School of Botany - Theses

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    Dissecting antibiotic targeting in the malaria parasite Plasmodium falciparum
    Johnson, Russell Andrew. (University of Melbourne, 2008)
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    The saltmarshes of the southern coast of Victoria : floristic composition, variation and distribution
    Gent, Martha L. (University of Melbourne, 2005)
    Although there has been some ecological analysis of Victoria�s saltmarshes, it has been predominantly based on observations and descriptive analyses. As Victorian saltmarshes face the continuing risk of destruction and degradation due to the effects of increasing urbanisation and global climate change, it is imperative that their composition and variation are quantified in order to develop appropriate conservation and management strategies. The past distribution of saltmarshes on the southern coast of Victoria was calculated using geographic and environmental data. Past distribution was compared to present distributions provided by the FIS database form the Department of Sustainability and Environment. The results indicate that only 45% of the saltmarsh that once covered this region remain intact. Many losses occurred prior to the legal protection of the coast from 1978 and are the result of land clearance for industrial uses such as salt production and waste treatment as well as agriculture the subsequent grazing of the region. Saltmarsh vegetation in Port Phillip and Western Port Bays was classified using the Department of Sustainability and Environment�s Flora Information Systems (FIS) database and compared with a 2003 field survey using a systematic, random sampling method. The non-metric multidimensional scaling (NMDS) ordination of the sites identified from the FIS database showed a distinct separation of samples from each of the saltmarsh communities sampled along the coast. In comparison, the 2003 survey results showed relatively little if any separation based on site location indicating that the sites all had similar vegetation composition. The exclusion of the non-indigenous species from both data sets indicated that non-indigenous species contribute to the convergence in the floristic composition between sites, but do not greatly effect the grouping of the sites. The differences between the two data sets were attributed to sampling methods and a number of limitations involved in using FIS data were identified. The usefulness of the FIS database for classifying saltmarsh vegetation would be improved with the inclusion of more information, such as quadrat size and placement details, when entering records. The results of the 2003 field survey were used to compare the floristic composition of Victorian saltmarsh vegetation along the southern coast of Victoria ranging from Portland to Shallow Inlet. A non-metric multidimensional scaling (NMDS) ordination and analysis of community similarity (ANOSIM) showed the floristics of each site to be very similar. The two most dominant species recorded were Sarcocomia quinqueflora and Sclerostegia arbuscula. Although the different communities from along the coast share similar floristic composition the presence of a number of less common species, which do not occur at all sites, contribute to the overall diversity of Victoria�s coastal saltmarshes. The lack of non-indigenous species in the vegetation indicates that they are not currently subject to exotic species invasion. This is most likely due to the harsh growing conditions that are typical of saltmarsh communities. However, the threat of invasion is always present due to surrounding areas of high weed cover. Environmental variables were correlated to the ordination of the sites indicating that although electrical conductivity is a factor in determining species composition it explains less than one third of the variation between sites
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    Determining the optimal captive management of the helmeted honeyeater (Lichenostomus melanops cassidix) using stochastic dynamic programming
    Meyer, Rachelle. (University of Melbourne, 2005)
    This thesis investigates the use of stochastic dynamic programming (SDP) in assisting managers of the helmeted honeyeater with decisions relating to the movement of birds in and out of captivity. SDP is a state dependent decision-making tool that requires a model to explain how the population responds to different management actions in different circumstances, or states. This model is then used to determine what strategy is best to meet a specified management objective. Three models were constructed, two addressing the optimal number of helmeted honeyeaters to move into or out of captivity and one addressing optimal resource allocation between two release methods. Optimal solutions produced from the SDP that used a general model of helmeted honeyeater dynamics were robust to moderate changes in most parameter values and performed better than strategies that moved a certain proportion of individuals into a population that fell below a given threshold. Results were similar to a investigation by Tenhumberg et al (2004), which also used SDP to determine the optimal number of individuals to move between wild and captive populations. The second and more complex model of helmeted honeyeater dynamics addressed most of the limitations of the previous model and incorporated a decision set that is more applicable to the helmeted honeyeater. Model structure and SDP parameters, such as timeframe and objective, could have very large effects on the optimal solution. Results suggest that more captures than have typically occurred at relatively large Yellingbo population sizes is the best option in most scenarios. To increase certainty in decisions at lower Yellingbo population size, more precise estimates of the cost of taking eggs from the wild and the benefit of bringing them into captivity are needed. When the captive population is full, and the target population is not, releases were optimal in almost every case. Recommendations for the current population sizes are releases in groups as large as possible from captivity and no captures from Yellingbo. The allocation of resources between two release methods was strongly influenced by the number of success previously achieved with the cheap method and the relative cost. For the levels of relative cost investigated, a very low level of cheap method success was necessary to allocate resources to the expensive strategy. If the range for the possible success rate for an expensive strategy is not substantially larger than that obtained with the cheap method resources should continue to be allocated to the cheap method. In the case of the helmeted honeyeater, optimistic estimates of expensive method success are large enough and cheap method success rate low enough to justify allocating resources to the more expensive strategy if it is three times the cost of the cheap strategy or less. This SDP provides an effective way of incorporating learning into a variety of decisions, and could be applied to any choice between methods that have individual trials, which can be classified as successes or failures.
