@phdthesis{Zwettler2021,
  author    = {Zwettler, Fabian Ulrich},
  title     = {Expansionsmikroskopie kombiniert mit hochaufl{\"o}sender Fluoreszenzmikroskopie},
  doi       = {10.25972/OPUS-21236},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212362},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {Fluorescence microscopy is a form of light microscopy that has developed during the 20th century and is nowadays a standard tool in Molecular and Cell biology for studying the structure and function of biological molecules. High-resolution fluorescence microscopy techniques, such as dSTORM (direct Stochastic Optical Reconstruction Microscopy) allow the visualization of cellular structures at the nanometre scale (10-9 m). This has already made it possible to decipher the composition and function of various biopolymers, such as proteins, lipids and nucleic acids, up to the three-dimensional (3D) structure of entire organelles. In practice, however, it has been shown that these imaging methods and their further developments still face great challenges in order to achieve an effective resolution below ∼ 10 nm. This is mainly due to the nature of labelling biomolecules. For the detection of molecular structures, immunostaining is often performed as a standard method. Antibodies to which fluorescent molecules are coupled, recognize and bind specifcally and with high affnity to the molecular section of the target structure, also called epitope or antigen. The fluorescent molecules serve as reporter molecules which are imaged with the use of a fluorescence microscope. However, the size of these labels with a length of about 10-15 nm in the case of immunoglobulin G (IgG) antibodies, cause a detection of the fluorescent molecules shifted to the real position of the studied antigen. In dense regions where epitopes are located close to each other, steric hindrance between antibodies can also occur and leads to an insuffcient label density. Together with the shifted detection of fluorescent molecules, these factors can limit the achievable resolution of a microscopy technique. Expansion microscopy (ExM) is a recently developed technique that achieves a resolution improvement by physical expansion of an investigated object. Therefore, biological samples such as cultured cells, tissue sections, whole organs or isolated organelles are chemically anchored into a swellable polymer. By absorbing water, this so-called superabsorber increases its own volume and pulls the covalently bound biomolecules isotropically apart. Routinely, this method achieves a magnifcation of the sample by about four times its volume. But protocol variants have already been developed that result in higher expansion factors of up to 50-fold. Since the ExM technique includes in the frst instance only the sample treatment for anchoring and magnifcation of the sample, it can be combined with various standard methods of fluorescence microscopy. In theory, the resolution of the used imaging technique improves linearly with the expansion factor of the ExM treated sample. However, an insuffcient label density and the size of the antibodies can here again impair the effective achievable resolution. The combination of ExM with high-resolution fluorescence microscopy methods represents a promising strategy to increase the resolution of light microscopy. In this thesis, I will present several ExM variants I developed which show the combination of ExM with confocal microscopy, SIM (Structured Illumination Microscopy), STED (STimulated Emission Depletion) and dSTORM. I optimized existing ExM protocols and developed different expansion strategies, which allow the combination with the respective imaging technique. Thereby, I gained new structural insights of isolated centrioles from the green algae Chlamydomonas reinhardtii by combining ExM with STED and confocal microscopy. In another project, I combined 3D-SIM imaging with ExM and investigated the molecular structure of the so-called synaptonemal complex. This structure is formed during meiosis in eukaryotic cells and contributes to the exchange of genetic material between homologous chromosomes. Especially in combination with dSTORM, the ExM method showed its high potential to overcome the limitations of modern fluorescence microscopy techniques. In this project, I expanded microtubules in mammalian cells, a polymer of the cytoskeleton as well as isolated centrioles from C. reinhardtii. By labelling after expansion of the samples, I was able to signifcantly reduce the linkage error of the label and achieve an improved label density. In future, these advantages together with the single molecule sensitivity and high resolution obtained by the dSTORM method could pave the way for achieving molecular resolution in fluorescence microscopy},
  subject      = {Fluoreszenzmikroskopie},
  language  = {en}
}
@phdthesis{Zachary2021,
  author    = {Zachary, Marie},
  title     = {Functional characterization of small non-coding RNAs of \(Neisseria\) \(gonorrhoeae\)},
