Dissertations / Theses on the topic 'Australian lizards'

[Truncated abstract] In ecomorphological or ecophysiological studies, variation in `design? traits (e.g. size, morphology and physiology) is thought to determine variation in ecologically-relevant performance traits, which in turn determines fitness in a particular habitat (Arnold 1983). Thus, natural selection is thought to act most directly on intermediate traits such as measures of locomotory performance. This thesis examined this process in the closely related group of Australian varanids lizards (Squamata: Varanidae). Phylogenetically, varanids are divided into three major clades. Size (mass and snout-to-vent length) is strongly correlated with these three clades. Two clades, (Gouldii and Komodoensis) are large, while the third clade (Odatria) has a smaller body size. Thus, there is considerable variation in size for various species. Size varied for species by three orders of magnitude. Size is also related to two ecological characteristics, foraging mode and habitat openness. Widely-foraging species were larger than sit-and-wait strategists, while species from open habitats were larger than species from semi-open or closed habitats. However, given the tight link between size and phylogeny we cannot separate adaptation of size to ecological traits from that of phylogenetic patterns. Of interest throughout this thesis was how variations in design (e.g. morphology and physiology) were related to ecological characteristics. Since body size also influences many of these morphological and physiological characteristics it is often necessary to remove the effects of size. Three design traits were examined in detail: body dimensions, vertebral number and metabolic rates. …Curiously, no performance variable linked differences in size-free body dimensions to retreat sites. This suggests that there is either a direct link between design and ecology (e.g. dorso-ventral compression), or some unmeasured performance variable related to retreat site. Given that most performance traits are thought to involve kinematic movements of the hindlimb limb and pelvis, and these were not best related to retreat site, then a direct link between design and ecology with respect to retreat site seems possible. In summary, this thesis provides evidence not only for links between design and ecology mediated by locomotory performance traits, but also direct links between design and ecology, for Australian varanid lizards.

Nonmammalian vertebrates possess some unusual features in their hormonal systems/ when compared to mammals. As a consequence, they can make an important contribution in investigations concerning the fundamental mechanisms operating in endocrinology. Such studies concerning androgens include inter alia their effects on developmental aspects in the brain of birds and related singing behaviour; the role of neural enzymes in reproductive processes in fish; and the relation between androgens and the stages of spermatogenesis in amphibia, The present thesis examines the biochemistry of androgens in the Australian lizard Tiliqua rugosa. The major compounds studied were testosterone and epitestosterone, which are known to be present in high concentrations in the plasma of the male animal. Previous investigations are expanded, particularly in the areas of steroid identification and testicular biosynthesis. In addition, preliminary studies on the metabolism in the brain (and other tissues) and plasma protein binding are reported. The presence of epitestosterone as a major free androgen in the plasma of the male lizard was confirmed. Other steroids were found in the sulphate fraction. Testosterone sulphate was the most rigorously identified compound, while some evidence was also found for the presence of conjugated 5-androstene-3β,17-diols, etiocholanolone and dehydroepiandrosterone (DHA). Epitestosterone does not appear to be extensively conjugated in this animal. Steroids were not found to be conjugated as glucuronides. The identification studies employed a novel method of electrochemical detection of steroids. This technique was investigated and extended in the current thesis. Biosynthetic studies were carried out on androgen interconversions in the testis, in vitro. The major enzyme activities detected were 17α-arid 17β-oxidoreductases (17α-OR and l7β-OR) and 3β-hydroxysteroid dehydrogenase (3β-HSD)/isonerase. No evidence was found for the presence of a steroid-17-epimerase that would directly interconvert testosterone and epitestosterone. The 17-oxidoreductases were found to be dependent on the cofactor NBDFH. Testosterone appears to be formed mainly via the 4-ene pathway, whereas epitestosterone is formed from both the 4- and 5-ene routes. The compound 5-androstene-3β, 17α-diol was found to be an intermediate in the synthesis of epitestosterone from DHA. Temperature was found to significantly affect 17α-OR activity (maximum at 32°C). In contrast,17β-OR activity was independent of this factor in the testis. Androgen metabolism in the testis was found to be regulated by cofactors, temperature and season. The major enzyme activities found in the male brain were 17α- and 17β-OR. 3βHSD/isomerase was not found; however a low activity of 5α-reductase was identified. Aromatase activity was not positively identified, but preliminary results suggest that it may be present at low levels. The 17-oxidoreductases were widespread throughout the brain. The 17α-OR