@phdthesis{deVera2018,
  author    = {de Vera, Jean-Pierre Paul},
  title     = {The relevance of ecophysiology in astrobiology and planetary research},
  school      = {Universit{\"a}t Potsdam},
  pages     = {219},
  year      = {2018},
  abstract  = {Eco-physiological processes are expressing the interaction of organisms within an environmental context of their habitat and their degree of adaptation, level of resistance as well as the limits of life in a changing environment. The present study focuses on observations achieved by methods used in this scientific discipline of "Ecophysiology" and to enlarge the scientific context in a broader range of understanding with universal character. The present eco-physiological work is building the basis for classifying and exploring the degree of habitability of another planet like Mars by a bio-driven experimentally approach. It offers also new ways of identifying key-molecules which are playing a specific role in physiological processes of tested organisms to serve as well as potential biosignatures in future space exploration missions with the goal to search for life. This has important implications for the new emerging scientific field of Astrobiology. Astrobiology addresses the study of the origin, evolution, distribution and future of life in the universe. The three fundamental questions which are hidden behind this definition are: how does life begin and evolve? Is there life beyond Earth and, if so, how can we detect it? What is the future of life on Earth and in the universe? It means that this multidisciplinary field encompasses the search for habitable environments in our Solar System and habitable planets outside our Solar System. It comprises the search for the evidence of prebiotic chemistry and life on Mars and other bodies in our Solar System like the icy moons of the Jovian and Saturnian system, laboratory and field research into the origins and early evolution of life on Earth, and studies of the potential for life to adapt to challenges on Earth and in space. For this purpose an integrated research strategy was applied, which connects field research, laboratory research allowing planetary simulation experiments with investigation enterprises performed in space (particularly performed in the low Earth Orbit.},
  language  = {en}
}
@phdthesis{Eckert2022,
  author    = {Eckert, Silvia},
  title     = {Trait variation in changing environments: Assessing the role of DNA methylation in non-native plant species},
  doi       = {10.25932/publishup-56884},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-568844},
  school      = {Universit{\"a}t Potsdam},
  pages     = {VIII, 134, CXXX},
  year      = {2022},
  abstract  = {The increasing introduction of non-native plant species may pose a threat to local biodiversity. However, the basis of successful plant invasion is not conclusively understood, especially since these plant species can adapt to the new range within a short period of time despite impoverished genetic diversity of the starting populations. In this context, DNA methylation is considered promising to explain successful adaptation mechanisms in the new habitat. DNA methylation is a heritable variation in gene expression without changing the underlying genetic information. Thus, DNA methylation is considered a so-called epigenetic mechanism, but has been studied in mainly clonally reproducing plant species or genetic model plants. An understanding of this epigenetic mechanism in the context of non-native, predominantly sexually reproducing plant species might help to expand knowledge in biodiversity research on the interaction between plants and their habitats and, based on this, may enable more precise measures in conservation biology. For my studies, I combined chemical DNA demethylation of field-collected seed material from predominantly sexually reproducing species and rearing offsping under common climatic conditions to examine DNA methylation in an ecological-evolutionary context. The contrast of chemically treated (demethylated) plants, whose variation in DNA methylation was artificially reduced, and untreated control plants of the same species allowed me to study the impact of this mechanism on adaptive trait differentiation and local adaptation. With this experimental background, I conducted three studies examining the effect of DNA methylation in non-native species along a climatic gradient and also between climatically divergent regions. The first study focused on adaptive trait differentiation in two invasive perennial goldenrod species, Solidago canadensis sensu latu and S. gigantea AITON, along a climate gradient of more than 1000 km in length in Central Europe. I found population differences in flowering timing, plant height, and biomass in the temporally longer-established S. canadensis, but only in the number of regrowing shoots for S. gigantea. While S. canadensis did not show any population structure, I was able to identify three genetic groups along this climatic gradient in S. gigantea. Surprisingly, demethylated plants of both species showed no change in the majority of traits studied. In the subsequent second study, I focused on the longer-established goldenrod species S. canadensis and used molecular analyses to infer spatial epigenetic and genetic population differences in the same specimens from the previous study. I found weak genetic but no epigenetic spatial variation between populations. Additionally, I was able to identify one genetic marker and one epigenetic marker putatively susceptible to selection. However, the results of this study reconfirmed that the epigenetic mechanism of DNA methylation