@phdthesis{CalderonQuinonez2023, author = {Calder{\´o}n Qui{\~n}{\´o}nez, Ana Patricia}, title = {Ecology and conservation of the jaguar (Panthera onca) in Central America}, doi = {10.25932/publishup-61367}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-613671}, school = {Universit{\"a}t Potsdam}, pages = {140}, year = {2023}, abstract = {Conservation of the jaguar relies on holistic and transdisciplinary conservation strategies that integratively safeguard essential, connected habitats, sustain viable populations and their genetic exchange, and foster peaceful human-jaguar coexistence. These strategies define four research priorities to advance jaguar conservation throughout the species' range. In this thesis I provide several relevant ecological and sociological insights into these research priorities, each addressed in a separate chapter. I focus on the effects of anthropogenic landscapes on jaguar habitat use and population gene flow, spatial patterns of jaguar habitat suitability and functional population connectivity, and on innovative governance approaches which can work synergistically to help achieve human-wildlife conviviality. Furthermore, I translate these insights into recommendations for conservation practice by providing tools and suggestions that conservation managers and stakeholders can use to implement local actions but also make broad scale conservation decisions in Central America. In Chapter 2, I model regional habitat use of jaguars, producing spatially-explicit maps for management of key areas of habitat suitability. Using an occupancy model of 13-year-camera-trap occurrence data, I show that human influence has the strongest impact on jaguar habitat use, and that Jaguar Conservation Units are the most important reservoirs of high quality habitat in this region. I build upon these results by zooming in to an area of high habitat suitability loss in Chapter 3, northern Central America. Here I study the drivers of jaguar gene flow and I produce spatially-explicit maps for management of key areas of functional population connectivity in this region. I use microsatellite data and pseudo-optimized multiscale, multivariate resistance surfaces of gene flow to show that jaguar gene flow is influenced by environmental, and even more strongly, by human influence variables; and that the areas of lowest gene flow resistance largely coincide with the location of the Jaguar Conservation Units. Given that human activities significantly impact jaguar habitat use and gene flow, securing viable jaguar populations in anthropogenic landscapes also requires fostering peaceful human-wildlife coexistence. This is a complex challenge that cannot be met without transdisciplinary academic research and cross-sectoral, collaborative governance structures that effectively respond to the multiple challenges of such coexistence. With this in mind, I focus in Chapter 4 on carnivore conservation initiatives that apply transformative governance approaches to enact transformative change towards human-carnivore coexistence. Using the frameworks of transformative biodiversity governance and convivial conservation, I highlight in this chapter concrete pathways, supported by more inclusive, democratic forms of conservation decision-making and participation that promote truly transformative changes towards human-jaguar conviviality.}, language = {en} } @book{Petersen2023, author = {Petersen, Jens}, title = {Studien zur juristischen Ideengeschichte}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-543-9}, doi = {10.25932/publishup-55980}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-559805}, publisher = {Universit{\"a}t Potsdam}, pages = {211}, year = {2023}, abstract = {Albert Hirschman hat sein schmales, aber {\"u}beraus gehaltvolles Werk {\"u}ber ‚Leidenschaften und Interessen' mit einer nachdenkenswerten Bemerkung beschlossen, die veranschaulicht, warum die Besch{\"a}ftigung mit der Ideen- und Geistesgeschichte auch aus heutiger Sicht noch lohnenswert ist: „Das ist wohl das einzige, was man vom Studium der Geschichte, insbesondere der Theorie- und Geistesgeschichte erwarten darf: Nicht, dass die Streitfragen entschieden, sondern dass das Niveau der Auseinandersetzung {\"u}ber sie gehoben wird." Die im vorliegenden Band abgedruckten Beitr{\"a}ge wurden in den 25 Jahren zwischen 1997 und 2022 in unterschiedlichen Zeit- und Festschriften ver{\"o}ffentlicht und f{\"u}r die vorliegende Zusammenstellung behutsam {\"u}berarbeitet.}, language = {de} } @phdthesis{Guill2022, author = {Guill, Christian}, title = {Structure, stability and functioning of food webs}, doi = {10.25932/publishup-56115}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-561153}, school = {Universit{\"a}t Potsdam}, pages = {250}, year = {2022}, abstract = {In this thesis, a collection of studies is presented that advance research on complex food webs in several directions. Food webs, as the networks of predator-prey interactions in ecosystems, are responsible for distributing the resources every organism needs to stay alive. They are thus central to our understanding of the mechanisms that support biodiversity, which in the face of increasing severity of anthropogenic global change and accelerated species loss is of highest importance, not least for our own well-being. The studies in the first part of the thesis are concerned with general mechanisms that determine the structure and stability of food webs. It is shown how the allometric scaling of metabolic rates with the species' body masses supports