School of Botany - Theses
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ItemDecision analysis for threatened species management across the captive-wild spectrum( 2015)Programs for the recovery of threatened species increasingly involve active management of variable intensity, such as captive breeding, reintroduction and translocation. Managers of such programs thus need to make decisions about whether and how to implement a given type of management, usually in the face of uncertainty and constraints. Structured decision making provides decision makers with a theoretical framework and practical methods to make rational decisions under uncertainty. In this thesis, I investigate how different principles and tools of structured decision making can assist decisions in threatened species management. The fundamental decision problems in threatened species management concern whether and how to implement a given type of management for the target species. In Chapter 2, I examine the case of whether the conservation of a species should incorporate ex-situ management, using the recovery plan for an endangered frog species in south-eastern Australia as an example. I demonstrate that this question can only be answered rationally after determining how the ex-situ component will benefit the overarching objectives of the recovery plan. This logical sequence of decisions (how before whether) is however followed only infrequently in real-world conservation. I illustrate how managers can implement it with the aid of decision trees and multi-criteria decision analysis. Since decisions are aimed at achieving objectives, they necessarily reflect the values and preferences of stakeholders. Using value functions, in Chapter 2 I demonstrate how the optimal decision depends on the relative importance attributed to different objectives (for example, maximising the probability of persistence of the target species and meeting budget limitations). In Chapter 3, I expand this analysis to demonstrate how to account for the attitude of decision makers towards the risk of negative outcomes. I use two case studies of recovery plans for threatened frog species to illustrate the application of stochastic dominance, a useful method to rank alternative actions in the face of uncertainty and risk. Structured decision making provides methods to make decisions under uncertainty. However, in some instances reducing the existing uncertainty by collecting additional information can allow more robust decisions. As a result, managers of threatened species programs almost always advocate further research, in the expectation that it will improve the outcomes of management. In Chapter 4, I apply a formal method to calculate the expected benefit of additional information to two examples in threatened species management. I demonstrate how the value of information is a function of the current knowledge, by the potential to react to new information, and by the effectiveness of the learning process. Value of information analysis can help managers determine whether and how to implement experiments and monitoring programs to improve the ultimate outcomes of management. For several threatened species programs, the scale and speed of the threatening processes often require decisions to be made immediately, leaving no time for formal experimental learning. Adaptive management describes a specific case of structured decision making in which managers learn by monitoring the outcomes of management and adjust actions accordingly. In Chapter 5, I analyse the conditions and challenges that exist to the application of adaptive management in threatened species programs. The temporal scale of such programs is often sufficient to allow managers to collect information and react by updating actions in subsequent time steps. Particularly for programs toward the captive end of the management spectrum, controlled conditions are also favourable for effective learning. Adaptive management requires the ability to clearly structure uncertainty into formal hypotheses, to allow effective and focused monitoring that addresses the most important sources of uncertainty. Most importantly, institutions and stakeholders must be committed and capable of implementing learning. For clearly defined decision problems, structured decision making can draw upon a range of technical approaches to determine optimal management strategies. In Chapter 6, I consider a reintroduction program in which management decisions are complicated by the complex life history of the target species and budget constraints. I combine demographic modelling and cost-effectiveness analysis to identify the optimal rates of translocation between captive and wild populations. This thesis illustrates how the iterative cycle of structured decision making can benefit all stages of the design of management strategies for threatened species conservation. First, it can help managers in thinking clearly about the decision problem, allowing a transparent assessment of subjective preferences and value. It can then ensure an objective evaluation of the available management alternatives, using qualitative or quantitative predictive approaches that explicitly recognise uncertainty. Finally, it can assist in finding solutions to trade-offs and incorporating additional knowledge to allow better decisions.
