This project will test the hypothesis that southern Africa came to acquire its unusually high average elevation-nearly all of it is above 1000 metres-30 million years ago when Africa stopped moving relative to the underlying mantle, and did not inherit its high elevation from the previously elevated super continent of Gondwana. Plate tectonics theory successfully explains how high mountain ranges form as a result of squeezing and thickening of the crust along converging plate boundaries (eg. Andes and Alps). It is less successful in explaining why extensive high plateaus exist in some continental regions far away from plate boundaries and unrelated to where plate boundaries existed in the geological past. The southern African plateau is the most significant of these 'topographic anomalies' on Earth-and is often referred to as the African superswell. While several different models have been proposed to explain the formation of the superswell, each suggests the high topography was formed at different times and at different rates. The most contentious of these ideas is that the first-order topography is not related to the break-up of Gondwana about 150 Myr ago but is much younger, less than 30 Myr, and is related to deeper mantle processes. Recent studies of the deep mantle have identified a region beneath southern Africa of hot, upward flowing mantle which originates close to the Earth's core. Some scientists now believe that it is this active flow that is literally pushing the Earth's surface upwards from below and is the cause of the unusually high elevation of southern Africa. This project will provide a definitive test of when the major topography of southern Africa was formed thus resolving a critical sticking point in understanding how continental topography evolves. We cannot test these models by precisely measuring when the surface uplift occurred because there is no direct evidence which enables us to reconstruct changes in elevation in the geological past. However, uplift of the surface at different times in the past would have caused an acceleration of erosion at these times as river gradients would have been steepened, especially around the edges of the uplifted region. Fortunately there are techniques which tell us about the history of erosion. These techniques provide a record of the temperatures that a rock experienced in the ancient geological past (over millions of years). This is relevant because when the Earth's surface erodes, rocks cool as they are brought up from deeper, hotter levels. The methods are based on measurement of the radioactive decay of U238 which occurs in trace amounts within the mineral apatite by two different processes; fission decay and alpha decay. Fission decay causes a 238U nucleus to split in two roughly equal parts which are rapidly repelled away from each other causing a linear zone or track of damage to the crystal lattice-we call these fission tracks. By counting the number of these tracks and measuring their lengths we can reconstruct the thermal history a rock has experienced because the track lengths are very sensitive to temperatures of 110-60 deg. C typical of the shallow crust. Alpha decay results in ejection of Helium nuclei, we call these alpha particles, from the 238U nucleus. By carefully measuring the amount of Helium gas that has accumulated within a grain of apatite we can determine how a rock has cooled from temperatures of c. 70-40 deg. C to its present temperature. Combined these techniques provide a powerful tool for measuring the deep erosion of continental topography over geological time scales. In this project we will analyse samples from deep bore holes across southern Africa and once we know the rocks' past temperatures and relate it to the depth at which those temperatures occurred in the crust, we can accurately determine when, and how much of, the land surface has eroded and hence resolve when the topography was created.

Determining the prevalence of natural selection (including the presence of deleterious and favourable variants) from genome sequence data is a major challenge in evolutionary genetics. A sizeable number of species in nature are hermaphrodites capable of self-fertilisation, where individuals produce both female and male gametes that can be used to reproduce. Emerging genome data from such species has yielded unusual selection signatures that cannot be explained by classic predictions, which assume selection acts on local genetic regions. Genetic variation is inherited as large linked regions in self-fertilising species, which can decrease diversity and cause linked selection to act over longer genetic distances. Yet punctuated regions of diversity also exist. SelectSelf will develop theoretical and genome-inference methods to determine how different selective forces interact with this reproductive mode. Work plan 1 will develop models and methods to establish the causes of punctuated diversity (balancing selection, introgression, exposure of deleterious mutations, or residual outcrossing) in self-fertilising species. Work plan 2 will investigate to what extent adaptation by a polygenic trait will lead to long-range selective sweeps and quantify the effect of pleiotropy on this process. Work plan 3 will quantify how the distribution of deleterious mutations are affected by linked selection due to either of these evolutionary mechanisms. Throughout, new methods and theory will be applied to data from Caenorhabditis species to infer the evolutionary impacts of hyperdiversity and linked selection in self-fertilising nematodes. This project will provide a step-change in knowledge of how natural selection and reproduction interact to determine how species persist in natural environments, resulting in new standards for analysing and interpreting genetic data from self-fertilising species.

Insects are the most abundant and diverse terrestrial animals on the planet, yet few are capable of surviving in Antarctica's inhospitable climate. Genetic evidence indicates that Antarctic insects, as well as other terrestrial arthropods, have persisted throughout the repeated glaciation events of the Pleistocene and earlier. Thus, these species are ideal test cases for modeling the biogeography of terrestrial Antarctica and evolutionary responses to changing environments. The midge Belgica antarctica is perhaps the best studied Antarctic terrestrial arthropod in terms of physiology and genetics. This species is the southernmost free-living insect, and we recently participated in sequencing the genome and transcriptome of this species. However, a lack of information from closely related species has hindered our ability to pinpoint the precise evolutionary mechanisms that permit survival in Antarctica. In this proposal, we establish an international collaboration with scientists from the US, UK, France, and Chile to expand physiological and genomic research of Antarctic and sub-Antarctic midges. In addition to B. antarctica, our project focuses on Eretmoptera murphyi, a sub-Antarctic endemic that has invaded the maritime Antarctic, Halirytus magellanicus, a strictly Magellanic sub-Antarctic species endemic to Tierra del Fuego, and B. albipes, a sub-Antarctic species found on Crozet Island in the Indian Ocean. These four species are closely related and span an environmental gradient from sub-Antarctic to Antarctic habitats. Our central hypothesis is that shared mechanisms drive both population-level adaptation to local environmental conditions and macroevolutionary changes that permit a select few insects to tolerate Antarctic climates. Our Specific Aims are 1) Characterize conserved and species-specific adaptations to extreme environments through comparative physiology and transcriptomics, 2) Comparative genomics of Antarctic and sub-Antarctic midges to identify macroevolutionary signatures of Antarctic adaptation, and 3) Investigate patterns of diversification and location adaptation using population genomics. Our Broader Impacts include deploying an education professional with our research team to coordinate outreach and continuing our partnership with a Kentucky non-profit focused on K-12 STEM programming.