their persistence in size-structured food webs (where predators are larger than their prey), and how this interacts with the adaptive adjustment of foraging efforts by consumer species to create stable food webs with a large number of coexisting species. The importance of the master trait body mass for structuring communities is further exemplified by demonstrating that the specific way the body masses of species engaging in empirically documented predator-prey interactions affect the predator's feeding rate dampens population oscillations, thereby helping both species to survive. In the first part of the thesis it is also shown that in order to understand certain phenomena of population dynamics, it may be necessary to not only take the interactions of a focal species with other species into account, but to also consider the internal structure of the population. This can refer for example to different abundances of age cohorts or developmental stages, or the way individuals of different age or stage interact with other species. Building on these general insights, the second part of the thesis is devoted to exploring the consequences of anthropogenic global change on the persistence of species. It is first shown that warming decreases diversity in size-structured food webs. This is due to starvation of large predators on higher trophic levels, which suffer from a mismatch between their respiration and ingestion rates when temperature increases. In host-parasitoid networks, which are not size-structured, warming does not have these negative effects, but eutrophication destabilises the systems by inducing detrimental population oscillations. In further studies, the effect of habitat change is addressed. On the level of individual patches, increasing isolation of habitat patches has a similar effect as warming, as it leads to decreasing diversity due to the extinction of predators on higher trophic levels. In this case it is caused by dispersal mortality of smaller and therefore less mobile species on lower trophic levels, meaning that an increasing fraction of their biomass production is lost to the inhospitable matrix surrounding the habitat patches as they become more isolated. It is further shown that increasing habitat isolation desynchronises population oscillations between the patches, which in itself helps species to persist by dampening fluctuations on the landscape level. However, this is counteracted by an increasing strength of local population oscillations fuelled by an indirect effect of dispersal mortality on the feeding interactions. Last, a study is presented that introduces a novel mechanism for supporting diversity in metacommunities. It builds on the self-organised formation of spatial biomass patterns in the landscape, which leads to the emergence of spatio-temporally varying selection pressures that keep local communities permanently out of equilibrium and force them to continuously adapt. Because this mechanism relies on the spatial extension of the metacommunity, it is also sensitive to habitat change. In the third part of the thesis, the consequences of biodiversity for the functioning of ecosystems are explored. The studies focus on standing stock biomass, biomass production, and trophic transfer efficiency as ecosystem functions. It is first shown that increasing the diversity of animal communities increases the total rate of intra-guild predation. However, the total biomass stock of the animal communities increases nevertheless, which also increases their exploitative pressure on the underlying plant communities. Despite this, the plant communities can maintain their standing stock biomass due to a shift of the body size spectra of both animal and plant communities towards larger species with a lower specific respiration rate. In another study it is further demonstrated that the generally positive relationship between diversity and the above mentioned ecosystem functions becomes steeper when not only the feeding interactions but also the numerous non-trophic interactions (like predator interference or competition for space) between the species of an ecosystem are taken into account. Finally, two studies are presented that demonstrate the power of functional diversity as explanatory variable. It is interpreted as the range spanned by functional traits of the species that determine their interactions. This approach allows to mechanistically understand how the ecosystem functioning of food webs with multiple trophic levels is affected by all parts of the food web and why a high functional diversity is required for efficient transportation of energy from primary producers to the top predators. The general discussion draws some synthesising conclusions, e.g. on the predictive power of ecosystem functioning to explain diversity, and provides an outlook on future research directions.