Dissertations / Theses on the topic 'Australian amphibians'

[Truncated abstract] This thesis explores the ecophysiology of cocooning and non-cocooning Australian burrowing desert frogs in order to specify the details of these two alternative survival strategies. Many details of these life-history strategies have not previously been determined for Australian frogs. In this study the detailed method of function and formation of the cocoon itself was investigated for the first time, as were the moulting cycles, which drive cocoon formation. Cocooning species had consistently shorter inter-moult-periods than non-cocooning species, which is presumably adaptive, allowing production of cocoon layers at a faster rate. Transmission electron microscopy revealed cocoon formation in Cyclorana platycephala to be a plastic, rather than static adaptation. The initial stages of cocoon formation appear to be the most critical. Cocoon layer formation is fastest in the first month and the initial layers produced are thicker than subsequent layers. Also, only in this initial stage does layer thickness appear to be influenced by soil moisture. Scanning electron microscopy confirmed the lips, eyelids and cloaca of cocooned frogs to be sealed by continuous layers of cocoon. However, it remains unclear precisely how the continuous junctions between cells from discreet sources, such as the upper and lower lip, are formed. Measurements of evaporative water loss and resistance over various relative humidity gradients suggested that water content within the cocoon structure is very low unless the external RH is > 93%. Therefore, anuran cocoon is confirmed to function as a specialised and highly effective barrier to water diffusion in arid-zone frogs. ... Within a dune swale, N. aquilonius burrows were an average depth of 1.13 m in loamy sand (clay = 6%, silt = 7%). Neobatrachus aquilonius excavated from the claypan had well formed cocoons, while those found in the dune swale had only one or two thin layers, indicating cocoon formation had only just commenced, although the last rainfall had been over six months prior. This suggests that N. aquilonius is able to switch between the cocooning and non-cocooning strategy in different soil types and different conditions. In summary, cocoon formation was found not to be an entirely passive accumulation of layers. Cocoon formation involved specialisation in the rate and thickness of epithelial layer production and the sealing of layers over lips, eyes and cloaca. Moreover, the cocoon was confirmed to operate effectively as a diffusion barrier at all except the highest external relative humidity. Like cocoon-forming species, Notaden nichollsi was found to metabolically depress to survive for longer periods underground. However, they cannot survive for the entire period

Surfactants are one of the more ubiquitous contaminants in aquatic systems. Their importance as toxic components of pesticide formulations has, however, been largely overlooked. Amphibians particularly, as inhabitants of shallow, temporary and often lentic aquatic environments may be at risk from exposure to these chemicals when they enter aquatic systems. This thesis presents data on the toxicity of surfactants to amphibians. Several experimental exposures were conducted with embryo-larval, tadpole and adult developmental stages of the Australian species- Crinia insignifera, Helcioporus eyrei, Limnodynastes dorsalis and Litoria moorei and the exotic species- Bufo marinus and Xenopus laevis. Animals were variously exposed to glyphosate formulations that contain a high proportion of nonionic surfactants, or commercial pesticide wetting agents (alcohol alkoxylate and nonylphenol ethoxylate (NPE) surfactants). Feeding stage tadpoles of C.insignifera, H. eyrei, L. dorsalis and L. moorei were exposed to three commercial glyphosate formulations, glyphosate isopropylamine and glyphosate acid in static-renewal acute toxicity tests. The 48-h LC50 values for Roundup Herbicide (MON 2139) tested against tadpoles of C. insignifera, H. eyrei, L. dorsalis and L. moorei ranged between 8.1 and 32.2 mg/L (2.9 and 11.6 mg/L glyphosate acid equivalent (ae)), while the 48-h LC50 values for Roundup Herbicide tested against adult and newly metamorphosed C. insignifera ranged from 137-144 mg/L (49.4-51.8 mg/L ae).Touchdown Herbicide (4 LC-E) tested against tadpoles of C. insignifera, H. eyrei, L. dorsalis and L. moorei was slightly less toxic than Roundup with 48-h LC50 values ranging between 27.3 and 48.7 mg/L (9.0 and 16.1 mg/L ae). Roundup Biactive (MON 77920) was practically non-toxic to tadpoles of the same four species producing 48-h LC50 values of 911 mg/L (328 mg/L ae) for L. moorei and >1000 mg/L (>360 mg/L ae) for C. insignifera, H. eyrei and L. dorsalis. Glyphosate isopropylamine was practically non-toxic producing no mortality amongst tadpoles of any of the four species over 48 h, at concentrations between 503 and 684 mg/L (343 and 466 mg/L ae). The toxicity of technical grade glyphosate acid (48-h LC50, 81.2-121 mg/L) is likely to be due to acid intolerance. Feeding stage tadpoles of B. marinus, X laevis, C. insignifera, H.eyrei, L. dorsalis and L. moorei were exposed to NPE and alcohol alkoxylate in static renewal acute toxicity tests. All species exhibited non-specific narcosis following exposure to both these surfactants. The 48-h EC50 values for NPE ranged between 1.1 mg/L (mild narcosis) and 12.1 mg/L (full narcosis). The 48-h EC50 values for alcohol alkoxylate ranged between 5.3 mg/L (mild narcosis) and 25.4 mg/L (full narcosis). Xenopus laevis was the most sensitive species tested. The sensitivity of the other five species was size dependent with larger species displaying greater tolerance. Replicate acute toxicity tests with B. marinus exposed to NPE at 30 degrees celsius over 96 hours indicated that the narcotic effects were not particularly time dependant.The mean 24, 48, 72 and 96-h EC50 (mild narcosis) were 3.6, 3.7, 3.5 and 3.5 mg/L respectively. The mean 24, 48, 72, and 96-h EC50 (full narcosis) values were 4.0, 4.1, 4.2 and 4.0 respectively. Acute toxicity tests with B. marinus exposed to NPE at 30 degrees celsius under conditions of low dissolved oxygen (0.8-2.3 mg/L) produced a two to threefold increase in toxicity. The 12-h EC50 values ranged from 1.4 to 2.2 mg/L. The embryotoxicity of NPE was determined in X. laevis, L. adelaidensis and C. insignifera using a Frog Embryo Teratogenesis assay-Xenopus (FETAX). The 96-h LC50, EC50 and MCIG (LOEC) values for X. laevis were 3.9 to 5.4 mg/L, 2.8 to 4.6 mg/L and 1.0 to 3.0 mg/L respectively. The 140-h LC50, ECSO and MCIG values for L. adelaidensis were 9.2 mg/L, 8.8 mg/L and 5.1 to 6.0 ing/L respectively. The 134-h LC50, EC50 and MCIG values for C. insignifera were 6.4 mg/L, 4.5 mg/L and 4.0 mg/L respectively. Teratogenicity indices for the three species ranged between 1.0 and 1.6 indicating either no or low teratogenicity. Xenopus laevis was the more sensitive of the three species and the only species that displayed indisputable terata. The acute toxicity data indicated that the amphibian species tested were of similar sensitivity to fish and some invertebrates. Developmental retardation and oestrogenic effects following exposure to nonylphenol ethoxylate were indicated by sublethal toxicity tests. Crinia insignifera embryos were exposed during early embryogenesis to sublethal concentrations of NPE.Exposure to NPE did not affect either weight nor size (snout-vent length) at metamorphosis. Exposure to 5.0mg/L NPE resulted in a significant delay in the time required to reach metamorphosis. Also, exposure to 3.0 mg/L NPE for the first 6 days of embryonic development or exposure to 5.0 mg/L NPE from day 2 to day 6 resulted in a statistically significant predominance in the female phenotype amongst metamorphosing froglets. Exposure for the first five days to 1.5 ing/L or 3.0 mg/L NPE had no effect on sex ratio. The results indicated that exposure to NPEs has endocrine disruptive effects in this species and that a narrow window of susceptibility exists for the induction of predominantly female phenotype. This study has also followed the degradation of a mixture of NPE oligomers and the concomitant formation of individual oligomers in static die-away tests with and without illumination in freshwater. Over 33 days in darkness there was a progressive and complete loss of long chain oligomers (NPEO(subscript)8-17), transient increases and subsequent loss of short to medium chain oligomers (NPE0(subscript)4-7), and large persistent increases (approximately 1000%) in short chain oligomers (NPE0(subscript)1-3). In the presence of illumination, biodegradation was retarded and heterotrophic bacterial proliferation was inhibited. After 33 days there was complete loss of long chain oligomers (NPE0(subscript)9-17), incomplete loss of medium chain oligomers (NPE0(subscript)6.8) and increases in short chain oligomers (NPE0(subscript)1-5).This thesis discusses the importance of persistent metabolites of NPE degradation as it pertains to the habitat, developmental time frame and ecology of amphibians. Degradation of NPE is likely to occur over a time frame that is longer than that required for complete embryogenesis and metamorphosis of many species of amphibians, and may easily encompass those critical stages of development during which oestrogenic metabolites can affect development.