  doi       = {10.25972/OPUS-24582},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-245826},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {During infection, bacteria need to adapt to a changing environment and have to endure various stress conditions. Small non-coding RNAs are considered as important regulators of bacterial gene expression and so allow quick adaptations by altering expression of specific target genes. Regulation of gene expression in the human-restricted pathogen Neisseria gonorrhoeae, the causative agent of the sexually transmitted disease gonorrhoea, is only poorly understood. The present study aims a better understanding of gene regulation in N. gonorrhoeae by studying small non-coding RNAs. The discovery of antisense RNAs for all opa genes led to the hypothesis of asRNA-mediated degradation of out-of-frame opa transcripts. Analysis of asRNA expression revealed a very low abundance of the transcripts and inclusion of another phase-variable gene in the study indicates that the asRNAs are not involved in degradation of out-of-frame transcripts. This doctoral thesis focuses on the analysis of trans-acting sRNAs. The sibling sRNAs NgncR_162 and NgncR_163 were discovered as post-transcriptional regulators altering expression of genes involved in metabolic processes, amino acid uptake and transcriptional regulation. A more detailed analysis by in silico and transcriptomic approaches showed that the sRNAs regulate a broad variety of genes coding for proteins of central metabolism, amino acid biosynthesis and degradation and several transport processes. Expression levels of the sibling sRNAs depend on the growth phase of the bacteria and on the growth medium. This indicates that NgncR_162 and NgncR_163 are involved in the adaptation of the gonococcal metabolism to specific growth conditions. This work further initiates characterisation of the sRNA NgncR_237. An in silico analysis showed details on sequence conservation and a possible secondary structure. A combination of in silico target prediction and differential RNA sequencing resulted in the identification of several target genes involved in type IV pilus biogenesis and DNA recombination. However, it was not successful to find induction conditions for sRNA expression. Interestingly, a possible sibling sRNA could be identified that shares the target interaction sequence with NgncR_237 and could therefore target the same mRNAs. In conclusion, this thesis provides further insights in gene regulation by non-coding RNAs in N. gonorrhoeae by analysing two pairs of sibling sRNAs modulating bacterial metabolism or possibly type IV pilus biogenesis.},
  subject      = {Neisseria gonorrhoeae},
  language  = {en}
}
@phdthesis{Vollmuth2021,
  author    = {Vollmuth, Nadine},
  title     = {Role of the proto-oncogene c-Myc in the development of Chlamydia trachomatis},
  doi       = {10.25972/OPUS-20365},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-203655},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {Chlamydia trachomatis, an obligate intracellular human pathogen, is the world's leading cause of infection related blindness and the most common, bacterial sexually transmitted disease. In order to establish an optimal replicative niche, the pathogen extensively interferes with the physiology of the host cell. Chlamydia switches in its complex developmental cycle between the infectious non-replicative elementary bodies (EBs) and the non-infectious replicative reticulate bodies (RBs). The transformation to RBs, shortly after entering a host cell, is a crucial process in infection to start chlamydial replication. Currently it is unknown how the transition from EBs to RBs is initiated. In this thesis, we could show that, in an axenic media approach, L glutamine uptake by the pathogen is crucial to initiate the EB to RB transition. L-glutamine is converted to amino acids which are used by the bacteria to synthesize peptidoglycan. Peptidoglycan inturn is believed to function in separating dividing Chlamydia. The glutamine metabolism is reprogrammed in infected cells in a c-Myc-dependent manner, in order to accomplish the increased requirement for L-glutamine. Upon a chlamydial infection, the proto-oncogene c-Myc gets upregulated to promote host cell glutaminolysis via glutaminase GLS1 and the L-glutamine transporter SLC1A5/ASCT2. Interference with this metabolic reprogramming leads to limited growth of C. trachomatis. Besides the active infection, Chlamydia can persist over a long period of time within the host cell whereby chronic and recurrent infections establish. C. trachomatis acquire a persistent state during an immune attack in response to elevated interferon-γ (IFN-γ) levels. It has been shown that IFN-γ activates the catabolic depletion of L-tryptophan via indoleamine 2,3-dioxygenase (IDO), resulting in the formation of non-infectious atypical chlamydial forms. In this thesis, we could show that IFN-γ depletes the key metabolic regulator c-Myc, which has been demonstrated to be a prerequisite for chlamydial development and growth, in a STAT1-dependent manner. Moreover, metabolic analyses revealed that the pathogen de routs the host cell TCA cycle to enrich pyrimidine biosynthesis. Supplementing pyrimidines or a-ketoglutarate helps the bacteria to partially overcome the persistent state. Together, the results indicate a central role of c-Myc induced host glutamine metabolism reprogramming and L-glutamine for the development of C. trachomatis, which may provide a basis for anti-infectious strategies. Furthermore, they challenge the longstanding hypothesis of L-tryptophan shortage as the sole reason for IFN-γ induced persistence and suggest a pivotal role of c-Myc in the control of the C. trachomatis dormancy.},
  language  = {en}
}
@phdthesis{Staus2021,
  author    = {Staus, Madlen},
  title     = {Glutathione-dependent reprogramming in melanoma},
  doi       = {10.25972/OPUS-16842},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-168424},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {These days, treatment of melanoma patients relies on targeted therapy with BRAF/MEK inhibitors and on immunotherapy. About half of all patients initially respond to existing therapies. Nevertheless, the identification of alternative therapies for melanoma patients with intrinsic or acquired resistance is of great importance. In melanoma, antioxidants play an essential role in the maintenance of the redox homeostasis. Therefore, disruption of the redox homeostasis is regarded as highly therapeutically relevant and is the focus of the present work. An adequate supply of cysteine is essential for the production of the most important intracellular antioxidants, such as glutathione. In the present work, it was investigated whether the depletion of cysteine and glutathione is therapeutically useful. Depletion of glutathione in melanoma cells could be achieved by blocking cysteine supply, glutathione synthesis, and NADPH regeneration. As expected, this led to an increased level of reactive oxygen species (ROS). Surprisingly, however, these changes did not impair the proliferation and survival of the melanoma cells. In contrast, glutathione depletion led to cellular reprogramming which was characterized by the induction of mesenchymal genes and the repression of differentiation markers (phenotypic switch). This was accompanied by an increased migration and invasion potential which was favored by the induction of the transcription factor FOSL1. To study in vivo reprogramming, Gclc, the first and rate-limiting enzyme in glutathione synthesis, was knocked out by CRISPR/Cas9 in murine melanoma cells. The cells were devoid of glutathione, but were fully viable and showed a phenotypic switch, the latter only in MITF-expressing B16F1 cells and not in MITF-deficient D4M3A.781 cells. Following subcutaneous injection into immunocompetent C57BL/6 mice, Gclc knockout B16F1 cells grew more aggressively and resulted in an earlier tumor onset than B16F1 control cells. In summary, this work demonstrates that inhibition of cysteine supply and thus, glutathione synthesis leads to cellular reprogramming in melanoma. In this context, melanoma cells show metastatic capabilities, promoting a more aggressive form of the disease.},
  subject      = {Melanom},
  language  = {en}
}
@phdthesis{Solger2021,
  author    = {Solger, Franziska},
  title     = {Central role of sphingolipids on the intracellular survival of \(Neisseria\) \(gonorrhoeae\) in epithelial cells},
  doi       = {10.25972/OPUS-24753},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-247534},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {Neisseria gonorrhoeae are Gram-negative bacteria with diplococcal shape. As an obligate human pathogen, it is the causative agent of gonorrhoea, a sexually transmitted disease. Gonococci colonize a variety of mucosal tissues, mainly the urogenital tract in men and women. Occasionally N. gonorrhoeae invades the bloodstream, leading to disseminated gonococcal infection. These bacteria possess a repertoire of virulence factors, which expression patterns can be adapted to the environmental conditions of the host. Through the accumulation of antibiotic resistances and in absence of vaccines, some neisserial strains have the potential to spread globally and represent a major public health threat. Therefore, it is necessary to understand the exact molecular mechanisms underlying the successful infection and progression of gonococci within their host. This deeper understanding of neisserial infection and survival mechanisms is needed for the development of new therapeutic agents. In this work, the role of host-cell sphingolipids on the intracellular survival of N. gonorrhoeae was investigated. It was shown that different classes of sphingolipids strongly interact with invasive gonococci in epithelial cells. Therefore, novel and highly specific clickable