere soil was gathered from pot grown I. glandulifera plants, the results were mixed. Initial samples inhibited growth, whereas those collected from dying plants over a period of weeks stimulated growth. Further experimentation is required before the indications of allelopathic interactions demonstrated here can be applied to the behaviour of wild populations of I. glandulifera.

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Richards, Jeannine Hyde. "From 'useful and interesting' to 'evil invaders': evolving perceptions of non-native species in the United States." Thesis, Boston University, 2002. https://hdl.handle.net/2144/27749.

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Boston University. University Professors Program Senior theses.
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
2031-01-02

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Ainsworth, Alison. "Interactive influences of wildfire and nonnative species on plant community succession in Hawaii Volcanoes National Park /." Connect to this title online, 2007. http://hdl.handle.net/1957/4504.

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Holmes, P. M. "A comparative study of the seed bank dynamics of two congeneric alien invasive species." Doctoral thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/17724.

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Includes bibliographies.
The unique vegetation in the lowlands of the fynbos biome is threatened by alien Acacia encroachment. The seed bank dynamics of the two most widespread invaders in the region, Acacia saligma and A. cyclops, was studied to elucidate those factors contributing most to their invasive success. This information was then used to assist in developing optimal control methods. On the basis of information available prior to this study, it was predicted that both species would have large, persistent seed banks in the so.il, and that seed bank processes would provide the - key to invasive success: namely, high seed longevity and heat-stimulated germination. Seed banks were monitored for several years following clearing of the parent stand, using either sites sampled in an earlier study, or sites providing chronosequences of clearing dates. Concurrently, a demographic study of the species' seed banks, including processes from seed rain through to seedling emergence and survival, was done in dense Acacia stands and in fynbos vegetation. Acacia saligma seed banks conformed to predictions, being large and persistent owing to high percentage viability and water-impermeable dormancy. Seed banks accumulate rapidly under dense stands and are "disturbance-coupled" as they have potentially high longevity unless stimulated to germinate by fire. Although A. cyclops seed banks also may be large and long-lived, they display variable percentage viability and dormancy, with the majority of a seed cohort surviving less than a year. Acacia cyclops seed banks do not respond to heat treatment and appear to be "disturbance-uncoupled".

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29

Ramaswiela, Tshililo. "The spatial distribution of alien and invasive vascular plant species on sub-Antarctic Marion Island." Thesis, Stellenbosch : Stellenbosch University, 2010. http://hdl.handle.net/10019.1/5471.