appears to be hardly involved in adaptive processes within the new range in S. canadensis. Finally, I conducted a third study in which I reciprocally transplanted short-lived plant species between two climatically divergent regions in Germany to investigate local adaptation at the plant family level. For this purpose, I used four plant families (Amaranthaceae, Asteraceae, Plantaginaceae, Solanaceae) and here I additionally compared between non-native and native plant species. Seeds were transplanted to regions with a distance of more than 600 kilometers and had either a temperate-oceanic or a temperate-continental climate. In this study, some species were found to be maladapted to their own local conditions, both in non-native and native plant species alike. In demethylated individuals of the plant species studied, DNA methylation had inconsistent but species-specific effects on survival and biomass production. The results of this study highlight that DNA methylation did not make a substantial contribution to local adaptation in the non-native as well as native species studied. In summary, my work showed that DNA methylation plays a negligible role in both adaptive trait variation along climatic gradients and local adaptation in non-native plant species that either exhibit a high degree of genetic variation or rely mainly on sexual reproduction with low clonal propagation. I was able to show that the adaptive success of these non-native plant species can hardly be explained by DNA methylation, but could be a possible consequence of multiple introductions, dispersal corridors and meta-population dynamics. Similarly, my results illustrate that the use of plant species that do not predominantly reproduce clonally and are not model plants is essential to characterize the effect size of epigenetic mechanisms in an ecological-evolutionary context.},
  language  = {en}
}
@phdthesis{Raatz2021,
  author    = {Raatz, Larissa},
  title     = {Boon and bane},
  doi       = {10.25932/publishup-51965},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-519653},
  school      = {Universit{\"a}t Potsdam},
  pages     = {130},
  year      = {2021},
  abstract  = {Semi-natural habitats (SNHs) in agricultural landscapes represent important refugia for biodiversity including organisms providing ecosystem services. Their spill-over into agricultural fields may lead to the provision of regulating ecosystem services such as biological pest control ultimately affecting agricultural yield. Still, it remains largely unexplored, how different habitat types and their distributions in the surrounding landscape shape this provision of ecosystem services within arable fields. Hence, in this thesis I investigated the effect of SNHs on biodiversity-driven ecosystem services and disservices affecting wheat production with an emphasis on the role and interplay of habitat type, distance to the habitat and landscape complexity. I established transects from the field border into the wheat field, starting either from a field-to-field border, a hedgerow, or a kettle hole, and assessed beneficial and detrimental organisms and their ecosystem functions as well as wheat yield at several in-field distances. Using this study design, I conducted three studies where I aimed to relate the impacts of SNHs at the field and at the landscape scale on ecosystem service providers to crop production. In the first study, I observed yield losses close to SNHs for all transect types. Woody habitats, such as hedgerows, reduced yields stronger than kettle holes, most likely due to shading from the tall vegetation structure. In order to find the biotic drivers of these yield losses close to SNHs, I measured pest infestation by selected wheat pests as potential ecosystem disservices to crop production in the second study. Besides relating their damage rates to wheat yield of experimental plots, I studied the effect of SNHs on these pest rates at the field and at the landscape scale. Only weed cover could be associated to yield losses, having their strongest impact on wheat yield close to the SNH. While fungal seed infection rates did not respond to SNHs, fungal leaf infection and herbivory rates of cereal leaf beetle larvae were positively influenced by kettle holes. The latter even increased at kettle holes with increasing landscape complexity suggesting a release of natural enemies at isolated habitats within the field interior. In the third study, I found that also ecosystem service providers benefit from the presence of kettle holes. The distance to a SNH decreased species richness of ecosystem service providers, whereby the spatial range depended on species mobility, i.e. arable weeds diminished rapidly while carabids were less affected by the distance to a SNH. Contrarily, weed seed predation increased with distance suggesting that a higher food availability at field borders might have diluted the predation on experimental seeds. Intriguingly, responses to landscape complexity were rather mixed: While weed species richness was generally elevated with increasing landscape complexity, carabids followed a hump-shaped curve with highest species numbers and activity-density in simple landscapes. The latter might give a hint that carabids profit from a minimum endowment of SNHs, while a further increase impedes their mobility. Weed seed predation was affected differently by landscape complexity depending on weed species displayed. However, in habitat-rich landscapes seed predation of the different weed species converged to similar rates, emphasising that landscape complexity can stabilize the provision of ecosystem services. Lastly, I could relate a higher weed seed predation to an increase in wheat yield even though seed predation did not diminish weed cover. The exact mechanisms of the provision of weed control to crop production remain to be investigated in future studies. In conclusion, I found habitat-specific responses of ecosystem (dis)service providers and their functions emphasizing the need to evaluate the effect of different habitat types on the provision of ecosystem services not only at the field scale, but also at the landscape scale. My findings confirm that besides identifying species richness of ecosystem (dis)service providers the assessment of their functions is indispensable to relate the actual delivery of ecosystem (dis)services to crop production.},
