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Consumer behaviour changes and strategic management decisions are driving adaptations in manufacturing routines. Based on the theory of situational strength, we investigated how contextual and person-related factors influence workers’ adaptation in a two-worker position routine. Contextual factors, like retrieval cues (Study 1), time pressure (Study 2), and convenience (Study 3), were varied. Person-related factors included retentivity, general and routine-specific self-efficacy, and perceived adaptation costs. Dependent variables included various error types and production time before and after adaptation. In each study, 148 participants were trained in a production routine at t1 and executed an adapted routine at t2, one week later. Repeated measures ANOVA for performance at t1 and t2, and MANOVA for performance at t2, revealed that time increased for all groups at t2. For participants in Studies 1 & 2, error rates remained consistent. Retentivity significantly impacted errors at both t1 and t2, emphasising that routine changes in a ‘running business’ take time, regardless of contextual factors. Workers with lower retentivity may require additional support.
This systematic literature review highlights the gap in demand forecasting in the manufacturing sector, which is challenged by complex supply chains and rapid market change. Traditional methods fall short in this dynamic environment, highlighting the need for an approach that combines advanced forecasting techniques, high-quality data, and industry-specific insights. Our research contributes by evaluating advanced forecasting methods, the effectiveness of AI and data strategies to improve accuracy. Our analysis reveals a shift towards machine learning and deep learning to improve accuracy and highlights the untapped potential of external data sources. Key findings provide both researchers and practitioners with guidance on effective forecasting strategies and key data types and offer an integrated framework for improving forecasting accuracy and strategic decision-making in manufacturing. This work fills a critical research gap and provides stakeholders with actionable insights to manage the complexity of modern manufacturing, representing a significant advance in forecasting practice.
Without fear or favour
(2024)
Learning in virtual, immersive environments must be well-designed to foster learning instead of overwhelming and distracting the learner. So far, learning instructions based on cognitive load theory recommend keeping the learning instructions clean and simple to reduce the extraneous cognitive load of the learner to foster learning performance. The advantages of immersive learning, such as multiple options for realistic simulation, movement and feedback, raise questions about the tension between an increase of excitement and flow with highly realistic environments on the one hand and a reduction of cognitive load by developing clean and simple surroundings on the other hand. This study aims to gain insights into learners' cognitive responses during the learning process by continuously assessing cognitive load through eye-tracking. The experiment compares two distinct immersive learning environments and varying methods of content presentation.
We study the effect of energy and transport policies on pollution in two developing country cities. We use a quantitative equilibrium model with choice of housing, energy use, residential location, transport mode, and energy technology. Pollution comes from commuting and residential energy use. The model parameters are calibrated to replicate key variables for two developing country cities, Maputo, Mozambique, and Yogyakarta, Indonesia. In the counterfactual simulations, we study how various transport and energy policies affect equilibrium pollution. Policies may induce rebound effects from increasing residential energy use or switching to high emission modes or locations. In general, these rebound effects tend to be largest for subsidies to public transport or modern residential energy technology.
Migrant integration is a prime example of intergovernmental coordination and multilevel governance; first because no level of government can carry out this task alone, and second because its cross-cutting nature often leads to fragmented institutional structures that must be overcome. Within the research strand of intergovernmental relations (IGR), the focus has been on executive actors and governmental decision-makers, resulting in an underexposure of the role of public administration, known as inter-administrative relations (IAR). Against this backdrop, we aim to remedy some of the deficits in IGR research by (1) adopting an explicit IAR perspective which systematically addresses the role of local governments; (2) including a comparative dimension in IAR research that accounts for different administrative ‘starting conditions’ in European countries; and (3) using the policy area of migrant integration as a case in point to empirically investigate developments of institutional convergence and divergence in IAR patterns. It is argued that the coordination of migrant integration in the three countries examined has moved towards more intergovernmental coordination, on the one hand, and that the role of municipalities in this context has been enhanced—varying degrees of (de-)centralization notwithstanding. While certain convergent patterns of inter-governmental coordination have become apparent during the migration crisis, historical path dependencies and administrative cultures still appear to be factors that influence institutional development.
