Thesis--Wisconsin. / Includes bibliographical references (leaves 49-52).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1980. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 189-200).

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 125-128).

The objectives of this study were to determine effects of Eurasian watermilfoil (Myriophyllum spicatum) removal on bluegill feeding habits relative to diet composition, size, and feeding selectivity. Data were collected from 2003 through 2007 in four Minnesota lakes during June and September using boat electrofishing. Two lakes received an herbicide application of Endothall 2, 4-D, whereas remaining lakes were untreated and used as a reference. Bluegill diet composition, diets relative to size, and feeding selectivity were unaffected by vegetation removal, but varied seasonally with macroinvertebrate availability. Therefore, removal of Eurasian watermilfoil had minimal effects on bluegill feeding habits.

Myriophyllum spicatum L. (Haloragaceae), a submerged macrophyte, has been recorded in southern Africa since 1829, but only considered problematic as recently as 2005. In light of this, water resource managers are looking to control M. spicatum in southern African water bodies where it is problematic. Amongst control options available in South Africa, biological control is potentially the most cost effective and sustainable option for M. spicatum. However, there is a debate over the status of this plant in southern Africa with several authors reporting it as a native component of the aquatic ecosystem, while others argue that it has been introduced from Europe or Asia. The aim of this thesis is to use a multifaceted approach to resolve the status of M. spicatum, by studying aspects of its history, distribution, mechanisms of its adaptations, biotic interactions and genetic relationships in southern Africa. By resolving the status of this plant as either native or exotic, appropriate management strategies can be initiated for its control in situations where it is considered a problem.A review of the evidence collected from this thesis does not provide convincing evidence for the anthropogenic introduction of M. spicatum into southern Africa, and it is probably native to the region. The disjunct distribution as well as regular local extinctions of populations is relatively common for species that are at the edge of their range. The populations in southern Africa could thus be relics from a much wider distribution in the past. The development of local adaptations in southern Africa provides evidence for this and suggests that the populations have been isolated for a substantial period of time and have had a long evolutionary history in the region. The lack of specialist herbivores should suggest that M. spicatum has been introduced, but the complete lack of herbivores, including generalists, may weaken that argument. The lack of herbivores could be a result of something inherent in the plant, irrespective of a lack of evolutionary history in the region. The genetic evidence suggests a European origin, but is characteristic of a population (southern Africa as a whole) that has been isolated for a considerable time. Despite the findings of this research, M. spicatum is considered problematic in southern Africa and warrants control in certain systems. Whether or not biological control should be a component of the management strategy is open to further debate. The benefits in a southern African context may outweigh the risks, based on the specificity of the biological control agent proposed. However, the perceived negative impacts of M. spicatum are likely to be a symptom of a more serious underlying cause, such as nutrient loading and changes in land use patterns. Therefore the control of this native species is a water resource management issue and not a biological control issue.

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 188-195).

A 2 x 2 factorial design investigated effects of sediment nitrogen and water potassium levels on autofragment production. Reduced nitrogen levels significantly increased autofragment production whereas potassium levels did not significantly alter production. Up to 50% of autofragment production abscised from parent plants grown under low nitrogen conditions compared to 12% or less under high nitrogen conditions.

No description available.

Eurasian watermilfoil (Myriophyllum spicatum) habitat was predicted at multiple scales, including a lake, regional, and national level. This dissertation illustrates how habitat can be predicted for M. spicatum using publically-available data for both presence and environmental variables. Models were generated using statistical procedures and quantative methods to determine where the greatest likelihood of presence was located. For the single lake, presence and absence data were available, but the larger-scale models used presence-only methods of prediction. These models were paired with a Geographic Information System so that data could be visualized on a map. For the selected lake, Pend Oreille (Idaho), spatial analysis using general linear mixed models was used to show that depth and fetch could be used to predict habitat, although differences were seen in their importance between the littoral and pelagic zones. For the states of Minnesota and Wisconsin, Mahalanobis distance and maximum entropy methods were used to demonstrate that available habitat will not always mean presence of M. spicatum. The differing approaches to management in these states illustrated how an aggressive public education campaign can limit spread of M. spicatum, even when habitat is available. Bass habitat appeared to be the largest predictor of M. spicatum in Minnesota, although this was due to the similar environmental preferences by these species. Using maximum entropy, on a national level, presence of M. spicatum appeared to be best predicted by annual precipitation. Again, results showed that habitat is colonized as time permits, and not necessarily as conditions permit.

No description available.