@phdthesis{Stiegler2023,
  author    = {Stiegler, Jonas},
  title     = {Mobile link functions in unpredictable agricultural landscapes},
  doi       = {10.25932/publishup-62202},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-622023},
  school      = {Universit{\"a}t Potsdam},
  pages     = {155},
  year      = {2023},
  abstract  = {Animal movement is a crucial aspect of life, influencing ecological and evolutionary processes. It plays an important role in shaping biodiversity patterns, connecting habitats and ecosystems. Anthropogenic landscape changes, such as in agricultural environments, can impede the movement of animals by affecting their ability to locate resources during recurring movements within home ranges and, on a larger scale, disrupt migration or dispersal. Inevitably, these changes in movement behavior have far-reaching consequences on the mobile link functions provided by species inhabiting such extensively altered matrix areas. In this thesis, I investigate the movement characteristics and activity patterns of the European hare (Lepus europaeus), aiming to understand their significance as a pivotal species in fragmented agricultural landscapes. I reveal intriguing results that shed light on the importance of hares for seed dispersal, the influence of personality traits on behavior and space use, the sensitivity of hares to extreme weather conditions, and the impacts of GPS collaring on mammals' activity patterns and movement behavior. In Chapter I, I conducted a controlled feeding experiment to investigate the potential impact of hares on seed dispersal. By additionally utilizing GPS data of hares in two contrasting landscapes, I demonstrated that hares play a vital role, acting as effective mobile linkers for many plant species in small and isolated habitat patches. The analysis of seed intake and germination success revealed that distinct seed traits, such as density, surface area, and shape, profoundly affect hares' ability to disperse seeds through endozoochory. These findings highlight the interplay between hares and plant communities and thus provide valuable insights into seed dispersal mechanisms in fragmented landscapes. By employing standardized behavioral tests in Chapter II, I revealed consistent behavioral responses among captive hares while simultaneously examining the intricate connection between personality traits and spatial patterns within wild hare populations. This analysis provides insights into the ecological interactions and dynamics within hare populations in agricultural habitats. Examining the concept of animal personality, I established a link between personality traits and hare behavior. I showed that boldness, measured through standardized tests, influences individual exploration styles, with shy and bold hares exhibiting distinct space use patterns. In addition to providing valuable insights into the role of animal personality in heterogeneous environments, my research introduced a novel approach demonstrating the feasibility of remotely assessing personality types using animal-borne sensors without additional disturbance of the focal individual. While climate conditions severely impact the activity and, consequently, the fitness of wildlife species across the globe, in Chapter III, I uncovered the sensitivity of hares to temperature, humidity, and wind speed during their peak reproduction period. I found a strong response in activity to high temperatures above 25°C, with a particularly pronounced effect during temperature extremes of over 35°C. The non-linear relationship between temperature and activity was characterized by contrasting responses observed for day and night. These findings emphasize the vulnerability of hares to climate change and the potential consequences for their fitness and population dynamics with the ongoing rise of temperature. Since such insights can only be obtained through capturing and tagging free-ranging animals, I assessed potential impacts and the recovery process post-collar attachment in Chapter IV. For this purpose, I examined the daily distances moved and the temporal-associated activity of 1451 terrestrial mammals out of 42 species during their initial tracking period. The disturbance intensity and the speed of recovery varied across species, with herbivores, females, and individuals captured and collared in relatively secluded study areas experiencing more pronounced disturbances due to limited anthropogenic influences. Mobile linkers are essential for maintaining biodiversity as they influence the dynamics and resilience of ecosystems. Furthermore, their ability to move through fragmented landscapes makes them a key component for restoring disturbed sites. Individual movement decisions determine the scale of mobile links, and understanding variations in space use among individuals is crucial for interpreting their functions. Climate change poses further challenges, with wildlife species expected to adjust their behavior, especially in response to high-temperature extremes, and comprehending the anthropogenic influence on animal movements will remain paramount to effective land use planning and the development of successful conservation strategies. This thesis provides a comprehensive ecological understanding of hares in agricultural landscapes. My research findings underscore the importance of hares as mobile linkers, the influence of personality traits on behavior and spatial patterns, the vulnerability of hares to extreme weather conditions, and the immediate consequences of collar attachment on mammalian movements. Thus, I contribute valuable insights to wildlife conservation and management efforts, aiding in developing strategies to mitigate the impact of environmental changes on hare populations. Moreover, these findings enable the development of methodologies aimed at minimizing the impacts of collaring while also identifying potential biases in the data, thereby benefiting both animal welfare and the scientific integrity of localization studies.},