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Thesis (MSc )--Stellenbosch University, 2010.
ENGLISH ABSTRACT: The patterns of spread of non-indigenous species and the factors influencing their distribution have been studied infrequently on Southern Ocean Islands, where the prevention and control of biological invasions is a priority for conservation management. Owing to its remoteness and relatively small size, sub-Antarctic Marion Island provides an ideal opportunity to investigate the patterns of spread of invasive species and the factors likely influencing the distribution of alien species. Therefore, this study provides a spatially explicit documentation of the alien and invasive vascular plant species on Marion Island, the change in their distribution patterns through time, an assessment of the correlates of the current distributions, documentation of species rich areas, and provides recommendations for control based on these data and life history data available for each species. To ensure comprehensive coverage for the current estimate of distributions, a combination of a systematic (spatially explicit) survey and an ad hoc data collection method was used to examine the abundance and occupancy of each alien plant species across the island. The spatially explicit survey was used to identify sampling sites on a ½ minute by ½ minute scale (926 m × 926 m) which resulted in 348 sites across the island, whereas 2356 additional presence records were added during the ad hoc sampling. The residence time of each species was also estimated from the first records reported in various literature. While it has been documented in many studies that residence time is an important factor explaining species distribution, this study showed that distribution of alien species on Marion Island is not explained by residence time. The alien plant species on Marion Island differ markedly in their occupancy, distribution and rate of expansion. Agrostis stolonifera, Cerastium fontanum, Poa annua and Sagina procumbens are all expanding their ranges, whereas the range of Stellaria media appears to be contracting. Cerastium fontanum is the most widespread species on Marion Island while Sagina procumbens is the most abundant (number of records) and most rapidly expanding species on both Marion and Prince Edward Islands. Generalized linear models demonstrated that altitude, distance to human disturbed sites, and nearest neighbour presence are all significant and often strong correlates of spatial variation in alien vascular plant species richness and individual species presences on Marion Island. In particular, alien species richness on Marion Island declines sharply with increasing elevation, and that the distribution of the most widespread species is spatially aggregated. The surroundings of the Meteorological station and Mixed Pickle hut exhibit high richness and a high likelihood of the presence of individual species. None of the models developed for this study resulted in habitat type being significant explanatory variable for the distribution of any of the alien plant species, although from the records alone it is clear that the salt spray vegetation type is avoided. Together with assessments of the life history of the species, the current distribution data suggest that few alien plant species can be easily eradicated. Most are already too widespread already for cost effective eradication. Moreover, given the current rate of spread of Agrostis stolonifera, Cerastium fontanum, Poa annua and Sagina procumbens, and their apparent lack of habitat preference, it seems likely that within the next few decades many lowland habitats will be dominated by these species. By contrast, Rumex acestosella, Agrostis gigantea, Agropyron repens, Juncus effusus, Luzula cf. multiflora and the newly established shrub species should be the subject of control or eradication efforts. This thesis provides comprehensive baseline data on alien vascular plant distributions as a benchmark for future assessments.
AFRIKAANSE OPSOMMING: Die verspreidingspatrone van uitheemse spesies en die faktore wat hulle verspreiding beïnvloed is selde op Suidelike Oseaan Eilande bestudeer, waar die voorkoming en beheer van biologiese indringing ‘n prioriteit is vir bewaringsbestuur. Te danke aan sy afgeleëndheid en relatiewe klein grootte, voorsien sub-Antarktiese Marion Eiland ‘n ideale geleentheid om die patrone van verspreiding van indringer spesies en die faktore wat moontlik die verspreiding van uitheemse spesies beïnvloed te ondersoek. Daarom voorsien hierdie studie ‘n ruimtelik eksplisiete dokumentering van die uitheemse en indringer vaatplant spesies op Marion Eiland, die verandering in hulle verspreidingspatrone oor tyd, ‘n bepaling van die korrelasies van die huidige verspreidings, dokumentering van spesiesryke areas, en voorsien aanbevelings vir beheer gebasseer op hierdie data en die lewensloopdata beskikbaar vir elke spesie. Om omvattende dekking vir die huidige skatting van vespreidings te verseker, is ‘n kombinasie van sistematiese en ad hoc metodes gebruik om die talrykheid en besetting van elke uitheemse spesie oor die eiland te ondersoek. Die ruimtelik eksplisiete opname is gebruik om moniteringsplotte op ‘n ½ minuut by ½ minuut skaal (926 m × 926 m), met die resultaat van 348 plotte oor die eiland, terwyl 2356 addisionele voorkomsrekords bygevoeg is tydens die ad hoc versameling. Die verblyftyd van elke spesie is ook beraam vanaf die eerste rekords in die literatuur. Terwyl dit aangeteken is dat verblyftyd ‘n belangrike faktor is om spesie verspreiding te verduidelik, wys hierdie studie dat verspreiding van uitheemse spesies op Marion Eiland nie verduidelik word deur verblyftyd nie. Die uitheemse spesies op Marion Eiland verskil aansienlik in hulle besetting, verspreiding en tempo van uitbreiding. Agrostis stolonifera, Cerastium fontanum, Poa annua en Sagina procumbens brei almal hulle areas uit, terwyl die area van Stellaria media bleik te krimp. Cerastium fontanum is die mees wydverspreide spesie op Marion Eiland, terwyl Sagina procumbens die oorvloedigste (aantal rekords) en die vinnigste uitbreidende spesie is op beide Marion en Prince Edward Eiland. Veralgemeende lineêre modelle het aangetoon dat hoogte, afstand na menslike versteurde plotte, en naaste buurman teenwoordigheid almal betekenisvol is en gereeld sterk korreleer met ruimtelike variasie in uitheemse vaatplant spesierykheid en individuele spesie voorkoms op Marion Eiland. Uitheemse spesierykheid op Marion Eiland neem in besonder sterk af met ‘n toename in hoogte en die verspreiding van die mees wyduitgebreide spesies is ruimtelik saamgesteld. Die omgewing om die Weerstasie en Mixed Pickle hut toon hoë rykheid en ‘n hoë waarskynlikheid van die voorkoms van individuele spesies. Nie een van die modelle wat vir hierdie studie ontwikkel is toon ‘n belangrikheid in habitat tipe as ‘n verduidelikbare veranderlike vir die verspreiding van enige van die uitheemse plant spesies nie, alhoewel vanuit die rekords alleen is dit duidelik dat soutsproei plantegroei nie verkies word nie. Tesame met ondersoeke oor die lewensloop van die spesies, stel die huidige verspreidingsdata voor dat min uitheemse plant spesies maklik uitgeroei kan word. Die meeste is eenvoudig te wydverspreid vir koste effektiewe uitroeiing. Voorts, gegewe die huidige tempo van uitbreiding van Agrostis stolonifera, Cerastium fontanum, Poa annua en Sagina procumbens en hulle skynbare gebrek aan habitat voorkeur, is dit hoogs waarskynlik dat baie van die laerliggende habitatte binne die volgende paar dekades gedomineer sal word deur hierdie spesies. In teenstelling, Rumex acestosella, Agrostis gigantea, Agropyron repens, Juncus effusus, Luzula cf. multiflora en die nuutgevestigde struik spesie moet die fokus wees van beheer/uitroeiing pogings. Hierdie tesis voorsien omvattende basislyn data oor uitheemse vaatplantverspreidings as ‘n standaard vir toekomstige ondersoeke.
This project was funded by the South African National Antarctic Programme of the National Research Foundation (NRF – SANAP). Additional funding was provided by The Prince Edward Islands book fund.

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30

Jasson, René. "Management of Acacia species seed banks in the Table Mountain National Park, Cape Peninsula, South Africa /." Link to the online version, 2005. http://hdl.handle.net/10019/1059.

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Van, Wilgen Nicola Jane. "Alien invaders and reptile traders : risk assessment and modelling of trends, vectors and traits influencing introduction and establishment of alien reptiles and amphibians." Thesis, Stellenbosch : Stellenbosch University, 2010. http://hdl.handle.net/10019.1/5468.