sphingolipid analogues were applied to study these interactions with this pathogen. The formation of intra- and extracellular sphingosine vesicles, which were able to target gonococci, was observed. This direct interaction led to the uptake and incorporation of sphingosine into the neisserial membrane. Together with in vitro results, sphingosine was identified as a potential bactericidal reagent as part of the host cell defence. By using different classes of sphingolipids and their clickable analogues, essential structural features, which seem to trigger the bacterial uptake, were detected. Furthermore, effects of key enzymes of the sphingolipid signalling pathway were tested in a neutrophil infection model. In conclusion, the combination of click chemistry and infection biology made it possible to shed some light on the dynamic interplay between cellular sphingosine and N. gonorrhoeae. Thereby, a possible "catch-and-kill" mechanism could have been observed.},
  subject      = {Neisseria gonorrhoeae},
  language  = {en}
}
@phdthesis{Schuster2021,
  author    = {Schuster, Sarah},
  title     = {Analysis of \(Trypanosoma\) \(brucei\) motility and the infection process in the tsetse fly vector},
  doi       = {10.25972/OPUS-19269},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-192691},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {African trypanosomes are protist pathogens that are infective for a wide spectrum of mammalian hosts. Motility has been shown to be essential for their survival and represents an important virulence factor. Trypanosoma brucei is transmitted by the bite of the bloodsucking tsetse fly, the only vector for these parasites. The voyage through the fly is complex and requires several migration, proliferation and differentiation steps, which take place in a defined order and in specific fly tissues. The first part of this doctoral thesis deals with the establishment of the trypanosome tsetse system as a new model for microswimmer analysis. There is an increasing interdisciplinary interest in microbial motility, but a lack of accessible model systems. Therefore, this work introduces the first enclosed in vivo host parasite system that is suitable for analysis of diverse microswimmer types in specific microenvironments. Several methods were used and adapted to gain unprecedented insights into trypanosome motion, the fly´s interior architecture and the physical interaction between host and parasite. This work provides a detailed overview on trypanosome motile behavior as a function of development in diverse host surroundings. In additional, the potential use of artificial environments is shown. This can be used to partly abstract the complex fly architecture and analyze trypanosome motion in defined nature inspired geometries. In the second part of the thesis, the infection of the tsetse fly is under investigation. Two different trypanosome forms exist in the blood: proliferative slender cells and cell cycle arrested stumpy cells. Previous literature states that stumpy cells are pre adapted to survive inside the fly, whereas slender cells die shortly after ingestion. However, infection experiments in our laboratory showed that slender cells were also potentially infective. During this work, infections were set up so as to minimize the possibility of stumpy cells being ingested, corroborating the observation that slender cells are able to infect flies. Using live cell microscopy and fluorescent reporter cell lines, a comparative analysis of the early development following infection with either slender or stumpy cells was performed. The experiments showed, for the first time, the survival of slender trypanosomes and their direct differentiation to the procyclic midgut stage, contradicting the current view in the field of research. Therefore, we can shift perspectives in trypanosome biology by proposing a revised life cycle model of T. brucei, where both bloodstream stages are infective for the vector.},
  subject      = {Motilit{\"a}t},
  language  = {en}
}
@phdthesis{Ruedenauer2021,
  author    = {R{\"u}denauer, Fabian},
  title     = {Nutrition facts of pollen: nutritional quality and how it affects reception and perception in bees},
  doi       = {10.25972/OPUS-21254},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212548},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {Nutrients belong to the key elements enabling life and influencing an organism's fitness. The intake of nutrients in the right amounts and ratios can increase fitness; strong deviations from the optimal intake target can decrease fitness. Hence, the ability to assess the nutritional profile of food would benefit animals. To achieve this, they need the according nutrient receptors, the ability to interpret the receptor information via perceptive mechanisms, and the ability to adjust their foraging behavior accordingly. Additionally, eventually existing correlations between the nutrient groups and single nutrient compounds