Surfactants are one of the more ubiquitous contaminants in aquatic systems. Their importance as toxic components of pesticide formulations has, however, been largely overlooked. Amphibians particularly, as inhabitants of shallow, temporary and often lentic aquatic environments may be at risk from exposure to these chemicals when they enter aquatic systems. This thesis presents data on the toxicity of surfactants to amphibians. Several experimental exposures were conducted with embryo-larval, tadpole and adult developmental stages of the Australian species- Crinia insignifera, Helcioporus eyrei, Limnodynastes dorsalis and Litoria moorei and the exotic species- Bufo marinus and Xenopus laevis. Animals were variously exposed to glyphosate formulations that contain a high proportion of nonionic surfactants, or commercial pesticide wetting agents (alcohol alkoxylate and nonylphenol ethoxylate (NPE) surfactants). Feeding stage tadpoles of C.insignifera, H. eyrei, L. dorsalis and L. moorei were exposed to three commercial glyphosate formulations, glyphosate isopropylamine and glyphosate acid in static-renewal acute toxicity tests. The 48-h LC50 values for Roundup Herbicide (MON 2139) tested against tadpoles of C. insignifera, H. eyrei, L. dorsalis and L. moorei ranged between 8.1 and 32.2 mg/L (2.9 and 11.6 mg/L glyphosate acid equivalent (ae)), while the 48-h LC50 values for Roundup Herbicide tested against adult and newly metamorphosed C. insignifera ranged from 137-144 mg/L (49.4-51.8 mg/L ae).
Touchdown Herbicide (4 LC-E) tested against tadpoles of C. insignifera, H. eyrei, L. dorsalis and L. moorei was slightly less toxic than Roundup with 48-h LC50 values ranging between 27.3 and 48.7 mg/L (9.0 and 16.1 mg/L ae). Roundup Biactive (MON 77920) was practically non-toxic to tadpoles of the same four species producing 48-h LC50 values of 911 mg/L (328 mg/L ae) for L. moorei and >1000 mg/L (>360 mg/L ae) for C. insignifera, H. eyrei and L. dorsalis. Glyphosate isopropylamine was practically non-toxic producing no mortality amongst tadpoles of any of the four species over 48 h, at concentrations between 503 and 684 mg/L (343 and 466 mg/L ae). The toxicity of technical grade glyphosate acid (48-h LC50, 81.2-121 mg/L) is likely to be due to acid intolerance. Feeding stage tadpoles of B. marinus, X laevis, C. insignifera, H.eyrei, L. dorsalis and L. moorei were exposed to NPE and alcohol alkoxylate in static renewal acute toxicity tests. All species exhibited non-specific narcosis following exposure to both these surfactants. The 48-h EC50 values for NPE ranged between 1.1 mg/L (mild narcosis) and 12.1 mg/L (full narcosis). The 48-h EC50 values for alcohol alkoxylate ranged between 5.3 mg/L (mild narcosis) and 25.4 mg/L (full narcosis). Xenopus laevis was the most sensitive species tested. The sensitivity of the other five species was size dependent with larger species displaying greater tolerance. Replicate acute toxicity tests with B. marinus exposed to NPE at 30 degrees celsius over 96 hours indicated that the narcotic effects were not particularly time dependant.
The mean 24, 48, 72 and 96-h EC50 (mild narcosis) were 3.6, 3.7, 3.5 and 3.5 mg/L respectively. The mean 24, 48, 72, and 96-h EC50 (full narcosis) values were 4.0, 4.1, 4.2 and 4.0 respectively. Acute toxicity tests with B. marinus exposed to NPE at 30 degrees celsius under conditions of low dissolved oxygen (0.8-2.3 mg/L) produced a two to threefold increase in toxicity. The 12-h EC50 values ranged from 1.4 to 2.2 mg/L. The embryotoxicity of NPE was determined in X. laevis, L. adelaidensis and C. insignifera using a Frog Embryo Teratogenesis assay-Xenopus (FETAX). The 96-h LC50, EC50 and MCIG (LOEC) values for X. laevis were 3.9 to 5.4 mg/L, 2.8 to 4.6 mg/L and 1.0 to 3.0 mg/L respectively. The 140-h LC50, ECSO and MCIG values for L. adelaidensis were 9.2 mg/L, 8.8 mg/L and 5.1 to 6.0 ing/L respectively. The 134-h LC50, EC50 and MCIG values for C. insignifera were 6.4 mg/L, 4.5 mg/L and 4.0 mg/L respectively. Teratogenicity indices for the three species ranged between 1.0 and 1.6 indicating either no or low teratogenicity. Xenopus laevis was the more sensitive of the three species and the only species that displayed indisputable terata. The acute toxicity data indicated that the amphibian species tested were of similar sensitivity to fish and some invertebrates. Developmental retardation and oestrogenic effects following exposure to nonylphenol ethoxylate were indicated by sublethal toxicity tests. Crinia insignifera embryos were exposed during early embryogenesis to sublethal concentrations of NPE.
Exposure to NPE did not affect either weight nor size (snout-vent length) at metamorphosis. Exposure to 5.0mg/L NPE resulted in a significant delay in the time required to reach metamorphosis. Also, exposure to 3.0 mg/L NPE for the first 6 days of embryonic development or exposure to 5.0 mg/L NPE from day 2 to day 6 resulted in a statistically significant predominance in the female phenotype amongst metamorphosing froglets. Exposure for the first five days to 1.5 ing/L or 3.0 mg/L NPE had no effect on sex ratio. The results indicated that exposure to NPEs has endocrine disruptive effects in this species and that a narrow window of susceptibility exists for the induction of predominantly female phenotype. This study has also followed the degradation of a mixture of NPE oligomers and the concomitant formation of individual oligomers in static die-away tests with and without illumination in freshwater. Over 33 days in darkness there was a progressive and complete loss of long chain oligomers (NPEO(subscript)8-17), transient increases and subsequent loss of short to medium chain oligomers (NPE0(subscript)4-7), and large persistent increases (approximately 1000%) in short chain oligomers (NPE0(subscript)1-3). In the presence of illumination, biodegradation was retarded and heterotrophic bacterial proliferation was inhibited. After 33 days there was complete loss of long chain oligomers (NPE0(subscript)9-17), incomplete loss of medium chain oligomers (NPE0(subscript)6.8) and increases in short chain oligomers (NPE0(subscript)1-5).
This thesis discusses the importance of persistent metabolites of NPE degradation as it pertains to the habitat, developmental time frame and ecology of amphibians. Degradation of NPE is likely to occur over a time frame that is longer than that required for complete embryogenesis and metamorphosis of many species of amphibians, and may easily encompass those critical stages of development during which oestrogenic metabolites can affect development.