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Thesis (PhD)--Stellenbosch University, 2010.
ENGLISH ABSTRACT: Biological invasions are a growing threat to biodiversity, trade and agriculture in South Africa. Though alien reptiles and amphibians (herpetofauna) are not currently a major issue, escalating problems worldwide and increased trade in South Africa suggest a possible increase in future problems. In this thesis I explore practical measures for risk assessment implementable under national legislation. I began by documenting record-keeping and legislative differences between provinces in South Africa. This revealed some serious deficiencies, complicating attempts to compile accurate inventories and discern import trends. International trade data, however, revealed an exponential increase in the number of imports to South Africa over the last 30 years. Characterising the abundance of species in this trade is important as species introduced in large numbers pose a higher establishment risk. In South Africa, I found a tendency for venomous and expensive species to be traded in low numbers, whereas species that are easy to breed and handle, or that are colourful or patterned are traded in higher numbers. Unlike South Africa, California and Florida have had a large number of well-documented herpetofaunal introductions. These introductions were used to verify the role of several key predictors in species establishment. I first evaluated the role of each variable separately. I examined different approaches for bioclimatic modelling, the predictive power of different sources of distribution data, and methods of assigning a climate-match score. I also present the first test of Darwin’s naturalization hypothesis for land vertebrates using two new phylogenies inferred for native and introduced reptiles in California and Florida. I then used boosted regression trees (BRT) to infer the relative contribution of each factor to species establishment success. Results from the BRTs were incorporated into a user-friendly spreadsheet model for use by assessors inexperienced in complex modelling techniques. Introduction effort was found to be the strongest contributor to establishment success. Furthermore, species with short juvenile periods were more likely to establish than species that started breeding later, as were species with more distant relatives in regional biotas. Average climate match and life form were also important. Of the herpetofaunal groups, frogs and lizards were most likely to establish, while snakes and turtles established at much lower rates, though analysis of all recorded herpetofaunal introductions shows slightly different patterns. Predictions made by the BRT model to independent data were relatively poor, though this is unlikely to be unique to this study and can be partially explained by missing data. Though numerous uncertainties remain in this field, many can be lessened by applying case by case rules rather than generalising across all herpetofaunal groups. The purpose for import and potential trade volume of a species will influence the threat it poses. Considering this in conjunction with a species’ environmental tolerances and previous success of species with similar life histories, should provide a reasonable and defendable estimate of establishment risk. Finally, a brief summary of the potential impacts of introduced alien herpetofauna is provided in the thesis.
AFRIKAANSE OPSOMMING: Indringer spesies hou ‘n al groter bedreiging in vir die biodiversiteit, handel en landbou van Suid- Afrika. Alhoewel uitheemse reptiele en amfibieërs (herpetofauna) tans nie ‘n groot bedreiging in Suid-Afrika is nie, dui groeiende probleme wêreldwyd asook 'n toename in plaaslike handel op moontlike toekomstige probleme. In hierdie tesis, ondersoek ek praktiese metodes vir risikobepaling wat onder nasionale wetgewing toegepas kan word. Ek begin deur die verskille in stoor van rekords en wetgewing tussen provinsies te dokumenteer. Hierdie proses het ernstige tekortkominge uitgewys, wat pogings om akkurate inventarisse saam te stel en invoertendense te bepaal, bemoeilik. Internasionale handelsdata het egter getoon dat daar ‘n eksponensiële toename in die hoeveelheid invoere na Suid-Afrika oor die laaste 30 jaar was. Die hoeveelheid spesies in hierdie handel is belangrik omdat spesies wat in groot hoeveelhede ingevoer word, ‘n hoër vestigingsrisiko het. In Suid-Afrika is ‘n tendens gevind vir handel in giftige en duur spesies teen lae hoeveelhede, terwyl spesies wat maklik teel, maklik hanteer kan word en kleurvol is of mooi patrone het, in groter hoeveelhede mee handel gedryf word. Kalifornië and Florida, in teenstelling met Suid-Afrika, het ‘n hoë aantal goed-gedokumenteerde gevalle van herpetofauna wat in die natuur vrygestel is. Hierdie introduksies was gebruik om die rol van verskeie belangrike faktore in die vestiging van populasies te bepaal. Eerstens het ek die rol van elke faktor apart ondersoek. Ek het verskillende benaderinge vir bioklimatiese model-bou ondersoek, die akuraatheid van verskillende bronne van distribusiedata getoets en drie metodes om ‘n “climate match score” te bereken, voorgestel. Ek bied ook die eerste toets van Darwin se naturalisasie-hipotese vir landwerveldiere aan, deur gebruik te maak van twee nuwe filogenieë wat ek gebou het vir inheemse en ingevoerde reptiele in Kalifornië en Florida. Ek het verder gebruik gemaak van “boosted regression trees” (BRT) om die relatiewe bydrae van elke faktor tot die vestigings-potensiaal van spesies te bepaal. Resultate van hierdie BRTs was ingekorporeerd in ‘n gebruikersvriendelike ontledingstaat wat deur bestuurders, onervare in komplekse modelboutegnieke, gebruik kan word. Invoer-hoeveelheid was die faktor wat die sterktste bygedra het tot suksesvolle vestiging. Verder is spesies met kort jeugperiodes en dié met verlangse familie in streeks-biotas, meer geskik om suksesvol te vestig. Gemiddelde klimaatooreenstemming en lewensvorm was ook belangrik. Paddas en akkedisse was die mees waarskynlikste van die herpetofauna groepe om populasies te vestig, terwyl slange en skilpaaie teen laer tempo’s populasies gevestig het, alhoewel analise van alle gedokumenteerde gevalle van herpetofauna-invoerings wêreldwyd effens verskillende tendense toon. Voorspellings wat deur die BRT-model vir onafhangklike data gemaak is was redelik swak, alhoewel hierdie resultaat onwaarskynlik nie uniek aan die studie is nie, en word gedeeltelik verduidelik deur die gebrek aan data. Alhoewel talle onsekerhede steeds bestaan, kan dié verminder word deur geval-tot-geval reëls toe te pas eerder as om vir herpetofauna as ‘n groep te veralgemeen. Die doel van invoer en potensiële handel-volumes van ‘n spesie, sal die bedreiging wat die spesie toon, bepaal. Hierdie faktore moet saam met omgewingstoleransie en voorafgaande sukses van spesies met soortgelyke lewenswyses oorweeg word, om ‘n aanvaarbare en verdedigbare beraming van vestigingsrisiko te gee. Laastens, word ‘n kort opsomming van die effekte wat uitheemse herpetofauna mag hê, verskaf.