}, 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} } @article{Grote2021, author = {Grote, Mathias}, title = {„Aus dem Kleinen bauen sich die Welten" - Christian Gottfried Ehrenbergs {\"o}kologische Mikrobiologie avant la lettre}, series = {HiN : Alexander von Humboldt im Netz = Christian Gottfried Ehrenberg}, volume = {XXII}, journal = {HiN : Alexander von Humboldt im Netz = Christian Gottfried Ehrenberg}, number = {42}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, issn = {1617-5239}, doi = {https://doi.org/10.18443/318}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-515016}, pages = {19 -- 32}, year = {2021}, abstract = {Die Geschichte der Mikrobiologie als Laborwissenschaft des sp{\"a}ten 19. Jahrhunderts hat f{\"u}r Ehrenberg keinen Platz. Unmodern, ja fehlerhaft scheinen die Befunde dieses „Humboldt en miniature", der die Belebtheit von Wasser oder Luft mikroskopisch untersuchte, der Proben aus aller Welt sammelte und so zahlreiche „Infusorien" genannte Mikroben sowie deren Effekte etwa bei Blutwundern beschrieb, deren Beteiligung an Infektionskrankheiten aber verneinte. Zugleich scheint sein {\"o}kologischer Blick auf den Mikrokosmos die Gegenwart auf {\"u}berraschende Weise anzusprechen - einerseits weil Mikroben omnipr{\"a}sentes Faszinosum wie Bedrohung bleiben, andererseits weil viele der Pr{\"a}missen von Pasteur und Koch im Zeitalter der Genomik {\"u}berholt erscheinen. Ausgehend von der zwiesp{\"a}ltigen Position Ehrenbergs fragt dieser Artikel, warum er m{\"o}glicherweise gerade deswegen spannender ist, als ihn die Historiographie bislang hat erscheinen lassen.}, language = {de} } @phdthesis{Stark2021, author = {Stark, Markus}, title = {Implications of local and regional processes on the stability of metacommunities in diverse ecosystems}, doi = {10.25932/publishup-52639}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-526399}, school = {Universit{\"a}t Potsdam}, pages = {x, 167}, year = {2021}, abstract = {Anthropogenic activities such as continuous landscape changes threaten biodiversity at both local and regional scales. Metacommunity models attempt to combine these two scales and continuously contribute to a better mechanistic understanding of how spatial processes and constraints, such as fragmentation, affect biodiversity. There is a strong consensus that such structural changes of the landscape tend to negatively effect the stability of metacommunities. However, in particular the interplay of complex trophic communities and landscape structure is not yet fully understood. In this present dissertation, a metacommunity approach is used based on a dynamic and spatially explicit model that integrates population dynamics at the local scale and dispersal dynamics at the regional scale. This approach allows the assessment of complex spatial landscape components such as habitat clustering on complex species communities, as well as the analysis of population dynamics of a single species. In addition to the impact of a fixed landscape structure, periodic environmental disturbances are also considered, where a periodical change of habitat availability, temporally alters landscape structure, such as the seasonal drying of a water body. On the local scale, the model results suggest that large-bodied animal species, such as predator species at high trophic positions, are more prone to extinction in a state of large patch isolation than smaller species at lower trophic levels. Increased metabolic losses for species with a lower body mass lead to increased energy limitation for species on higher trophic levels and serves as an explanation for a predominant loss of these species. This effect is particularly pronounced for food webs, where species are more sensitive to increased metabolic losses through dispersal and a change in landscape structure. In addition to the impact of species composition in a food web for diversity, the strength of local foraging interactions likewise affect the synchronization of population dynamics. A reduced predation pressure leads to more asynchronous population dynamics, beneficial for the stability of population dynamics as it reduces the risk of correlated extinction events among habitats. On the regional scale, two landscape aspects, which are the mean patch isolation and the formation of local clusters of two patches, promote an increase in \$\beta\$-diversity. Yet, the individual composition and robustness of the local species community equally explain a large proportion of the observed diversity patterns. A combination of periodic environmental disturbance and patch isolation has a particular impact on population dynamics of a species. While the periodic disturbance has a synchronizing effect, it can even superimpose emerging asynchronous dynamics in a state of large patch isolation and unifies trends in synchronization between different species communities. In summary, the findings underline a large local impact of species composition and interactions on local diversity patterns of a metacommunity. In comparison, landscape structures such as fragmentation have a negligible effect on local diversity patterns, but increase their impact for regional diversity patterns. In contrast, at the level of population dynamics, regional characteristics such as periodic environmental disturbance and patch isolation have a particularly strong impact and contribute substantially to the understanding of the stability of population dynamics in a metacommunity. These studies demonstrate once again the complexity of our ecosystems and the need for further analysis for a better understanding of our surrounding environment and more targeted conservation of biodiversity.