[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.

Riparian vegetation has been impacted by urbanisation in many parts of Australia, resulting in population declines of numerous species of stream-associated frogs. This study was the first to investigate movement and microhabitat use of the stream-associated frog, Mixophyes fasciolatus, in sites that differed in the ecological condition of riparian vegetation in south-east Queensland. Twenty-nine frogs were tracked over a 48-hour period and their fine-scale movements and microhabitat use were examined and found to be related to riparian vegetation condition. These results have significant implications for the conservation management of this species.

Amphibians secrete potent host defence compounds from dorsal glands onto the skin when stressed, sick or under attack by predators and microbials. Many of these defence compounds, such as biologically active peptides, provide potential targets for new biotechnological and therapeutic investigation. The research presented in this study focuses on the isolation and investigation of peptides from Australian frogs of the genera Litoria and Crinia and endeavours to determine the biological activity and important structural and mechanistic features of these biological compounds. Isolation and identification of the skin peptide profile of the Eastern Dwarf Tree Frog Litoria fallax has revealed a number of novel peptides named fallaxidins. This frog species is quite unique in that it does not secrete a peptide that displays potent broad spectrum antimicrobial activity nor a peptide that inhibits nitric oxide formation through the enzyme neuronal nitric oxide synthase. Instead it secretes several narrow spectrum antimicrobial peptides, including fallaxidin 3.1. In addition, there are numerous small peptides displaying unique primary structures with unknown biological function. Interestingly, L. fallax produces a skin peptide profile that is quite distinct from the skin peptide profiles of other related Litoria species. The majority of anurans from the Litoria genus contain at least one peptide in their skin secretion that inhibits the enzyme neuronal nitric oxide synthase. These peptides exert this action by preventing the association of the regulatory cofactor Ca²⁺ calmodulin to the enzyme binding site. The non-covalent binding of the potent neuronal nitric oxide synthase inhibitor dahlein 5.6 (L. dahlii) to calmodulin in the presence of Ca²⁺ is confirmed by electrospray ionisation mass spectrometry. A peptide-protein complex was observed in the gas-phase with a 1:1:4 calmodulin/dahlein 5.6/Ca²⁺ stoichiometry. In addition, the structure and binding interactions have been investigated by means of nuclear magnetic resonance spectroscopy. These experiments illustrated that upon binding dahlein 5.6, Ca²⁺ calmodulin undergoes a substantial conformational transition towards a globular complex with the helical dahlein 5.6 engulfed in a hydrophobic channel. Typically, the granular secretion of amphibians contains numerous peptides that exert activities in the central nervous system, termed neuropeptides. The biological activities, in particular smooth muscle action, proliferation of lymphocytes and opioid action are investigated to provide insight into the role of these peptides in the host defence. The structure activity relationships of disulfide peptides, caerulein peptides, tryptophyllins, rothein 1 and its related synthetically modified peptides has identified several important structural features essential for their corresponding biological function. Peptides from the granular secretion of anurans are synthesized within and released from larger precursors molecules. The genes that encode for the skin peptides of Crinia riparia and several Litoria species were isolated and identified. The cDNA sequence of the precursors provides a mechanism by which the evolution of amphibian species can be traced and information about the relationships existing among closely or distantly related species be obtained. All prepropeptides isolated from the Litoria species illustrated sequence homology to those isolated from numerous ranid and hylid frogs and demonstrate that the skin prepropeptides originated from a common ancestral gene. The precursors of peptides from C. riparia are significantly diverse and suggest that these prepropeptides either originated from the same common ancestral gene but have undergone substantial divergent evolution relative to the ranid and hylid frogs or that they have originated from distinct ancestral genes.
Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2008