Urban climate strategies have become central tools for steering climate policy in cities. Local policymakers must coordinate a wide range of actors, among them sub-municipal administrative units and neighbouring administrations, in order to ensure legitimate, socially accepted and effective policy. The study examines, from a comparative perspective, how intergovernmental relations (IGR) play out in the formulation and implementation of climate strategies in the metropolitan areas of Berlin and Paris. Embedded in different institutional contexts, both cities followed a trajectory initiated by relatively centralized strategy formulation with an ongoing shift towards more decentralized and coordinated intergovernmental approaches with their respective district administrations. In terms of horizontal IGR, Berlin took a decoupled approach with limited coordination with the state of Brandenburg, whereas Paris was much more closely integrated with its surrounding areas through the inter-municipal metropolis of Greater Paris. Institutional capacity, multilevel coordination and participation demands are identified as three challenges for the existing IGR structures. Addressing these challenges places significant strains on local administrative capacity. The findings highlight the limitations of centralized approaches to IGR at the local level and the importance of aligning the distribution of functional responsibilities with the rights of consultation and participation in climate policy formulation processes.
This open access book assesses the consequences of contemporary economic and political crises for intergovernmental relations in Europe. Focusing on the crises arising from the Covid-19 pandemic, climate change, surges in migration, and the resurgence of regional nationalist movements, it explores the shifting power balances within intergovernmental relations’ systems. The book takes a comparative analytical perspective on how intergovernmental relations are changing across Europe, and how central governments have responded to coordination challenges as recent crises have disrupted established service delivery chains and their underpinning political and bureaucratic arrangements. It also examines the relationship between recent crises and the sub-national resurgence of territorial politics in many European countries. The book will appeal to those with interests in public administration, sub-national governance and European politics.
In 2015, German Chancellor Angela Merkel decided to allow over a million asylum seekers to cross the border into Germany. One key concern was that her decision would signal an open-door policy to aspiring migrants worldwide – thus further increasing migration to Germany and making the country permanently more attractive to irregular and humanitarian migrants. This ‘pull-effect’ hypothesis has been a mainstay of policy discussions ever since. With the continued global rise in forced displacement, not appearing welcoming to migrants has become a guiding principle for the asylum policy of many large receiving countries. In this article, we exploit the unique case study that Merkel's 2015 decision provides for answering the fundamental question of whether welcoming migration policies have sustained effects on migration towards destination countries. We analyze an extensive range of data on migration inflows, migration aspirations and online search interest between 2000 and 2020. The results reject the ‘pull effect’ hypothesis while reaffirming states’ capacity to adapt to changing contexts and regulate migration.
The field of healthcare is characterized by constant innovation, with gender-specific medicine emerging as a new subfield that addresses sex and gender disparities in clinical manifestations, outcomes, treatment, and prevention of disease. Despite its importance, the adoption of gender-specific medicine remains understudied, posing potential risks to patient outcomes due to a lack of awareness of the topic. Building on the Innovation Decision Process Theory, this study examines the spread of information about gender-specific medicine in online networks. The study applies social network analysis to a Twitter dataset reflecting online discussions about the topic to gain insights into its adoption by health professionals and patients online. Results show that the network has a community structure with limited information exchange between sub-communities and that mainly medical experts dominate the discussion. The findings suggest that the adoption of gender-specific medicine might be in its early stages, focused on knowledge exchange. Understanding the diffusion of gender-specific medicine among medical professionals and patients may facilitate its adoption and ultimately improve health outcomes.
In the aftermath of the Shoah and the ostensible triumph of nationalism, it became common in historiography to relegate Jews to the position of the “eternal other” in a series of binaries: Christian/Jewish, Gentile/Jewish, European/Jewish, non-Jewish/Jewish, and so forth. For the longest time, these binaries remained characteristic of Jewish historiography, including in the Central European context. Assuming instead, as the more recent approaches in Habsburg studies do, that pluriculturalism was the basis of common experience in formerly Habsburg Central Europe, and accepting that no single “majority culture” existed, but rather hegemonies were imposed in certain contexts, then the often used binaries are misleading and conceal the complex and sometimes even paradoxical conditions that shaped Jewish life in the region before the Shoah.
The very complexity of Habsburg Central Europe both in synchronic and diachronic perspective precludes any singular historical narrative of “Habsburg Jewry,” and it is not the intention of this volume to offer an overview of “Habsburg Jewish history.” The selected articles in this volume illustrate instead how important it is to reevaluate categories, deconstruct historical narratives, and reconceptualize implemented approaches in specific geographic, temporal, and cultural contexts in order to gain a better understanding of the complex and pluricultural history of the Habsburg Empire and the region as a whole.