  language  = {en}
}
@phdthesis{Milles2022,
  author    = {Milles, Alexander},
  title     = {Sources and consequences of intraspecific trait variation in movement behaviour},
  doi       = {10.25932/publishup-56501},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-565011},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xvi, 225},
  year      = {2022},
  abstract  = {Variation in traits permeates and affects all levels of biological organisation, from within individuals to between species. Yet, intraspecific trait variation (ITV) is not sufficiently represented in many ecological theories. Instead, species averages are often assumed. Especially ITV in behaviour has only recently attracted more attention as its pervasiveness and magnitude became evident. The surge in interest in ITV in behaviour was accompanied by a methodological and technological leap in the field of movement ecology. Many aspects of behaviour become visible via movement, allowing us to observe inter-individual differences in fundamental processes such as foraging, mate searching, predation or migration. ITV in movement behaviour may result from within-individual variability and consistent, repeatable among-individual differences. Yet, questions on why such among-individual differences occur in the first place and how they are integrated with life-history have remained open. Furthermore, consequences of ITV, especially of among-individual differences in movement behaviour, on populations and species communities are not sufficiently understood. In my thesis, I approach timely questions on the sources and consequences of ITV, particularly, in movement behaviour. After outlining fundamental concepts and the current state of knowledge, I approach these questions by using agent-based models to integrate concepts from behavioural and movement ecology and to develop novel perspectives. Modern coexistence theory is a central pillar of community ecology, yet, insufficiently considers ITV in behaviour. In chapter 2, I model a competitive two-species system of ground-dwelling, central-place foragers to investigate the consequences of among-individual differences in movement behaviour on species coexistence. I show that the simulated among-individual differences, which matched with empirical data, reduce fitness differences betweem species, i.e. provide an equalising coexistence mechanism. Furthermore, I explain this result mechanistically and, thus, resolve an apparent ambiguity of the consequences of ITV on species coexistence described in previous studies. In chapter 3, I turn the focus to sources of among-individual differences in movement behaviour and their potential integration with life-history. The pace-of-life syndrome (POLS) theory predicts that the covariation between among-individual differences in behaviour and life-history is mediated by a trade-off between early and late reproduction. This theory has generated attention but is also currently scrutinised. In chapter 3, I present a model which supports a recent conceptual development that suggests fluctuating density-dependent selection as a cause of the POLS. Yet, I also identified processes that may alter the association between movement behaviour and life-history across levels of biological organization. ITV can buffer populations, i.e. reduce their extinction risk. For instance, among-individual differences can mediate portfolio effects or increase evolvability and, thereby, facilitate rapid evolution which can alleviate extinction risk. In chapter 4, I review ITV, environmental heterogeneity, and density-dependent processes which constitute local buffer mechanisms. In the light of habitat isolation, which reduces connectivity between populations, local buffer mechanisms may become more relevant compared to dispersal-related regional buffer mechanisms. In this chapter, I argue that capacities, latencies, and interactions of local buffer mechanisms should motivate more process-based and holistic integration of local buffer mechanisms in theoretical and empirical studies. Recent perspectives propose to apply principles from movement and community ecology to study filamentous fungi. It is an open question whether and how the arrangement and geometry of microstructures select for certain movement traits, and, thus, facilitate coexistence-stabilising niche partitioning. As a coauthor of chapter 5, I developed an agent-based model of hyphal tips navigating in soil-like microstructures along a gradient of soil porosity. By measuring network properties, we identified changes in the optimal movement behaviours along the gradient. Our findings suggest that the soil architecture facilitates niche partitioning. The core chapters are framed by a general introduction and discussion. In the general introduction, I outline fundamental concepts of movement ecology and describe theory and open questions on sources and consequences of ITV in movement behaviour. In the general discussion, I consolidate the findings of the core chapters and critically discuss their respective value and, if applicable, their impact. Furthermore, I emphasise promising avenues for further research.},
  language  = {en}
}
@phdthesis{Kuerschner2022,
  author    = {K{\"u}rschner, Tobias},
  title     = {Disease transmission and persistence in dynamic landscapes},
  doi       = {10.25932/publishup-56468},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-564689},
