Here are a range of specific projects currently advertised on the University of Tasmania’s Graduate Research Office Website. This is not an exhaustive list and if you are interested in alternative topics please contact Erik or Geoff.
Title: Causes and consequences of hybridisation: From behaviour to evolution (Wall lizards)
Project Description: Geographic patterns of genetic and phenotypic variation demonstrate that hybridization is common in animals. However, rarely do we understand how those patterns come about and when hybridization will shape the evolution of organisms and their genomes. In wall lizards, divergence in male competitive ability drives the introgression of suites of sexually selected characters from one lineage to another. However, phenotypic and genomic variation across the landscape suggests that (i) introgression of a small part of the genome is responsible for large shifts in phenotype; (ii) sexually selected introgression is counter-balanced by natural selection at high altitude; and (iii) this results in sexually antagonistic selection across altitudinal clines. This PhD project will take an integrated approach to try and understand the processes responsible for this geographic variation in introgression and its consequences for the evolution of sexual dimorphism – from genomes to phenotypes. This will involve i) monitoring of individually marked animals in the wild to generate estimates of ongoing selection in hybrid regions; ii) experiments on captive animals to test hypothesis regarding the sources of sexually antagonistic selection and iii) analyses of single nucleotide polymorphisms, mapped onto the sequenced wall lizard genome, to test predictions regarding how selective processes shape genomes.
Title: The evolutionary origins of family living (Egernia)
Project Description: Social groups are extraordinarily diverse in form and function across the animal kingdom. Whereas we understand well how many social systems are maintained, what predispose certain lineages to evolve sociality in the first place is poorly resolved. The Australian lizard group, Egernia are particularly useful model organisms in this context because they display huge diversity in social organisation between species, from species that are largely solitary to those that live in large extended family groups. Social organisation is also highly variable within species. This provides us with a fantastic opportunity to ask what factors influence variation in social organisation within a species and how this may explain diversification in social organisation across species. The advertised PhD project will use a combination of experimental, molecular, theoretical and comparative techniques to exploit this opportunity. It would focus primarily on one particular species, Liopholis whitii, to study micro-evolutionary processes acting on individual social strategies. This would involve the integration of data collected from a long-term field study with detailed experimental manipulations using large outdoor enclosures. It would then combine this with similar work on species across the group, allowing us to link these micro-evolutionary processes with macro-evolutionary patterns of social diversification across species.
Title: Linking sex allocation and family living (Egernia)
Project Description: The fields of sex allocation (how much resources females invest in male vs female offspring) and social evolution are intricately linked because different social strategies have sex specific fitness returns for offspring. This PhD project will integrate molecular approaches with laboratory and field studies to explore these links using a group of family living lizards, the Egernia group. These lizards are excellent model organisms for this challenge because they display relatively simple forms of family life that are amenable to experimental manipulation offering us the opportunity to target causal links between family life and sex allocation. The project would consist of several integrated components. First, the development of genetic markers to identify sex of offspring at birth using next generation sequencing. Second, the utilisation of genetic samples already collected as part of our long-term monitoring to examine the potential links between sex allocation and family living (sex specific dispersal, sex specific sibling-competition, sex determination). Third, the combination of the above with targeted experiments to address the causal links between family life and sex allocation. Finally, examine the extent to which genetic markers cross amplify across Egernia species allowing for a sophisticated comparative analysis of sex allocation across the group.
Title: The mechanisms behind evolutionary transmissions between genetic- and temperature-dependent sex determination (Snow Skinks)
Project Description: Sex determination is a fundamental biological process, yet its mechanisms are remarkably diverse. In vertebrates, sex can be determined by inherited genetic factors or by the temperature experienced during embryonic development. However, the evolutionary causes of this diversity remain an enigma. In this project you will have the opportunity to build from our recent work that showed that live-bearing lizards from different climates differ in their sex-determining mechanisms, with temperature-dependent sex-determination in warm areas and genotypic sex determination in cold alpine areas. A theoretical model parameterized with field data accurately predicted this divergence in sex-determining systems and the consequence thereof for variation in cohort sex ratios among years with predictions of shifts in chromosomal control of sex determination. While our results established an adaptive explanation for intra-specific divergence in sex-determining systems driven by phenotypic plasticity and ecological selection, we lack knowledge of the mechanisms behind these shifts.