was significantly lower in the forebrain than other brain sections. The 170-OR activity did not vary significantly throughout the organ, although there was a trend for its activity to be higher in the midbrain region (containing the hypothalamus in these sections). The concentration of endogenous steroids in brain tissue was estimated by radioimmunoassay. Epitestosterone was found throughout the organ structure, whereas testosterone was found mainly in the midbrain (containing hypothalamic regions in these sections). Correlations between enzyme activities and steroid concentrations in brain regions suggested that the main function of 17α-OR is to produce epitestosterone, whereas the 17β-OR may catalyse a more reversible reaction in vivo. Temperature was found to significantly affect both 17α- and 17β-OR activities in the brain. In contrast to the testis, the maximum activity of the brain enzymes occurred at 37°C. The level of 17α-OR activity in the male lizard (100 nmol/g tissue/h) is the highest reported for this enzyme in vertebrates. Both activities were found to be quantitatively similar in the whole brain homogenates of male and female animals, and did not vary seasonally when examined in the male. The 17-oxidoreductases were also found in most other tissues in T.rugosa, including epididymis, adrenal, kidney and liver (but not blood). This suggests that the high activities of both 17α-OR and 17β-OR are dominant features of the steroid system in this animal. The formation of 11-oxygenated compounds was found in the adrenal, in addition to the formation of polar metabolites in the kidney and liver (possibly polyhydroxylated and conjugated steroids). A preliminary investigation into the plasma binding of androgens was carried out. The insults suggest that there are several binding sites for testosterone; one with high affinity and low capacity; the other with low affinity and high capacity. Binding experiments were carried out at 32°C. At this temperature, specific binding was greater than at 25 or 37°C. From the results of competition studies it was suggested that epitestosterone (with a K(i)= 3 X 10 (-6)M for testosterone binding) regulates the binding of testosterone (K(i)=10(-7)M) and hence the concentrations of the latter steroid as a free compound in plasma. In general, the study has shown that the biochemistry of androgens in the reptile T.rugosa is largely similar to that found in other vertebrates. The major difference is a greatly increased activity of 17α-OR, which causes a higher concentration of 17α-compounds to be present in the tissues of this lizard. The physiological roles for epitestosterone are not yet clear. However it appears from this study that this steroid regulates testosterone concentrations in several tissues by either steroidogenic or binding mechanisms. Several major influences on this regulation include temperature, availability of cofactors and seasonal effects.

Reptiles are polyphyletic, and previous studies of renal anatomy and physiology in reptiles have covered a wide diversity of species of different phylogeny and habitat. To date, no study has examined the renal morphology and function of a group of closely related reptiles from different environments, yet this design has a number of advantages. Firstly, phylogenetic effects are reduced while adaptive specialisations in renal function or structure can be elucidated, and secondly, the variation in renal form and function between closely related species may be quantified in an effort to appreciate better the variation between more distantly related species. In this thesis, kidney morphology and renal function were studied in three Western Australian agamid lizards inhabiting environments differing in the availability of water. These key species were Pogona minor, Ctenophorus nuchalis and Ctenophorus salinarum. The renal anatomy of the three key lizards was characterised by determining glomerular diameter, volume density, surface area and number in each. Allometric relationships between kidney, colon and body mass were investigated in these and an additional 11 species of agamid lizard. Patterns of response to osmotic challenge were recorded by measuring renal variables such as urine flow rate, glomerular filtration rate and fractional reabsorption of filtrate among the three key species, and concurrent measurements of circulating arginine vasotocin in P. minor and C. nuchalis allowed the response of this hormone to homeostatic imbalance in these species to be gauged. The gross morphology and the glomerular characteristics of the kidneys was remarkably similar between species. Glomerular number and other characters varied as a function of body size rather than species, contrasting with reports in the literature suggesting that a given species has a particular number of glomeruli. ... Thus, kidney morphology is constrained among species and the response of each species to osmotic perturbation is similar. However, the mechanisms underlying antidiuresis and the hormonal control of this process differ subtly between species, and there is some evidence to suggest that P. minor is more adapted to a mesic environment than the other two lizards examined in this study. The hypothesis that renal form and function reflect the environment in which a lizard lives therefore receives partial support, although the reptilian bauplan is able to mitigate many of the forces that could potentially lead to renal specialisation.