In the wet tropics of Queensland, Australia eight species of stream dwelling frogs have experienced population declines, and individuals have been found with fungal infections of Batrachochytrium dendrobatidis, an emerging infectious disease of amphibians. I examined infection prevalence in stream frog assemblages and determined that amphibian chytrid infection is now endemic and persists in adults and tadpoles of declining and non-declining species at all eight streams surveyed. Infection prevalence varied among species, and between adult and tadpole life history stages, seasons, and elevations. Prevalences were higher during the dry season (May to September) and at high elevations (600-800 m). Tadpoles of Litoria nannotis, L. rheocola, and Mixophyes shevilli may be carrier hosts in this system; they have infection prevalences between 48 and 76%, and appear to be resistant to disease. Non-carrier hosts may include adults of all species and tadpoles of some species, with infection prevalence below 10%. I found no relationships between infection prevalence and body condition, fluctuating asymmetry of hind limbs, population density, or the presence of metamorphosing tadpoles and juvenile frogs. I examined how environmental temperature and moisture regimes influenced the chytrid pathogen on frog hosts and in culture. Infected Litoria chloris juveniles survived at the lowest rates in constant mist and constant 20°C conditions, but frogs in constant dry or rain conditions survived longer. All frogs exposed to 37°C on days 12 and 13 after infection survived in good health for 9 mo after infection, and were found to be free of infection. I modelled growth of chytrid populations using in vitro experiments to estimate the parameters zoospore production, zoospore survival rate, zoospore settlement rate, and time to sporulation of sporangia. The chytrid lifecycle may be faster at higher temperatures (23°C) than at lower temperatures (8°C), but relatively greater production of zoospores and better survival rates at lower temperatures may cause chytrid colonies to grow faster under cold conditions. In addition to environmental effects, host immune function and behaviour may also alter host-pathogen dynamics. I found that leukocyte populations in juvenile Litoria chloris responded to infection but not to environmental conditions. Skin peptide immune defences were more effective in common species (Litoria lesueuri, Litoria genimaculata, Mixophyes shevilli) and less effective in some endangered species (Litoria rheocola, Nyctimystes dayi). Skin peptide defences against the chytrid were also better in those species that showed greater survival when experimentally infected with B. dendrobatidis. Environmental conditions may also affect skin peptide immune response, with poorer responses under colder conditions. The behaviour of captive Litoria chloris juveniles varied with thermal and hydric environments and time of day, but not infection status. Litoria genimaculata tadpole behaviour did vary with infection status; tadpoles exposed to chytrid sporangia showed a behavioural fever of 6.2 to 7.1°C. The conservation status of the rainforest stream frog species examined was correlated with their ranking on a disease risk assessment of behaviour; however, their current infection prevalence is not well correlated with disease risk. This agrees with epidemiological theory, which suggests that a disease involved in population declines should be present in both common and endangered species, but should have higher infection prevalence in species with stable populations. These stable species are also less at risk from chytridiomycosis based on behavioural and immunological assessments. The emergence of chytridiomycosis may occur when a particular host-pathogen interaction is achieved involving the complex arrangement of species assemblage structure and environmental conditions.

Bibliography: leaves 148-161.
168 leaves : ill. (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--Adelaide University, Dept. of Environmental Biology, 2001

The study of morphological diversity and the processes that have driven it is a topic of uppermost importance in evolutionary biology. Frogs and toads offer a study group that is remarkably diverse in body shape and ecology, particularly in Australia, where biome diversity and isolation have provided excellent opportunities for comparative analyses of broad-scale macroevolutionary patterns. My PhD thesis focuses on morphological evolution in Australian frogs. I gathered an extensive dataset based on external morphology and climatic data, for almost all frog species in Australia (97%), including the two extinct gastric-brooding frog species. I collected x-ray micro-CT scans for representative species of each genera of myobatrachid frogs, which provided detailed 3D morphological information of skeletal structures. I also obtained locomotion and jumping performance data for 61 species of Australian frogs, which represents 67% of the clade diversity and includes all four native families, as well as the invasive cane toad Rhinella marina. I employed phylogenetic comparative methods throughout all of my analyses in order to add evolutionary context. Finally, I describe a simple geometric rigid rotation method, which removes the effect of random translation and rotations, enabling consistent morphological analysis of articulated structures in 3D. The main aim of my thesis was to understand body size and shape evolution in Australian frogs, by asking a series of questions concerning morphological adaptation to environmental pressures, convergence, niche opportunities, integrative and modular evolution of body structures, and the association between form and function. I provide evidence for a close association between morphology and environment through and behaviour and performance, which can lead to convergence patterns between distantly-related lineages. I found that frog species from the same ecotype displayed morphological and physiological similarities, which were even more conspicuous in fossorial species, due to adaptations to arid environments. Despite phylogenetic conservatism, adaptation to similar environments can result in morphological diversification and convergence both between and within clades, erasing the signature of ancestral morphotypes. Specifically, I found that most of the overall body shape differences were concentrated on the limbs: morphology of fore- and hind-limbs was highly integrated and shaped by ecology, locomotion, and burrowing behaviour, whereas skull shape was highly phylogenetically constrained and conserved within subfamilies. Locomotor modes and jumping performance were extremely diverse across Australian frog species. Jumping performance had no phylogenetic signal, and was not directly associated with body size or shape. However, there was a strong pattern of convergence in locomotor modes among species from different families in the same ecotypes. Disparity of locomotor type differed among ecotypes, and fossorial species were confined to the smallest region of the morphospace, probably due to their specialised fossorial morphology. I also demonstrated that the invasive cane toad Rhinella marina occupies an empty morphological niche in Australia, despite overlapping in environmental niche with most native species. This undoubtedly contributed to its extreme invasion success, and shows the importance of morphological niches. To conclude, I discuss morphological evolution of Australian frogs in the context of their ecology, locomotion, burrowing behaviour, and phylogenetic relationships.

Using 2 - D NMR spectroscopy, the structure of the sex pheromone from Litoria splendida has been determined, in order to elucidate its mode of transport through the aquatic environment. The peptide was found form an α - helical structure, with a central flexible hinge region. The mode of transport through the aquatic environment has been discussed in relation to the structure. Previous work indicated that the Australian amphibian host defence skin peptides that inhibit neuronal nitric oxide synthase ( nNOS ) were likely to act indirectly on the enzyme, by binding to the co - enzyme of nNOS, calmodulin. [superscript 15] N labelled calmodulin was expressed and purified via a bacterial protein expression system and a series of 2 - D NMR [superscript 15] N - HSQC titrations was performed with Australian amphibian host defence skin peptides. in order to determine whether these peptides bind to calmodulin. The three peptides tested were found to bind, and with differing strengths of interaction. One of these was selected for further study. [superscript 15] N and [superscript 13] C doubly labelled calmodulin was then prepared in order to study the complex between this protein and the selected peptide, caerin 1.8, an Australian amphibian skin peptide isolated from Litoria chloris. A series of 3 - D NMR spectra has been recorded on this complex. The backbone atom resonances have been assigned for free calmodulin and for the calmodulin - peptide complex, using a combination of main chain directed and sequential assignment strategies. By analysing the changes in chemical shift that occur upon binding the peptide, it was determined that the mode of binding involves a stronger interaction with the C - terminal domain than the N - terminal domain.
Thesis (Ph.D.)--School of Chemistry and Physics, 2006.

