This thesis investigates the optimal ex-ante mix of self-protection and self-insurance technologies employed to reduce the risk of biological invaders in the presence of exogenous variables within the probability and damage functions. This is accomplished by using a theoretical endogenous risk model that extends previously developed frameworks. This thesis contributes to the previous work in two ways. (1) Employing a general framework with simultaneous decision making over self-protection and self-insurance, this thesis analyzes how each parameter including income, the costs of each activity, an exogenous factor that affects only the probability of an invasion, and a separate exogenous factor that affects only the damages influence the level of self-protection and self-insurance. (2) The comparative static results are derived in the benchmark case of risk neutral preferences and qualitatively compared to an extended case of risk averse preferences. The results of the analysis indicate that under risk neutral preferences the signs of the comparative statics are unambiguous while under risk aversion the results are not clearly defined. Thus, the ambiguity of signs in the latter case can be attributed to the unobservable utility terms present under risk averse preferences. Therefore, it can be concluded that the model is not capable of yielding a decision criteria that will hold universally because the results are dependent on the nature of the risk averse curve

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

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

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 115-118). Also available on the World Wide Web.

Thesis (M.C.M.) -- Lincoln University, 2010. / Also available via the World Wide Web.

Biological invasions represent both an urgent conservation problem and an opportunity to advance ecological theory. Development of pertinent research questions and proactive management strategies require knowledge of which introduced species are present and of spatiotemporal trends in the distribution of natives and invaders. In Chapter 2 we developed a quantitative framework to identify spreaders and decliners and estimate invasion chronologies based on a historical fish presence data set for upper and middle New River (UMNR) tributaries. Our framework accounts for spatiotemporal variability in sampling effort by aggregating presences by watershed and expressing range size as a function of the number of watersheds sampled per time period. The majority (55%) of fish species present in the study area were introduced, 51% of which were spreaders. Most spreaders (84%) appeared to be spreading exponentially. The rate of new introductions detected in the study area has slowed since the mid-20th century. Two natives, the mound-spawning bluehead chub Nocomis leptocephalus and its strong nest associate (reproductive mutualist), mountain redbelly dace Chrosomus oreas, were among the most rapid spreaders. Four natives showed evidence of decline. Our framework leverages historical presence data to reconstruct temporal trends in species distributions. It sets the stage for further study of factors driving stream fish invasions and declines in the Appalachian region, and is transferable to diverse taxonomic groups and geographic regions. Species traits and human activities mediating stream-fish invasions remain poorly understood. In Chapter 3 we modeled the contribution of species traits to invasion success of UMNR tributary fishes during the colonization and spread stages. Biological traits accurately explained colonization and spread success, whereas ecological traits resulted in less accurate models. Colonization success was positively related to time since introduction, benthic feeding, an equilibrium life history, and nest spawning. Successful spread was positively related to winter air temperature in the native range and an equilibrium life history. Variables estimating human use and propagule pressure were non-informative. Traits that influenced invasion success were consistent with the hypothesis that human land-use practices have increased the invasibility of highland watersheds by creating novel conditions suited to lowland and equilibrium invaders. / Master of Science

MSc., Faculty of Science, University of the Witwatersrand, 2011 / Both indigenous “Tamarix usneoides” and alien T. ramosissima co-occur in South Africa. Tamarix usneoides is potentially a metal and salt phytoremediation species. However, hybridisation is occurring between the two species and hybrids growth characteristics are deemed to be invasive. This study was undertaken at two sites on one Highveld gold mine, characterised by different soil types, where plant growth, reproductive potential and insect abundance and diversity were measured. This aims to establish the growth of T. usneoides in two site-species trials, and to identify differences between Tamarix taxa that are consistent across different environmental conditions and can be used for identification. This study also set out to establish if higher reproductive effort and enemy release are promoting the invasiveness of T. ramosissima. Trees in one site (a water logged, clayey “Glenrosa” soil) displayed significantly greater percentage survival, growth and reproductive effort than trees in the other site (a well drained, sandy “Hutton” soil). Extensive hybridisation between T. usneoides and T. ramosissima was observed with two hybrid states, morphologically similar to each parent species. The reproductive effort is consistently greater in T. ramosissima and T. ramosissima hybrid than T. usneoides and T. usneoides hybrid. After sampling 217 trees in this study, the three characteristics of (1) insertion of filaments into the nectar disc, (2) petal shape and (3) presence of salt glands on leaves most accurately distinguished between T. usneoides and T. ramosissima taxa. Three insect species have been identified from this study as potentially damaging agents on Tamarix spp. Insects can discern between the Tamarix tree taxa and T. ramosissima is being released from insect herbivore pressure, as very few insects and a lower diversity were recorded on T. ramosissima and its hybrids (T. ramosissima hybrids > T. ramosissima). To achieve phytoremediation objectives, careful tree identification and selection of genetically pure individuals for cloning is recommended. Additionally the removal of existing alien and hybrid plants, and further research to find a suitable host specific insect biological agent to control alien Tamarix is necessary.