Assessing the impact of global change on hydrological systems is one of the greatest hydrological challenges of our time. Changes in land cover, land use, and climate have an impact on water quantity, quality, and temporal availability. There is a widespread consensus that, given the far-reaching effects of global change, hydrological systems can no longer be viewed as static in their structure; instead, they must be regarded as entire ecosystems, wherein hydrological processes interact and coevolve with biological, geomorphological, and pedological processes. To accurately predict the hydrological response under the impact of global change, it is essential to understand this complex coevolution. The knowledge of how hydrological processes, in particular the formation of subsurface (preferential) flow paths, evolve within this coevolution and how they feed back to the other processes is still very limited due to a lack of observational data.
At the hillslope scale, this intertwined system of interactions is known as the hillslope feedback cycle. This thesis aims to enhance our understanding of the hillslope feedback cycle by studying the coevolution of hillslope structure and hillslope hydrological response. Using chronosequences of moraines in two glacial forefields developed from siliceous and calcareous glacial till, the four studies shed light on the complex coevolution of hydrological, biological, and structural hillslope properties, as well as subsurface hydrological flow paths over an evolutionary period of 10 millennia in these two contrasting geologies. The findings indicate that the contrasting properties of siliceous and calcareous parent materials lead
to variations in soil structure, permeability, and water storage. As a result, different plant species and vegetation types are favored on siliceous versus calcareous parent material, leading to diverse ecosystems with distinct hydrological dynamics. The siliceous parent material was found to show a higher activity level in driving the coevolution. The soil pH resulting from parent material weathering emerges as a crucial factor, influencing vegetation development, soil formation, and consequently, hydrology. The acidic weathering of the siliceous parent material favored the accumulation of organic matter, increasing the soils’ water storage capacity and attracting acid-loving shrubs, which further promoted organic matter accumulation and ultimately led to podsolization after 10 000 years. Tracer experiments revealed that the subsurface flow path evolution was influenced by soil and vegetation development, and vice versa. Subsurface flow paths changed from vertical, heterogeneous matrix flow to finger-like flow paths over a few hundred years, evolving into macropore flow, water storage, and lateral subsurface flow after several thousand years. The changes in flow paths among younger age classes were driven by weathering processes altering soil structure, as well as by vegetation development and root activity. In the older age
class, the transition to more water storage and lateral flow was attributed to substantial organic matter accumulation and ongoing podsolization. The rapid vertical water transport in the finger-like flow paths, along with the conductive sandy material, contributed to podsolization and thus to the shift in the hillslope hydrological response.
In contrast, the calcareous site possesses a high pH buffering capacity, creating a neutral to basic environment with relatively low accumulation of dead organic matter, resulting in a lower water storage capacity and the establishment of predominantly grass vegetation. The coevolution was found to be less dynamic over the millennia. Similar to the siliceous site, significant changes in subsurface flow paths occurred between the young age classes. However, unlike the siliceous site, the subsurface flow paths at the calcareous site only altered in shape and not in direction. Tracer experiments showed that flow paths changed from vertical, heterogeneous matrix flow to vertical, finger-like flow paths after a few hundred to thousands of years, which was driven by root activities and weathering processes. Despite having a finer soil texture, water storage at the calcareous site was significantly lower than at the siliceous site, and water transport remained primarily rapid and vertical, contributing to the flourishing of grass vegetation.
The studies elucidated that changes in flow paths are predominantly shaped by the characteristics of the parent material and its weathering products, along with their complex interactions with initial water flow paths and vegetation development. Time, on the other hand, was not found to be a primary factor in describing the evolution of the hydrological response. This thesis makes a valuable contribution to closing the gap in the observations of the coevolution of hydrological processes within the hillslope feedback cycle, which is important to improve predictions of hydrological processes in changing landscapes. Furthermore, it emphasizes the importance of interdisciplinary studies in addressing the hydrological challenges arising from global change.
