Zoology - Theses
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ItemA molecular analysis of bryozoan dispersal(University of Melbourne, 2002)Cheilostome bryozoans disperse primarily via short-lived, non-feeding larvae. Shiphull fouling is the likely cause of recent introductions of some species. Patterns of genetic diversity of three invasive bryozoans were compared to determine the effects of modem range expansion on genetic structure. The influence of natural dispersal mechanisms and local geological factors was assessed in studies of the genetic variation of two bryozoans that occur naturally in south-eastern Australia. Mitochondrial COI gene sequences of 388-429 base pairs in length were compared for each species. In addition, an experiment was conducted to determine whether bryozoans and other organisms within a marina show different microscale recruitment responses in the presence of 'antifouling' paints used to prevent the settlement of marine organisms. The occurrence of high-tolerance responses in introduced populations could indicate effects of selection associated with hull-fouling. The three introduced species showed contrasting levels of mitochondrial nucleotide diversity. Bugula neritina occurred throughout temperate and tropical oceans at the time of first taxonomic records. Globally widespread sampling revealed a single cosmopolitan species with no detected COI nucleotide variation. This finding contrasts with previously reported COI evidence of multiple divergent cryptic species of B. neritina on the American coastline. Minimal sequence diversity was found in the introduced gene pool of Watersipora subtorquata, an Atlantic bryozoan that has recently colonised the Pacific (?30 = 0.0016). The genetic homogeneity suggests expansions of B. neritina and W. subtorquata originate from a single population source. Comparison of introduced populations of Watersipora arcuata, a bryozoan that has recently colonised Australia, Hawaii and other coastlines from an Eastern Pacific source, revealed comparatively high nucleotide diversity (?51 = 0.0221), suggesting range expansion originated from multiple ancestral isolates. Sequences demonstrated that the range of Bugula dentata, a species that occurs widely on tropical and subtropical reefs, consists of a complex of divergent species that formed during the Miocene. A shallow area of epicontinental shelf underlying the Bass Strait sea zone between Victoria and Tasmania has been periodically exposed as a result of Quaternary glacioeustatic fluctuation. Genetic diversity in south-eastern Australian marine species is potentially affected by isolation across the temporary land bridge and the pattern of interglacial recolonisation of Bass Strait. Populations of B. dentata, sampled at four areas in south-eastern Australia, had a shallow phylogeographic structure (?16= 0.003, Fst = 1.0), suggesting post-Pleistocene recolonisation from a single refuge zone. Mucropetraliella ellerii, a bryozoan that is endemic to the inner south-eastern Australian shelf, was shown to have high nucleotide diversity across its range (?53 =0.0724). Populations in southern and eastern Australia were separated by a net sequence divergence of 10.9% (K2P-corrected), suggesting a long-term (Miocene-Pliocene age) population break. Analysis of the demographic signal present within the sequence samples provided evidence of contrasting genetic effects related to recolonisation. Differences in sequence diversity of each of the two major M. ellerii isolates may be related to the area of continental shelf that houses refuge populations for recolonisation. In the marina experiment, a copper oxide and a Tributyltin (TBT)-based antifouling paint were used to create ion diffusions around settlement plates. Differences in the density of recruitment of different species among three treatments (control, copper and blank) were measured to test the hypothesis that introduced populations of shiphull fouling species have a higher chemical tolerance than non-introduced species. There was one substantive effect. Chemical treatments reduced densities of a native bryozoan Celloporaria nodulosa, whereas the introduced species Watersipora subtorquata showed a high tolerance of the effects of chemicals, increasing in density on plates surrounded by copper antifouling paint. The bryozoan fouling response thus exhibits species-level variance that is relevant to mechanisms of introduction and may prove to be a useful trait for studying how adaptation and population dynamics are linked.
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ItemThe effects of artificial watering points on the distribution and abundance of avifauna in an arid and semi-arid mallee environment(2002)The role of artificial watering points in the avifaunal dynamics of the semi-arid mallee woodlands of southeast Australia was examined. Species richness and abundance were monitored throughout the year at different distances from water to determine how birds were distributed around water points and how this changed in relation to environmental factors such as climate. Vegetation attributes were also measured to determine which factors explained patterns in the avifauna with distance from water, and also to allow a description of the vegetation in relation to the water points. Water points were monitored throughout the year to determine which species were utilising them, under which environmental circumstances and for what purposes. Knowledge of the water utilisation behaviour of individual bird species allowed some explanation of their distribution patterns, as well as an ability to predict the likely effects of water point closure on those bird species. The closure of two water points during the study allowed an assessment of the immediate effects of water point closure on avifauna (For complete abstract open document)
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ItemFertility control in the eastern grey kangaroo, Macropus giganteus(2002-02)In Australia, high local densities of macropodid marsupials in state parks, nature reserves and wildlife sanctuaries are threatening biodiversity and pose a considerable management challenge. The high public profile of these species places socio-political constraints on the management options available. The use of fertility control techniques appears to offer an alternative. However, before a contraceptive system can be developed a detailed knowledge of the reproductive processes for that species must be generated. In this thesis, sexual maturity, seasonal reproduction, aspects of the endocrinology of reproduction and fertility control were investigated in the eastern grey kangaroo. In Victoria the eastern grey kangaroo is capable of breeding at all times of the year, although breeding is more synchronous than in northern populations, with 41% of the females breeding between December and January. In Victorian populations the onset of sexual maturity is delayed in both sexes, with females reaching maturity at 22 ± 1.2months and some males not reaching sexual maturity by 32 months of age. Male kangaroos showed seasonal changes that closely tracked the reproductive activity of the female kangaroos. Plasma testosterone concentrations were significantly elevated during the peak breeding period compared to all other times of the year. Both prostate and testis weights were low during winter when the reproductive activity of the females is low, although the difference was not significant.