in food could help them to achieve this adjustment. A prominent interaction between food and consumer is the interaction between flowering plants (angiosperms) and animal pollinators. Usually both of the interacting partners benefit from this mutualistic interaction. Plants are pollinated while pollinators get a (most of the times) nutritional reward in form of nectar and/or pollen. As similar interactions between plants and animals seem to have existed even before the emergence of angiosperms, these interactions between insects and angiosperms very likely have co-evolved right from their evolutionary origin. Therefore, insect pollinators with the ability to assess the nutritional profile may have shaped the nutritional profile of plant species depending on them for their reproduction via selection pressure. In Chapter I of this thesis the pollen nutritional profile of many plant species was analyzed in the context of their phylogeny and their dependence on insect pollinators. In addition, correlations between the nutrients were investigated. While the impact of phylogeny on the pollen protein content was little, the mutual outcome of both of the studies included in this chapter is that protein content of pollen is mostly influenced by the plant's dependence on insect pollinators. Several correlations found between nutrients within and between the nutrient groups could additionally help the pollinators to assess the nutrient profile of pollen. An important prerequisite for this assessment would be that the pollinators are able to differentiate between pollen of different plant species. Therefore, in Chapter II it was investigated whether bees have this ability. Specifically, it was investigated whether honeybees are able to differentiate between pollen of two different, but closely related plant species and whether bumblebees prefer one out of three pollen mixes, when they were fed with only one of them as larvae. Honeybees indeed were able to differentiate between the pollen species and bumblebees preferred one of the pollen mixes to the pollen mix they were fed as larvae, possibly due to its nutritional content. Therefore, the basis for pollen nutrient assessment is given in bees. However, there also was a slight preference for the pollen fed as larvae compared to another non-preferred pollen mix, at least hinting at the retention of larval memory in adult bumblebees. Chapter III looks into nutrient perception of bumblebees more in detail. Here it was shown that they are principally able to perceive amino acids and differentiate between them as well as different concentrations of the same amino acid. However, they do not seem to be able to assess the amino acid content in pollen or do not focus on it, but instead seem to focus on fatty acids, for which they could not only perceive concentration differences, but also were able to differentiate between. These findings were supported by feeding experiments in which the bumblebees did not prefer any of the pollen diets containing less or more amino acids but preferred pollen with less fatty acids. In no choice feeding experiments, bumblebees receiving a diet with high fatty acid content accepted undereating other nutrients instead of overeating fat, leading to increased mortality and the inability to reproduce. Hence, the importance of fat in pollen needs to be looked into further. In conclusion, this thesis shows that the co-evolution of flowering plants and pollinating insects could be even more pronounced than thought before. Insects do not only pressure the plants to produce high quality nectar, but also pressure those plants depending on insect pollination to produce high quality pollen. The reason could be the insects' ability to receive and perceive certain nutrients, which enables them to forage selectively leading to a higher reproductive success of plants with a pollinator-suitable nutritional pollen profile.},
  subject      = {Pollen},
  language  = {en}
}
@phdthesis{Roeschert2021,
  author    = {R{\"o}schert, Isabelle},
  title     = {Aurora-A prevents transcription-replication conflicts in MYCN-amplified neuroblastoma},
  doi       = {10.25972/OPUS-24303},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-243037},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {Neuroblastoma is the most abundant, solid, extracranial tumor in early childhood and the leading cause of cancer-related childhood deaths worldwide. Patients with high-risk neuroblastoma often show MYCN-amplification and elevated levels of Aurora-A. They have a low overall survival and despite multimodal therapy options a poor therapeutic prognosis. MYCN-amplified neuroblastoma cells depend on Aurora-A functionality. Aurora-A stabilizes MYCN and prevents it from proteasomal degradation by competing with the E3 ligase SCFFBXW7. Interaction between Aurora-A and MYCN can be observed only in S phase of the cell cycle and activation of Aurora-A can be induced by MYCN in vitro. These findings suggest