In many areas of engineering, materials suffer deformation at high rates. This is the case when structures undergo impact, crash, blast, etc. but also in material forming like stamping or machining for instance. Therefore, it is essential for design engineers to have reliable mechanical models to predict the behaviour of the materials in such applications. This is enhanced by the spectacular progress in numerical simulation which now enables to perform detailed computations of very complex situations. However, robust experimental identification of refined high strain rate deformation models is lagging behind and hinders the delivery of the full potential of numerical simulations for the benefit of society: safer infrastructures (buildings, bridges, dams), safer means of transportation (crashworthiness of vehicles) etc. Indeed, in order to perform experimental identification of high strain rate material models, engineers only have a very limited toolbox based on test procedures developed decades ago. The best example is the so-called Split Hopkinson Pressure Bar (SHPB) which has proved extremely useful but has important intrinsic limitations due to the stringent assumptions required to process the test data. These assumptions are the consequence of the very limited instrumentation for which such tests were developed, usually a few strain gauge readings for the standard SHPB set-up. The recent advent of full-field deformation measurements using imaging techniques has allowed novel approaches to be developed and exciting new testing procedures to be imagined for the first time. The objective of the present project is to lay the foundations of a new era in dynamic testing of materials based on the availability of digital imaging technology to provide full-field deformation measurements at very high speeds. One can then use this information in conjunction with efficient numerical inverse identification tools such as the Virtual Fields Method to design novel test procedures to identify material parameters at high rates. The underpinning novelty is to exploit the inertial effects developed in high strain rate load. These have hitherto been regarded as undesirable in conventional testing. However, in the identification process they can play the role of a volume distributed load cell for which readings are embedded in the full-field deformation measurements. The idea is ground breaking as it has the potential to lift the current major limitations of high strain rate test, i.e. small specimen and constant velocity. The present proposal aims at providing a platform for the applicant to develop this methodology for many different types of situations in terms of materials, loading configuration and strain rate range. The project has the potential to revolutionize high strain rate testing of materials and hence enhance our knowledge of material behaviour. This will in turn benefit many sectors of engineering and society in the long term.

This project addresses how environmental change affects the movement of sediment through rivers and into our oceans. Understanding the movement of suspended sediment is important because it is a vector for nutrients and pollutants, and because sediment also creates floodplains and nourishes deltas and beaches, affording resilience to coastal zones. To develop our understanding of sediment flows, we will quantify recent variations (1985-present) in sediment loads for every river on the planet with a width greater than 90 metres. We will also project how these river sediment loads will change into the future. These goals have not previously been possible to achieve because direct measurements of sediment transport through rivers have only ever been made on very few (<10% globally) rivers. We are proposing to avoid this difficulty by using a 35+ years of archive of freely available satellite imagery. Specifically, we will use the cloud-based Google Earth Engine to automatically analyse each satellite image for its surface reflectance, which will enable us to estimate the concentration of sediment suspended near the surface of rivers. In conjunction with other methods that characterise the flow and the mixing of suspended sediment through the water column, these new estimates of surface Suspended Sediment Concentration (SSC) will be used to calculate the total movement of suspended sediment through rivers. We then analyse our new database (which, with a five orders of magnitude gain in spatial resolution relative to the current state-of-the-art, will be unprecedented in its size and global coverage) of suspended sediment transport using novel Machine Learning techniques, within a Bayesian Network framework. This analysis will allow us to link our estimates of sediment transport to their environmental controls (such as climate, geology, damming, terrain), with the scale of the empirical analysis enabling a step-change to be obtained in our understanding of the factors driving sediment movement through the world's rivers. In turn, this will allow us to build a reliable model of sediment movement, which we will apply to provide a comprehensive set of future projections of sediment movement across Earth to the oceans. Such future projections are vital because the Earth's surface is undergoing a phase of unprecedented change (e.g., through climate change, damming, deforestation, urbanisation, etc) that will likely drive large transitions in sediment flux, with major and wide reaching potential impacts on coastal and delta systems and populations. Importantly, we will not just quantify the scale and trajectories of change, but we will also identify how the relative contributions of anthropogenic, climatic and land cover processes drive these shifts into the future. This will allow us to address fundamental science questions relating to the movement of sediment through Earth's rivers to our oceans, such as: 1. What is the total contemporary sediment flux from the continents to the oceans, and how does this total vary spatially and seasonally? 2. What is the relative influence of climate, land use and anthropogenic activities in governing suspended sediment flux and how have these roles changed? 3. How do physiographic characteristics (area, relief, connectivity, etc.) amplify or dampen sediment flux response to external (climate, land use, damming, etc) drivers of change and thus condition the overall response, evolution and trajectory of sediment flux in different parts of the world? 4. To what extent is the flux of sediment driven by extreme runoff generating events (e.g. Tropical Cyclones) versus more common, lower magnitude events? How will projected changes in storm frequency and magnitude affect the world's sediment fluxes in the future? 5. How will the global flux of sediment to the oceans change over the course of the 21st century under a range of plausible future environmental change scenarios?