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ItemWarren-use, home range and activity levels in southern hairy nosed wombat, (Lasiorhinus latifrons)(2002-04)This study investigated burrow use, home range and activity levels in the southern hairy nosed wombat (lasiorhinus latifrons), in semi-arid South Australia. Sixteen adult wombats were fitted with radio-transmitters and monitored for approximately eight months, including winter, spring and summer. Data indicated that wombats generally used between one and five warrens and preferred larger warrens with multiple entrances. Animals showed a preference for one or two warrens. Across the study period there was no apparent change in burrow use within warrens. Radio-tracking indicated that animals spent very little time above ground (26% of 1115 fixes) during the study period and that most of their activity was centred around their warrens. Home ranges were estimated using the harmonic mean method from location data, obtained through triangulation and daytime warren fixes. Home ranges were between 1.3 and 4.8 ha however, due to the low activity of wombats, insufficient fixes were obtained to gain a comprehensive estimate of their home ranges. Males and females appeared to have similarly sized home ranges. The home ranges of radio-collared individuals overlapped substantially. The data highlights the importance of warrens to the southern hairy nosed wombats in shaping their foraging ranges. It seems likely that the use of warrens is an important energy saving strategy in the unpredictable arid environment inhabited by this species.
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ItemThe ecology of invertebrate associations with vertebrate carrion in Victoria, with reference to forensic entomology(2002-01)Assessing time of death is a notoriously difficult, yet critical component of coronial death investigations. Forensic entomoloy can provide reliable death time estimates using knowledge of local carrion insect species ecology and larval development times. However, inadequate data are available for Victoria, and thus forensic entomology techniques cannot be fully exploited in this jurisdiction. This study aimed to provide data that will enable a basic forensic entomology service to be provided in Victoria, as well as initiate further development of forensic entomology in this state. There are few quantitative data available on the carcass colonisation patterns of blowflies and flesh flies, however these data are forensically valuable. Colonising maggots form feeding masses that generate heat, and therefore speed the growth of their members. This should be integrated into larval age estimates, however there is little knowledge of the factors controlling mass size and persistence. Additionally, it is important to understand more clearly the behaviour of larvi- and ovipositing female flies since qualitative assessments of abnormal colonisation patterns may be used to indicate pre-mortem trauma to a body.
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ItemHistory, habitat and management: considerations in the selection of potential reintroduction and translocation sites for the brush-tailed rock-wallaby, Petrogale penicillata, in East Gippsland Victoria(2002)Currently, there are estimated to be no more than 25 Brush-tailed Rock-wallabies, Petrogale penicillata, of Victorian origin remaining, with half of these in captivity as part of a breeding program. The decline of Brush-tailed Rock-wallabies has been attributed to several factors including hunting, predation, competition and stochastic events such as wildfire and disease. In Victoria, rock-wallabies have continued to decline in number, even after the cessation of hunting and implementation of an intensive predator control program. Without the intervention of captive-breeding and reintroduction or translocation programs, this critically endangered species will soon become extinct in Victoria. Reintroduction and translocation are becoming increasingly popular in the recovery of endangered species, however, many past attempts have had unknown or poor success rates. Conditions influencing the success of reintroduction and translocation programs are not well understood and for the most part, past efforts have been conducted in an ad hoc manner with little monitoring and documentation. One of the factors considered important in success is identification and selection of sites with high habitat quality, as unfavourable habitat is likely to result in the loss of animals through dispersal, predation or lack of other essential requirements. In addition to Wakefield (1961) and Short's (1980) observations of Brush-tailed Rock-wallabies occupying restricted habitat, presumably in response to the introduction of the Red Fox, Vulpes vulpes, this study found that there has been further restrictions in habitat use in East Gippsland, Victoria since the 1960s. Extant Brush-tailed Rock-wallabies sites were found to be larger than unoccupied sites, face predominantly north to north-east, have a general slope greater than 45° and a greater number of ledges per 100m of transect. It was also found that rock-wallabies preferred larger refuges with more than one entrance, low exposure to weather and another refuge or ledge within 10m. Preferred ledges were also large, faced predominantly north to east and within 10m of another refuge or ledge. The advantages these characteristics offer in the selection of future reintroduction and translocation sites are discussed. However, habitat suitability is not the only factor important to the selection of reintroduction or translocation sites. The selection of release sites will need to consider the ability to effectively undertake monitoring and management activities, and balance these requirements with the ecological requirements. This study also investigated past and current management (e.g., burning and predator control) of the study area and found that there has been a substantial change in land use that may have contributed to the persistence of Brush-tailed Rock-wallabies at the current sites in East Gippsland. This knowledge offers clues to future management. Other factors influencing site management are also discussed, and release sites with secure land tenure, which are easily accessible throughout the year and have a good network of vehicle tracks are considered favourable for reintroduction and translocation. In addition, release sites should not be in areas that conflict with visitor activities and should have strong community support.