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Forsyth, Aurelia Therese. "Identifying and mapping invasive alien plant individuals and stands from aerial photography and satellite images in the central Hawequa conservation area." University of the Western Cape, 2012. http://hdl.handle.net/11394/5118.

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>Magister Scientiae - MSc
The Cape Floristic Region, situated at the southern tip of Africa, is one of the world’s most botanically diverse regions. The biodiversity of this region faces various types of threats, which can be divided into three main categories, namely increasing urbanisation, agriculture expansion, and the spread of invasive alien vegetation. It has been shown that botanically diverse areas are more prone to invasion by invasive alien plant (IAP) species. The Hawequa conservation area, in the south-western Cape, is particularly botanically diverse, such that it is very prone to aggressive invasion by IAP species. Therefore, conservation management of the Hawequa conservation area urgently need to map, prioritise and clear IAP species. Due to the topographical complexity of this mountainous area, it is not possible to map the distribution of IAP species throughout the protected area by conventional field methods. Remote sensing may be able to provide a suitable alternative for mapping. The aim of this research was to assess various image classification methods,using two types of high-resolution imagery (colour aerial photography and WorldView-2 satellite imagery), in order to map the distribution of IAP species, including small stands and individuals. Specifically, the study will focus on mapping Pinus and Acacia spp. in a study site of approximately 9 225ha in the Hawequa conservation rea. Supervised classification was performed using two different protocols, namely per-pixel and per-field. For the per-pixel classification Iterative Self-Organising Data Analyses Technique (ISODATA) was used, a method supported by ERDAS Imagine. The per-field (object-based) classification was done using fractal net evolution approach (FNEA), a method supported by eCognition. The per-pixel classification mapped the extent of Pinus and Acacia spp. in the study area as 1 205.8 ha (13%) and 80.1 ha (0.9%) respectively, and the perfield classification as 1 120.9 ha (12.1%) and 96.8 ha (1.1%) respectively. Accuracy assessments performed on the resulting thematic maps generated from these two classification methods had a kappa coefficient of 0.700 for the per-pixel classification and 0.408 for the per-field classification. Even though the overall extent of IAP species for each of these methods is similar, the reliability of the actual thematic maps is vastly different. These findings suggest that mapping IAP species (especially Pinus spp.) stands and individuals in highly diverse natural veld, the traditional per-pixel classification still proves to be the best method when using high-resolution images. In the case of Acacia spp., which often occurs along rivers, it is more difficult to distinguish them from the natural riverine vegetation. Using WorldView-2 satellite images for large areas can be very expensive (approximately R120 per km2 in 2011), but in comparison with the cost of mapping and the subsequent clearing, especially in inaccessible areas, it might be a worthwhile investment. Alternative image sources such as the high resolution digital colour infrared aerial photography must be considered as a good source for mapping IAP species in high altitude areas.

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Dixon, Gemma Michelle. "Allelopathic potential of the alien invader weed Campuloclinium macrocephalum(Less) D.C." Diss., Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-10052009-111802/.

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Pattison, Zarah. "Effects of invasive alien plants on riparian vegetation and their response to environmental factors." Thesis, University of Stirling, 2016. http://hdl.handle.net/1893/25404.

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Biological invasions are reportedly one of the major contributory factors to biodiversity loss worldwide. The impacts of invasive alien plant (IAP) species on native communities are widely documented in the scientific literature, however, there is still a lack of detailed information on their impacts within the most vulnerable habitats. Riparian habitats are highly dynamic systems and naturally disturbed, making them particularly vulnerable to invasion. Climate change, directly or indirectly, is also predicted to adversely impact river systems, which may subsequently alter invasion rates and the impacts of IAPs. However, the interactions between climate and IAPs and their combined effects on vegetation have rarely been examined. To address these knowledge gaps, this thesis investigates: (1) the role of environmental variables, such as sediment loading or climate-related changes to river flow regime, on the abundance of IAPs within riparian zones; (2) how variation in IAP abundance impacts native vegetation, relative to the effects of native dominant plant species and (3) some of the mechanisms underlying the effects of IAPs in riparian habitats. Historic and recent field survey data were used to investigate changes in riparian vegetation on British rivers during the last 20 years. Analyses indicate that IAPs had a negative but small effect on native plant diversity. Overall, changes in land use and differences in flow regime between recording periods were the most important predictors of plant community change. Specifically, IAPs had a greater probability of being present along lowland rivers that experienced increased frequency of high flow events. On a local scale across rivers in Scotland, the abundance of IAPs was constrained by greater soil moisture in summer, whilst greater abundance was associated with tree-lined banks. Both native dominant species and IAPs negatively affected subordinate species abundance to a greater extent than species richness, although this effect varied spatially with bank elevation. Artificial turf mats were used to quantify viable propagules within riverine sediment deposited over-winter along invaded riverbanks. The data indicate that there is a legacy effect of IAP abundance, with the most invaded sites being associated with higher sediment loading the following year, though, contrary to the general pattern, 12 sediment associated propagules were scarcer at invaded sites. Moreover, lower above-ground native diversity was associated with sites which had been previously invaded. Plant species composition in the propagule bank and above-ground vegetation were highly dissimilar, particularly closest to the water’s edge at highly invaded sites. This suggests that mono-specific stands of IAPs proliferate best under less disturbed environmental conditions, although fluvial disturbance events may be required to create opportunities for initial establishment. The propagule bank contributed very little to the above-ground vegetation, nor did it limit invasion, suggesting that above-ground plant composition is largely dictated by competitive interactions. The findings presented in this thesis suggest that invasion by IAPs is an additional stressor for native vegetation within riparian habitats, modifying above-ground plant communities via competition and suppressing recruitment from the propagule bank. However, native dominant species common in riparian habitats also negatively impact, subordinate species via competition, in some cases equalling the effect of IAPs. Native dominant and IAP species are differently affected by environmental factors operating in the riparian zone, which may provide future opportunities for reducing and managing invasions.