Fossil Agamidae from Western Australia have been the subject of limited study. To aid in fossil agamid identification, Hocknull (2002) examined the maxilla and dentary of several extant species from Australia and determined diagnostic characters for various species groups. In the study here, fossil agamids from two localities in Western Australia, Hastings Cave and Horseshoe Cave, were examined, grouped, and identified to the lowest unambiguous taxonomic level. Morphometric analyses were conducted to compare morphotypes, and find additional diagnostic characters. From Hastings Cave there were two maxilla morphotypes and three dentary morphotypes. Based on identifications, taxa present at this locality were Pogona and Ctenophorus. Horseshoe Cave contained three maxilla morphotypes and two dentary morphotypes; taxa present were Pogona, Tympanocryptis, and Ctenophorus. Morphometric analyses showed separation between groups; however, the dentary morphotype separation was not as clear. Each morphotype identification matched a species in the respective localities today, but identifications are cautious.

ABSTRACT Social relationships, habitat utilisation and life history characteristics provide a framework which enables the survival of populations in fluctuating ecological conditions. An understanding of behavioural ecology is critical to the implementation of Natural Resource Management strategies if they are to succeed in their conservation efforts during the emergence of climate change. Egernia whitii from Wedge Island in the Spencer Gulf of South Australia were used as a model system to investigate the interaction of life history traits, scat piling behaviour and chemosensory communication in social lizards. Juveniles typically took ¡Ý 3 years to reach sexual maturity and the results of skeletochronological studies suggested longevity of ¡Ý 13 years. Combined with a mean litter size of 2.2, a pregnancy rate estimated at 75% of eligible females during short-term studies, and highly stable groups, this information suggests several life history features. Prolonged juvenile development and adult longevity may be prerequisite to the development of parental care. Parental care may, in turn, be the determining factor that facilitates the formation of small family groups. In E. whitii parental care takes the form of foetal and neonatal provisioning and tolerance of juveniles by small family or social groups within established resource areas. Presumably, resident juveniles also benefit from adult territorialism. Research on birds suggests that low adult mortality predisposes cooperative breeding or social grouping in birds, and life history traits and ecological factors appear to act together to facilitate cooperative systems. E. whitii practice scat piling both individually and in small groups. Social benefits arising from signalling could confer both cooperative and competitive benefits. Permanent territorial markers have the potential to benefit conspecifics, congenerics and other species. The high incidence of a skink species (E. whitii) refuging with a gecko species (N. milii) on Wedge Island provides an example of interspecific cooperation. The diurnal refuge of the nocturnal gecko is a useful transient shelter for the diurnal skink. Scat piling may release a species ¡®signature¡¯ for each group that allows mutual recognition. Scat piling also facilitates intraspecific scent marking by individual members, which has the potential to indicate relatedness, or social or sexual status within the group. The discovery of cloacal scent marking activity is new to the Egernia genus. E. Whitii differentiate between their own scats, and conspecific and congeneric scats. They scent mark at the site of conspecific scats, and males and females differ in their response to scent cues over time. Scat piling has the potential to make information concerning the social environment available to dispersing transient and potential immigrant conspecifics, enabling settlement choices to be made. This thesis explores some of the behavioural strategies employed by E. whitii to reduce risks to individuals within groups and between groups. Scents eliciting a range of behavioural responses relevant to the formation of adaptive social groupings, reproductive activity, and juvenile protection until maturity and dispersal are likely to be present in this species. Tests confirming chemosensory cues that differentiate sex, kin and age would be an interesting addition to current knowledge. The interaction of delayed maturity, parental care, sociality, chemosensory communication and scat piling highlights the sophistication of this species¡¯ behaviour. An alternative method for permanently marking lizards was developed. Persistence, reliability and individual discrimination were demonstrated using photographic identification and the method was shown to be reliable for broad-scale application by researchers. Naturally occurring toe loss in the field provided a context against which to examine this alternative identification method and revealed the need to further investigate the consequences of routine toe clipping, as this practice appears to diminish survivorship.