  school      = {Universit{\"a}t Potsdam},
  pages     = {120, LXXIII},
  year      = {2022},
  abstract  = {Infectious diseases are an increasing threat to biodiversity and human health. Therefore, developing a general understanding of the drivers shaping host-pathogen dynamics is of key importance in both ecological and epidemiological research. Disease dynamics are driven by a variety of interacting processes such as individual host behaviour, spatiotemporal resource availability or pathogen traits like virulence and transmission. External drivers such as global change may modify the system conditions and, thus, the disease dynamics. Despite their importance, many of these drivers are often simplified and aggregated in epidemiological models and the interactions among multiple drivers are neglected. In my thesis, I investigate disease dynamics using a mechanistic approach that includes both bottom-up effects - from landscape dynamics to individual movement behaviour - as well as top-down effects - from pathogen virulence on host density and contact rates. To this end, I extended an established spatially explicit individual-based model that simulates epidemiological and ecological processes stochastically, to incorporate a dynamic resource landscape that can be shifted away from the timing of host population-dynamics (chapter 2). I also added the evolution of pathogen virulence along a theoretical virulence-transmission trade-off (chapter 3). In chapter 2, I focus on bottom-up effects, specifically how a temporal shift of resource availability away from the timing of biological events of host-species - as expected under global change - scales up to host-pathogen interactions and disease dynamics. My results show that the formation of temporary disease hotspots in combination with directed individual movement acted as key drivers for pathogen persistence even under highly unfavourable conditions for the host. Even with drivers like global change further increasing the likelihood of unfavourable interactions between host species and their environment, pathogens can continue to persist with heir hosts. In chapter 3, I demonstrate that the top-down effect caused by pathogen-associated mortality on its host population can be mitigated by selection for lower virulent pathogen strains when host densities are reduced through mismatches between seasonal resource availability and host life-history events. I chapter 4, I combined parts of both theoretical models into a new model that includes individual host movement decisions and the evolution of pathogenic virulence to simulate pathogen outbreaks in realistic landscapes. I was able to match simulated patterns of pathogen spread to observed patterns from long-term outbreak data of classical swine fever in wild boar in Northern Germany. The observed disease course was best explained by a simulated high virulent strain, whereas sampling schemes and vaccination campaigns could explain differences in the age-distribution of infected hosts. My model helps to understand and disentangle how the combination of individual decision making and evolution of virulence can act as important drivers of pathogen spread and persistence. As I show across the chapters of this thesis, the interplay of both bottom-up and top-down processes is a key driver of disease dynamics in spatially structured host populations, as they ultimately shape host densities and contact rates among moving individuals. My findings are an important step towards a paradigm shift in disease ecology away from simplified assumptions towards the inclusion of mechanisms, such as complex multi-trophic interactions, and their feedbacks on pathogen spread and disease persistence. The mechanisms presented here should be at the core of realistic predictive and preventive epidemiological models.},
  language  = {en}
}
@phdthesis{Scherer2019,
  author    = {Scherer, Philipp C{\´e}dric},
  title     = {Infection on the move},
  school      = {Universit{\"a}t Potsdam},
  pages     = {x, 107, XXXVIII},
  year      = {2019},
  abstract  = {Movement plays a major role in shaping population densities and contact rates among individuals, two factors that are particularly relevant for disease outbreaks. Although any differences in movement behaviour due to individual characteristics of the host and heterogeneity in landscape structure are likely to have considerable consequences for disease dynamics, these mechanisms are neglected in most epidemiological studies. Therefore, developing a general understanding how the interaction of movement behaviour and spatial heterogeneity shapes host densities, contact rates and ultimately pathogen spread is a key question in ecological and epidemiological research. In my thesis, I address this gap using both theoretical and empirical modelling approaches. In the theoretical part of my thesis, I investigated bottom-up effects of individual movement behaviour and landscape structure on host density, contact rates, and ultimately disease dynamics. I extended an established agent-based model that simulates ecological and epidemiological key processes to incorporate explicit movement of host individuals and landscape complexity. Neutral landscape models are a powerful basis for spatially-explicit modelling studies to imitate the complex characteristics of natural landscapes. In chapter 2, the first study of my thesis, I introduce two complementary R packages, NLMR and landscapetools, that I have co-developed to simplify the workflow of simulation and customization of such landscapes. To demonstrate the use of the packages I present a case study using the spatially explicit eco-epidemiological model