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Chucholl, Christoph [Verfasser]. "New alien crayfish species in Central Europe - introduction pathways, life histories, and ecological impacts / Christoph Chucholl." Ulm : Universität Ulm. Fakultät für Naturwissenschaften, 2012. http://d-nb.info/1026944406/34.

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Phiri, E. E. "Species occupancy, distribution and abundance : indigenous and alien invasive vascular plants on sub-Antarctic Marion Island." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/47001.

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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.

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Roberts, Anthony Paul. "Biological control of alien species (Prosopis) in South Africa : the role of introduced seed-feeding bruchids." Doctoral thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/6173.

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Includes bibliographical references (p. 206-231).
The use of bruchid beetles for biologicval control of mesquite, Prosopsis species, in South Africa is deemed to have failed because the beetles are supposed to be unable to compete with livestock which utilise the seed pods of mesquite extensively as forage. These assumptions have been made without any evidence as to how the beetles and livestock interact or as to whether mesquite is site or seed limited in South Africa. This study was initiated to test the hypothesis that the beetles are not coping with competition with livestock and that mesquite is site limited and not seed limited in South Africa.

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Peters, Koebraa. "Marine alien species in Western Cape harbours, South Africa: A tool for stategically focusing monitoring efforts." Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/9792.

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Alien species are the second most important cause for the loss in biodiversity globally, after habitat destruction. Marine alien species are transferred across the globe through various vectors, including ballast water, hull fouling, aquaculture facilities and the aquarium and pet trade. Ballast water has previously been considered as the primary vector of alien species transfer. However, fouling is becoming widely recognised as an important vector for the transfer of marine alien species both internationally, as well as in South Africa, where it has been reported to contribute 48% of marine species introductions. The objectives of this study were to document alien species from fouling assemblages in six South African harbours (St Helena Bay, Saldanha Bay, Table Bay, Hout Bay, Gansbaai and Mossel Bay) and to use the data collected to identify factors (such as vectors and other harbour characteristics and activities), that could be used by management authorities to target harbours upon which to focus monitoring efforts. This was done by taking subtidal scrape samples and visual samples from harbour walls and pillars. The prioritisation of harbours was obtained through the use of regression tree models utilising CART (Classification and Regression Trees).

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Fonche, Florentin Mongeng. "The impact of alien plant invasions on biodiversity in South Africa : the case of alien Acacia species in the Gauteng and Chromolaena odorata in the KwaZulu Natal Provinces." kostenfrei, 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=978419995.

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Viljoen, Morné. "A critical review of the South African freshwater angling legislative framework / Morné Viljoen." Thesis, North-West University, 2010. http://hdl.handle.net/10394/4235.

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Prior to 1993, freshwater angling in South Africa had been governed by the respective nature conservation legislation of the four South African provinces, the four “independent homelands" and the six so-called Bantustans. In 1993 a South Africa with nine provinces was created, of which only Limpopo and Mpumalanga promulgated its own laws governing freshwater angling. From 2008 angling for listed threatened and protected freshwater fish species has been regulated by the National Environmental Management: Biodiversity Act, supplemented by the Threatened or Protected Species Regulations. In addition, it is anticipated that the Alien and Invasive Species Regulations, which will regulate angling for listed alien and invasive freshwater fish, will be promulgated in the near future. The result is that freshwater angling is currently being governed by a plethora of pre-1993 provincial, homeland and Bantustan legislation, two post-1993 provincial acts, as well as post-1993 national legislation. In this dissertation the South African freshwater angling legislative framework was critically analysed. It was found that the multitude of fragmented and complex laws, created 15 “angling provinces” which leads to confusion amongst anglers and government officials alike. In the process legal certainty and reasonableness, cornerstones of a sound legal system, are being compromised, indigenous freshwater fish are not adequately protected and alien or invasive freshwater fish are not properly managed. In the light of the above, and after taking comments by anglers and enforcement officials into account, recommendations are made for an improved legislative framework for freshwater in South Africa. It is recommended that all freshwater fish species be managed and/or protected on a catchment basis, as opposed to the current provincial basis. This will ensure legal certainty and reasonableness and that all indigenous freshwater fish which are subject to the similar threats are protected adequately and uniformly.
Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2010.

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Richards, Michael Bruce. "Host specificity in the Rhizobium symbioses of two Aspalathus species and an invasive alien legume, Acacia saligna." Bachelor's thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/25788.