Fauna conservation outside protected areas can make an important complementary contribution to conservation within reserves. This thesis aimed to contribute new information and analytical frameworks to the science of fauna conservation in human-modified landscapes. Two approaches were used: (1) empirical data collection and analysis, and (2) the discussion and development of conceptual landscape models. ¶ Empirical work focused on lizard distribution patterns in two production landscapes in southeastern Australia. Lizards were targeted because ectotherms are frequently neglected by conservation biologists. The “Nanangroe grazing landscape” was used for sheep and cattle grazing. In this landscape, approximately 85% of pre-European woodland cover had been cleared, and understorey vegetation was sparse. Lizards were surveyed at 16 landscape units, which were stratified by aspect, topographic position and amount of tree cover. Each landscape unit contained three sites, and each site contained three plots. Regression modelling showed that different species responded differently to their environment. For example, the four-fingered skink (Carlia tetradactyla) and Boulenger’s skink (Morethia boulengeri) were more likely to occur at woodland sites with northerly aspects, whereas the striped skink (Ctenotus robustus) and olive legless lizard (Delma inornata) were more likely to inhabit sites with a simple microhabitat structure. Statistical analysis further showed that the habitat attributes that lizards were related to varied continuously through space, and over different spatial scales. For example, invertebrate abundance (a proxy for food availability) varied most strongly over tens of metres, whereas the amount of grass cover varied most strongly over hundreds to thousands of metres. Thus, work at Nanangroe revealed spatially complex patterns of lizard occurrence and habitat variables. ¶ The “Tumut plantation landscape” was a spatial mosaic of native eucalypt (Eucalyptus) forest patches embedded within a plantation of the introduced radiata pine (Pinus radiata). In this landscape, thirty sites were surveyed for lizards. Sites were stratified by forest type and patch size, and included eucalypt patches, pine sites, and extensive areas of eucalypt forest adjacent to the plantation. Regression modelling showed that lizard species responded to various habitat attributes, including elevation, the amount of eucalypt forest within 1 km of a site, invertebrate abundance and ground cover. Variables related to habitat fragmentation often were significant predictors of lizard occurrence. However, work at Tumut suggested that important additional insights into lizard distribution patterns could be obtained by considering variables related to food and shelter resources, and climatic conditions. ¶ The Nanangroe and Tumut landscapes were in close proximity, but together spanned an altitudinal gradient of 900 m. An investigation of changes in lizard community composition with altitude showed that (1) only one species was common to Nanangroe and Tumut, (2) different species had different altitudinal preferences, and (3) ecologically similar species replaced one another with increasing altitude. These results highlighted that even in highly modified landscapes, natural gradients (such as climate) can play an important role in shaping animal assemblage composition and species distribution patterns. ¶ Empirical work suggested that, in some landscapes, the frequently used “fragmentation model” is a relatively weak conceptual basis for the study of animal distribution patterns. The fragmentation model implicitly assumes that “habitat patches” can be defined unequivocally across many species, and that patches are located within a relatively inhospitable matrix. Where these assumptions are breached, conservation guidelines arising from the fragmentation model may be too simplified. In spatially complex production landscapes, it may be more appropriate to maintain habitat heterogeneity at multiple spatial scales than to focus solely on the management of large, pre-defined patches. ¶ Given the potential limitations of the fragmentation model, a new, more holistic landscape model was developed. The “continuum model” was derived from continuum theory as developed for plant ecology. The continuum model recognises (1) spatial continua of environmental variables, and (2) species’ individualistic responses to these variables. For animals, key environmental variables may be related to the availability of food, shelter, sufficient space, and suitable climatic conditions. Unlike the fragmentation model, the continuum model is inherently process-based and thus may help to link the perceived gap between patterns and processes in landscape ecology. ¶ Three general conclusions arise from this thesis: 1. Some heterogeneous production landscapes support many native species, and therefore represent important conservation opportunities. 2. In some modified landscapes, the fragmentation model does not capture the complexity of animal distribution patterns. In those landscapes, conservation recommendations derived from the fragmentation model may be overly simplistic. 3. The continuum model may be a useful extension of the fragmentation model. It provides a process-based conceptual basis for empirical work on animal distribution patterns.

