Univ., Diss--Düsseldorf, 2005.

Thesis (MSc)-- University of Stellenbosch, 2007. / Masters of Science (Geographic Information Systems - Environmental Geography) Bibliography. Also available via the Internet.

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.

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.

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.

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.

Reducing the cover of non-native species is one of the challenges of ecosystem restoration. The goal of this study is to identify native species traits that will increase native species cover and reduce non-native species cover in the first growing season at upland and wetland prairie restoration sites. Native and non-native prairie species were planted in the fall and harvested the following summer at both an upland and a wetland site. Native species traits, such as plant weight, leaf area, relative growth rate, leaf area ratio, leaf weight ratio, net assimilation rate, and specific leaf area were measured under laboratory conditions for 7- and 21-day old seedlings. Germination rate (laboratory) and phenology (field) were also measured. At the upland site, species with a large 7-day plant weight and a high germination rate also had high native cover in the field (P<0.00l, R��=0.83). At the wetland site, high 21-day leaf area, low 21-day leaf weight ratio, and high net assimilation rate predicted increased native cover in the field (P<0.00l, R��=0.87). An abundance of natives, as measured by native cover, native biomass, and number of individuals, likely results in fewer resources (light, nutrients, and water) available for the non-native species growth resulting in a reduction in the non-native cover. Intrinsic traits of native species also predicted the field performance of non-native species, although the amount of variation explained was lower than the amount of variation explained in the models that predicted native cover. In the upland site, native species with high leaf weight ratio (21-day) tended to have lower non-native cover in their field plots (P=0.087, R��=0.23). In the wetland site, the native species traits that predict non-native cover were low 21-day leaf area and high 21-day leaf weight ratio (P<0.00l, R��=0.46). These traits were similar to those that predicted native species cover at the wetland site. This study demonstrates the ability of species traits to predict field performance. Predictive models were generated using native species traits to select species for restoration that will increase native cover and decrease non-native cover in the first growing season. Traits can be measured for species not included in this study and the models generated can be used to predict the field performance of species at similar sites. / Graduation date: 2002

Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2008.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--University of Delaware, 2006. / Principal faculty advisor: Judith Hough-Goldstein, Dept. of Entomology & Wildlife Ecology. Includes bibliographical references.