The skin extracts from amphibians have been investigated for over fifty years and have been found to contain numerous components with therapeutic and medicinal uses. Host - defence compounds are secreted onto the dorsal surface of the animal from specialised granular glands in response to a variety of stimuli, such as stress induced by a predator. Isolated peptides can exhibit either pharmacological properties or antibiotic activity. Previous studies isolated a potent hypotensive neuropeptide, crinia angiotensin II, within skin secretions of the Australian frog Crinia georgiana. This prompted further investigations into the isolation and sequence determination of host - defence compounds from other species in this genus - C. signifera, C. riparia and C. deserticola. Fifteen novel peptides were identified. The major peptide components were potent disulfide containing neuropeptides of a type not observed in other Australian anurans that have been previously investigated. The remaining peptides demonstrate either antibiotic activity or inhibit the enzyme neuronal nitric oxide synthase. The skin components from anurans of the Litoria genus have been extensively studied, with a number of peptides exhibiting both antibacterial and pharmacological activity. The skin secretion of Litoria dentata has been investigated, with five novel peptides identified. The neuropeptide tryptophyllin L 1.3 was previously isolated from the related frog L. rubella. Other components that are unique in structure have not yet been tested for biological activity. The parasitic disease malaria is responsible for over one million deaths per year. The increase in resistance of current antimalarial compounds has led to the development of new treatments from various animal - derived peptide antimicrobials. A number of amphibian peptides and their derivatives were investigated as potential antiplasmodial agents against the malaria parasite Plasmodium falciparum. Results indicate that these compounds inhibit parasite growth with minimal haemolytic activity, making them promising tools for malaria research.The defence chemistry of amphibian neuropeptides has been extensively studied and is important in understanding both the ecology and physiology of the vertebrate. Neuropeptides are classified into groups with similar structural characteristics. Biological activity occurs via interaction with a G protein - coupled receptor. The most studied of all amphibian neuropeptides is caerulein, which has a similar spectrum of activity to the mammalian peptide cholecystokinin. This includes smooth muscle contraction that occurs via interaction with cholecystokinin receptors. The pharmacological activity of Australian anuran neuropeptides from various genera was investigated. Two biological assays were conducted - a smooth muscle contraction test and a lymphocyte proliferation assay. A range of neuropeptides contracted smooth muscle at nanomolar concentrations, while others only proliferated lymphocytes. Some peptides were inactive in both assays. Young marsupials are born at an immature stage of development and rely on immune protection provided by the mother. Eugenin is a host - defence compound isolated from pouch secretions of the Tammar wallaby. The immunomodulator activates CCK2 receptors, resulting in lymphocyte proliferation. Therefore, eugenin stimulates immune cells in the pouch providing vital immune protection for pouch young.
Thesis (Ph.D.)--School of Chemistry and Physics, 2006.

Globally, amphibians are the most endangered vertebrate taxon, with over one third of species at risk of extinction. A prominent driver of this extinction crisis is the disease chytridiomycosis, which is caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd). Bd has been implicated in major amphibian declines in Australia, Europe and the Americas. In this thesis, I investigated; (1) the spatial distribution of Bd and its impacts on amphibian species in Australia and Europe, and (2) the impact of Bd on amphibian demography in Australia. In a sub-alpine amphibian community in south-eastern Australia, I demonstrated that the presence of an amphibian reservoir host was strongly associated with increased Bd prevalence in a highly susceptible, sympatric amphibian species. At the landscape level, high reservoir host abundance was associated with increased severity of decline in the sympatric species, indicating that variation in disease susceptibility caused pathogen-mediated apparent competition, leading to extirpation of the susceptible species. In a heterogeneous landscape in central Romania, I examined the spatial distribution of Bd infection in an ephemeral pond breeding amphibian. I found that Bd presence was strongly associated with proximity to perennial water sources and forest cover. These results indicated that perennial water sources may act as source habitat for Bd, with amphibian movements resulting in Bd spill-over into ephemeral ponds. In south-eastern Australia, I investigated long-term changes in the distribution of a chytridiomycosis-impacted amphibian species. Using a 37 year dataset, I documented a period of decline between the mid-1970s and 1990s, consistent with the spatiotemporal emergence of Bd in eastern Australia. A sustained period of population re-expansion has occurred since the 1990s, despite high Bd prevalence in recovering populations. In a sub-alpine environment in south-eastern Australia, I investigated how remnant populations of a highly susceptible amphibian species are able to persist with Bd. I showed that Bd was associated with high adult mortality between years. Importantly, I found that adults breed before succumbing to chytridiomycosis and Bd prevalence is low in early life-history stages. This allows recruitment to remain sufficiently high to facilitate population persistence. I then compared population age structure of long-exposed populations, Bd-naive populations and historical specimens. I found that diseased populations exhibited severe age structure truncation. Individuals from diseased populations matured earlier in life and at smaller sizes, indicating that chytridiomycosis can drive phenotypic shifts in host life-history. I used population simulations to illustrate that this shift is likely to increase population vulnerability to stochastic events. Many of the insights gained from this research are highly relevant to amphibian conservation. I have combined these insights with a synthesis of the broader literature to develop a management framework for amphibians threatened by Bd. This framework is designed to help guide the implementation of intervention strategies to reduce extinction risk in chytridiomycosis-threatened species. Collectively, this thesis constitutes an important contribution to global amphibian-Bd research and has important implications both for understanding chytridiomycosis impacts and dynamics, and for developing effective conservation responses.

Bibliography: v. 1, leaves 277-300
2 v. : ill. (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, Dept. of Zoology, 1987

Using 2 - D NMR spectroscopy, the structure of the sex pheromone from Litoria splendida has been determined, in order to elucidate its mode of transport through the aquatic environment. The peptide was found form an α - helical structure, with a central flexible hinge region. The mode of transport through the aquatic environment has been discussed in relation to the structure. Previous work indicated that the Australian amphibian host defence skin peptides that inhibit neuronal nitric oxide synthase ( nNOS ) were likely to act indirectly on the enzyme, by binding to the co - enzyme of nNOS, calmodulin. [superscript 15] N labelled calmodulin was expressed and purified via a bacterial protein expression system and a series of 2 - D NMR [superscript 15] N - HSQC titrations was performed with Australian amphibian host defence skin peptides. in order to determine whether these peptides bind to calmodulin. The three peptides tested were found to bind, and with differing strengths of interaction. One of these was selected for further study. [superscript 15] N and [superscript 13] C doubly labelled calmodulin was then prepared in order to study the complex between this protein and the selected peptide, caerin 1.8, an Australian amphibian skin peptide isolated from Litoria chloris. A series of 3 - D NMR spectra has been recorded on this complex. The backbone atom resonances have been assigned for free calmodulin and for the calmodulin - peptide complex, using a combination of main chain directed and sequential assignment strategies. By analysing the changes in chemical shift that occur upon binding the peptide, it was determined that the mode of binding involves a stronger interaction with the C - terminal domain than the N - terminal domain.
Thesis (Ph.D.)--School of Chemistry and Physics, 2006.