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    The saltmarshes of the southern coast of Victoria : floristic composition, variation and distribution
    Gent, Martha L. (University of Melbourne, 2005)
    Although there has been some ecological analysis of Victoria�s saltmarshes, it has been predominantly based on observations and descriptive analyses. As Victorian saltmarshes face the continuing risk of destruction and degradation due to the effects of increasing urbanisation and global climate change, it is imperative that their composition and variation are quantified in order to develop appropriate conservation and management strategies. The past distribution of saltmarshes on the southern coast of Victoria was calculated using geographic and environmental data. Past distribution was compared to present distributions provided by the FIS database form the Department of Sustainability and Environment. The results indicate that only 45% of the saltmarsh that once covered this region remain intact. Many losses occurred prior to the legal protection of the coast from 1978 and are the result of land clearance for industrial uses such as salt production and waste treatment as well as agriculture the subsequent grazing of the region. Saltmarsh vegetation in Port Phillip and Western Port Bays was classified using the Department of Sustainability and Environment�s Flora Information Systems (FIS) database and compared with a 2003 field survey using a systematic, random sampling method. The non-metric multidimensional scaling (NMDS) ordination of the sites identified from the FIS database showed a distinct separation of samples from each of the saltmarsh communities sampled along the coast. In comparison, the 2003 survey results showed relatively little if any separation based on site location indicating that the sites all had similar vegetation composition. The exclusion of the non-indigenous species from both data sets indicated that non-indigenous species contribute to the convergence in the floristic composition between sites, but do not greatly effect the grouping of the sites. The differences between the two data sets were attributed to sampling methods and a number of limitations involved in using FIS data were identified. The usefulness of the FIS database for classifying saltmarsh vegetation would be improved with the inclusion of more information, such as quadrat size and placement details, when entering records. The results of the 2003 field survey were used to compare the floristic composition of Victorian saltmarsh vegetation along the southern coast of Victoria ranging from Portland to Shallow Inlet. A non-metric multidimensional scaling (NMDS) ordination and analysis of community similarity (ANOSIM) showed the floristics of each site to be very similar. The two most dominant species recorded were Sarcocomia quinqueflora and Sclerostegia arbuscula. Although the different communities from along the coast share similar floristic composition the presence of a number of less common species, which do not occur at all sites, contribute to the overall diversity of Victoria�s coastal saltmarshes. The lack of non-indigenous species in the vegetation indicates that they are not currently subject to exotic species invasion. This is most likely due to the harsh growing conditions that are typical of saltmarsh communities. However, the threat of invasion is always present due to surrounding areas of high weed cover. Environmental variables were correlated to the ordination of the sites indicating that although electrical conductivity is a factor in determining species composition it explains less than one third of the variation between sites
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    Determining the optimal captive management of the helmeted honeyeater (Lichenostomus melanops cassidix) using stochastic dynamic programming
    Meyer, Rachelle. (University of Melbourne, 2005)
    This thesis investigates the use of stochastic dynamic programming (SDP) in assisting managers of the helmeted honeyeater with decisions relating to the movement of birds in and out of captivity. SDP is a state dependent decision-making tool that requires a model to explain how the population responds to different management actions in different circumstances, or states. This model is then used to determine what strategy is best to meet a specified management objective. Three models were constructed, two addressing the optimal number of helmeted honeyeaters to move into or out of captivity and one addressing optimal resource allocation between two release methods. Optimal solutions produced from the SDP that used a general model of helmeted honeyeater dynamics were robust to moderate changes in most parameter values and performed better than strategies that moved a certain proportion of individuals into a population that fell below a given threshold. Results were similar to a investigation by Tenhumberg et al (2004), which also used SDP to determine the optimal number of individuals to move between wild and captive populations. The second and more complex model of helmeted honeyeater dynamics addressed most of the limitations of the previous model and