Reptiles exhibit marked diversity in sex-determining mechanisms. Many species exhibit genotypic sex determination (GSD) with male heterogamety (XX females/XY males), others have GSD with female heterogamety (ZW females/ZZ males), and still others exhibit temperature-dependent sex determination (TSD). The distribution of these mechanisms throughout the reptile phylogeny implies evolutionary lability in sex determination, and in some lineages there has been a number of transitions between GSD and TSD. Despite this diversity, GSD and TSD have traditionally been viewed as mutually-exclusive mechanisms of sex determination in reptiles, since there is little evidence for their co-occurrence. Considerable empirical and theoretical effort has been directed towards understanding the adaptive significance of TSD in reptiles. In comparison, there has been little focus on understanding how evolutionary transitions between GSD and TSD occur at a genetic and mechanistic level. I addressed this question by applying both empirical and theoretical approaches to investigate interaction of genotypic and temperature influences in the sex determination of two endemic species of Australian lizards. The three-lined skink, Bassiana duperreyi, has XX/XY chromosomal sex determination, yet a previous investigation reported a significant male bias in the sex ratio of eggs incubated at low temperatures. To enable an explicit test for temperature induced sex reversal in this species, a 185 bp Y chromosome marker was isolated by Amplified Fragment Length Polymorphism (AFLP) analysis. The marker was subsequently converted into a duplex PCR assay that co-amplified a 185 bp (or 92 bp) Y chromosome fragment and a 356 bp fragment of the single-copy nuclear gene C-mos (from both sexes) as a positive control. The accuracy of the PCR sex assay was tested on 78 individuals for which sex reversal was not expected. PCR genotype and sex phenotype were concordant for 96% of the animals. This is one of the very few sex tests developed for a reptile, and the first report of Y chromosome sequence from a reptile. The PCR assay was subsequently applied to genotype hatchlings from both cool (16-7.5C) and warm (22-7.5C) cyclical incubation temperature treatments, and identified sex reversal in 15% of genotypically female (XX) embryos (n=26) from the cool treatment, but no sex reversal in eggs from the warmer treatment (n=35). Thus, low incubation temperatures can over-ride genotypic sex determination in B. duperreyi, indicating that GSD and TSD co-occur in this species. The Central bearded dragon, Pogona vitticeps (Agamidae), has ZZ/ZW chromosomal sex determination, and is a member of a lizard family in which GSD and TSD are both widespread, indicating evolutionary lability in sex determination. AFLP analysis was applied to isolate homologous Z and W chromosome-linked markers (71 bp and 72 bp, respectively) from this species. The AFLP sequences were subsequently extended into larger genomic fragments by a reiterated genome walking procedure, producing three non-overlapping contigs of 1.7 kb, 2.2 kb and 4.5 kb. The latter two fragments were verified as distinct, homologous Z/W chromosome fragments by PCR analyses. An amplified 3 kb fragment of the 4.5 kb contig was physically mapped to metaphase spreads, identifying the W microchromosome, and for the first time in this species, the Z microchromosome. PCR analyses indicated the presence of homologous sequences in other Australian agamid species, including both GSD and TSD species. The isolated sequences should therefore prove useful as a comparative genomic tool for investigating the genomic changes that have occurred in evolutionary transitions between sexdetermining mechanisms in agamids, by enabling the identification of chromosomes in TSD species that are homologous to the sex chromosomes of P. vitticeps. The isolated sequences were further converted into a duplex DNA sex assay that co-amplified a 224 bp W chromosome fragment and a 963 bp positive control fragment in both sexes. This PCR assay diagnosed chromosomal sex in three Pogona species, but was not effective outside the genus. Incubation treatment of P. vitticeps eggs revealed a strong and increasing female bias at high constant temperatures (34-36C), but an unbiased sex ratio between 22-32C. Hatchlings from three clutches split between 28C and 34 or 36C incubation treatments were genotyped with the W chromosome AFLP marker. At 28C, the sex ratio was 1:1 but the high temperature treatments produced 2 males and 33 females. All but one of the 30 lizards (97%) incubated at 28C had concordant sex phenotype and genotype, but only 18 of 35 animals (51%) from the high temperature treatment were concordant. All discordant animals were genotypic males (ZZ) that developed as females. Thus, temperature and genotypic influences can interact to determine sex in P. vitticeps. These empirical findings for B. duperreyi and P. vitticeps were extended into a novel theory for the evolution of sex-determining mechanisms in reptiles, working within the framework that species with temperature-induced reversal of chromosomal sex determination are a window to transitional stages of evolution between GSD and TSD. A model was derived from the observation that in both lizards, an extreme of incubation temperature causes sex reversal of the homogametic genotype. In this model, the strength of a genetic regulatory signal for sex determination must exceed a threshold for development of the homogametic sex to occur (male in Pogona, female in Bassiana). The strength of this signal is also temperature-sensitive, so diminishes at extremes of temperature. Simulation modelling demonstrated that increasing the relative magnitude of the threshold for sexual development can cause evolutionary transitions between GSD and TSD. Even more remarkably, decreasing the relative magnitude of the threshold value causes an evolutionary transition between female and male heterogametic GSD. Quantitative adjustment of a single model parameter (the threshold value) thus charts a continuous evolutionary pathway between the three principal mechanisms of sex determination in reptiles (XX/XY-ZZ/ZW-TSD), which were previously considered to be qualitatively distinct mechanisms. The experimental demonstration of temperature-induced reversal of chromosomal sex determination in both B. duperreyi and P. vitticeps presents a challenge to the traditional view that reptilian sex determination is strictly dichotomous (GSD or TSD), and suggests instead that sex determination in reptiles consists of a continuum of systems of interaction between genotypic and temperature influences. Simulation modelling provided solid theoretical support for this proposition, demonstrating that transitions along this continuum are effected simply through shifts in the mean population value for the sex-determining threshold, without requiring substantial genotypic innovation. An important implication of this theory is that transitions between XX/XY and ZZ/ZW modes of GSD may retain the same sex chromosome pair, and the same primary sexdetermining gene, in contrast to previous models for heterogametic transitions. A more immediate implication of these findings is that many reptile species believed to have strict TSD (in particular, lizards and crocodilians), may in fact have a sex-determining system of GSD-TSD interaction, where there is an equilibrium between GSD and TSD individuals within the population.