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The symbiotic specificity of Aspalathus capensis and A. carnosa in relation to their geographical distribution, was investigated by growing plants in soil and in tubes containing soil solutions plus nitrogen-free nutrient solutions. Soila were collected from three sites within their distribution and two from 90km outside. Both species formed nodules in all three soils from within their distribution and A. capensis in one from outside. A. carnosa did not survive in tube culture. The possible role of hostspecificity in the distribution of A. capensis and A. carnosa is discussed. A widespread invasive alien legume, Acacia saligna . was grown in the same soils and soil solutions. It formed nodules only in the three soils from within the distribution of Aspalathus capensis. The degree of nodulation varied between these soils. The possible importance of host-strain specificity in the invasive ability of alien legumes is discussed.

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Ewald, Michael [Verfasser], and S. [Akademischer Betreuer] Schmidtlein. "Remote Sensing of the Ecosystem Impact of Invasive Alien Plant Species / Michael Wolfgang Ewald ; Betreuer: S. Schmidtlein." Karlsruhe : KIT-Bibliothek, 2020. http://d-nb.info/1206646918/34.

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Ewald, Michael Wolfgang [Verfasser], and S. [Akademischer Betreuer] Schmidtlein. "Remote Sensing of the Ecosystem Impact of Invasive Alien Plant Species / Michael Wolfgang Ewald ; Betreuer: S. Schmidtlein." Karlsruhe : KIT-Bibliothek, 2020. http://d-nb.info/1206646918/34.

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Lemke, Dawn. "Alien plants and their invasion of the forested landscape of the southeastern United States." Thesis, University of Canterbury. Department of Mathematics and Statistics, 2012. http://hdl.handle.net/10092/7107.

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In this thesis, I have assessed and modelled invasion of alien plant species in the forest of the southeastern United States. There are over 380 recognized invasive plants in southeastern forests and grasslands with 53 ranked as high-to-medium risk to natural communities. I have focused on ten of these: Chinese lespedeza, tall fescue, Japanese honeysuckle, Chinese privet, autumn olive, princesstree, silktree, chinaberry, tree of heaven, tallowtree. Assessing them at differing scales, locally (Chapter 2 and 3), eco-regionally (Chapter 4 and 5) and regionally (Chapters 6 and 7), using field based measurements integrated with remotely sensed and digital datasets, and applying both parametric and non-parametric modelling approaches. Data from field based measurements as well as digitally available sources was evaluated, bringing together freely available data with time consuming, intensively collected data. Once models were developed application to assessing long term impacts was done by integrating potential climate change scenarios. At the local level Chinese lespedeza and Japanese Honeysuckle were the most prevalent, with models at the local level dominated by remotely sensed variables. At an eco-regional level Japanese honeysuckle was the most prevalent with models primarily dominated by environmental variables. At a regional level, where only trees were assessed, potential distributions of the invasive species ranged from 12 to 33 percent of the southeastern forests under current conditions with this dramatically increasing for chinaberry and tallowtree under most climate change scenarios, up as high as 66 percent of southeastern forest sites. In this thesis information on anthropogenic factors added some value to the models, however it was rarely dominant. Roads and land use (proportion of forest or distance to forest) were the most useful anthropogenic variables. In all models evaluated, only six times did any one anthropogenic variable represent more than 25 percent of the models, four of these were at the local scale. At the regional and eco-regional level, roads had a greater than 25 percent contribution to the silktree models, at a local level, distance to forest and distance roads contributed more than 25 percent to three of the species evaluated, sawtooth oak, Japanese honeysuckle and privet. Human activities have the most influence on invasion progression through dispersal (movement and introduction rate) and disturbance of the landscape (increased resource availability). Anthropogenic variables such as roads are likely to be a mechanism of spread, thus the more a model is driven by anthropogenic variables, the more likely the invasive plant is to be in the early stages of invasion process. Thus our results suggest that many of these species have moved through the first stages of invasion. Environmental characteristics play an important role in determining a site’s vulnerability to invasion. At an eco-region and regional scale, environmental characteristics dominated (>50%) all but one model (silktree at the regional scale). At the eco-region level elevation was the dominant variable, and at a regional level minimum temperature was the dominant variable. These have some correlation, with higher elevation often relating to lower temperatures, particularly at a smaller scale. This confirms the validity of matching the climate ranges of native species with the range of potential invasion, and the approach of integrating elevation, latitude and longitude to estimate potential distribution. It also suggests that climate change will influence the distribution and that variation in climate should be integrated into models. Two different modelling approaches, logistic regression and maximum entropy, were used throughout my thesis, and applied to the same data. Agreement between different modelling types adds strength to conclusions, while disagreement can assist in asking further questions. The inclusion in the models of similar variables with the same direction of relationships gives confidence to any inference about the importance of these variables. The geographical agreement between models adds confidence to the probability of occurrence in the area. Alternatively using the same model but different datasets can give you similar information. Overall for all models created by both logistic regression and MaxEnt, the logistic regression had slightly better omission rates and the MaxEnt model had better AUC’s. Logistic regression models also often predicted larger geographical areas of occurrences when the threshold of maximum sensitivity plus specificity was used, thus the lower omission rates is related to the less stringent model that predicts a larger area. The selection of appropriate data to answer the question was shown to be fundamental in Chapter 7. When data were used outside of the area of interest it generalized the models and increased the potential for invasion significantly. There was more value in the intensive surveyed data but this was less dramatic than in using the defined areas of interest to select the data for models.

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Rassati, Davide. "From arrival to spread: improving the early-detection of alien wood-boring beetles." Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3424640.