incorporated a decision set that is more applicable to the helmeted honeyeater. Model structure and SDP parameters, such as timeframe and objective, could have very large effects on the optimal solution. Results suggest that more captures than have typically occurred at relatively large Yellingbo population sizes is the best option in most scenarios. To increase certainty in decisions at lower Yellingbo population size, more precise estimates of the cost of taking eggs from the wild and the benefit of bringing them into captivity are needed. When the captive population is full, and the target population is not, releases were optimal in almost every case. Recommendations for the current population sizes are releases in groups as large as possible from captivity and no captures from Yellingbo. The allocation of resources between two release methods was strongly influenced by the number of success previously achieved with the cheap method and the relative cost. For the levels of relative cost investigated, a very low level of cheap method success was necessary to allocate resources to the expensive strategy. If the range for the possible success rate for an expensive strategy is not substantially larger than that obtained with the cheap method resources should continue to be allocated to the cheap method. In the case of the helmeted honeyeater, optimistic estimates of expensive method success are large enough and cheap method success rate low enough to justify allocating resources to the more expensive strategy if it is three times the cost of the cheap strategy or less. This SDP provides an effective way of incorporating learning into a variety of decisions, and could be applied to any choice between methods that have individual trials, which can be classified as successes or failures.
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    Effective survey methods for detecting plants
    Baran, Natalie A. (University of Melbourne, 2001)
    Plant survey methods widely used in Australia to compile species lists and conduct baseline surveys are evaluated. In general flora surveys use one of two methods, a fixed- area quadrat or a wandering search. An untested assertion exists in the literature that suggests search sampling is better than quadrat sampling for detecting species. In order to test this claim empirically, an area of sclerophyll forest in southern Australia was sampled intensively using systematic quadrat sampling and search sampling. The number of species detected within quadrat samples was compared to the number detected in search samples. The pattern of species accumulation with time is modeled according to three types of botanical experience: the novice, average and expert searcher. The models are then used to predict the number of species gained with further sampling time. The likelihood of quadrat sampling to detect the same species within search samples is investigated. The expectation of life-form bias in the collections of individual searchers is also analysed. The results suggest that the number of samples taken should be guided by a consideration of how confidently the survey should detect the presence of relatively scarce species. A survey of botanists and biologists confirmed that individuals are poor judges of sample size and subjective estimates should be avoided. The results also suggest that in many circumstances, fixed-area quadrat sampling is preferable to search sampling. Measures of the adequacy of vegetation surveys are suggested.
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    Effective survey methods for detecting plants
    Baran, Natalie A. (University of Melbourne, 2001)
    Plant survey methods widely used in Australia to compile species lists and conduct baseline surveys are evaluated. In general flora surveys use one of two methods, a fixed- area quadrat or a wandering search. An untested assertion exists in the literature that suggests search sampling is better than quadrat sampling for detecting species. In order to test this claim empirically, an area of sclerophyll forest in southern Australia was sampled intensively using systematic quadrat sampling and search sampling. The number of species detected within quadrat samples was compared to the number detected in search samples. The pattern of species accumulation with time is modeled according to three types of botanical experience: the novice, average and expert searcher. The models are then used to predict the number of species gained with further sampling time. The likelihood of quadrat sampling to detect the same species within search samples is investigated. The expectation of life-form bias in the collections of individual searchers is also analysed. The results suggest that the number of samples taken should be guided by a consideration of how confidently the survey should detect the presence of relatively scarce species. A survey of botanists and biologists confirmed that individuals are poor judges of sample size and subjective estimates should be avoided. The results also suggest that in many circumstances, fixed-area quadrat sampling is preferable to search sampling. Measures of the adequacy of vegetation surveys are suggested.