and show that landscape complexity per se increases the probability of disease persistence. By using simple rules to simulate explicit host movement, I highlight in chapter 3 how disease dynamics are affected by population-level properties emerging from different movement rules leading to differences in the realized movement distance, spatiotemporal host density, and heterogeneity in transmission rates. As a consequence, mechanistic movement decisions based on the underlying landscape or conspecific competition led to considerably higher probabilities than phenomenological random walk approaches due directed movement leading to spatiotemporal differences in host densities. The results of these two chapters highlight the need to explicitly consider spatial heterogeneity and host movement behaviour when theoretical approaches are used to assess control measures to prevent outbreaks or eradicate diseases. In the empirical part of my thesis (chapter 4), I focus on the spatiotemporal dynamics of Classical Swine Fever in a wild boar population by analysing epidemiological data that was collected during an outbreak in Northern Germany persisting for eight years. I show that infection risk exhibits different seasonal patterns on the individual and the regional level. These patterns on the one hand show a higher infection risk in autumn and winter that may arise due to onset of mating behaviour and hunting intensity, which result in increased movement ranges. On the other hand, the increased infection risk of piglets, especially during the birth season, indicates the importance of new susceptible host individuals for local pathogen spread. The findings of this chapter underline the importance of different spatial and temporal scales to understand different components of pathogen spread that can have important implications for disease management. Taken together, the complementary use of theoretical and empirical modelling in my thesis highlights that our inferences about disease dynamics depend heavily on the spatial and temporal resolution used and how the inclusion of explicit mechanisms underlying hosts movement are modelled. My findings are an important step towards the incorporation of spatial heterogeneity and a mechanism-based perspective in eco-epidemiological approaches. This will ultimately lead to an enhanced understanding of the feedbacks of contact rates on pathogen spread and disease persistence that are of paramount importance to improve predictive models at the interface of ecology and epidemiology.},
  language  = {en}
}
@phdthesis{Schaefer2019,
  author    = {Sch{\"a}fer, Merlin},
  title     = {Understanding and predicting global change impacts on migratory birds},
  doi       = {10.25932/publishup-43925},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-439256},
  school      = {Universit{\"a}t Potsdam},
  pages     = {XIV, 153},
  year      = {2019},
  abstract  = {This is a publication-based dissertation comprising three original research stud-ies (one published, one submitted and one ready for submission; status March 2019). The dissertation introduces a generic computer model as a tool to investigate the behaviour and population dynamics of animals in cyclic environments. The model is further employed for analysing how migratory birds respond to various scenarios of altered food supply under global change. Here, ecological and evolutionary time-scales are considered, as well as the biological constraints and trade-offs the individual faces, which ultimately shape response dynamics at the population level. Further, the effect of fine-scale temporal patterns in re-source supply are studied, which is challenging to achieve experimentally. My findings predict population declines, altered behavioural timing and negative carry-over effects arising in migratory birds under global change. They thus stress the need for intensified research on how ecological mechanisms are affected by global change and for effective conservation measures for migratory birds. The open-source modelling software created for this dissertation can now be used for other taxa and related research questions. Overall, this thesis improves our mechanistic understanding of the impacts of global change on migratory birds as one prerequisite to comprehend ongoing global biodiversity loss. The research results are discussed in a broader ecological and scientific context in a concluding synthesis chapter.},
  language  = {en}
}
@phdthesis{Ullmann2018,
  author    = {Ullmann, Wiebke},
  title     = {Understanding animal movement behaviour in dynamic agricultural landscapes},
  doi       = {10.25932/publishup-42715},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-427153},
  school      = {Universit{\"a}t Potsdam},
  pages     = {vii, 183},
  year      = {2018},
  abstract  = {The movement of organisms has formed our planet like few other processes. Movements shape populations, communities, entire ecosystems, and guarantee fundamental ecosystem functions and services, like seed dispersal and pollination. Global, regional and local anthropogenic impacts influence animal movements across ecosystems all around the world. In particular, land-use modification, like habitat loss and fragmentation disrupt movements between habitats with profound consequences, from increased disease transmissions to reduced species richness and abundance. However, neither the influence of anthropogenic change on animal movement processes nor the resulting effects on ecosystems are well understood. Therefore, we need a coherent understanding of organismal movement processes and their underlying mechanisms to predict and prevent altered animal movements and their consequences for