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The introduction of alien species in new habitats is a global and growing problem worldwide. Since the discovery of the Americas about 10,000 species have been introduced in Europe, mainly plants and insects. Among the latter, wood-boring beetles (mainly Scolytinae, Cerambycidae and Buprestidae) are recognized as one of the most successful group of invaders. These insects can be transported in almost all types of woody materials and, once introduced and established, they can cause enormous damage to ecosystems and economies of the invaded countries. In addition to traditional control methods, in the last years several countries have implemented other kinds of tools, such as traps baited with attractive lures, in order to enhance the chances of alien wood-boring beetles interception. Resources available for these activities are however limited while the number of sites that should be monitored is extremely high. For this reason, it is of utmost importance to have reliable and efficient trapping protocols as well as to understand where surveillance efforts should be focused. However, the general solution of this problem is strictly related to a better comprehension of the three steps characterizing the invasion process: arrival, establishment and spread. This thesis has two main aims: first, to enhance the early-detection of alien wood-boring beetles at high-risk sites located both in coastal and continental areas, and second, to gain insight into the mechanisms driving the alien wood-boring beetle invasion process. The first study concerns the development of efficient early-detection protocols that can be adopted for the interception of alien wood-boring beetles arriving at European ports of entry. This is focused on how different use of attractive lures, different trap models and trap positions (inside ports vs surrounding areas) may influence the chances of interception of alien species. The results suggest the use of multi-funnel traps baited with different lures for monitoring alien wood-boring beetles. The deployment of traps outside the port is also recommended to validate the surveillance program. The second study concerns how port size, in terms of amount of imported commodities, and characteristics of the landscape surrounding the ports, in terms of forest cover and forest composition, may affect the early-detection of alien wood-boring beetles. The results suggest that surveillance should be focused mainly in large ports and in the surrounding broadleaf forests, deploying traps simultaneously in both habitats. The third study is focused on the comparison between ports of entry and wood waste landfills, considered as the final destination of a large part of wood packaging materials imported together with goods. The results show that wood waste landfills are a crucial site where detecting alien species associated with woody materials, even in continental areas far away from the coasts. The forth and fifth studies investigate how the main climatic and environmental variables affect the establishment and spread of alien bark and ambrosia beetles at both regional and continental scale. The main results demonstrate that the invasion process of exotic scolytids is not random and that both climate and forest composition play a key role in shaping their communities and their spatial distribution in the invaded environment. However, these mechanisms occur differently according to the feeding guild of the two main groups of scolytids, the bark beetles and the ambrosia beetles. In general, the five studies carried out in this thesis provide suggestions to increase the probability of an early-detection of alien species both in coastal and continental areas, describing a protocol applicable both at local and international scale. At the same time, they contribute to improve the knowledge about the mechanisms characterizing the invasion process of alien wood-boring beetles, information that can be of utmost importance for the development of future strategies focused to reduce economic and environmental damage due to alien species.
L’introduzione di organismi esotici è un processo che avviene ormai da secoli ed è considerato a tutti gli effetti come una minaccia a livello globale. Dalla scoperta dell’America in Europa sono state introdotte circa 10.000 specie esotiche, principalmente piante e insetti. Tra questi ultimi hanno particolare rilevanza i coleotteri xilofagi, per lo più appartenenti alle famiglie scolitidi, cerambicidi e buprestidi. Questi insetti possono essere trasportati all’interno di pressoché qualsiasi tipo di materiale legnoso e, una volta arrivati e stabiliti nel nuovo ambiente, possono causare gravi danni al patrimonio forestale del paese di introduzione con gravi conseguenze sia sotto il profilo economico che ambientale. Da alcuni anni si è iniziato ad affiancare alle tradizionali metodologie di controllo diretto delle merci importate l’utilizzo di strumenti, quali trappole associate a sostanze attrattive, che permettono di aumentare le probabilità di intercettazione delle specie esotiche. Ad ogni modo, considerando le limitate risorse che vengono destinate per questo tipo di attività, diventa fondamentale avere a disposizione efficaci protocolli di monitoraggio ed individuare i punti a maggiore rischio di nuove introduzioni dove concentrare le risorse stesse. Questo non può però prescindere da una migliore conoscenza del processo di invasione biologica e delle tre fasi in cui esso viene comunemente diviso: l’arrivo, l’insediamento e la diffusione nel nuovo ambiente. Questa tesi si pone due obiettivi principali: il primo è quello di migliorare l’efficacia degli esistenti protocolli di monitoraggio al fine di aumentare le possibilità di intercettazione di specie esotiche di insetti del legno sia in aree costiere che continentali, mentre il secondo è quello di approfondire i meccanismi che guidano il processo di invasione biologica. Il primo studio riguarda lo sviluppo di un protocollo di monitoraggio utilizzabile per l’intercettazione di specie esotiche di insetti del legno nei porti europei e considera l’effetto di diverse tecniche di diffusione delle sostanze attrattive e di diversi modelli di trappole, nonché del loro posizionamento all’esterno o all’interno dell’area portuale, sulle possibilità di cattura delle specie esotiche stesse. I risultati indicano come l’utilizzo di trappole modello “multi-funnel”, attivate contemporanemante con più sostanze attrattive, rappresenti un’importante integrazione dei tradizionali metodi di ispezione. Essi inoltre suggeriscono l’impiego di trappole anche nelle aree circostanti il porto per rafforzare i programmi di monitoraggio. Il secondo studio indaga come il volume annuale di importazioni e il paesaggio circostante i porti, espresso in termini di copertura e tipologia forestale (conifere vs latifoglie), influenzano la cattura e l’intercettazione di specie esotiche di insetti del legno. I risultati dimostrano come il monitoraggio dovrebbe essere effettuato utilizzando trappole sia all’interno che all’esterno dell’area portuale, concentrando gli sforzi di campionamento nei porti che ricevono annualmente i volumi più elevati di merci e nei boschi misti di latifoglie localizzati nei primi chilometri attorno al porto. Il terzo studio confronta le catture di specie esotiche ottenute in aree portuali e in siti di riciclaggio o smaltimento di materiali legnosi, considerati come destinazione finale di parte degli imballaggi associati alle merci importate. Lo studio dimostra come tali siti possano essere considerati come utili punti da monitorare per aumentare le possibilità di intercettazione nelle aree continentali. Il quarto e quinto studio indagano il ruolo delle principali variabili climatiche e ambientali sui meccanismi ecologici che regolano il processo di stabilizzazione e diffusione di scolitidi esotici rispettivamente a scala regionale e continentale. I risultati dimostrano che il processo di invasione non è casuale e che sia le variabili climatiche, in termini di temperatura e precipitazioni, che la diversità ambientale, in termini di composizione forestale, giocano un ruolo fondamentale nel modellare le comunità di specie esotiche e la loro distribuzione nel nuovo ambiente, ma che questo avviene in modo differente nei due gruppi principali di coleotteri scolitidi, gli scolitidi xilematici e quelli floematici. Nel complesso, i cinque contributi di questa tesi forniscono indicazioni per aumentare le possibilità di intercettazione di specie esotiche di insetti del legno sia in aree costiere che continentali, descrivendo un approccio applicabile anche a scala internazionale. Allo stesso tempo contribuiscono ad approfondire i meccanismi che caratterizzano il processo di invasione degli insetti del legno, informazioni che risultano essere fondamentali in vista di futuri approcci applicativi volti alla riduzione dei danni ambientali ed economici attribuibili alle specie esotiche.