}, language = {en} } @misc{MarkschiesPaesslerGroteetal.2021, author = {Markschies, Christoph and P{\"a}ßler, Ulrich and Grote, Mathias and Greenwood MacKinney, Anne and Kusber, Wolf-Henning and Jahn, Regine and Damaschun, Ferdinand and B{\"o}hme, Katrin}, title = {HiN : Alexander von Humboldt im Netz = Christian Gottfried Ehrenberg}, volume = {XXII}, number = {42}, editor = {Ette, Ottmar and Knobloch, Eberhard and P{\"a}ßler, Ulrich}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, issn = {2568-3543}, doi = {10.25932/publishup-50141}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-501413}, pages = {169}, year = {2021}, abstract = {-Christoph Markschies: Geleitwort -Ulrich P{\"a}ßler: Christian Gottfried Ehrenberg: Lebensbilder eines Naturforschers -Mathias Grote: „Aus dem Kleinen bauen sich die Welten" - Christian Gottfried Ehrenbergs {\"o}kologische Mikrobiologie avant la lettre -Anne Greenwood MacKinney: Die Inszenierung naturforschender Gelehrsamkeit beim Sammeln: Christian Gottfried Ehrenbergs und Wilhelm Hemprichs nordafrikanische Forschungsreise (1820 - 1825) -Ulrich P{\"a}ßler: Reisen im Nahen Osten. Zeichnungen -Ulrich P{\"a}ßler: Christian Gottfried Ehrenberg und die Biogeographie: Die russisch-sibirische Reise mit Alexander von Humboldt (1829) -Ulrich P{\"a}ßler: Russisch-Sibirische Reise. Zeichnungen -Wolf-Henning Kusber, Regine Jahn: Christian Gottfried Ehrenbergs Zeichnungen: Eine fr{\"u}he wissenschaftliche Dokumentation mikroskopischer Organismen -Ferdinand Damaschun: Christian Gottfried Ehrenberg und die Entwicklung der Mikroskop-Technik im 19. Jahrhundert -Ulrich P{\"a}ßler: Die Reise ins Kleinste der Natur. Zeichnungen -Katrin B{\"o}hme: Das große Ganze: Christian Gottfried Ehrenberg und die Gesellschaft Naturforschender Freunde zu Berlin}, language = {de} } @phdthesis{Kolk2019, author = {Kolk, Jens}, title = {The long-term legacy of historical land cover changes}, doi = {10.25932/publishup-43939}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-439398}, school = {Universit{\"a}t Potsdam}, pages = {196}, year = {2019}, abstract = {Over the last years there is an increasing awareness that historical land cover changes and associated land use legacies may be important drivers for present-day species richness and biodiversity due to time-delayed extinctions or colonizations in response to historical environmental changes. Historically altered habitat patches may therefore exhibit an extinction debt or colonization credit and can be expected to lose or gain species in the future. However, extinction debts and colonization credits are difficult to detect and their actual magnitudes or payments have rarely been quantified because species richness patterns and dynamics are also shaped by recent environmental conditions and recent environmental changes. In this thesis we aimed to determine patterns of herb-layer species richness and recent species richness dynamics of forest herb layer plants and link those patterns and dynamics to historical land cover changes and associated land use legacies. The study was conducted in the Prignitz, NE-Germany, where the forest distribution remained stable for the last ca. 100 years but where a) the deciduous forest area had declined by more than 90 per cent (leaving only remnants of "ancient forests"), b) small new forests had been established on former agricultural land ("post-agricultural forests"). Here, we analyzed the relative importance of land use history and associated historical land cover changes for herb layer species richness compared to recent environmental factors and determined magnitudes of extinction debt and colonization credit and their payment in ancient and post-agricultural forests, respectively. We showed that present-day species richness patterns were still shaped by historical land cover changes that ranged back to more than a century. Although recent environmental conditions were largely comparable we found significantly more forest specialists, species with short-distance dispersal capabilities and clonals in ancient forests than in post-agricultural forests. Those species richness differences were largely contingent to a colonization credit in post-agricultural forests that ranged up to 9 species (average 4.7), while the extinction debt in ancient forests had almost completely been paid. Environmental legacies from historical agricultural land use played a minor role for species richness differences. Instead, patch connectivity was most important. Species richness in ancient forests was still dependent on historical connectivity, indicating a last glimpse of an extinction debt, and the colonization credit was highest in isolated post-agricultural forests. In post-agricultural forests that were better connected or directly adjacent to ancient forest patches the colonization credit was way smaller and we were able to verify a gradual payment of the colonization credit from 2.7 species to 1.5 species over the last six decades.}, language = {en} } @article{Ette2019, author = {Ette, Ottmar}, title = {Faszination AvH}, series = {HiN : Alexander von Humboldt im Netz ; international review for Humboldtian studies}, volume = {XX}, journal = {HiN : Alexander von Humboldt im Netz ; international review for Humboldtian studies}, number = {38}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, issn = {1617-5239}, doi = {10.25932/publishup-43469}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-434694}, pages = {5 -- 13}, year = {2019}, abstract = {Alexander von Humboldts Forschungsreise in die Neue Welt ist ein Gr{\"u}ndungsmoment moderner Wissenschaft. Sie liefert uns Impulse und Grundlagen f{\"u}r ein 21. Jahrhundert, das im Zeichen des Zusammendenkens und Zusammenlebens stehen muss. Von der lange versch{\"u}tteten Tradition einer Humboldt'schen Wissenschaft aus lassen sich heute, am Ausgang unserer aktuellen Globalisierungsphase, neue Zuk{\"u}nfte denken und entfalten. Das Zusammendenken von Natur und Kultur im Horizont einer {\"O}kologie, die sich mit Gesellschafts- und Wirtschaftsstrukturen vernetzt; der Entwurf einer Kosmopolitik, die nicht auf Machtasymme­trie, Inferiorisierung und Abh{\"a}ngigkeit abzielt, sondern die Zirkulation von Wissen zur Grundlage einer sich demokratisierenden Weltgesellschaft macht: Dies sind Kreuzungspunkte eines Denkens, das nicht nur an Aktualit{\"a}t, sondern im Zeichen neu entfachter Nationalismen, neuer Fundamentalismen und neuer globaler Ausgrenzungen vor allem an Dringlichkeit gewonnen hat.