ecosystem functions. In this thesis I aim at understanding the influence of anthropogenically caused land-use change on animal movement processes and their underlying mechanisms. In particular, I am interested in the synergistic influence of large-scale landscape structure and fine-scale habitat features on basic-level movement behaviours (e.g. the daily amount of time spend running, foraging, and resting) and their emerging higher-level movements (home range formation). Based on my findings, I identify the likely consequences of altered animal movements that lead to the loss of species richness and abundances. The study system of my thesis are hares in agricultural landscapes. European brown hares (Lepus europaeus) are perfectly suited to study animal movements in agricultural landscapes, as hares are hermerophiles and prefer open habitats. They have historically thrived in agricultural landscapes, but their numbers are in decline. Agricultural areas are undergoing strong land-use changes due to increasing food demand and fast developing agricultural technologies. They are already the largest land-use class, covering 38\% of the world's terrestrial surface. To consider the relevance of a given landscape structure for animal movement behaviour I selected two differently structured agricultural landscapes - a simple landscape in Northern Germany with large fields and few landscape elements (e.g. hedges and tree stands), and a complex landscape in Southern Germany with small fields and many landscape elements. I applied GPS devices (hourly fixes) with internal high-resolution accelerometers (4 min samples) to track hares, receiving an almost continuous observation of the animals' behaviours via acceleration analyses. I used the spatial and behavioural information in combination with remote sensing data (normalized difference vegetation index, or NDVI, a proxy for resource availability), generating an almost complete idea of what the animal was doing when, why and where. Apart from landscape structure (represented by the two differently structured study areas), I specifically tested whether the following fine-scale habitat features influence animal movements: resource, agricultural management events, habitat diversity, and habitat structure. My results show that, irrespective of the movement process or mechanism and the type of fine-scale habitat features, landscape structure was the overarching variable influencing hare movement behaviour. High resource variability forces hares to enlarge their home ranges, but only in the simple and not in the complex landscape. Agricultural management events result in home range shifts in both landscapes, but force hares to increase their home ranges only in the simple landscape. Also the preference of habitat patches with low vegetation and the avoidance of high vegetation, was stronger in the simple landscape. High and dense crop fields restricted hare movements temporarily to very local and small habitat patch remnants. Such insuperable barriers can separate habitat patches that were previously connected by mobile links. Hence, the transport of nutrients and genetic material is temporarily disrupted. This mechanism is also working on a global scale, as human induced changes from habitat loss and fragmentation to expanding monocultures cause a reduction in animal movements worldwide. The mechanisms behind those findings show that higher-level movements, like increasing home ranges, emerge from underlying basic-level movements, like the behavioural modes. An increasing landscape simplicity first acts on the behavioural modes, i.e. hares run and forage more, but have less time to rest. Hence, the emergence of increased home range sizes in simple landscapes is based on an increased proportion of time running and foraging, largely due to longer travelling times between distant habitats and scarce resource items in the landscape. This relationship was especially strong during the reproductive phase, demonstrating the importance of high-quality habitat for reproduction and the need to keep up self-maintenance first, in low quality areas. These changes in movement behaviour may release a cascade of processes that start with more time being allocated to running and foraging, resulting into an increased energy expenditure and may lead to a decline in individual fitness. A decrease in individual fitness and reproductive output will ultimately affect population viability leading to local extinctions. In conclusion, I show that landscape structure has one of the most important effects on hare movement behaviour. Synergistic effects of landscape structure, and fine-scale habitat features, first affect and modify basic-level movement behaviours, that can scales up to altered higher-level movements and may even lead to the decline of species richness and abundances, and the disruption of ecosystem functions. Understanding the connection between movement mechanisms and processes can help to predict and prevent anthropogenically induced changes in movement behaviour. With regard to the paramount importance of landscape structure, I strongly recommend to decrease the size of agricultural fields and increase crop diversity. On the small-scale, conservation policies should assure the year round provision of areas with low vegetation height and high quality forage. This could be done by generating wildflower strips and additional (semi-) natural habitat patches. This will not only help to increase the populations of European brown hares and other farmland species, but also ensure and protects the continuity of mobile links and their intrinsic value for sustaining important ecosystem functions and services.},
  language  = {en}
}