the existence of a profound interconnection between Aurora-A and MYCN in S phase. Nevertheless, the details remain elusive and were investigated in this study. Fractionation experiments show that Aurora-A is recruited to chromatin in S phase in a MYCN-dependent manner. Albeit being unphosphorylated on the activating T288 residue, Aurora-A kinase activity was still present in S phase and several putative, novel targets were identified by phosphoproteomic analysis. Particularly, eight phosphosites dependent on MYCN-activated Aurora-A were identified. Additionally, phosphorylation of serine 10 on histone 3 was verified as a target of this complex in S phase. ChIP-sequencing experiments reveal that Aurora-A regulates transcription elongation as well as histone H3.3 variant incorporation in S phase. 4sU-sequencing as well as immunoblotting demonstrated that Aurora-A activity impacts splicing. PLA measurements between the transcription and replication machinery revealed that Aurora-A prevents the formation of transcription-replication conflicts, which activate of kinase ATR. Aurora-A inhibitors are already used to treat neuroblastoma but display dose-limiting toxicity. To further improve Aurora-A based therapies, we investigated whether low doses of Aurora-A inhibitor combined with ATR inhibitor could increase the efficacy of the treatment albeit reducing toxicity. The study shows that the combination of both drugs leads to a reduction in cell growth as well as an increase in apoptosis in MYCN-amplified neuroblastoma cells, which is not observable in MYCN non-amplified neuroblastoma cells. This new approach was also tested by a collaboration partner in vivo resulting in a decrease in tumor burden, an increase in overall survival and a cure of 25\% of TH-MYCN mice. These findings indicate indeed a therapeutic window for targeting MYCN-amplified neuroblastoma.},
  subject      = {Neuroblastom},
  language  = {en}
}
@phdthesis{Roth2021,
  author    = {Roth, Nicolas M{\´e}riadec Max Andr{\´e}},
  title     = {Temporal development of communities with a focus on insects, in time series of one to four decades},
  doi       = {10.25972/OPUS-23549},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-235499},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {Changes and development are fundamental principles in biocenoses and can affect a multitude of ecological processes. In insect communities phenological and density changes, changes in species richness and community composition, as well as interactions between those changes, are the most important macro processes. However, climate change and other factors like habitat degradation and loss alter these processes leading to shifts and general biodiversity declines. Even though knowledge about insect decline in central Europe increased during the last decades, there are significant knowledge gaps about the development of insect communities in certain habitats and taxa. For example, insect communities in small lentic as well as in forested habitats are under-sampled and reported to be less endangered than communities in other habitats. Furthermore, the changes within habitats and taxa are additionally influenced by certain traits, like host or feeding specialization. To disentangle these influences and to increase the knowledge about the general long-term development of insect communities, comprehensive long-term monitoring studies are needed. In addition, long-term effects of conservation strategies should also be evaluated on large time scales in order to be able to decide on a scientific base which strategies are effective in promoting possibly declining taxa. Hence, this thesis also tackles the effects of an integrative conservation strategy on wood dependent beetle and fungi, beside the development of water beetle and macro moth communities over multiple decades. In Chapter 2 I present a study on the development of water beetle communities (Dytiscidae, Haliplidae, Noteridae) in 33 water bodies in Southern Germany from 1991 to 2018. Time-standardized capture per waterbody was used during three periods: between 1991 and 1995, 2007 and 2008, and 2017 and 2018. Results showed annual declines in both species number (ca. -1\%) and abundance (ca. -2\%). In addition, community composition shifted over time in part due to changing pH values. Hence, the recorded changes during the 28-year study period partly reflect natural succession processes. However, since also moor-related beetle species decreased significantly, it is likely that water beetles in southern Germany are also threatened by non-successional factors, including desiccation, increased nitrogen input and/or mineralization, as well as the loss of specific habitats. The results suggest, that in small to midsize lentic waterbodies, current development should aim for constant creation of new water bodies and protection of moor waterbodies in order to protect water beetle communities on a landscape scale. In Chapter 3 I present