The plant cell wall plays several crucial roles during plant development with its integrity acting as key signalling component for growth regulation during biotic and abiotic stresses. Cellulose microfibrils, the principal load-bearing components is the major component of the primary cell wall, whose synthesis is mediated by microtubule-associated CELLULOSE SYNTHASE (CESA) COMPLEXES (CSC). Previous studies have shown that CSC interacting proteins COMPANION OF CELLULOSE SYNTHASE (CC) facilitate sustained cellulose synthesis during salt stress by promoting repolymerization of cortical microtubules. However, our understanding of cellulose synthesis during salt stress remains incomplete.
In this study, a pull-down of CC1 protein led to the identification of a novel interactor, termed LEA-like. Phylogenetic analysis revealed that LEA-like belongs to the LATE EMBRYOGENESIS ABUNDANT (LEA) protein family, specifically to the LEA_2 subgroup, showing a close relationship with the CC proteins. Roots of the double mutants lea-like and its closest homolog emb3135 exhibited hypersensitivity when grown on cellulose synthesis inhibitors. Further analysis of higher-order mutants of lea-like, emb3135, and cesa6 demonstrated a genetic interaction between them indicating a significant role in cellulose synthesis.
Live-cell imaging revealed that both LEA-like and EMB3135 migrated with the CSC at the plasma membrane along microtubule tracks in control and oryzalin-treated conditions which destabilize microtubules, suggesting a tight interaction. Investigation of fluorescently labeled lines of different domains of the LEA-like protein revealed that the N-terminal cytosolic domain of LEA-like colocalizes with microtubules, suggesting a physical association between the two.
Considering the established role of LEA proteins in abiotic stress tolerance, we performed phenotypic analysis of the mutant under various stresses. Growth of double mutants of lea-like and emb3135 on NaCl containing media resulted in swelling of root cell indicating a putative role in salt stress tolerance. Supportive of this the quadruple mutant, lacking LEA-like, EMB3135, CC1, and CC2 proteins, exhibited a severe root growth defect on NaCl media compared to control conditions. Live-cell imaging revealed that under salt stress, the LEA-like protein forms aggregates in the plasma membrane.
In conclusion, this study has unveiled two novel interactors of the CSC that act with the CC proteins that regulate plant growth in response to salt stress providing new insights into the intricate regulation of cellulose synthesis, particularly under such conditions.
Hardy inequalities on graphs
(2024)
The dissertation deals with a central inequality of non-linear potential theory, the Hardy inequality. It states that the non-linear energy functional can be estimated from below by a pth power of a weighted p-norm, p>1. The energy functional consists of a divergence part and an arbitrary potential part. Locally summable infinite graphs were chosen as the underlying space. Previous publications on Hardy inequalities on graphs have mainly considered the special case p=2, or locally finite graphs without a potential part.
Two fundamental questions now arise quite naturally: For which graphs is there a Hardy inequality at all? And, if it exists, is there a way to obtain an optimal weight? Answers to these questions are given in Theorem 10.1 and Theorem 12.1. Theorem 10.1 gives a number of characterizations; among others, there is a Hardy inequality on a graph if and only if there is a Green's function. Theorem 12.1 gives an explicit formula to compute optimal Hardy weights for locally finite graphs under some additional technical assumptions. Examples show that Green's functions are good candidates to be used in the formula.
Emphasis is also placed on illustrating the theory with examples. The focus is on natural numbers, Euclidean lattices, trees and star graphs. Finally, a non-linear version of the Heisenberg uncertainty principle and a Rellich inequality are derived from the Hardy inequality.
Laser induced switching offers an attractive possibility to manipulate small magnetic domains for prospective memory and logic devices on ultrashort time scales. Moreover, optical control of magnetization without high applied magnetic fields allows manipulation of magnetic domains individually and locally, without expensive heat dissipation. One of the major challenges for developing novel optically controlled magnetic memory and logic devices is reliable formation and annihilation of non-volatile magnetic domains that can serve as memory bits in ambient conditions. Magnetic skyrmions, topologically nontrivial spin textures, have been studied intensively since their discovery due to their stability and scalability in potential spintronic devices. However, skyrmion formation and, especially, annihilation processes are still not completely understood and further investigation on such mechanisms are needed. The aim of this thesis is to contribute to better understanding of the physical processes behind the optical control of magnetism in thin films, with the goal of optimizing material parameters and methods for their potential use in next generation memory and logic devices.