Fungal diseases pose a serious threat to animal and plant health. The emergence of the disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), has resulted in the declines or extinctions of many amphibian species worldwide, although the severity of its effects varies widely among host species. Antibiotic-producing bacterial symbionts present on amphibian skin can protect their hosts from disease-related mortality. Bioaugmentation of naturally occurring bacteria that are antagonistic to Bd offers great potential for disease prevention in field settings. However, there is a paucity of knowledge on the ecological interactions of cutaneous bacteria with their hosts and Bd; this needs to be addressed prior to development and application of probiotics. This thesis addresses technical issues associated with culture and testing of bacterial isolates in the laboratory, investigates variation among rainforest-dwelling frogs in the activity of their bacterial symbionts against Bd, and assesses the temporal stability of frog bacterial assemblages. One factor that might limit the development of effective probiotics is the potentially low proportion of bacteria that can be cultured from environmental samples; commonly believed to be approximately 1%. If the great majority of bacteria on amphibian skin are not culturable, many species with desirable properties are likely to be unavailable for bioaugmentation research. I used both culture and culture-independent techniques to estimate the proportion of isolates that are not culturable and determine the proportion of cultured bacteria that are missed during the process of colony selection for isolation. On average, 75% of the bacteria on individual green-eyed treefrogs, Litoria serrata, were culturable. My results thus indicate that the proportion of culturable bacteria present on frog skin is much higher than the traditional 1%. However, of those culturable bacteria, only 53% were selected for isolation. This discrepancy is likely due to morphologically identical colonies present on agar plates but not selected for isolation. Therefore, apparently morphologically identical colonies should be over-selected during initial isolation to reduce the proportion that are missed, and ensure that most bacteria with potential for bioaugmentation research are likely to be cultured. Another factor that might affect the detection of bacterial symbionts with activity against Bd is the method used to screen bacterial isolates for inhibition. Previous studies have used agar-based in vitro challenge assays to identify candidates for bacterial supplementation trials. However, agar-based assays can be difficult to set up and to replicate reliably. To overcome these difficulties, I developed a semi-quantitative spectrophotometric challenge assay technique. Cell-free supernatants were prepared from filtered bacterial cultures and added to 96-well plates in replicated wells containing Bd zoospores suspended in TGhL broth medium. Plates were then read daily on a spectrophotometer until positive controls reached maximum growth in order to determine growth curves for Bd. I tested the technique by screening skin bacteria from L. serrata. Thirty-one percent of bacteria tested showed strong Bd inhibition, while some may have promoted Bd growth, a previously unknown effect. My technique avoids a number of issues associated with agar-plate assays and thus provides a useful contribution to the expanding field of bioaugmentation research. One aspect of community ecology theory suggests that complex communities, with higher numbers of taxa and hence more potential interactions, are more resistant to invasion than simple communities with fewer taxa. In the Australian Wet Tropics, the severity of Bd effects varied among sites and frog species, and some species have since reappeared or recolonised, despite Bd now being enzootic. The available range of variation in history among species and sites provided an opportunity to investigate the role of anti-fungal cutaneous bacteria in protection of frogs against Bd infection. I conducted in vitro challenge assays to determine the capacity of bacteria, isolated from five species of rainforest frogs at five sites in northern Queensland, Australia, to inhibit Bd. I then used DNA sequencing to identify Bd-inhibitory bacteria and determine whether cutaneous bacterial taxa were associated with particular frog species, sites, infection status of frogs or intensity of Bd infection. Ninety-four percent of bacterial isolates came from just three families; Pseudomonadaceae, Enterobacteriaceae and Xanthomonadaceae, which were present across all frog species and sites. Bd infection intensity was negatively correlated with number of inhibitory genera present on frogs, suggesting that increased diversity of Bd-inhibitory taxa may play a role in reducing the intensity of Bd infections, hence facilitating frog coexistence with enzootic Bd. There was evidence suggesting that Bd-inhibitory bacteria may have facilitated the reappearance of frogs at one of two upland Wet Tropics sites I surveyed. Frogs at this site had greater cultured bacterial isolate richness, a greater number of inhibitory bacterial genera, and a higher proportion of inhibitory isolates than their lowland conspecifics. They also had a significantly higher proportion of individuals with one or more Bd-inhibitory bacterial species. My results also suggest that alternative mechanisms for decreasing susceptibility to Bd infection are likely to have evolved at the other Wet Tropics upland site I monitored where frogs have reappeared. While the possibility of bioaugmentation offers hope for frogs threatened with extirpation, the stability of the symbiotic microbial assemblage is likely to affect its susceptibility to manipulation, and thus the success of bacterial supplementation. A microbial assemblage that changes little with time may have highly stable species interactions and therefore be difficult to supplement, while a dynamic microbial assemblage may be more amenable to manipulation. I collected swab samples from 14 individual rainforest frogs captured multiple times over the course of a year, and compared the bacterial assemblage profile generated for each swab sample among frogs grouped by date sampled and by patterns of Bd infection. Twenty-five of 114 unique bacterial strains found eight times or more constituted the dominant assemblage members, with five core strains each occurring in greater than 65% of samples. The proportion of core bacterial strains was significantly higher in frogs that were not infected with Bd prior to sampling than in frogs that were infected or had recently lost infection. The taxonomic composition of the dominant microbial assemblage also differed significantly between these two groups of frogs. Bacterial species richness decreased over the year, with a corresponding statistically significant change in assemblage composition. The temporal changes observed suggest that the microbiota would be amenable to manipulation through bioaugmentation of Bd-inhibitory bacteria. However, turnover of core strains was low, suggesting that bioaugmentation success might be enhanced by application of dominant assemblage members. I have presented evidence for the importance of amphibian cutaneous microbiota in protection of wild amphibians against Bd; greater taxonomic richness of cutaneous bacteria is associated with lower Bd infection intensity. With this knowledge, an improved technique to screen bacteria for inhibitory effects against Bd, and an understanding of the natural changes that occur in bacterial assemblages over time, there is now further support for the use of bioaugmentation as a tool to protect amphibians against the devastating effects of chytridiomycosis.