an analysis of the development of nocturnal macro moth species richness, abundance and biomass over four decades in forests of southern Germany. Two local scale data sets featuring a coppiced oak forest as well as an oak high forest were analysed separately from a regional data set representing all forest types in the temperate zone of Central Europe. At the regional scale species richness, abundance and biomass showed annual declines of ca. 1 \%, 1.3 \% and 1.4 \%, respectively. These declines were more pronounced in plant host specialists and in dark coloured species. In contrast, species richness increased by ca. 1.5 \% annually in the coppiced forest, while no significant trends were found in the high forest. In contrast to past assumptions, insect decline apparently affects also hyper diverse insect groups in forests. Since host specialists and dark coloured species were affected more heavily by the decline than other groups, habitat loss and climate change seem to be potential drivers of the observed trends. However, the positive development of species richness in the coppiced oak forest indicates that maintaining complex and diverse forest ecosystems through active management might compensate for negative trends in biodiversity. Chapter 4 features a study specifically aiming to investigate the long-term effect of deadwood enrichment as an integrative conservation strategy on saproxylic beetles and fungi in a central European beech forest at a landscape scale. A before-after control-impact design, was used to compare assemblages and gamma diversities of saproxylic organisms (beetles and fungi) in strictly protected old-growth forest areas (reserves) and previously moderately and intensively managed forest areas. Forests were sampled one year before and a decade after starting a landscape-wide strategy of dead-wood enrichment. Ten years after the start of the dead-wood enrichment, neither gamma diversities of saproxylic organisms nor species composition of beetles did reflect the previous management types anymore. However, fungal species composition still mirrored the previous management gradient. The results demonstrated that intentional enrichment of dead wood at the landscape scale can effectively restore communities of saproxylic organisms and may thus be a suitable strategy in addition to permanent strict reserves in order to protect wood dependent organisms in Europe. In this thesis I showed, that in contrast to what was assumed and partly reported so far, also water beetles in lentic water bodies and macro moths in forests decreased in species richness, abundance and biomass during the last three to four decades. In line with earlier studies, especially dark coloured species and specialists decreased more than light-coloured species and generalists. The reasons for these declines could partly be attributed to natural processes and pollution and possibly to climate change. However, further studies, especially experimental ones, will be needed to achieve a better understanding of the reasons for insect decline. Furthermore, analyses of time series data should be interpreted cautiously especially if the number of sampling years is smaller than ten years. In addition, validation techniques such as left- and right- censoring and cross validation should be used in order to proof the robustness of the analyses. However, the lack of knowledge, we are still facing today, should not prevent scientists and practitioners from applying conservation measures. In order to prove the effectiveness of such measures, long-term monitoring is crucial. Such control of success is essential for evidence based and thus adapted conservation strategies of threatened organisms.},
  subject      = {climate change},
  language  = {en}
}
@phdthesis{Mayr2021,
  author    = {Mayr, Antonia Veronika},
  title     = {Following Bees and Wasps up Mt. Kilimanjaro: From Diversity and Traits to hidden Interactions of Species},
  doi       = {10.25972/OPUS-18292},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-182922},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {Chapter 1 - General Introduction One of the greatest challenges of ecological research is to predict the response of ecosystems to global change; that is to changes in climate and land use. A complex question in this context is how changing environmental conditions affect ecosystem processes at different levels of communities. To shed light on this issue, I investigate drivers of biodiversity on the level of species richness, functional traits and species interactions in cavity-nesting Hymenoptera. For this purpose, I take advantage of the steep elevational gradient of Mt. Kilimanjaro that shows strong environmental changes on a relatively small spatial scale and thus, provides a good environmental scenario for investigating drivers of diversity. In this thesis, I focus on 1) drivers of species richness at different trophic levels (Chapter 2); 2) seasonal patterns in nest-building