}, language = {de} } @phdthesis{Teckentrup2019, author = {Teckentrup, Lisa}, title = {Understanding predator-prey interactions}, doi = {10.25932/publishup-43162}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-431624}, school = {Universit{\"a}t Potsdam}, pages = {ix, 133}, year = {2019}, abstract = {Predators can have numerical and behavioral effects on prey animals. While numerical effects are well explored, the impact of behavioral effects is unclear. Furthermore, behavioral effects are generally either analyzed with a focus on single individuals or with a focus on consequences for other trophic levels. Thereby, the impact of fear on the level of prey communities is overlooked, despite potential consequences for conservation and nature management. In order to improve our understanding of predator-prey interactions, an assessment of the consequences of fear in shaping prey community structures is crucial. In this thesis, I evaluated how fear alters prey space use, community structure and composition, focusing on terrestrial mammals. By integrating landscapes of fear in an existing individual-based and spatially-explicit model, I simulated community assembly of prey animals via individual home range formation. The model comprises multiple hierarchical levels from individual home range behavior to patterns of prey community structure and composition. The mechanistic approach of the model allowed for the identification of underlying mechanism driving prey community responses under fear. My results show that fear modified prey space use and community patterns. Under fear, prey animals shifted their home ranges towards safer areas of the landscape. Furthermore, fear decreased the total biomass and the diversity of the prey community and reinforced shifts in community composition towards smaller animals. These effects could be mediated by an increasing availability of refuges in the landscape. Under landscape changes, such as habitat loss and fragmentation, fear intensified negative effects on prey communities. Prey communities in risky environments were subject to a non-proportional diversity loss of up to 30\% if fear was taken into account. Regarding habitat properties, I found that well-connected, large safe patches can reduce the negative consequences of habitat loss and fragmentation on prey communities. Including variation in risk perception between prey animals had consequences on prey space use. Animals with a high risk perception predominantly used safe areas of the landscape, while animals with a low risk perception preferred areas with a high food availability. On the community level, prey diversity was higher in heterogeneous landscapes of fear if individuals varied in their risk perception compared to scenarios in which all individuals had the same risk perception. Overall, my findings give a first, comprehensive assessment of the role of fear in shaping prey communities. The linkage between individual home range behavior and patterns at the community level allows for a mechanistic understanding of the underlying processes. My results underline the importance of the structure of the landscape of fear as a key driver of prey community responses, especially if the habitat is threatened by landscape changes. Furthermore, I show that individual landscapes of fear can improve our understanding of the consequences of trait variation on community structures. Regarding conservation and nature management, my results support calls for modern conservation approaches that go beyond single species and address the protection of biotic interactions.}, language = {en} } @phdthesis{Martin2013, author = {Martin, Benjamin}, title = {Linking individual-based models and dynamic energy budget theory : lessons for ecology and ecotoxicology}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-67001}, school = {Universit{\"a}t Potsdam}, year = {2013}, abstract = {In the context of ecological risk assessment of chemicals, individual-based population models hold great potential to increase the ecological realism of current regulatory risk assessment procedures. However, developing and parameterizing such models is time-consuming and often ad hoc. Using standardized, tested submodels of individual organisms would make individual-based modelling more efficient and coherent. In this thesis, I explored whether Dynamic Energy Budget (DEB) theory is suitable for being used as a standard submodel in individual-based models, both for ecological risk assessment and theoretical population ecology. First, I developed a generic implementation of DEB theory in an individual-based modeling (IBM) context: DEB-IBM. Using the DEB-IBM framework I tested the ability of the DEB theory to predict population-level dynamics from the properties of individuals. We used Daphnia magna as a model species, where data at the individual level was available to parameterize the model, and population-level predictions were compared against independent data from controlled population experiments. We found that DEB theory successfully predicted population growth rates and peak densities of