First part of the thesis is dedicated to investigation of all-optical helicity-dependent switching (AO-HDS) as a method for magnetization manipulation. AO-HDS in Co/Pt multilayer and CoFeB alloys with and without the presence of Dzyaloshinskii-Moriya interaction (DMI), which is a type of exchange interaction, have been investigated by magnetic imaging using photo-emission electron microscopy (PEEM) in combination with X-ray magnetic circular dichroism (XMCD). The results show that in a narrow range of the laser fluence, circularly polarized laser light induces a drag on domain walls. This enables a local deterministic transformation of the magnetic domain pattern from stripes to bubbles in out-of-plane magnetized Co/Pt multilayers, only controlled by the helicity of ultrashort laser pulses. The temperature and characteristic fields at which the stripe-bubble transformation occurs has been calculated using theory for isolated magnetic bubbles, using as parameters experimentally determined average size of stripe domains and the magnetic layer thickness.
The second part of the work aims at purely optical formation and annihilation of magnetic skyrmions by a single laser pulse. The presence of a skyrmion phase in the investigated CoFeB alloys was first confirmed using a Kerr microscope. Then the helicity-dependent skyrmion manipulation was studied using AO-HDS at different laser fluences. It was found that formation or annihilation individual skyrmions using AO-HDS is possible, but not always reliable, as fluctuations in the laser fluence or position can easily overwrite the helicity-dependent effect of AO-HDS. However, the experimental results and magnetic simulations showed that the threshold values for the laser fluence for the formation and annihilation of skyrmions are different. A higher fluence is required for skyrmion formation, and existing skyrmions can be annihilated by pulses with a slightly lower fluence. This provides a further option for controlling formation and annihilation of skyrmions using the laser fluence. Micromagnetic simulations provide additional insights into the formation and annihilation mechanism.
The ability to manipulate the magnetic state of individual skyrmions is of fundamental importance for magnetic data storage technologies. Our results show for the first time that the optical formation and annihilation of skyrmions is possible without changing the external field. These results enable further investigations to optimise the magnetic layer to maximise the energy gap between the formation and annihilation barrier. As a result, unwanted switching due to small laser fluctuations can be avoided and fully deterministic optical switching can be achieved.
Cities and other human settlements are major contributors to climate change and are highly vulnerable to its impacts. They are also uniquely positioned to reduce greenhouse gas emissions and lead adaptation efforts. These compound challenges and opportunities require a comprehensive perspective on the public policy of human settlements. Drawing on core literature that has driven debate around cities and climate over recent decades, we put forward a set of boundary objects that can be applied to connect the knowledge of epistemic communities and support an integrated urbanism. We then use these boundary objects to develop the Goals-Intervention-Stakeholder-Enablers (GISE) framework for a public policy of human settlements that is both place-specific and provides insights and tools useful for climate action in cities and other human settlements worldwide. Using examples from Berlin, we apply this framework to show that climate mitigation and adaptation, public health, and well-being goals are closely linked and mutually supportive when a comprehensive approach to urban public policy is applied.
The global drylands cover nearly half of the terrestrial surface and are home to more than two billion people. In many drylands, ongoing land-use change transforms near-natural savanna vegetation to agricultural land to increase food production. In Southern Africa, these heterogenous savanna ecosystems are also recognized as habitats of many protected animal species, such as elephant, lion and large herds of diverse herbivores, which are of great value for the tourism industry. Here, subsistence farmers and livestock herder communities often live in close proximity to nature conservation areas. Although these land-use transformations are different regarding the future they aspire to, both processes, nature conservation with large herbivores and agricultural intensification, have in common, that they change the vegetation structure of savanna ecosystems, usually leading to destruction of trees, shrubs and the woody biomass they consist of.
Such changes in woody vegetation cover and biomass are often regarded as forms of land degradation and forest loss. Global forest conservation approaches and international programs aim to stop degradation processes, also to conserve the carbon bound within wood from volatilization into earth’s atmosphere. In search for mitigation options against global climate change savannas are increasingly discussed as potential carbon sinks. Savannas, however, are not forests, in that they are naturally shaped by and adapted to disturbances, such as wildfires and herbivory. Unlike in forests, disturbances are necessary for stable, functioning savanna ecosystems and prevent these ecosystems from forming closed forest stands. Their consequently lower levels of carbon storage in woody vegetation have long been the reason for savannas to be overlooked as a potential carbon sink but recently the question was raised if carbon sequestration programs (such as REDD+) could also be applied to savanna ecosystems. However, heterogenous vegetation structure and chronic disturbances hamper the quantification of carbon stocks in savannas, and current procedures of carbon storage estimation entail high uncertainties due to methodological obstacles. It is therefore challenging to assess how future land-use changes such as agricultural intensification or increasing wildlife densities will impact the carbon storage balance of African drylands.
