[Truncated abstract] Wild radish (Raphanus raphanistrum L.), an outcrossing annual plant, is one of the most widespread and successful colonising weeds in the Australian wheat belt. It was introduced accidentally during the latter part of the 19th century, apparently independently through the major ports of southern Australia. The widespread success of wild radish, and therefore the likelihood of distinct populations, gives us the opportunity to study the colonizing process with adaptation in annual outbreeding species, and to explore their genetic diversity. The aims of this thesis were to study the genetic diversity of wild radish and to investigate which factors are important in its success. After an initial review of the literature (chapter 2), the thesis describes experiments where genetic variation between and within populations was compared at 55 sites in transects across the wheat belt and high rainfall zones of temperate Western Australia (chapter 3). In chapter 4, variation in life history traits was compared with variation in AFLP molecular markers. The role of seed dormancy in the survival of the species was examined in chapter 5, and variation in the oil content of seeds and their fatty acid composition was examined in chapter 6. Finally, the results were discussed in chapter 7 with special reference to the adaptive value of outcrossing in annual weeds. The results suggest that wild radish has evolved to fit the Australian environment. However, measurement of 14 morphological and phenological characters showed that in most cases within site variation was much greater than that between sites. Most of the variation between sites was associated with geoclusters, a name given to zones of similar environmental conditions in regard to rainfall and temperature. Thus plants from areas with high rainfall and low temperature produced longer, wider pods with more segments, heavier seeds and flowered later than plants from more arid areas.

[Truncated abstract] The Laverton Greenstone Belt (LGB), located in the northeastern part of the Eastern Goldfields Province (EGP) of the Yilgarn Craton, Western Australia, has a total contained gold endowment of over 690t. An important feature of the gold deposits in the LGB is their close spatial association with granitoids, with many gold deposits located adjacent to, or hosted by, granitoids. Recently-proposed genetic models for Archaean orogenic gold deposits have emphasised the role of granitoids in the formation of ore-deposits, but differ significantly in the nature of that role. Some models suggest that the granitoids are a source of ore-fluids and solutes, whereas others suggest that granitoids exert an important structural control on gold mineralisation. Such competing genetic models for gold mineralisation variably propose either a proximal-magmatic or distal-metamorphic, or less commonly distal-magmatic, source for goldbearing fluids, or mixing of fluids from multiple sources. Isotope geochemistry and geochronological studies are used to constrain the source and timing of auriferous fluids at nine gold deposits in the LGB in an attempt to differentiate between conflicting genetic models. To overcome the lack of detailed deposit-scale geological constraints inherent to any regional study, hypotheses generated from regional datasets are tested in a detailed case-study of the Wallaby gold deposit. The Pb-isotope compositions of ore-related sulphides from deposits in the LGB plot along the line representing crustal-Pb in the Norseman-Wiluna Belt of the EGP, with individual deposits clustering with other nearby deposits based on their geographic location. This trend is similar to that recorded in the Kalgoorlie-Norseman region in the southern EGP, and is consistent with a basement Pb reservoir for gold-bearing fluids. As such, data are consistent with a similar fluid source for all gold deposits. The Nd and Sr isotopic composition of goldrelated scheelite in the LGB clusters very tightly. The inferred ore-fluid composition has a slightly positive εNd, similar to ore fluids at other gold deposits in the EGP for which a proximal magmatic source is highly improbable. As such, Sr and Nd data are consistent with a similar fluid source for the gold deposits analysed in the LGB, but cannot unequivocally define that source. The median S, C and O isotopic compositions of ore minerals from all nine different gold deposits studied in the LGB fall in a very narrow range

[Truncated abstract] Amidst concern over the global phenomenon of declining amphibians, there is an increasing appreciation of the importance of understanding population dynamics at both local and regional scales. Data on the viability and persistence of species in landscapes altered by humans are scarce but an understanding of these dynamics is essential for enabling long-term species conservation in a modified world. Habitat loss, fragmentation and ensuing salinisation are of particular concern for species in Australia’s temperate agricultural regions where the rapid conversion of continuously vegetated landscapes to small fragments has occurred in less than 200 years. This thesis investigated the local and metapopulation structure of Heleioporus albopunctatus to determine the current population structure and likely future of this species in a highly degraded landscape: the wheat and sheep growing areas of southwestern Australia ... The life-history attributes of H. albopunctatus, including high fecundity, high adult longevity and low to moderate dispersal contribute to a robust regional metapopulation, responsive to changes, but with a strong chance of persistence over the long-term. H. albopunctatus appears to have adjusted to a radically modified landscape but its long-term persistence may be dependent on the existence of a small number of source populations that recruit in most years.