experimental Daphnia populations in multiple experimental settings, but failed to capture the decline phase, when the available food per Daphnia was low. Further assumptions on food-dependent mortality of juveniles were needed to capture the population dynamics after the initial population peak. The resulting model then predicted, without further calibration, characteristic switches between small- and large-amplitude cycles, which have been observed for Daphnia. We conclude that cross-level tests help detecting gaps in current individual-level theories and ultimately will lead to theory development and the establishment of a generic basis for individual-based models and ecology. In addition to theoretical explorations, we tested the potential of DEB theory combined with IBMs to extrapolate effects of chemical stress from the individual to population level. For this we used information at the individual level on the effect of 3,4-dichloroanailine on Daphnia. The individual data suggested direct effects on reproduction but no significant effects on growth. Assuming such direct effects on reproduction, the model was able to accurately predict the population response to increasing concentrations of 3,4-dichloroaniline. We conclude that DEB theory combined with IBMs holds great potential for standardized ecological risk assessment based on ecological models.}, language = {en} } @misc{Langer2011, type = {Master Thesis}, author = {Langer, Marco}, title = {The effect of native forest dynamics upon the arrangements of species in oak forests-analysis of heterogeneity effects at the example of epigeal arthropods}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-55588}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {The heterogeneity in species assemblages of epigeal spiders was studied in a natural forest and in a managed forest. Additionally the effects of small-scale microhabitat heterogeneity of managed and unmanaged forests were determined by analysing the spider assemblages of three different microhabitat structures (i. vegetation, ii. dead wood. iii. litter cover). The spider were collected in a block design by pitfall traps (n=72) in a 4-week interval. To reveal key environmental factors affecting the spider distribution abiotic and biotic habitat parameters (e.g. vegetation parameters, climate parameters, soil moisture) were assessed around each pitfall trap. A TWINSPAN analyses separated pitfall traps from the natural forest from traps of the managed forest. A subsequent discriminant analyses revealed that the temperature, the visible sky, the plant diversity and the mean diameter at breast height as key discriminant factors between the microhabitat groupings designated by the TWINSPAN analyses. Finally a Redundant analysis (RDA) was done revealing similar environmental factors responsible for the spider species distribution, as a good separation of the different forest types as well as the separation of the microhabitat groupings from the TWINSPAN. Overall the study revealed that the spider communities differed between the forest types as well as between the microhabitat structures and thus species distribution changed within a forest stand on a fine spatial scale. It was documented that the structure of managed forests affects the composition of spider assemblages compared to natural forests significantly and even small scale-heterogeneity seems to influence the spider species composition.}, language = {en} } @phdthesis{Tirok2008, author = {Tirok, Katrin}, title = {Predator-prey dynamics under the influence of exogenous and endogenous regulation : a data-based modeling study on spring plankton with respect to climate change}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-24528}, school = {Universit{\"a}t Potsdam}, year = {2008}, abstract = {Understanding the interactions of predators and their prey and their responses to environmental changes is one of the striking features of ecological research. In this thesis, spring dynamics of phytoplankton and its consumers, zooplankton, were considered in dependence on the environmental conditions in a deep lake (Lake Constance) and a shallow marine water (mesocosms from Kiel Bight), using descriptive statistics, multiple regression models, and process-oriented dynamic simulation models. The development of the spring phytoplankton bloom, representing a dominant feature in the plankton dynamics in temperate and cold oceans and lakes, may depend on temperature, light, and mixing intensity, and the success of over-wintering phyto- and zooplankton. These factors are often correlated in the field. Unexpectedly, irradiance often dominated algal net growth rather than vertical mixing even in deep Lake Constance. Algal net losses from the euphotic layer to larger depth were induced by vertical mixing, but were compensated by the input from larger depth when algae were uniformly distributed over the water column. Dynamics of small, fast-growing algae were well predicted by abiotic variables, such as surface irradiance, vertical mixing intensity, and temperature. A simulation model additionally revealed that even in late winter, grazing may represent an important loss factor of phytoplankton during calm periods when losses due to mixing are small. The importance of losses by mixing and grazing changed rapidly as it depended on the variable mixing intensity. Higher temperature, lower global irradiance and enhanced mixing generated lower algal biomass and primary production in the dynamic simulation model. This suggests that