  language  = {en}
}
@phdthesis{Kahl2022,
  author    = {Kahl, Sandra},
  title     = {Evolutionary adaptive responses to rapid climate change in plants},
  doi       = {10.25932/publishup-55648},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-556483},
  school      = {Universit{\"a}t Potsdam},
  pages     = {127},
  year      = {2022},
  abstract  = {The ongoing climate change is altering the living conditions for many organisms on this planet at an unprecedented pace. Hence, it is crucial for the survival of species to adapt to these changing conditions. In this dissertation Silene vulgaris is used as a model organism to understand the adaption strategies of widely distributed plant species to the current climate change. Especially plant species that possess a wide geographic range are expected to have a high phenotypic plasticity or to show genetic differentiation in response to the different climate conditions they grow in. However, they are often underrepresented in research. In the greenhouse experiment presented in this thesis, I examined the phenotypic responses and plasticity in S. vulgaris to estimate its' adaptation potential. Seeds from 25 wild European populations were collected along a latitudinal gradient and grown in a greenhouse under three different precipitation (65 mm, 75 mm, 90 mm) and two different temperature regimes (18°C, 21°C) that resembled a possible climate change scenario for central Europe. Afterwards different biomass and fecundity-related plant traits were measured. The treatments significantly influenced the plants but did not reveal a latitudinal difference in response to climate treatments for most plant traits. The number of flowers per individual however, showed a stronger plasticity in northern European populations (e.g., Swedish populations) where numbers decreased more drastically with increased temperature and decreased precipitation. To gain an even deeper understanding of the adaptation of S. vulgaris to climate change it is also important to reveal the underlying phylogeny of the sampled populations. Therefore, I analysed their population genetic structure through whole genome sequencing via ddRAD. The sequencing revealed three major genetic clusters in the S. vulgaris populations sampled in Europe: one cluster comprised Southern European populations, one cluster Western European populations and another cluster contained central European populations. A following analysis of experimental trait responses among the clusters to the climate-change scenario showed that the genetic clusters significantly differed in biomass-related traits and in the days to flowering. However, half of the traits showed parallel response patterns to the experimental climate-change scenario. In addition to the potential geographic and genetic adaptation differences to climate change this dissertation also deals with the response differences between the sexes in S. vulgaris. As a gynodioecious species populations of S. vulgaris consist of female and hermaphrodite individuals and the sexes can differ in their morphological traits which is known as sexual dimorphism. As climate change is becoming an important factor influencing plant morphology it remains unclear if and how different sexes may respond in sexually dimorphic species. To examine this question the sex of each individual plant was determined during the greenhouse experiment and the measured plant traits were analysed accordingly. In general, hermaphrodites had a higher number of flowers but a lower number of leaves than females. With regards to the climate change treatment, I found that hermaphrodites showed a milder negative response to higher temperatures in the number of flowers produced and in specific leaf area (SLA) compared to females. Synthesis - The significant treatment response in Silene vulgaris, independent of population origin in most traits suggests a high degree of universal phenotypic plasticity. Also, the three European intraspecific genetic lineages detected showed comparable parallel response patterns in half of the traits suggesting considerable phenotypic plasticity. Hence, plasticity might represent a possible adaptation strategy of this widely distributed species during ongoing and future climatic changes. The results on sexual dimorphism show that females and hermaphrodites are differing mainly in their number of flowers and females are affected more strongly by the experimental climate-change scenario. These results provide a solid knowledge basis on the sexual dimorphism in S. vulgaris under climate change, but further research is needed to determine the long-term impact on the breeding system for the species. In summary this dissertation provides a comprehensive insight into the adaptation mechanisms and consequences of a widely distributed and gynodioecious plant species and leverages our understanding of the impact of anthropogenic climate change on plants.},
  language  = {en}
}