Les plantes envahissantes sont considérées comme l'une des plus grandes menaces sur les espèces, mais leurs impacts sur les amphibiens demeurent peu connus. L’objectif de ce projet est de déterminer l’effet de l’établissement du roseau commun (Phragmites australis) sur la répartition des amphibiens et sur leur développement larvaire. Il est présumé que cette plante s'accapare l'espace et les ressources disponibles en produisant une importante biomasse, qu’elle peut modifier l’hydrologie des marais et la structure des communautés d’amphibiens. J’ai évalué les facteurs influençant la répartition des amphibiens selon les caractéristiques des étangs et du paysage dans 50 sites envahis ou non à divers degrés. Des expériences ont également été menées afin d’étudier les répercussions de trois densités de roseau sur des têtards de la Grenouille des bois (Lithobates sylvaticus) et sur la qualité de son habitat. Mes résultats suggèrent que le roseau à forte densité ralentit le développement larvaire de la grenouille des bois et influence les assemblages phytoplanctoniques. Cependant, il n’y a aucune relation entre la densité de la plante et la survie, la morphologie des têtards et les caractéristiques biotiques et abiotiques de l’eau. Dans notre aire d’étude, le paysage autour des étangs a une plus grande influence sur la répartition des amphibiens que l'établissement du roseau. Toutefois, la probabilité d’assèchement est plus élevée lorsque la plante est établie en grande quantité, ce qui, si l’envahissement s’intensifie, aura un effet néfaste sur la survie des têtards et mettra en péril la persistance des populations.
Invasive plants are considered one of the greatest threats to species, but their impact on amphibians is still poorly understood. The objective of this project is to determine the effect of the establishment of common reed (Phragmites australis) on amphibian distribution and larval development. It is thought that this plant monopolizes space and resources by producing a large biomass, and may alter wetland hydrology and amphibian community structure. I evaluated the factors influencing amphibian distribution according to the characteristics of ponds and the surrounding landscape in 50 sites invaded or not by reeds to varying degrees. Experiments were also conducted to study the impacts of three reed densities on wood frog tadpoles (Lithobates sylvaticus) and the quality of their habitat. My results suggest that high reed density slows wood frog larval development and influences phytoplankton assemblages. However, there is no relationship between, plant density and survival, tadpole morphology and water biotic and abiotic characteristic. In our study area, the landscape surrounding ponds has a greater influence on amphibian distribution than does reed establishment. However, the desiccation probability is higher when the plant is established in high quantities, which, if the invasion intensifies, will have an adverse effect on tadpole survival and therefore population persistence.

Research Doctorate - Doctor of Philosophy (PhD)
The Earth is experiencing a period of mass extinction due to human development and expansion (Wake & Vredenburg 2008). It has been estimated that 866 animal, plant, fungi and protist species have become extinct in recent history, and 25,821 species were declared either Critically Endangered, Endangered or Vulnerable in 2017 (IUCN 2017). Causal agents of population declines and biodiversity loss include climate change, land clearing, habitat modification and the introduction of exotic competitor or predator species (Vitousek et al. 1997) and disease (Skerratt et al. 2007) which affect species from global to local scales. The magnitude of species loss and threat of further extinctions has caused worldwide attention, instigating efforts to identify and conserve species at risk (Redford & Richter 1999). Species management programs typically aim to identify causal agents of decline, assess species requirements for survival and reproduction and understand population proce sses so that informed decisions can be made to reverse population declines. An important step in this process is gaining an understanding of the factors which affect species distribution (Guisan et al. 2013; Noss et al. 1997). Conservation programs often aim to understand an animal’s distribution by identifying what constitutes habitat. Factors commonly examined include abiotic and biotic attributes of the landscape including available shelter and food, as well as an animal’s interaction with heterospecifics (Campomizzi et al. 2008). In the instance that these factors or interactions correlate with species presence or abundance either positively or negatively, it is assumed that these factors are actively selected for or avoided (Batt 1992). However, additional behavioural factors can affect distribution, such as attraction to (Ahlering et al. 2010) or avoidance of conspecifics (same species) (Keren-Rotem et al. 2006; Stamps 1983), causing strong aggregations or segregation of animal distribution over a landscape, respectively. Despite the influence of these factors on distribution, conspecific attraction and avoidance are not commonly considered by conservation programs when attempting to understand, predict and alter species distributions (Campomizzi et al. 2008). As animals experiencing conspecific attraction or avoidance may deviate from the correlation model assumed by habitat selection, research programs aimed at assisting endangered species cannot afford to ignore conspecific interactions (Manly et al. 2009). A last resort for conservation initiatives is breeding animals in captivity, creating or restoring habitat and translocating animals back into populations that are experiencing population decline or have become locally extinct. Current research in conservation biology has focused on identifying and assessing animal behaviour which can limit the success of conservation initiatives such as; multi-spatial-level habitat selection (McGarigal et al. 2016), conspecific attraction (Campomizzi et al. 2008) and mate selection within captive breeding (Chargé et al. 2014a; Chargé et al. 2014b). As these factors influence species distribution and survival, they therefore affect the success of habitat construction programmes and the persistence of naturally occurring or translocated populations. Amphibians are a globally threatened taxon with 33 extinct species and 2,100 species declared either critically endangered, endangered or vulnerable (IUCN 2017). Factors causing amphibian decline include the human facilitated spread of chytrid fungus (Batrachochytrium dendrobatidis) (Skerratt et al. 2007), global climate change, introduced species as well as habitat loss and modification (Brown et al. 2012; Stuart et al. 2004). Considerable research has been undertaken on causal agents of decline, along with understanding population processes and habitat requirements that affect the persistence of populations (Wake & Vredenburg 2008). Despite the fact that many amphibian species show signs of conspecific attraction and/or avoidance, the influence of conspecific interactions on spatial distribution and subsequent declines of amphibians is under-investigated. This current research project explores the potential for particular behaviours which may influence species distribution and the success of habitat creation and translocation programmes for the green and golden bell frog (Litoria aurea). For the first research paper, I assessed conspecific call attraction in L. aurea. Over a landscape, animal distributions can be skewed as a result of conspecific attraction and aggregation. This can hinder habitat restoration and creation programmes as species may fail to colonise available habitat, despite its suitability. It has been noted from past research that L. aurea uses particular habitat and has distributional traits which suggest the presence of conspecific attraction, and using speakers playing calls can successfully attracted L. aurea at short distances, forming new aggregations (James et al. 2015: Attachment 1). In the first research chapter, I aimed to use speaker systems playing calls to manipulate the landscape distribution of L. aurea. I placed a stand with a speaker playing call broadcast in a treatment waterbody (T), a stand with no calls broadcasted as a manipulative control (MC) and no stand or speakers as a control (C). This design was replicated in five areas on Kooragang Island, Australia, and waterbodies were surveyed to measure changes in abundance and calling over two and a half breeding seasons. We found that speaker introduction did not increase abundance or calling at T relative to MC and C. We did, however, find that the length of time males called was longer at T, compared to MC and C. As the length of calling time may be extended using conspecific call broadcast , provision of conspecific stimulation at translocation sites may improve breeding activity and retention of the population post-release by reducing dispersal. For the second research chapter, I assessed habitat selection of L. aurea. The site selection of breeding individuals is a crucial component of a species habitat selection and can help to direct conservation programmes. However, very little is known about the microhabitat selection of calling male L. aurea. This study aimed to distinguish if male aggregations are associated with specific habitat features within a waterbody and describe their use of available habitat structures. Within waterbodies we compared calling locations relative to non-calling locations for water variables (temperature, salinity, dissolved oxygen), microclimate (temperature, humidity, average and maximum wind speed) and habitat (percentage coverage of water, ground, emergent vegetation and floating vegetation). Overall, males were associated with lower salinity and higher dissolved oxygen, higher percentage coverage of emergent vegetation and bare ground, and low percentage coverage of open water. Males were most commonly found in the water floating between or beside emergent vegetation or perched on emergent vegetation above water level. This suggests that males may select habitat to protect themselves from predators, or for breeding; providing appropriate vegetation, dissolved oxygen and salinity for embryo and tadpole development. This provides supportive information for previous studies on habitat selection, indicating what habitat is preferred by breeding males to improve monitoring, habitat creation and rehabilitation. For the third research chapter, I assess a habitat construction programme. Habitat creation programmes are often used to compensate for the loss of habitat for endangered species, with varying results. I describe an early stage wetland construction programme implemented for L. aurea on Ash Island, NSW Australia. Seven ephemeral (flooding) and two permanent waterbodies were constructed near an existing population. The wetland was designed to increase landscape aquatic habitat, based on adaptive management learnings from past research. In this study, I assess the initial use of this habitat by L. aurea, and initial findings on the design suitability. Surveys in constructed wetlands and in the broader Kooragang area showed that L. aurea rapidly colonised and called at constructed ephemeral wetlands but not permanent wetlands. The chorus size in constructed wetlands was large in comparison to other populations in coastal NSW, and a range of other frog species also bred onsite. Female L. aurea used a nearby remnant wetland (adjacent to the constructed wetlands), and used different habitat to males. Similar habitat use variation between sexes was reflected in the broader population. Most male and female L. aurea captured on Ash Island were under 12 months of age, and body condition in the constructed wetlands was higher than in the broader population. Waterbody design successfully protected waterbodies from overland flooding, and ephemeral waterbodies dried, which suggests the drying regime may protect the constructed habitat long-term from infestation of predatory fish. Elevated salinity from ground water in permanent waterbodies (intended to ameliorate chytrid disease in the landscape) was higher than anticipated and requires further monitoring. It is hoped that this programme may help guide other conservation projects creating habitat for amphibians under threat. For the fourth research paper, I assess sexual selection in L. aurea. As a conservation strategy for L. aurea, captive breeding programmes supplement at-risk populations and translocate individuals to their former ranges. However, breeding programmes are undertaken with very little information on sexual selection and its exclusion can reduce the fitness of released animals. The aim of the fourth study was to assess whether forms of sexual selection occur for L. aurea to inform captive breeding programmes. In the wild I studied mate selection. Firstly, we aimed to assess if the size and body condition of amplexing individuals (grasping to breed), differed from other individuals in the population as an indication of female sexual selection or male-male competition. Secondly, we investigated if male and female amplexing pairs were size correlated as an indicator of size assortative mating, and thirdly we made observations on behavioural interactions in the breeding waterbody to complement the analysis. In Whangarei, New Zealand, we captured L. aurea over 4 survey nights, undertaking capture-mark-recapture and measuring morphometrics of snout vent length (SVL), right tibia length (RTL) and weight, calculated body condition. We compared the SVL, RTL and weight of breeding individuals to non-breeding individuals and found that amplexing males were larger with better body condition, however, female size did not differ. Male-female pairs were not size assortative and aggressive interactions were recorded between males. Larger male size may be an indicator of either female selectivity or larger-male mating advantage through aggressive interactions. As removal of sexual selection in captive breeding programmes can reduce fitness and place conservation initiatives at risk, I recommend incorporating sexual selection by placing multiple males of varying sizes in breeding tanks with females to facilitate female selectivity or larger-male mating advantage. Based on the results of the current studies, I have identified possible constraints on the use of conspecific attraction for this species, and also recognised its potential use in translocations programmes to improve project outcomes. As a result of microhabitat assessment, habitat creation and management programmes can use specific parameters to design, maintain and monitor habitat for calling males. Assessment of a habitat construction project designed from previous research recommendations shows initial project success and provides information to refine future habitat construction programmes. Finally, assessment of sexual selection in L. aurea provides vital information to conservation programmes breeding animals for translocation to work toward improving the fitness of released individuals. Overall, the current study provides key aspects of L. aurea’s biology and ecology that have not been clearly addressed in the literature and aims to improve conservation efforts. In light of recent extinctions and increasing pressures on wildlife, continued research on key threatening processes and behavioural ecology is crucial to help guide conservation.

