Ongoing major research projects in the lab
We are developing new statistical approaches to infer spatio-temporal trajectories of megafauna extirpations and initial human colonisation patterns in Sahul, Eurasia, and North America. (collaborators: Chadoeuf, Friedrich, McDowell, Timmerman, Ulm)
We are examining the demographic and spatial patterns of human colonisation of Sahul (Australia, New Guinea & Tasmania) using state-of-the-art demographic and lattice network models. (collaborators: Bird, Clarkson, Friedrich, Jacobs, Llamas, Norman, Roberts, Ulm, Weyrich, Williams)
How did vegetation respond to post-glacial climate change in the Neotropics, and how did this contribute to shape ecosystems over time? The Quaternary climate alternated between cold glacial and warm interglacial periods that strongly affected ecosystems over the last ~ 2.58 million years. The last great worldwide period of glaciation was marked by a maximum ice sheet coverage between ~ 26,500 and 19,000 years ago (the so-called Last Glacial Maximum). The subsequent global warming generated ecosystem turnovers, including biome boundary shifts, altered fire regimes, and modifications of both animal and plant communities. Vegetation is a key component of an ecosystem because this is the base of all food webs, and provides structural wildlife habitat. However, the causes and consequences of vegetation changes at this time are still poorly understood, mainly in the Neotropics where this period coincided with both the colonisation of Homo sapiens across the continent, and other megafauna (> 44 kg) extinction events that also eroded South American ecosystems.
We are using mechanistic mathematical models taking into account ecological processes such as disturbances, competition, and/or facilitation, to (1) predict post-glacial vegetation patterns in the Neotropics, and to (2) understand their interactions with megaherbivore extinctions, fire regimes changes, and human colonisation. (collaborators: Hickler)
Tracing the role of environmental fluctuations on the evolution of Australia’s natural history has long been hampered by a lack of reasonable reconstructions of vegetation communities over spatial times scales of sufficient magnitude to test hypotheses. For example, to what extent did changing vegetation arising from climate change affect animal extinctions over the Late Pleistocene and early Holocene? How did vegetation communities influence the distribution and movements of ancient human societies? To what extent did climate, fire and grazing interact to alter these same vegetation communities, and what were the implications of these feedbacks on the taxa exploiting them for food and shelter? We are examining these questions through dynamic vegetation models. (collaborators: Hickler, Bird, Rowe)
Australia’s extinct megafauna, including Megalania — a 7-metre-long lizard, Diprotodon — a massive marsupial the size of a hippo, and Genyornis — a bird more than 4 times the size of an emu, are a source of fascination to children and adults alike. These ancient species are unlike any animal living in Australia (or anywhere) today. Indeed, Australia has few surviving megafauna — a group defined arbitrarily as animals with a body mass over 45 kg. This raises the questions: What happened to all these unique animals? And what determined which species became extinct and which survived? While many hypotheses for the drivers of megafauna extinctions have been suggested, the most likely contenders are human arrival in Australia and /or Late Pleistocene (126000 to 11700 years ago) climate change. It is, however, difficult to assess the role these factors played in megafauna extinctions, given the extinctions occurred over 40000 years ago. Researchers have attempted to find evidence of humans hunting Australian megafauna, as well as correlations between the timing of megafauna extinctions and human arrival, shifts in climate and vegetation change. Unfortunately, these efforts have not been able to isolate the driver(s) of Australia’s megafauna extinctions, and debate continues. If progress is to be made, new methods of addressing these questions are required.