In this thesis, I address the research gap of accurately quantifying carbon storage in vegetation and soils of disturbance-prone savanna ecosystems. I further analyse relevant drivers for both ecosystem compartments and their implications for future carbon storage under land-use change. Moreover, I show that in savannas different carbon storage pools vary in their persistence to disturbance, causing carbon bound in shrub vegetation to be most likely to experience severe losses under land-use change while soil organic carbon stored in subsoils is least likely to be impacted by land-use change in the future.
I start with summarizing conventional approaches to carbon storage assessment and where and for which reasons they fail to accurately estimated savanna ecosystem carbon storage. Furthermore, I outline which future-making processes drive land-use change in Southern Africa along two pathways of land-use transformation and how these are likely to influence carbon storage. In the following chapters, I propose a new method of carbon storage estimation which is adapted to the specific conditions of disturbance-prone ecosystems and demonstrate the advantages of this approach in relation to existing forestry methods. Specifically, I highlight sources for previous over- and underestimation of savanna carbon stocks which the proposed methodology resolves. In the following chapters, I apply the new method to analyse impacts of land-use change on carbon storage in woody vegetation in conjunction with the soil compartment. With this interdisciplinary approach, I can demonstrate that indeed both, agricultural intensification and nature conservation with large herbivores, reduce woody carbon storage above- and belowground, but partly sequesters this carbon into the soil organic carbon stock. I then quantify whole-ecosystem carbon storage in different ecosystem compartments (above- and belowground woody carbon in shrubs and trees, respectively, as well as topsoil and subsoil organic carbon) of two savanna vegetation types (scrub savanna and savanna woodland). Moreover, in a space-for-time substitution I analyse how land-use changes impact carbon storage in each compartment and in the whole ecosystem. Carbon storage compartments are found to differ in their persistence to land-use change with carbon bound in shrub biomass being least persistent to future changes and subsoil organic carbon being most stable under changing land-use. I then explore which individual land-use change effects act as drivers of carbon storage through Generalized Additive Models (GAMs) and uncover non-linear effects, especially of elephant browsing, with implications for future carbon storage. In the last chapter, I discuss my findings in the larger context of this thesis and discuss relevant implications for land-use change and future-making decisions in rural Africa.
Resolving the evolutionary history of two hippotragin antelopes using archival and ancient DNA
(2024)
African antelopes are iconic but surprisingly understudied in terms of their genetics, especially when it comes to their evolutionary history and genetic diversity. The age of genomics provides an opportunity to investigate evolution using whole nuclear genomes. Decreasing sequencing costs enable the recovery of multiple loci per genome, giving more power to single specimen analyses and providing higher resolution insights into species and populations that can help guide conservation efforts. This age of genomics has only recently begun for African antelopes. Many African bovids have a declining population trend and hence, are often endangered. Consequently, contemporary samples from the wild are often hard to collect. In these cases, ex situ samples from contemporary captive populations or in the form of archival or ancient DNA (aDNA) from historical museum or archaeological/paleontological specimens present a great research opportunity with the latter two even offering a window to information about the past. However, the recovery of aDNA is still considered challenging from regions with prevailing climatic conditions that are deemed adverse for DNA preservation like the African continent. This raises the question if DNA recovery from fossils as old as the early Holocene from these regions is possible.
This thesis focuses on investigating the evolutionary history and genetic diversity of two species: the addax (Addax nasomaculatus) and the blue antelope (Hippotragus leucophaeus). The addax is critically endangered and might even already be extinct in the wild, while the blue antelope became extinct ~1800 AD, becoming the first extinct large African mammal species in historical times. Together, the addax and the blue antelope can inform us about current and past extinction events and the knowledge gained can help guide conservation efforts of threatened species. The three studies used ex situ samples and present the first nuclear whole genome data for both species. The addax study used historical museum specimens and a contemporary sample from a captive population. The two studies on the blue antelope used mainly historical museum specimens but also fossils, and resulted in the recovery of the oldest paleogenome from Africa at that time.