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Comont, Richard Francis. "Modelling the impact of an alien invasion : Harmonia axyridis in Britain." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:08de972b-1c12-4862-bb7d-95d614a9e011.

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Harmonia axyridis is a ladybird native to Asia, but introduced widely as a biocontrol agent. It is invasive and detrimental to native species in North America, which meant its arrival in Britain was met with concern. Establishment was seen as an opportunity to track the spread of an invasive alien species (IAS) whilst also monitoring impacts on native species. The aims of this thesis were to examine the responses of native British ladybirds to the arrival of H. axyridis, to establish the effect of the IAS on native ladybirds when compared to other drivers, and to investigate the possible facilitation of the H. axyridis invasion by natural enemy release. Modelling ladybird distributions with life-history and resource-use traits found that species predatory on a wide range of prey families had larger range sizes than those which ate fewer prey types. This suggests that the wide diet breadth of the IAS is likely to have played a critical role in the species’ rapid spread. Dietary niche overlap between H. axyridis and native ladybirds showed positive correlation with declines of native ladybirds. This indicates that the IAS is playing an important role, but the significance of urbanisation suggests habitat destruction is also significant. Abundance of H. axyridis was influenced by habitat type and aphid abundance, but not by the native ladybird community, suggesting the spread of the IAS will not be slowed by biotic resistance. Harmonia axyridis is attacked by native parasitoids, but at a much lower rate than is the native Coccinella septempunctata, in line with natural-enemy release theory. There was no evidence of attack rate increasing with time since arrival in an area. Overall, H. axyridis is an extremely successful IAS, with detrimental effects on native ladybirds which are likely to continue.

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Selge, Sebastian. "Public and scientific discourses on biological invasions : social representations of invasive non-native species in Scotland." Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=183833.

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Invasive non-native species are believed to be one of the biggest threats to biodiversity. Until now biological invasions have been mainly studied from a biological perspective and much research has been undertaken to investigate species’ ecology and potential options for management. Comparatively little attention has been devoted to questions regarding the social construction of the issue. This is despite invasion biologists increasingly acknowledging the fundamental importance of human perceptions, beliefs, attitudes and values inherent in debates about invasive non-native species. This thesis employs a mix of methods from the social sciences to investigate the social construction of biological invasions. Research conducted here is based on the theory of social representations. Thus, taking a social scientific perspective, the thesis contributes to both the development of the theory and an identification of beliefs inherent in the debate on biological invasions and their relationship to people’s attitudes towards species and their management. Those species attributes that predominantly shape the debate – but yet appear to be under-researched – are identified. Based on the findings in this thesis I argue that invasion biology would benefit from a more explicit and transparent use of its concepts and terminology. This will have implications also for the communication with policy makers, conservation managers and the general public. Recommendations for future research are discussed along with limitations of the thesis.

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Kellnreitner, Florian [Verfasser]. "The trophic structure of a Wadden Sea fish community and its feeding interactions with alien species / Florian Kellnreitner." Kiel : Universitätsbibliothek Kiel, 2012. http://d-nb.info/1053682921/34.

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Ahmadi, Firouzabad Abdolhadi. "Introgression of resistance to powdery mildew (Erysiphe graminis f.sp. tritici) from alien species into bread wheat (Triticum aestivum)." Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340688.

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Naicker, Isayvani. "The role of science in issue advocacy : invasive alien plant species in the fynbos vegetation of South Africa." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610726.

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Dissertations / Theses on the topic 'Alien Species'

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