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    Role of Ribulose-1,5-Bisphosphate Carboxylase
    Kelly, Michael (Michael Ernest) (University of Melbourne, 1998)
    Physiological adaptations by plants in order to better utilise sunflecks were studied using plants from the rainforest understorey. Transgenic Rubisco and wild-type Nicotiana tabacum L., from the Solanaceae family, were used to model these adaptations and to better characterise the light induced activation kinetics. Tobacco plants with varying Rubisco concentrations were used to obtain plants with differing Activase to Rubisco stoichiometry. An increase in the stoichiometry caused proportional changes in the rate of Rubisco activation. This was reflected in a decrease in the relaxation times from 2.5 to 3 minutes down to 35 to 40 seconds. This faster rate of activation lead to a reduction in the amount of C02 assimilation effectively forgone due to the activation process. In wild-type tobacco this amount of forgone photosynthesis was found to be, on average, 23.5 ?mol C02 m-2 compared to 6.0 ?mol C02 m-2 for Rubisco mutant tobacco plants. Understorey plants from the rainforest of Cape Tribulation National Park (QLD) were examined to see if they adjusted their stoichiometry of Activase and Rubisco in order to increase C02 assimilation in sunflecks. Gas exchange analysis of the rainforest plants showed them to behaved in a similar fashion to the Rubisco mutant tobacco. Examination of the kinetics of Rubisco activation in rainforest and Rubisco mutant tobacco plants found, on average, comparable relaxation times (58 and 67 seconds, respectively) and similar initial activation rates (46.6 and 46.1 nmol active sites m-2 s-1, respectively). When compared to wild-type tobacco, the rainforest plants on average were found to have over 5.5 times the ratio of Activase to Rubisco. This leads to a reduction in the average amount of forgone photosynthesis from 23.5 ?mol C02 m-2 for wild-type to 4.2 ?mol C02 m-2 for rainforest plants. These results suggest that plants grown under fluctuating light environments alter their stoichiometry in order to better utilise sunflecks for carbon gain.
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    Role of Ribulose-1,5-Bisphosphate Carboxylase
    Kelly, Michael (Michael Ernest) (University of Melbourne, 1998)
    Physiological adaptations by plants in order to better utilise sunflecks were studied using plants from the rainforest understorey. Transgenic Rubisco and wild-type Nicotiana tabacum L., from the Solanaceae family, were used to model these adaptations and to better characterise the light induced activation kinetics. Tobacco plants with varying Rubisco concentrations were used to obtain plants with differing Activase to Rubisco stoichiometry. An increase in the stoichiometry caused proportional changes in the rate of Rubisco activation. This was reflected in a decrease in the relaxation times from 2.5 to 3 minutes down to 35 to 40 seconds. This faster rate of activation lead to a reduction in the amount of C02 assimilation effectively forgone due to the activation process. In wild-type tobacco this amount of forgone photosynthesis was found to be, on average, 23.5 ?mol C02 m-2 compared to 6.0 ?mol C02 m-2 for Rubisco mutant tobacco plants. Understorey plants from the rainforest of Cape Tribulation National Park (QLD) were examined to see if they adjusted their stoichiometry of Activase and Rubisco in order to increase C02 assimilation in sunflecks. Gas exchange analysis of the rainforest plants showed them to behaved in a similar fashion to the Rubisco mutant tobacco. Examination of the kinetics of Rubisco activation in rainforest and Rubisco mutant tobacco plants found, on average, comparable relaxation times (58 and 67 seconds, respectively) and similar initial activation rates (46.6 and 46.1 nmol active sites m-2 s-1, respectively). When compared to wild-type tobacco, the rainforest plants on average were found to have over 5.5 times the ratio of Activase to Rubisco. This leads to a reduction in the average amount of forgone photosynthesis from 23.5 ?mol C02 m-2 for wild-type to 4.2 ?mol C02 m-2 for rainforest plants. These results suggest that plants grown under fluctuating light environments alter their stoichiometry in order to better utilise sunflecks for carbon gain.
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    Investigations into the mechanisms of morphogenesis in Desmids
    Berry, Andrew J. (University of Melbourne, 1994)
    Whether a neuron in a mammalian brain or a guard cell from leaf stomata, the shape of a cell is often vital to its function. Yet morphogenesis, the 'creation of form', is one of the least understood phenomena in cell biology. In order to understand the processes behind morphogenesis, it is reasonable to select a simple organism in which to initiate an investigation. Once this system is understood, the knowledge and concepts may then be applied to other, more complex organisms. The potential of desmids, a group of freshwater green algae from the order Zygnematales (Fritsch 1935), for the study of morphogenesis was first recognised by Waris (1950). There are several reasons why the desmids are particularly well suited for investigation of morphogenesis: the cells are large, making them easy to observe and handle; the asexual lifecycle is predictable and can be completed in 3-8 days; they can be grown in simple inexpensive media; they are found all around the world; and, perhaps most importantly, they display elaborate symmetrical cell patterns which are reproduced every division.