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ItemRiparian vegetation in an agricultural landscape: assessment and analysis of condition and change( 2013)Vegetation assessment is done using a wide range approaches depending on the assessment aims and constraints. Two approaches to sampling with vastly different targets, designs, and costs, are snapshot (single time period) or longitudinal (multiple time period) studies. Each approach has a range of strengths and weaknesses for vegetation assessment that allow interrogation of different research objectives. The collection and analysis of data within each sampling approach contains an array of challenges for any given study. The research reported here uses a case study of riparian vegetation in northern Victoria, Australia to explore the use of snapshot and longitudinal surveys for understanding riparian vegetation attributes and the effectiveness of different management actions in an agricultural landscape in northern Victoria. Riparian vegetation is a valuable component of the landscape that acts as the interface between aquatic systems and terrestrial environments. Healthy riparian zones are important for maintaining aquatic ecosystems by providing habitat, shade, banks stability, sediment filtration and nutrient processing. They also support terrestrial ecosystems through provision of ecosystem services. Riparian vegetation is valued for agricultural and recreational uses, which has led to high levels of degradation worldwide. In Victoria, extensive clearing and uncontrolled stock access continues to be a major pressure on riparian vegetation condition. The impact of livestock grazing on riparian systems is predominantly negative. There is a global wealth of knowledge on grazing management, but many gaps exist on the effectiveness of management in different systems and the methods used to evaluate this. Field vegetation surveys remain an essential component of conservation management. Riparian vegetation contains gradients in resources, structure and function, which provides a challenge to survey techniques. Therefore, this research used a quantitative sampling approach designed to capture variation along the gradients of distance from the creek edge, distance along the creek and seasonality. These data were used to characterise the variation in vegetation composition across all sites, in order to inform a new method of sampling riparian vegetation based on delimited zones. This zoned approach was then used in combination with published benchmarks of vegetation condition to evaluate livestock grazing management in this system. Vegetation condition assessments record various vegetation attributes as measures of the value, quality or condition of a site. Comparisons to published benchmarks suggested that the study sites had low cover of all native ground cover life forms, especially medium tufted graminoids and herbs. However, tree canopy cover was at or above expected levels for most sites. Results indicated that livestock grazing was associated with an increase in cover of bare ground and exotic annual herbs and a decrease in cover of native shrubs, herbs and native tufted graminoids. In addition, the effects of grazing varied with distance from the creek. Grazing exclusion through fencing and revoking grazing licences may have benefits for native vegetation condition, but the positive effect of grazing on reducing exotic perennial graminoid cover should also be considered. Evaluating management against vegetation change over time is superior to that of a single point in time as it allows identification of the rate and trajectory of change. Assessment of change requires multiple comparable surveys through time but these data are expensive and slow to acquire. In the absence of these data, historical data sets can provide valuable insights into past vegetation condition and structure. However, historical data collection methods that were not designed for the purposes of monitoring change will produce data not directly comparable to data from more detailed methods. The comparison of unequal datasets is common in ecology and many other fields, but the most appropriate method for comparing unequal data sets is not clearly established. This thesis addresses this issue through applying two methods, one existing and one novel, and comparing their performance in predicting vegetation change through time in order to inform management. The two alternative methods used different approaches to reinterpret coarse historical data. The novel method used data calibration via a double sampling approach, whereas existing methods used Bayesian prior distributions. Data calibration was superior to the existing method in two out of three examined vegetation variables. However, calibration methods required more field surveys and more complicated data analysis. Grazing management indicators were as good or better predictors of vegetation change than a selection of site and environmental variables. Fencing and grazing licence changes had varied effects on different vegetation attributes across sites. The data analyses used were effective tools for evaluating change and effects of management, but made uncertain predictions due to high variation between sites and the thorough accounting of data uncertainties in the models used.
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ItemA primary ecological survey of the Kentbruck Heath( 1970)Introduction: The Kentbruck Heath is an area in the far southwest of Victoria, about six miles in from the coast, and almost mid-way between Portland and Nelson. The flora of the area is exceptionally rich and diverse, and is relatively undamaged. The western two thirds of the area was proclaimed as part of the Lower Glenelg National Park in 1969. For these reasons it was decided to investigate it by means of a primary ecological survey. This survey occupied only 12 months, and this limited the type of work which could be undertaken. The area known as the Kentbruck Heath can be broadly delineated on a map by the Kentbruck Road and F.V.C pine plantations on the west, Inkpot Road on the north, Heath Road and Kentbruck Settlement on the east, and other agricultural development on the south. The detailed survey was restricted to a representative square mile of this, but general observations confirm the validity of some extrapolations from the data obtained. By way of comparison, an area to the west known as Bulley Ranges has also been the subject of preliminary survey.