potential consequences of climate change may partly counteract each other. The negative effect of higher temperatures on phytoplankton biomass was due to enhanced temperature-sensitive grazing losses. Comparing the results from deep Lake Constance to those of the shallow mesocosm experiments and simulations, confirmed the strong direct effect of light in contrast to temperature, and the importance of grazing already in early spring as soon as moderate algal biomasses developed. In Lake Constance, ciliates dominated the herbivorous zooplankton in spring. The start of ciliate net growth in spring was closely linked to that of edible algae, chlorophyll a and the vertical mixing intensity but independent of water temperature. The duration of ciliate dominance in spring was largely controlled by the highly variable onset of the phytoplankton bloom, and little by the less variable termination of the ciliate bloom by grazing of meta-zooplankton. During years with an extended spring bloom of algae and ciliates, they coexisted at relatively high biomasses over 15-30 generations, and internally forced species shifts were observed in both communities. Interception feeders alternated with filter feeders, and cryptomonads with non-cryptomonads in their relative importance. These dynamics were not captured by classical 1-predator-1-prey models which consistently predict pronounced predator-prey cycles or equilibria with either the predator or the prey dominating or suppressed. A multi-species predator-prey model with predator species differing in their food selectivity, and prey species in their edibility reproduced the observed patterns. Food-selectivity and edibility were related to the feeding and growth characteristics of the species, which represented ecological trade-offs. For example, the prey species with the highest edibility also had the highest maximum growth rate. Data and model revealed endogenous driven ongoing species alternations, which yielded a higher variability in species-specific biomasses than in total predator and prey biomass. This holds for a broad parameter space as long as the species differ functionally. A more sophisticated model approach enabled the simulation of a continuum of different functional types and adaptability of predator and prey communities to altered environmental conditions, and the maintenance of a rather low model complexity, i.e., low number of equations and free parameters. The community compositions were described by mean functional traits --- prey edibility and predator food-selectivity --- and their variances. The latter represent the functional diversity of the communities and thus, the potential for adaptation. Oscillations in the mean community trait values indicated species shifts. The community traits were related to growth and grazing characteristics representing similar trade-offs as in the multi-species model. The model reproduced the observed patterns, when nonlinear relationships between edibility and capacity, and edibility and food availability for the predator were chosen. A constant minimum amount of variance represented ongoing species invasions and thus, preserved a diversity which allows adaptation on a realistic time-span.}, language = {en} } @techreport{OPUS4-8354, title = {Kurzbericht zur Luftg{\"u}te des Jahres 2006}, series = {Materialien zur Umwelt}, journal = {Materialien zur Umwelt}, number = {1/2007}, address = {G{\"u}strow}, organization = {Landesamt f{\"u}r Umwelt, Naturschutz und Geologie Mecklenburg-Vorpommern}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-bbdig-102}, pages = {27}, year = {2007}, language = {de} } @techreport{OPUS4-8357, title = {Kurzbericht zur Luftg{\"u}te des Jahres 2005}, series = {Materialien zur Umwelt}, journal = {Materialien zur Umwelt}, number = {1}, address = {G{\"u}strow}, organization = {Landesamt f{\"u}r Umwelt, Naturschutz und Geologie Mecklenburg-Vorpommern}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-bbdig-92}, pages = {26}, year = {2006}, language = {de} } @phdthesis{Schwager2005, author = {Schwager, Monika}, title = {Climate change, variable colony sizes and temporal autocorrelation : consequences of living in changing environments}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-5744}, school = {Universit{\"a}t Potsdam}, year = {2005}, abstract = {Natural and human induced environmental changes affect populations at different time scales. If they occur in a spatial heterogeneous way, they cause spatial variation in abundance. In this thesis I addressed three topics, all related to the question, how environmental changes influence population dynamics. In the first part, I analysed the effect of positive temporal autocorrelation in environmental noise on the extinction risk of a population, using a simple population model. The effect of autocorrelation depended on the magnitude of the effect of single catastrophic events of bad environmental conditions on a population. If a population was threatened by extinction only, when bad conditions occurred repeatedly, positive autocorrelation increased extinction risk. If a population could become extinct, even if bad conditions occurred only once, positive autocorrelation decreased extinction risk. These opposing effects could be explained by two features of an autocorrelated time series. On the one hand, positive autocorrelation increased the probability of series of bad environmental conditions, implying a negative effect on populations. On the other hand, aggregation of bad years also implied longer