activity, life-history traits and ecological rates in three different functional groups and at different elevations (Chapter 3) and 3) changes in cuticular hydrocarbons, pollen composition and microbiomes in Lasioglossum bees caused by climatic variables (Chapter 4). Chapter 2 - Climate and food resources shape species richness and trophic interactions of cavity-nesting Hymenoptera Drivers of species richness have been subject to research for centuries. Temperature, resource availability and top-down regulation as well as the impact of land use are considered to be important factors in determining insect diversity. Yet, the relative importance of each of these factors is unknown. Using trap nests along the elevational gradient of Mt. Kilimanjaro, we tried to disentangle drivers of species richness at different trophic levels. Temperature was the major driver of species richness across trophic levels, with increasing importance of food resources at higher trophic levels in natural antagonists. Parasitism rate was both related to temperature and trophic level, indicating that the relative importance of bottom-up and top-down forces might shift with climate change. Chapter 3 - Seasonal variation in the ecology of tropical cavity-nesting Hymenoptera Natural populations fluctuate with the availability of resources, presence of natural enemies and climatic variations. But tropical mountain seasonality is not yet well investigated. We investigated seasonal patterns in nest-building activity, functional traits and ecological rates in three different insect groups at lower and higher elevations separately. Insects were caught with trap nests which were checked monthly during a 17 months period that included three dry and three rainy seasons. Insects were grouped according to their functional guilds. All groups showed strong seasonality in nest-building activity which was higher and more synchronised among groups at lower elevations. Seasonality in nest building activity of caterpillar-hunting and spider-hunting wasps was linked to climate seasonality while in bees it was strongly linked to the availability of flowers, as well as for the survival rate and sex ratio of bees. Finding adaptations to environmental seasonality might imply that further changes in climatic seasonality by climate change could have an influence on life-history traits of tropical mountain species. Chapter 4 - Cryptic species and hidden ecological interactions of halictine bees along an elevational Gradient Strong environmental gradients such as those occurring along mountain slopes are challenging for species. In this context, hidden adaptations or interactions have rarely been considered. We used bees of the genus Lasioglossum as model organisms because Lasioglossum is the only bee genus occurring with a distribution across the entire elevational gradient at Mt. Kilimanjaro. We asked if and how (a) cuticular hydrocarbons (CHC), which act as a desiccation barrier, change in composition and chain length along with changes in temperature and humidity (b), Lasioglossum bees change their pollen diet with changing resource availability, (c) gut microbiota change with pollen diet and climatic conditions, and surface microbiota change with CHC and climatic conditions, respectively, and if changes are rather influenced by turnover in Lasioglossum species along the elevational gradient. We found physiological adaptations with climate in CHC as well as changes in communities with regard to pollen diet and microbiota, which also correlated with each other. These results suggest that complex interactions and feedbacks among abiotic and biotic conditions determine the species composition in a community. Chapter 5 - General Discussion Abiotic and biotic factors drove species diversity, traits and interactions and they worked differently depending on the functional group that has been studied, and whether spatial or temporal units were considered. It is therefore likely, that in the light of global change, different species, traits and interactions will be affected differently. Furthermore, increasing land use intensity could have additional or interacting effects with climate change on biodiversity, even though the potential land-use effects at Mt. Kilimanjaro are still low and not impairing cavity-nesting Hymenoptera so far. Further studies should address species networks which might reveal more sensitive changes. For that purpose, trap nests provide a good model system to investigate effects of global change on multiple trophic levels and may also reveal direct effects of climate change on entire life-history traits when established under different microclimatic conditions. The non-uniform effects of abiotic and biotic conditions on multiple aspects of biodiversity revealed with this study also highlight that evaluating different aspects of biodiversity can give a more comprehensive picture than single observations.},
  subject      = {land use},
  language  = {en}
}