[Truncated abstract] This work was the first large-scale biological oceanographic study to be undertaken in the coastal eastern Indian Ocean adjacent to Western Australia, and covered both northwest (Exmouth Peninsula to the Abrolhos Islands) and southwest (Cape Naturaliste to Cape Leeuwin) regions. The study area was dominated by the Leeuwin Current (LC), an anomalous eastern boundary current that transports tropical water poleward and prevents deep nutrients from reaching the surface by creating large-scale downwelling. Indeed, LC and offshore waters were consistently associated with low nitrate concentrations and low phytoplankton biomass and production (< 200 mg C m-2 d-1). However, the physical forcing of the LC was offset, during the summer months, by upwelling associated with wind-driven inshore countercurrents (Ningaloo and Capes Currents), which provided a mechanism to access high nutrient concentrations normally confined to the base of the LC. ... Limited seasonal investigations off the Capes region of southwestern Australia showed that the winter production scenario can be very different than summer conditions, with strong Leeuwin Current flow that meanders onto the continental shelf and entrains seasonally nutrient-enriched shelf waters. However, production in the LC was still low (≤450 mg C m-2 d-1) due to light limitation resulting from both increased light attenuation and reduced surface irradiance characteristic of the winter months. This investigation provides fundamental knowledge on physical-biological coupling off Western Australia, with implications for fisheries management in view of seasonal and inter-annual variability in the strength of both the Leeuwin Current and inshore countercurrents.

The Gascoyne continental shelf is located along the north-central coastline of Western Australia between latitudes 21° and 28°S. This study presents CTD and ADCP data together with concurrent wind and satellite imagery, to provide a description of the summer surface circulation pattern along the continental margin, and the hydrography present in the upper 1km of ocean, between latitudes 21° and 35°S. It also discusses the outcome of a numerical modelling study that examined the physical factors contributing to a bifurcation event persistently observed in satellite imagery at Point Cloates. The region comprises a complex system of four surface water types and current systems. The Leeuwin Current dominated the surface flow, transporting lower salinity, warmer water poleward along the shelf-break, and causing downwelling. Its signature ‘aged’ from a warm (24.7°C), lower salinity (34.6) water in the north to a cooler (21.9°C), more saline (35.2) water in the south, as a result of 2-4Sv geostrophic inflow of offshore waters. The structure and strength of the current altered with changing bottom topographies. The Ningaloo Current flowed along the northernmost inner coast of the Gascoyne shelf, carrying upwelled water and re-circulated Leeuwin Current water from the south. Bifurcation of the Ningaloo Current was seen south of the coastal promontory at Point Cloates. Numerical modelling demonstrated a combination of southerly winds and coastal and bottom topography off Point Cloates to be responsible for the recirculation, and indicated that the strength of southerly winds affect recirculation. Hypersaline Shark Bay outflow influenced shelf waters at the Bay’s mouth and to the south of the Bay. The Capes Current, a wind-driven current from south of the study region was identified as a cooler, more saline water mass flowing northward. Results of the hydrography study show five different water masses present in the upper-ocean. Their orientations were affected by the geopotential gradient driven Leeuwin Current/Undercurrent system at the continental margin. The Leeuwin Undercurrent was found at the shelf-slope, carrying (>252 μM/L) Subantarctic Mode Water at a depth of 400m