Theses (Ph.D.)--University of New Hampshire (Dept. of Zoology), 2007. / Includes bibliographical references. Also available online.

The commercial forest industry in South Africa is predominantly dependent on large tracts of exotic monoculture plantations. While this simplifies management practice, there is always the inherent danger posed by introduced pests and diseases. Classical biological control is usually the most effective control method against introduced exotic pests. Climatic factors and seasonal differences may negatively affect the ability of the natural enemies to establish successfully at the new location. Successful establishment of the natural enemies usually results in control over the pest within four years. Sirex noctilio naturally occurs in the mediterranean countries of Europe and North Africa. It is the only member of the Siricid family capable of killing living pine trees. Sirex noctilio was accidentally introduced into New Zealand from Europe during the early 1900s. It has since been found in Australia, Brazil, Argentina South Africa and Chile. Initial biological control in New Zealand and Tasmania was through the release of Siricid specific parasitoid wasps from Europe and North America. The discovery of the accidental introduction of the entomophagous nematode Beddingia siricidicola and its subsequent artificial culturing for release provided the platform for the biological control methodology, which brought the Sirex woodwasp under control. The methods and natural enemies used in New Zealand and Australia were introduced by the South American countries and in the Western Cape of South Africa. Successful biological control was achieved in the Western Cape within two years after the initial introduction of the nematode B. siricidicola. The migration of S. noctilio into the summer rainfall regions of South Africa occurred in the absence of the associated natural enemies. This resulted in rapid population growth of the pest and substantial damage was caused to plantations of Pinus patula in the Eastern Cape and KwaZulu-Natal. Initial attempts at introducing B. siricidicola during 2004 were not very successful. This study contributes to the understanding and adaptation of the biological control methods to the summer rainfall climate. The key finding was that in the summer rainfall climate, only the bottom third of nematode inoculated S. noctilio infested trees produced parasitized adults during the emergence period. A comparative study was done on log samples from S. noctilio infested trees collected in the Western Cape and KwaZulu-Natal. iv An adapted nematode inoculation technique for pulpwood plantations in the summer rainfall regions was developed and implemented in mass inoculations with B. siricidicola during 2007 and 2008. Locally available herbicides were tested for suitability of use in the establishment of trap trees, which would attract ovipositing S. noctilio females in situations where low numbers of the woodwasp occur. Determination of the levels of natural B. siricidicola parasitism in S. noctilio adults during the 2008 emergence period indicate successful establishment of the nematode in KwaZulu-Natal. Successful introduction of the parasitoid wasp Ibalia leucospoides into the summer rainfall regions has also been achieved.

A dissertação realiza uma comparação entre etnografias que analisam o tema dos casamentos entre índios e brancos nas terras baixas sul-americanas, voltando-se ainda a outros trabalhos em etnologia que debatem o parentesco e as relações com não indígenas na região. A leitura comparada do material levantado demonstra que a interpretação etnológica desses casamentos leva em conta dois movimentos inversos: o virar branco e a domesticação dos brancos, aos quais frequentemente se acrescentam o virar índio e a domesticação dos índios. Esses movimentos são debatidos, por toda a dissertação, à luz das contribuições da etnologia americanista contemporânea. / The dissertation compares ethnographies that analyse the theme of marriages between indians and whites in south american lowlands, also turning itself to other works that debate kinship and relations with nonindigenous in the region. The compared analysis of the material demonstrates that the ethnological interpretation of these marriages take into account two inverse movements: becoming white and domestication of whites, to which are frequently added the movements becoming indian and domestication of indians. These four movements are debated in the light of current contributions of contemporaneous americanist ethnology.