The aim of the first study was to assess the genetic diversity and the evolutionary history of the addax. It found that the historical wild addax population showed only limited phylogeographic structuring, indicating that the addax was a highly mobile and panmictic population and suggesting that the current European captive population might be missing the majority of the historical mitochondrial diversity. It also found the nuclear and mitochondrial diversity in the addax to be rather low compared to other wild ungulate species. Suggestions on how to best save the remaining genetic diversity are presented. The European zoo population was shown to exhibit no or only minor levels of inbreeding, indicating good prospects for the restoration of the species in the wild. The trajectory of the addax’s effective population size indicated a major bottleneck in the late Pleistocene and a low effective population size well before recent human impact led to the species being critically endangered today.
The second study set out to investigate the identities of historical blue antelope specimens using aDNA techniques. Results showed that six out of ten investigated specimens were misidentified, demonstrating the blue antelope to be one of the scarcest mammal species in historical natural history collections, with almost no bone reference material. The preliminary analysis of the mitochondrial genomes suggested a low diversity and hence low population size at the time of the European colonization of southern Africa.
Study three presents the results of the analyses of two blue antelope nuclear genomes, one ~200 years old and another dating to the early Holocene, 9,800–9,300 cal years BP. A fossil-calibrated phylogeny dated the divergence time of the three historically extant Hippotragus species to ~2.86 Ma and demonstrated the blue and the sable antelope (H. niger) to be sister species. In addition, ancient gene flow from the roan (H. equinus) into the blue antelope was detected. A comparison with the roan and the sable antelope indicated that the blue antelope had a much lower nuclear diversity, suggesting a low population size since at least the early Holocene. This concurs with findings from the fossil record that show a considerable decline in abundance after the Pleistocene–Holocene transition. Moreover, it suggests that the blue antelope persisted throughout the Holocene regardless of a low population size, indicating that human impact in the colonial era was a major factor in the blue antelope’s extinction.
This thesis uses aDNA analyses to provide deeper insights into the evolutionary history and genetic diversity of the addax and the blue antelope. Human impact likely was the main driver of extinction in the blue antelope, and is likely the main factor threatening the addax today. This thesis demonstrates the value of ex situ samples for science and conservation, and suggests to include genetic data for conservation assessments of species. It further demonstrates the beneficial use of aDNA for the taxonomic identification of historically important specimens in natural history collections. Finally, the successful retrieval of a paleogenome from the early Holocene of Africa using shotgun sequencing shows that DNA retrieval from samples of that age is possible from regions generally deemed unfavorable for DNA preservation, opening up new research opportunities. All three studies enhance our knowledge of African antelopes, contributing to the general understanding of African large mammal evolution and to the conservation of these and similarly threatened species.
State space models enjoy wide popularity in mathematical and statistical modelling across disciplines and research fields. Frequent solutions to problems of estimation and forecasting of a latent signal such as the celebrated Kalman filter hereby rely on a set of strong assumptions such as linearity of system dynamics and Gaussianity of noise terms.
We investigate fallacy in mis-specification of the noise terms, that is signal noise
and observation noise, regarding heavy tailedness in that the true dynamic frequently produces observation outliers or abrupt jumps of the signal state due to realizations of these heavy tails not considered by the model. We propose a formalisation of observation noise mis-specification in terms of Huber’s ε-contamination as well as a computationally cheap solution via generalised Bayesian posteriors with a diffusion Stein divergence loss resulting in the diffusion score matching Kalman filter - a modified algorithm akin in complexity to the regular Kalman filter. For this new filter interpretations of novel terms, stability and an ensemble variant are discussed. Regarding signal noise mis-specification, we propose a formalisation in the frame work of change point detection and join ideas from the popular CUSUM algo-
rithm with ideas from Bayesian online change point detection to combine frequent reliability constraints and online inference resulting in a Gaussian mixture model variant of multiple Kalman filters. We hereby exploit open-end sequential probability ratio tests on the evidence of Kalman filters on observation sub-sequences for aggregated inference under notions of plausibility.
Both proposed methods are combined to investigate the double mis-specification problem and discussed regarding their capabilities in reliable and well-tuned uncertainty quantification. Each section provides an introduction to required terminology and tools as well as simulation experiments on the popular target tracking task and the non-linear, chaotic Lorenz-63 system to showcase practical performance of theoretical considerations.