Downy mildew, caused by the biotrophic Oomycete Plasmopara viticola, is one of the most important diseases of grapevines world wide. It is particularly destructive in temperate viticultural regions that experience warm wet conditions during the vegetative growth of the vine (Wong et al., 2001). The disease is not normally a problem in mediterranean climates where the growing season tends to be hot and dry (Mullins et al., 1992; Sivasithamparam, 1993). Grape downy mildew is however a major disease in Australian viticulture (McLean et al., 1984; Magarey et al., 1991). Grape downy mildew was first reported in Europe in 1878 (Viennot-Bourgin, 1981). In Australia, it was recorded for the first time in 1917 at Rutherglen in Victoria (Vic) (de Castella, 1917). The first recorded outbreak of the disease in Western Australia (WA) occurred in 1997 in a small planting of vines in the far north of the state. In the subsequent year, it was detected in widespread commercial viticulture in the Swan Valley production area, near Perth (McKirdy et al., 1999). The pathogen has since been found in all grape growing regions of WA. Since its introduction into European vineyards in the 1880?s, P. viticola has become one of the world?s most investigated grapevine pathogens. Many aspects its basic biology however remain unknown (Wong et al., 2001). Due to the recent detection of P. viticola in WA, little is known of the nature of strains of the pathogen in the state and their response to local environmental conditions. Much of the research concerning the influence of environmental factors on the development of P. viticola has been conducted in Europe e.g. parts of France and Germany. Due to significant differences in climatic conditions and a shorter selection time on the pathogen in WA, much of the information described in European studies may not be directly applicable to the grape downy mildew disease situation in WA. The focus of this thesis was to examine epidemiological aspects of P. viticola in the mediterranean climate of WA. The environmental conditions that could favour the development of epidemics by strains of the pathogen that have been detected in the state were determined. The existence of P. viticola ecotypes and genetic variation among strains from WA and the Eastern states of Australia was also investigated.

[Truncated abstract] Banded iron formations of the ~27702405 Ma Hamersley Province of Western Australia were locally upgraded to high-grade hematite ore during the Early Palaeoproterozoic by a combination of hypogene and supergene processes after the initial rise of atmospheric oxygen. Ore genesis was associated with the stratigraphic break between Lower and Upper Wyloo Groups of the Ashburton Province, and has been variously linked to the Ophthalmian orogeny, late-orogenic extensional collapse, and anorogenic continental extension. Small spot PbPb dating of in situ baddeleyite by SHRIMP (sensitive highresolution ion-microprobe) has resolved the ages of two key suites of mafic intrusions constraining for the first time the tectonic evolution of the Ashburton Province and the age and setting of iron-ore formation. Mafic sills dated at 2208 ± 10 Ma were folded during the Ophthalmian orogeny and then cut by the unconformity at the base of the Lower Wyloo Group. A mafic dyke swarm that intrudes the Lower Wyloo Group and has close genetic relationship to iron ore is 2008 ± 16 Ma, slightly younger than a new syneruptive 2031 ± 6 Ma zircon age for the Lower Wyloo Group. These new ages constrain the Ophthalmian orogeny to the period <2210 to >2030 Ma, before Lower Wyloo Group extension, sedimentation, and flood-basalt volcanism. The ~2010 Ma dykes present a new maximum age for iron-ore genesis and deposition of the Upper Wyloo Group, thereby linking ore genesis to a ~21002000 Ma period of continental extension similarly recorded by Palaeoproterozoic terrains worldwide well after the initial oxidation of the atmosphere at ~2320 Ma. The Lower Wyloo Group contains, in ascending order, the fluvial to shallow-marine Beasley River Quartzite, the predominantly subaqueously emplaced Cheela Springs flood basalt and the Wooly Dolomite, a shelf-ramp carbonate succession. Field observations point to high subsidence of the sequence, rather than the mainly subaerial to shallow marine depositional environment-interpretation described by earlier workers. Abundant hydro-volcanic breccias, including hyaloclastite, peperite and fluidal-clast breccia all indicate quench-fragmentation processes caused by interaction of lava with water, and support the mainly subaqueous emplacement of the flood basalt which is also indicated by interlayered BIF-like chert/mudstones and below-wave-base turbiditic mass-flows.