periods with relatively good conditions. Therefore, for a given time period, the overall probability of occurrence of at least one extremely bad year was reduced in autocorrelated noise. This can imply a positive effect on populations. The results could solve a contradiction in the literature, where opposing effects of autocorrelated noise were found in very similar population models. In the second part, I compared two approaches, which are commonly used for predicting effects of climate change on future abundance and distribution of species: a "space for time approach", where predictions are based on the geographic pattern of current abundance in relation to climate, and a "population modelling approach" which is based on correlations between demographic parameters and the inter-annual variation of climate. In this case study, I compared the two approaches for predicting the effect of a shift in mean precipitation on a population of the sociable weaver Philetairus socius, a common colonially living passerine bird of semiarid savannahs of southern Africa. In the space for time approach, I compared abundance and population structure of the sociable weaver in two areas with highly different mean annual precipitation. The analysis showed no difference between the two populations. This result, as well as the wide distribution range of the species, would lead to the prediction of no sensitive response of the species to a slight shift in mean precipitation. In contrast, the population modelling approach, based on a correlation between reproductive success and rainfall, predicted a sensitive response in most model types. The inconsistency of predictions was confirmed in a cross-validation between the two approaches. I concluded that the inconsistency was caused, because the two approaches reflect different time scales. On a short time scale, the population may respond sensitively to rainfall. However, on a long time scale, or in a regional comparison, the response may be compensated or buffered by a variety of mechanisms. These may include behavioural or life history adaptations, shifts in the interactions with other species, or differences in the physical environment. The study implies that understanding, how such mechanisms work, and at what time scale they would follow climate change, is a crucial precondition for predicting ecological consequences of climate change. In the third part of the thesis, I tested why colony sizes of the sociable weaver are highly variable. The high variation of colony sizes is surprising, as in studies on coloniality it is often assumed that an optimal colony size exists, in which individual bird fitness is maximized. Following this assumption, the pattern of bird dispersal should keep colony sizes near an optimum. However, I showed by analysing data on reproductive success and survival that for the sociable weaver fitness in relation to colony size did not follow an optimum curve. Instead, positive and negative effects of living in large colonies overlaid each other in a way that fitness was generally close to one, and density dependence was low. I showed in a population model, which included an evolutionary optimisation process of dispersal that this specific shape of the fitness function could lead to a dispersal strategy, where the variation of colony sizes was maintained.}, subject = {Populationsbiologie}, language = {en} } @phdthesis{Clodong2004, author = {Clodong, S{\´e}bastien}, title = {Recurrent outbreaks in ecology : chaotic dynamics in complex networks}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0001626}, school = {Universit{\"a}t Potsdam}, year = {2004}, abstract = {Gegenstand der Dissertation ist die Untersuchung von wiederkehrenden Ausbr{\"u}chen (wie z.B. Epidemien) in der Natur. Dies gelang anhand von Modellen, die die Dynamik von Phytoplankton und die Ausbreitung von Krankheiten zwischen St{\"a}dten beschreiben. Diese beide Systeme bilden hervorragende Beispiele f{\"u}r solche Ph{\"a}nomene. Die Frage, ob die in der Zeit wiederkehrenden Ausbr{\"u}che ein Ausdruck chaotischer Dynamik sein k{\"o}nnen, ist aktuell in der {\"O}kologie und fasziniert Wissenschaftler dieser Disziplin. Wir konnten zeigen, dass sich das Plankton-Modell im Falle von periodischem Antreiben {\"u}ber die N{\"a}hrstoffe in einem chaotischen Regime befindet. Diese Dynamik wurde als die komplexe Wechselwirkung zweier Oszillatoren verstanden. Ebenfalls wurde die Ausbreitung von Epidemien in Netzwerken wechselwirkender St{\"a}dte mit unterschiedlichen Gr{\"o}ssen untersucht. Daf{\"u}r wurde zun{\"a}chst die Kopplung zwischen zwei St{\"a}dten als Verh{\"a}ltnis der Stadtgr{\"o}ssen eingef{\"u}hrt. Es konnte gezeigt werden, dass das System sich in einem globalen zweij{\"a}hrigen Zyklus, der auch in den realen Daten beobachtet wird, befinden kann. Der Effekt von Heterogenit{\"a}t in der Gr{\"o}sseverteilung ist durch gewichtete Kopplung von generischen Modellen (Zelt- und Logistische Abbildung) in Netzwerken im Detail untersucht worden. Eine neue Art von Kopplungsfunktion mit nichtlinearer S{\"a}ttigung wurde eingef{\"u}hrt, um die Stabilit{\"a}t des Systems zu gew{\"a}hrleisten. Diese Kopplung beinhaltet einen Parameter, der es erlaubt, die Netzwerktopologie von globaler Kopplung in gerichtete Netzwerke gleichm{\"a}ssig umzuwandeln. Die Dynamik des Systems wurde anhand von Bifurkationsdiagrammen untersucht. Zum Verst{\"a}ndnis dieser Dynamik wurde eine effektive Theorie, die die beobachteten Bifurkationen sehr gut nachahmt, entwickelt.}, language = {en} }