Title: Manna farming in Forty-Spotted Pardalotes: a genes-to-ecosystems approach (Pardalotes)
Project Description: The behaviour of individual animals can have substantial implications for the structure and function of whole communities and ecosystems. This project will focus on the Forty-spotted pardalote (Pardalotus quadragintusi), a small endangered bird, that forages for a sugary exudate from Eucalypt species known as manna. Manna is acquired by the pardalotes through ‘farming’ whereby adult birds create small incisions in the stem surface promoting the flow of manna. Importantly, manna is an key food resource for many other woodland species, and the behaviour of foraging pardalotes strongly influences the availability of manna. Therefore, Forty-spotted pardalotes may play a fundamental role in the occurrence and abundance of other manna dependent species and thus community composition. This project will address several questions regarding the causes and consequences of pardalote mining behaviour. First, it will quantify manna composition and the extent to which this varies within and between Eucalypt populations. Second, it will use large common garden trials to determine the extent to which variation in manna composition is underpinned by a genetic vs environmental variation. Third, it will quantify the extent to which variation in manna quality influences pardalote foraging behaviour. Fourth, it will examine the consequences of padalote manna farming behaviour for higher levels of biological organisation (e.g., community structure). In addressing these aims, this project will offer new insights into how intraspecific variation in key tree traits and animal behaviour affects whole communities and ecosystems and in doing so will provide crucial information on the habitat requirements of a critically endangered species.
Title: Exploring the causes and consequences of an extended phenotype: burrow construction and its consequences across the Egernia (Egernia)
Project Description: Extended phenotypes are any trait of an individual that extends beyond that individuals physical being. Sounds complicated! But there are many examples of relatively simple extended phenotypes in nature – think about a beavers dam, a wombats burrow or a birds nest. Importantly, these phenotypic extensions can have fundamental impacts on the environment and also influence key evolutionary processes (this is known as niche construction). Importantly, extended phenotypes are often easier to measure and quantify than actual phenotypic traits (especially behaviour) thus they offer us the potential to ask questions about the causes and consequences of such traits. A key ecological component of Egernia lizards is that they rely on deep and complex burrow systems which they construct. These burrows act as extended phenotypes which provide shelter for the Egernia’s family group. This PhD project would consist of several integrated components aimed at examining the causes and consequences of burrow construction. First, it would aim to quantify variation in burrow construction both within and between burrowing Egernia species. Second, it would use state-of-the-art molecular techniques to examine the developmental and genetic architecture of burrow construction. Finally, it would examine the extent to which burrow construction mediates the emergence of morphological and social diversification both within and between species. In addressing these aims, this project will offer new insights into how extended phenotypes evolve in natural systems and the consequences of this for the evolution of a suite of related characteristics.
Title: Exploring the impacts of climate change on social behaviour (Egernia)
Project Description: Many species are directly impacted by climate change via its effects on basic biological processes. As a result climate change can have important consequences for the ecological trajectory of a population, in some cases leading to population collapse. What is less well understood is the extent to which climate change has consequences for the evolutionary trajectory of a population. This is particularly the case in the context of social evolution, where subtle differences in climate can mediate how individuals interact with one another and thus shape how selection may act on social behaviour itself. This PhD project will integrate molecular, field and experimental approaches with theoretical modelling to address this short coming. To achieve this, it will utilise the family living lizard, Liopholis whitii, which displays relatively simple forms of family life that are amenable to experimental manipulation. This offers a fantastic opportunity to test the causal links between variation in climate and key social traits that either promote or reduce social complexity at the population level. This can then be combined with theoretical models to explore the broader consequences of these relationships for the social trajectory of populations across evolutionary time.
Title: Unravelling the mechanisms of live birth (Egernia)
Project Description: Giving birth to live young represents a major biological innovation that has facilitated the evolution of a wide range of morphological, physiological and behavioural adaptations and has been shown to contribute to rates of diversification. However, understanding the mechanisms that facilitated the evolution of live birth itself remains a major challenge. This PhD project will address this. It will take advantage of a radiation of Australian lizards, the Egernia group, in which females not only give birth to live young, but have fine-scale control of exactly when they give birth to individual offspring. Specifically, females birth their young one at a time, retaining fully developed offspring in their reproductive tract for several days following the birth of each offspring (termed birthing asynchrony). This is thought to be adaptive, as it allows females to mediate the competitive environment of their brood. There is also considerable variation within and between species in the extent of birthing asynchrony. This is unique within amniotes and provides us with an opportunity to explore the mechanisms that underpin this behaviour. This project will integrate molecular, field and experimental approaches to determine a) the physiological and molecular mechanisms underpinning birthing asynchrony, b) the role, if any, that offspring play in mediating birthing asynchrony, and c) the evolutionary history of birthing asynchrony across the Egernia and the extent to which it co-varies with ecological and social factors. As birthing asynchrony must have evolved via the fine-scale modification of the mechanisms that govern live birth itself, this will provide unparalleled insights into how live birth first evolved that will be applicable across a wide range of organisms.