This study examined the ant communities of several grasslands of the Australian Capital Territory (ACT) and their relevance to the pink-tailed legless lizard, Aprasia parapulchella (Pygopodidae). A. parapulchella is a fossorial species that shares burrows with, and eats the brood of, several grassland ant species. Foraging ants were collected from sites by pitfall trapping throughout one calendar year and comparisons of ant communities made between seasons and sites of differing vegetation structure. Competition between ant species for artificial nest sites and the effects of temperature on selection of nest site selection were also studied. The role that ants play in the distribution of A. parapulchella was investigated by (i) comparing ant faunas from several sites throughout the geographic range of the lizard, including sites in New South Wales and Victoria, (ii) performing feeding preference experiments with A. parapulchella, and (iii) investigating the seasonal nature of brood production and nest establishment by ants in ACT grasslands. Major findings were used to make recommendations to assist in the management, including rehabilitation, of A. parapulchella grassland sites. Low insolation appears to significantly affect the ant species composition of grassland sites in the ACT relative to other Australian vegetation types. In the ACT grassland sites, large species of the Dominant Dolichoderinae functional group were absent, or present only in very low numbers. The communities were species-poor relative to other Australian studies with only 60 species being recorded across all sites studied, with no more than 21 species recorded at any site on any sampling occasion. Whilst ant species community structure was highly variable between seasons and sites, more than 95% of ants were from the three functional groups, Dominant Dolichoderinae, Generalized Myrmicinae and Opportunists. The communities were numerically dominated throughout the year by the ubiquitous species groups Iridomyrmex 'rufoniger' and Rhytidoponera 'metallica'. Almost all taxa increased in foraging abundance during summer months and Pheidole spp., Monomorium spp., Crematogaster sp. Paratrechina sp. and Notoncus ectalomoides were occasionally locally abundant. There were no significant relationships between ant and vegetation community structures, but Solenopsis sp. showed an alliance with sites that had a high abundance of Themeda australis (kangaroo grass), whilst Crematogaster sp. and Paratrechina sp. are potential bioindicators of disturbance from grazing or pasture improvement. Iridomyrmex 'rufoniger' were the numerically dominant foraging ants, making up 50% of all captures, but they held only 80% of their nest sites when faced with competition from other species. R. 'metallica' and Pheidole spp. on the other hand, gained 80% more nests than they lost to other taxa. I. 'rufoniger' and R. 'metallica' both preferred nest sites with warmer temperature regimes when given the choice, and this assisted them to tend brood throughout the year. All ant species in ACT grasslands had summer peaks in brood production. Most nests were inactive throughout the cooler months and nest founding was predominantly between September and November. The common species, Iridomyrmex spp., Paratrechina sp. and R. 'metallica' held winged reproductives in their nests from April and all ant taxa had released all alates by mid- November. Although there were differences in ant community structure throughout the range of A. parapulchella, the ubiquitous R. 'metallica' and I. 'rufoniger' were always abundant, whilst again, Dominant Dolichoderinae and associated subordinate taxa were absent or present only in relatively low numbers. The lizards consumed brood from all the common ant species in ACT grasslands and showed preference for consuming brood of, and living with, small Iridomyrmex spp. The range of the small Iridomyrmex spp. preferred by A. parapulchella extends far beyond that of the lizard. Its distribution is apparently not restricted by the range of its ant prey species. For rehabilitation of A. parapulchella sites in the ACT, it is recommended that a significant ground cover of native grasses is established to ensure the low abundance of large and territorial ants from the Dominant Dolichoderinae functional group. Along with a high abundance of shallow surface rocks, this will ensure the establishment of ant communities that are numerically dominated by small Iridomyrmex spp., which are preferred by A. parapulchella for homesite sharing and as a food source.