[Truncated abstract] This study focussed on how isolation and environmental heterogeneity in salt lakes has influenced intraspecific variation in the calanoid copepod Calamoecia clitellata. Calamoecia clitellata relies on passive vectors for dispersal, and this, coupled with the insular nature of salt lakes, may promote genetic divergence at a molecular level. When contrasting environments are involved, genetic divergence may also occur at the life history level, possibly due to local adaptation. I examined the distribution of genetic variation among 14 populations in Western Australia using molecular genetic markers, and examined variation in life history traits among contrasting environments. To ascertain how isolation had influenced molecular genetic variation, I determined population genetic structure and used a phylogeographic approach to infer the impact of historical events. Environmentally induced variation was also evident in the field, with a switch from subitaneous egg production to resting egg production coinciding with changing environmental conditions. It is proposed that plasticity in life history traits has evolved in response to temporal environmental heterogeneity … It can be concluded that isolation in salt lakes in Western Australia has influenced molecular and phenotypic variation in C. clitellata in contrasting ways. At the molecular level, contemporary and historical isolation have promoted genetic divergence of populations, yet when coupled with environmental heterogeneity, marked phenotype plasticity has arisen. This study raises questions as to whether phenotype plasticity is a widespread phenomena in zooplankton found in temporary saline waters and an adaptive strategy to tolerate marked temporal environmental heterogeneity

[Truncated abstract] This study investigated the organisational role of environmental stability on the fish communities that inhabit the Fortescue River, an intermittent and variable system in north-Western Australia. It did so by examining the relationships between pool stability (measured by persistence of water through time, and variation in maximum pool depth through time) and the number and type of species within pools, temporal fluctuations in total fish abundance and intra-specific abundance, population size frequency distributions, and growth rate. It also examined the association between life history traits and the stability of the environments occupied within the river, and the stability of the river at large. The results indicated that environmental stability was the major factor structuring the fish communities. Among-pool comparisons revealed that unstable pools contained fewer species, a greater fraction of juvenile size classes, and underwent greater fluctuations in total and intra-specific numerical abundance through time, than stable pools . . . Stability affected community structure by determining (or describing) the probability that a pool would undergo periods of extreme shrinkage, that is, the likelihood that fish will be exposed to extreme physico-chemical fluctuations and complete eradication. While the physical environment (acting through stability) primarily structured the fish communities of the Fortescue River there was indirect evidence that even within this variable river system, biological interactions played a role, albeit minor. Future investigations into the role of environmental stability will benefit from the use of accepted and quantitative methods by all stream ecologists.

[Truncated abstract] The role of marine microzooplankton in aquatic food webs has been studied in most regions of the world’s oceans, with the exception of the subtropical/temperate eastern Indian Ocean. This thesis addresses this gap in knowledge by investigating microzooplankton from five stations on a cross continental shelf transect and in two mesoscale features ∼300 km offshore of south west Western Australia. My primary focus was to measure and evaluate microzooplankton community change over space and time and their impact on phytoplankton on a cross shelf transect, sampling five stations from February 2002 December 2004 as part of a large multidisciplinary investigation into the pelagic ecosystem on the shelf (Chapter 2). This transect was named the Two Rocks transect. I also investigated an eddy pair (Chapter 5), which had originated from water in the vicinity of the Two Rocks transect, also undertaken as part of a larger study, investigating biophysical coupling within mesoscale eddies off south west Western Australia . . . The distribution of mixotrophic cells differed across the transect. Those mixotrophs that use photosynthesis as their primarily energy source exploited nutrient limited conditions inshore consuming particles, while mixotrophs that are primarily heterotrophic survived low prey conditions offshore by photosynthesizing. In the eddies, the grazing behaviour of microzooplankton was dependent on the specific phytoplankton assemblage in each eddy. The warm core eddy had a resident population of diatoms that were consumed by heterotrophic dinoflagellates present in high numbers. The cold core eddy had a warm cap which prevented upwelled water reaching the surface, resulting in stratification and a very active microbial food web, particularly in the surface.