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ItemThe sanitisation of urban ecosystems: simplification of the ground layer in eucalypt woodlands and the effects on arthropod communities( 2011)Green spaces in urban environments can provide valuable habitat for maintaining local and regional biodiversity. Many urban green spaces are, however, managed for human recreation, where the vegetation structure is reduced, and critical resources such as leaf litter and woody debris are removed. Reductions in ground layer resources have been implicated in the decline of urban vertebrate biodiversity, but the effects of this process on arthropod communities is poorly understood. The response of the ground-active arthropod community to differences in ground layer resources was studied in green spaces managed for human recreation compared to areas maintained in a ‘natural’ state, at 21 field sites in Melbourne, Australia. Sites were separated into two categories: 1) areas with high leaf litter levels (remnant woodland patches) and 2) areas with reduced leaf litter layers, which were regularly mown (public parks). All sites had overstoreys of Eucalyptus camaldulensis. Site assessments confirmed litter layers were greatly reduced in abundance and extent in public parks, and also showed that these sites had less vegetation in the mid- and over-storey, and fewer dead wood resources. The arthropod communities at the sites were examined at order level, and millipede (Diplopoda), slater (Isopoda: Oniscidea), ant (Hymenoptera: Formicidae) and beetle (Coleoptera) communities were examined at species-level. The millipede and slater (macrodetritivores) communities were made up almost exclusively of introduced species from Europe. Although they were able to persist in both Parks and Remnants, their abundance was greatest where there was more leaf litter and shrub cover. In contrast, the ant fauna was diverse, abundant and native at all sites, but had a different community composition at Parks compared to Remnants. These differences were associated with both local- and landscape-scale features of the sites. The beetle community showed strong changes in composition and diversity in response to differences in the leaf litter layer as well as to the composition of the ground layer species. The response of the invertebrate fauna to small-scale manipulations of common urban ground covers – bare ground, leaf litter, woodchips and grass – was investigated experimentally at a semi-field site. Diverse arthropods rapidly colonised previously cleared plots under all four ground covers and were most abundant in grass plots. This is likely to be related to the landscape context of the experiment and has important implications for small-scale landscape management for biodiversity conservation. This thesis provides information on the role of urban, managed green spaces for arthropod biodiversity conservation, and contributes to our understanding of the effects of management practices that influence the arthropod community composition and diversity in these areas. Green open spaces (parks) were not found to provide the same resources for ground-dwelling arthropods as woodland remnants, and this was associated with marked changes in their community composition. The findings have important implications for biodiversity conservation in an urbanising world.
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ItemThe intersection of ecology and evolution: a case study of Eucalyptus in the Grampians Ranges, Australia( 2011)This thesis explores the ecology and evolution of Eucalyptus species in the Grampians ranges, Australia. The Grampians ranges are an ancient isolated collection of three ranges with steep habitat gradients relative to the surrounding homogeneous landscape. This region is a local centre of species diversity and endemism, in which many closely related species interact. I use a range of approaches to understand the ecological and evolutionary history of contemporary patterns of species distribution, traits, and co-occurrence. First, I investigate speciation and gene flow for a clade of Eucalyptus endemic to high elevation rocky outcrops in the Grampians. I document chloroplast DNA structure for the three high elevation species (E. serraensis, E. verrucata, and E. victoriana) and a neighbouring species E. baxteri, which surrounds endemic populations. I found generally high chloroplast diversity, local genetic structuring, and local interspecific gene-sharing. Second, I broaden the scope to include all 20 Eucalyptus species in the region. I am generally interested in relations between species, functional traits, and environments. I model the distribution of species across environmental gradients using a modern niche modelling technique. I incorporate species interaction terms and model groups of species across a taxonomic hierarchy to explore species and clade interactions. Using a subset of variables found to be important in niche models, I then used a hierarchical modelling approach that describes how species responses to environmental variables change as a function of their traits. I used traits from the leaf-height-seed strategy scheme (specific leaf area (SLA), maximum height and seed mass). I found a range of important trait-habitat associations. For example, SLA modified species responses to rock cover such that thicker, denser leaves were found on rocky areas with less soil. Seed mass was associated with edaphic variables such as valley bottom flatness and soil texture. Maximum height of species increased with solar radiation and rainfall. Third, I explored the evolutionary history of these trait-habitat associations with phylogenetically independent contrasts using a phylogeny and niche model estimates. I found a general progression from early divergence of seed mass-edaphic associations to late divergence of height-climatic associations. SLA diverged early with edaphic associations and later with climatic associations. I interpret the early edaphic- late climatic- associations divergences with the paleoclimatic and geologic processes of the Grampians region. Finally, I again explore trait, niches, and phylogenetic relationship, this time in the context of local species assemblages. I address the longstanding observation that within large genera, closely related species do not co-occur in local neighborhoods. I find that habitat drives species assemblages except when species interbreed. I attribute the lack of co-occurrence of reproductively compatible species to reproductive interference via hybridization and introgression. Results from the initial genetics study confirm the importance of geneflow for these species. This approach describes a genetic mechanism underlying an ecological pattern and provides a cohesive story of the ecology and evolution of Eucalyptus in this region.
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ItemThe ecology of Acacia malanoxylon R. Br.( 1973)The genus Acacia Mill. consists of more than 750 species of shrubs and trees (Willis, 1966) found throughout much of the tropical, sub-tropical and warm temperate zones of the world. It is usually divided into two main sections, the Bipinnatae and the Phyllodineae. Species in the former section possess bipinnate leaves throughout their entire life-span, and are found on the Australian, African, Indian and North American continents. In the Phyllodineae the rachis of the bipinnate leaf expands vertically to form the adult foliage of phyllodes. Some examples of transitional stages between these two foliage forms are shown in Fig. 1.1. With the exception of a few species on islands in the Indian and Pacific Oceans, the Phyllodineae is confined to Australia. (From Introduction)