Alien species are a key driver of the ongoing biodiversity crisis. Changing patterns in the number and identity of transported alien species, and recent changes in the importance of different pathways for transporting alien species (e.g., recent decline in the role of acclimatisation societies vs. the increase in importance of the pet trade), means that there is a novel pool of alien species available for introduction. There is a pressing need to evaluate the biosecurity risks posed by these emergent alien species and their pathways. In this thesis, I focussed on unravelling the patterns and processes driving the transport, introduction, and establishment of novel vertebrate taxa (e.g., alien amphibians, reptiles, and fishes) in Australia and the world. Complementarily, I have also developed approaches to support the implementation of early detection activities for emergent alien reptile species. My results have highlighted the large number of new alien vertebrates being transported around the world, and particularly in Australia. The wildlife trade transports a substantial portion of all alien vertebrates, whereas unintentional pathways (i.e., stowaways) move fewer numbers of alien vertebrates (in terms of species transported). My research found that propagule number, the minimum number of release events of an alien species, is the main predictor of establishment success of self-sustaining reproductive alien populations. My global analysis of the relationship between the trade in Nearctic pet turtles and their establishment success revealed the complexities associated with managing novel pathways. The probability of introduction of a turtle species in a country (release or escape into the recipient environment) relates to the number of turtles imported, whereas the probability of establishment was associated with propagule numbers (number of releases) but not the number of individuals imported. My research on the establishment of alien fishes in Australia demonstrated substantial modern changes in the importance of transport pathways, with the recent rise of the ornamental fish trade as the key source of new alien species. These shifts in the importance of pathways for alien fish transport have also altered the processes governing the establishment success of alien fishes in Australia. The prevention of the establishment of new alien species is the best course for managing their potential impacts. However, even the best of prevention strategies cannot realistically aspire to be perfect. In order to be successful at preventing new alien species, it is important to implement early detection systems. I have developed and evaluated a quantitative approach for the early detection of alien reptiles on Christmas Island. The results indicate that large surveying efforts have to be conducted to ensure the absence of new alien reptiles with confidence. Drawing from the results of my research, I conclude with some suggestions to improve preventive management strategies for alien species. Particularly, I argue in favour of incorporating economic considerations in prevention strategies (e.g., the benefits of early detection activities vs. delayed intervention and eradication), conducting further research into the importance and drivers of different transport pathways, and examining potential management alternatives to species-based risk assessments.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Biological Sciences, 2017.