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ItemAn investigation of hypothesis testing and power analysis in impact assessment, using case studies of marine infauna(2002)Statistical analysis is now widely used in impact assessment, and a common approach is to use a BACI design which considers changes Before and After a disturbance occurs, in conjunction with differences between the potentially Impacted location and one or more Control locations. The statistical power of an assessment is the confidence with which a nominated difference may be detected by a formal hypothesis test, and power analysis provides a means of quantifying this confidence. Despite the effort that goes into many impact assessments, results may be inconclusive or even wrong. Retrospective examination of completed assessments is one means of identifying factors which contribute to their success or failure. In this thesis, several BACI-style statistical tests for impact and their statistical power were examined, using case studies of marine infaunal assemblages in the vicinity of coastal wastewater discharges. The infauna is an assemblage often used in impact assessment, but is also known for large and often unpredictable natural changes in abundance which can make the identification of disturbance-related changes particularly difficult. Estimates of variance of infaunal abundance generated from the case study data were themselves extremely variable, with 43% differing from a best estimate by 50% or more. Even estimates for the same taxon, from studies in the same region and using identical sampling methods, differed by an order of magnitude or more in 25% of cases. The worst estimates of variance were usually obtained from single surveys, which had no component of large-scale temporal variation. Such variability in estimates of variance suggests that those based on single sampling times may be particularly unreliable, and that it may be desirable to allow for a larger than expected error variance by initially sampling more replicates than are expected to be needed. The specification of an alternate hypothesis, and subsequently an effect size, is an essential step in calculating the power of an hypothesis test, but it may be difficult to specify an effect size that is meaningful for the particular situation. The effect sizes actually observed in the infaunal data were very variable, with the most extreme being in excess of 10000% change. However, many of the observed effects, including some of the most extreme cases, appeared to be natural events rather than the result of a disturbance. The main alternative to the Control versus Impact designs is a gradient approach, which identifies changes in an ecological variable along a disturbance-related environmental gradient. This is usually done at a single time, resulting in possible confounding of a naturally-existing gradient with one imposed on the fauna by a disturbance. Including Before/After comparisons of gradients from multiple times within each period in a BAG design reduces this confounding. In contrast to the more common BACI-style assessments, it also provides an indication of the spatial extent of an impact, although comparison with a more conventional BACIP design suggested it might be more costly to undertake. The use of soft sediment infauna in impact assessment is often an expensive undertaking, because manual sorting of macrofauna from large quantities of sediment can be very time consuming. A process of compositing and subsampling may be effective for infaunal samples in assessments where random samples are taken at a range of spatial scales. When hierarchical analysis of variance is used, an arithmetic averaging of data from lower levels in the hierarchy occurs for tests which use the variance among higher levels as their error term. Subsampling of composite samples for each location in an MBACI design would produce physically averaged values which reflect the overall state of each location. Using these physical means would result in an identical test statistic to that resulting from the arithmetic averaging of lower level data within the hierarchical anova, provided that the compositing and subsampling process itself did not bias the estimates of the location means. Data from infaunal samples collected specifically for this compositing exercise established that the process did not appear to generate bias. Using hypothetical monitoring programs, cost savings of approximately 40% were possible with the use of compositing and subsampling in one scenario, while in another, additional sampling could be undertaken to increase power from 0.47 to 0.81 while still achieving an overall cost saving of 17%. The patterns of variability seen in the case studies, particularly in the space x time interactions, resulted in some large and unpredictable error variances and observed effect sizes. These patterns were not dissimilar to those seen in other published studies, suggesting that impact assessments in general could be prone to the problems identified in this study. Thus, responses to those problems, such as not relying on single sampling times for estimates of error variance in long-term programs, or considering compositing and subsampling when laboratory processing time is a concern, may also be applicable.