This research project examined the role of environmental time cues and circadian rhythms in mediating seasonal adjustments in the body temperature and locomotoractivity patterns in the Australian sleepy lizard, Tiliqua rugosa (Gray 1827). The first component of this study investigated whether daily rhythms of behavioural thermoregulation and locomotor activity that T. rugosa displays in the field are endogenous circadian rhythms. In each season, there was significant variation in each of these rhythms in lizards released on laboratory thermal gradients under prevailing light-dark (LD) cycles. Both rhythms persisted when lizards were released in constant darkness (DD) and exhibited the same free-running period suggesting a single circadian pacemaker drives both rhythms. The first component of this study revealed that seasonal changes in the expression of daily behavioural thermoregulatory and locomotor activity rhythms are mediated by the circadian system in T. rugosa. The second component of this project comprised three experiments that determined the relative importance of 24 h LD and temperature cycles (TCs) in entraining the locomotor activity rhythm. In the first experiment, lizards were held under LD 12:12 and were subjected to either a TC of 33:15C in phase with the LD cycle or a reversed TC. Following LD 12:12, lizards were maintained under the same TCs but were subjected to DD. Activity was restricted to the thermophase in LD irrespective of the lighting regime and during the period of DD that followed, suggesting entrainment by the TC. In the second experiment, lizards were held under LD 12.5:11.5 and were subjected to one of three treatments; (1) constant 30C, (2) normal TC (30:20C), or (3) reversed TC. Following LD, all lizards were subjected to DD and constant 30C. Post-entrainment free-run records revealed that LD cycles and TCs both entrain locomotor activity rhythms of T. rugosa. Although there was large variation in the phasing of the rhythm in relation to the LD cycle in reversed TC lizards, TCs presented in phase with the LD cycle most accurately synchronised the rhythm to the photocycle. In the third experiment, lizards were held in DD at constant 30C before being subjected to a further period of DD and one of four treatments; (1) normal TC (06:00 h to 18:00 h thermophase), (2) delayed TC (12:00 h to 00:00 h thermophase), (3) advanced TC (00:00 h to 12:00 h thermophase) or (4) control (no TC, constant 30C). While control lizards continued to free-run in DD at constant temperature, locomotor rhythms of lizards subjected to TCs rapidly entrained to TCs irrespective of whether TCs were phase advanced or delayed by 6 h. The results of this experiment excluded the possibility that masking effects were responsible for locomotor responses of lizards to TCs. This study demonstrated that seasonal changes in the expression of this species‟ daily behavioural thermoregulatory and locomotor rhythms are mediated by a circadian system that is sensitive to both light and temperature. The sensitivity of the circadian system to temperature, in particular, may allow T. rugosa to restrict its activity to times of the year that are thermally favourable.