Ecological network modelling is a method used to understand the interdependence of groups of organisms in an ecosystem. It involves modelling the flow of a biologically relevant currency, such as energy or a particular nutrient, through a system. Importantly, it can be used to model the effects of environmental change on an ecosystem. For example, ecological networks can be used to investigate the cascading effects of the addition of a new species (e.g., invasive species), the loss of a species, or changes in forcing functions (i.e., external factors) such as temperature and rainfall. Network modelling has been widely applied to marine systems, where it is used in resource management to guide the harvesting of fish and other marine organisms. This method can also be used to model ancient extinction events. However, network modelling has rarely been applied in this way. This research aims to use ecological network modelling to understand the late Pleistocene megafauna extinctions. This novel research will provide insight into the processes that could cause extinction patterns similar to those observed in the Late Pleistocene, helping us understand the drivers of megafauna extinction, and the processes responsible for determining the composition of Australia’s current biodiversity. (collaborators: Strona, Johnson, Stouffer)
Invasive species threaten ecosystems, the distributions of specific plant species, as well as agricultural production. Predicting the impact of climate change on the current and future distributions of these unwanted species forms an important category of ecological research. We aim to evaluate whether climate alteration might lead to spatial changes in the distribution and overlap of specific invasive species in Australia. Our goal is to understand how the number of selected invasive species changes under future warming scenarios, and to identify how these species could affect ongoing conservation efforts. (collaborators: Ahmadi)
Despite modern humans (Homo sapiens) being the only surviving representatives of the Hominin group, they coexisted in Eurasia from ~ 45 ka (ka = 1000 years) ago up until ~ 30 ka ago with Neanderthals (Homo neanderthalensis), sharing both morphological similarities and genetics. They inhabited mutual territories during almost 15 ka throughout the last cold episode of the Pleistocene (Marine Isotope Stage 3; ~ 60 to 25 ka) until Neanderthal populations disappeared entirely. It is unclear if and to what extent modern humans contributed to the demise of Neanderthals because the nature of these interactions with each other is still highly debated (i.e., cultural sharing, kinship, conflicts, etc.). This research evaluate the plausible causes of Neanderthal range shifts related to these questions.
We aim to identify the Neanderthal population timing of extinction across Eurasia during the Middle to Upper Palaeolithic transition (~ 120 ka to 25 ka) related to Homo sapiens colonisation and Marine Isotope Stage 3 climate changes. We are first identifying and quantifying changes in Neanderthal distribution until their extinction from archaeological data by defining their regional pattern and trajectories of extirpation (local extinction). To identify which factors (i.e., H. sapiens’ expansion and vegetation/climate changes) best correlate with it, we are mapping the regional timing of arrival of modern humans in Europe as model predictors along with climate variables. We are also building non-spatial and spatial demographic models for the overall Neanderthal population driven by temporal climate variability and modern human interactions to simulate Neanderthal abundance trajectories. (collaborators: Higham)
We are using remote units to record the calling behaviours of male frogs in the Riverlands region of South Australia. Together with environmental data, we are examining which conditions signal the reproductive readiness in male and female frogs. We are also developing laboratory experiments to measure tadpole development under different scenarios of temperature means and variability, as well as population viability models to inform the duration of environmental watering to maximise frog reproductive success in the Murray-Darling Basin. (collaborators: Ye, Wassens, Young)
We are predicting population size and trends, genetic structure and constraints, and environmental impacts of the South Australia mainland population of koalas to determine their fate in response to future climate and potential management interventions. (collaborators: Beheregaray, Johnson, Rogers, Burke Da Silva)
Maddie Thiele is leading this research programme for her PhD thesis. She is testing and development shark-bite mitigation measures and modelling the probability of shark bites under different management interventions. (collaborators: Huveneers)
Future child health under environmental and demographic change (Bradshaw)
We are modelling the impacts of environmental degradation and rising human densities on the probable implications of future child health. (collaborators: Le Souëf)
Palaeo-ecology of the Ediacaran biota (Bradshaw)
We are developing mathematical models for community-assembly rules for the first communities of metazoans. These fossil Ediacaran species (~ 550 million years old) are found in the Flinders Ranges of South Australia, and have astounding preservation of entire, intact communities. (collaborators: Droser, García-Bellido, Gehling, He)