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Thesis(Ph.D.)-- University of Adelaide, School of Medical Sciences, 2010

There is a global effort to research the impacts of habitat fragmentation and degradation on wildlife. There is, however, still a need for greater understanding of ecological processes at work in fragmented and degraded habitat in peri-urban and agricultural areas. The study was undertaken in order to enable insights to be gained to provide a basis for management of fragmented habitat, using a single species as a focus. Eastern Bearded Dragon Pogona barbata is a reptile icon in Australia, but which is regarded anecdotally as being in decline, and for which little is known of the ecology. The aim of the study was to research the biology and spatial ecology of a species that had a dependent relationship on structural habitat of the nature of that found in peri-urban areas. Pogona barbata was selected as being an appropriate species in being terrestrial l /arboreal, having a territorial social structure, being an ecological generalist species, and being of a suitable size for study in relation to the size of fragmented habitat in western Sydney. Wild populations in relatively undisturbed habitat in the peri-urban area of western Sydney, Australia, were observed from 2000 to 2002, with additional data gained from museum collections and road-killed animals. Morphometrics were analysed by taking the ratio of a character to snout-vent length, and plotting that value against snout-vent length in order to more clearly see allometric change. Detailed tracking of animals using spool threads was used to collect data on microhabitat use, spatial activity and home range. The distribution of P. barbata across its range coincided with open forest and woodland habitat, which in some areas is subject to intensive urban and agricultural impacts. Pogona barbata is found to be insectivorous as a juvenile and omnivorous as an adult. As hatchlings grow, the relative length of the tail increases (positive allometry) until sexual maturity, and this coincides with an insectivorous diet. The onset of sexual maturity occurs just after the diet becomes omnivorous, and the relative tail length decreases (negative allometry) to a value that can be less than that of hatchlings. The gracile body form of juveniles is different from the robust body form of adults, and this is consistent with the difference in diet and microhabitat use. Factors affecting the persistence of the species were identified. Eggs were eaten by foxes on a regular basis, and hatchlings and juveniles were very rare, indicating an unbalanced demographic structure. The apparent rarity of hatchlings and juveniles may be due to crypsis. Road death was found to remove important breeding individuals from the population. An improved method of estimating testis volumes in lizards using three dimensions was used, which showed that the anatomy of P. barbata testes is bilaterally asymmetrical. It is currently assumed that reptile testes are at least bilaterally regular, but this is not the case in P. barbata. The outcome of this finding is that reproductive and other studies that rely on measurement of a single testis in two dimensions may miss significant data. Testis volumes for P. barbata in western Sydney in the past 20 years are highly abnormal, which coincides with increasing air pollution in the area. Extremes of testis condition were absent testes, very small testes, and extreme differences of testis size in individual animals. Resource partitioning was found, with microhabitat use, to be significantly different for juveniles, males and females. Juveniles and hatchlings used dense habitat with a high incidence of fine and coarse woody debris. The fine matter in the habitat upon which adult females also rely is lost in frequent fires that are used to control bushfire hazard. Pogona barbata is generally regarded as a sit-and-wait predator, on the basis of its being commonly observed on obvious perches. This study demonstrates that such perches are not the most important component of its habitat and that its foraging mode is that of a grazing omnivore. This study appears to be the first that addresses a seasonal shift in microhabitat use for a reptile in general terms. The pattern of daily activity changes with season, and changes in daily habitat preference based on age, sex and season, indicated that P. barbata required a diverse structural habitat. This habitat is affected by frequent hazard reduction fires. A new method of estimating animal home range is presented. The method consists of daily spool trace polygons collected by GPS and analysed in ArcView 3.2, with a spatial analysis output that indicates an estimated total home range and a confidence interval for that estimate. A typical result is an acceptable estimate within 20-30 sequential days of tracking an animal. That outcome is a considerable improvement on the currently accepted minimum of 50 independent days, being at least 100 calendar days. Pogona barbata ‘breaks the rules’ for a number of concepts in the biology of reptiles, and in this study has displayed some new insights in testis morphology, ontology and ecology. It was rare in the areas studied, lending support to the perception that the species is in decline. Reproductive suppression was suspected to affect the population in western Sydney. Pogona barbata has shown a range of characteristics that makes it useful as an umbrella species for the purpose of managing fragmented and degraded habitat in peri-urban and agricultural areas. A range of biological and ecological measures is required to enable effective habitat management of any species, and this study has provided some appropriate techniques for that purpose.
Doctor of Philosophy (PhD)

Impacts of ecological competition are reduced when organisms play different roles in their environment. More individuals can survive on varied but finite sets of resources when organisms eat different kinds of prey, live in different places, or are active at different times. Species within an assemblage of small fossorial snakes have ecologies that vary mostly by diet. Different species eat very different things. Species live in different habitats on sand ridges, but the differences are less dramatic than in diet. Disparity in resource use typically varies the most according to species, so that individuals of the same species are more similar to each other than they are to individuals of other species. However, variation exists in resource use within species over time and space. Wide variation exists in dietary resource use in four well-sampled species of comb-eared skinks. However, where species occur at the same study site there are clear distinctions in resource use between species despite the wide variation in diets observed between individuals of the same species. Additionally, strict ecological distances in diet between species are maintained during five censuses that were conducted over a 16-year period. These results illustrate the basic ecological principals of fundamental and realized niches. Here, individuals ate many different food items and species have the potential to overlap in diet but that overlap is reduced because of realized ecological boundaries between species within a single place and time, which result in decreased competition for resources.
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