Institut für Ökologie, Evolution und Diversität
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In almost all parts of the world the industrialisation grows continuously and thus, the chemical pollution of natural waters has become a major public concern. A major consequence and one of the key environmental problems we are facing today is the increasing contamination of freshwater systems with chemicals. The chemicals are detected in wastewater, surface (river) water, ground water and drinking water ubiquitously in natural waters and not only in industrialised areas. The main point sources for water pollution and the release of these synthetic organic substances of human origin, so called micropollutants (MPs), are wastewater treatment plants (WWTPs). These MPs such as pharmaceuticals, personal care products, disinfectant chemicals, chemicals used in the industry and in households, contraceptives, hormones, food additives, artificial sweeteners, pesticides, biocides, and many emerging contaminants are only incompletely removed by the existing conventional wastewater treatment technologies. The MPs end up in the water cycle and have adverse effects on wildlife aquatic ecosystems and human health even at very low concentrations. Therefore, advanced wastewater treatment (AWWT) technologies, such as ozonation, treatment with activated carbon, biofiltration, membrane bioreactors (MBRs) or exposure to ultraviolet light are investigated as options to upgrade conventional WWTPs. However, several studies show that especially the ozonation of wastewater generates diverse transformation products (TPs) with unknown properties. These TPs could be more toxic than the mother compound. Thus, a post-treatment after the ozonation process is required.
The present thesis was part of the BMBF-funded TransRisk project dealing with “the characterisation, communication, and minimisation of risks of emerging pollutants and pathogens in the water cycle”. One main objective was the investigation of conventional treated wastewater after a full-scale ozonation with four post-treatments (each non-aerated and aerated granular activated carbon (GAC) filtration and biofiltration) in comparison to a MBR treatment of raw (untreated) wastewater separately and in combination with an additional ozonation on a pilot WWTP. For this purpose, the wastewater samples were characterised with a comprehensive battery of in vitro and in vivo bioassays. The in vitro bioassays were performed to detect endocrine activities (such as (anti)estrogenic and (anti)androgenic activities), genotoxicity, and mutagenicity. The results showed a decreased estrogenic activity due to the conventional wastewater treatment as well as the ozonation, but a distinct increase of the anti-estrogenic activity and the mutagenicity in the ozonated wastewater, possibly caused by new formed TPs, that were reduced after the post-treatments whereas the GAC filtration performed better than the biofiltration. The in vivo bioassays included for example the impact of the wastewater on mortality, reproduction, development, and energy reserves of the test organisms. The in vivo on-site tests with the mudsnail Potamopyrgus antipodarum and with the amphipod Gammarus fossarum indicated a major impact of conventional treated wastewater, ozonated wastewater, and MBR treated wastewater. The flow channel experiments in the laboratory with Gammarus pulex pointed to a serious impact of an estrogenic effluent on life-history traits of the amphipod. Finally, an ozonation of the wastewater with subsequent GAC filtration represented the most promising option. In addition, chemical analyses of 40 selected MPs, so called tracer substances, performed in parallel to the in vitro and in vivo bioassays underlined this assumption.
A second main objective was the optimisation of the preparation of water and wastewater samples for ecotoxicological in vitro bioassays because common sample preparation techniques are predominantly adapted for chemical analyses. Therefore, the impact of sample filtration, long-term acidification with following neutralisation as well as the enrichment with solid phase extraction (SPE) in combination with short-term acidification were investigated using amongst others raw (untreated) wastewater, hospital wastewater, conventional treated and ozonated wastewater, surface water, and ground water. Overall, eleven in vitro bioassays were performed for the detection of endocrine activities, genotoxicity, and mutagenicity. The results show that sample filtration and acidification/neutralisation significantly affected the outcome of the bioassays especially the anti-estrogenic activity and the mutagenicity whereas the sample filtration had a minor impact than the acidification. Thus, the testing of untreated (waste)water samples is advisable because the sample is minimally processed. Furthermore, the SPE extracts showed in parts high cytotoxic effects whereby no conclusions on the results of the bioassays were possible. However, the enrichment of endocrine activity and mutagenicity was predominantly effective but depended on the used SPE cartridge and the pH value of the (waste)water samples. Based on the results the use of a Telos C18/ENV cartridge and an acidified sample is recommendable. In the end, there is a need to optimise the sample preparation for in vitro bioassays to reach their maximum outcome for the best possible assessment of the water quality.
Methods using environmental DNA to explore and analyze biodiversity from previously unexplored habitats and ecosystems have become increasingly popular in recent years. This is particularly due to the potential reduction in necessary taxonomic expertise, the opportunity to assess microorganismal communities, and decreased time investments required to cover large spatial extents. In forests, the surface of tree bark is an important habitat for epiphytic diversity. Because of the large surface area rich in micro-niches, the seasonal stability of the substrate, and the longevity of trees, tree bark surfaces provide an ideal habitat for many species. Yet, we lack a comprehensive understanding of their communities and the environmental drivers behind the community assembly. These missing links hinder the exploration of the forest microbiome as a whole and limits our understanding of functions of a large forest habitat and its connections to other forest microbiomes. With a holistic eDNA metabarcoding approach, encompassing samples of three major taxonomic groups (e.g. bacteria, fungi, and green algae), as well as simultaneous collections from multiple forest habitats we can contribute to closing these gaps and increase our knowledge of the forest microbiome.
My dissertation is set within the framework of the Biodiversity Exploratories and was conducted in four parts: I. the establishment of an eDNA metabarcoding workflow to reveal the local diversity of the bark surface microbiome; II. the upscaling of the method to large geographic and environmental gradients to uncover the drivers of the microbiome; III. the integration of soil and bark samples to investigate compositional differences in two important forest habitats; IV. the evaluation of eDNA metabarcoding as a tool for biodiversity assessments of lichen diversity in forests.
In the first part, I developed a simple, cost-effective and fast sampling strategy to acquire eDNA samples from the bark of trees in forest ecosystems. Using readily available medical-specimen-collection swabs I sampled bark surfaces of individual trees in Central German forests and used metabarcoding to amplify marker genes of green algae, fungi and bacteria. From the sequencing reads I calculated the first diversity estimates of the major organismal groups of bark surface microbiomes from Central European forests. Overall the methodology produced reliable results, allowing for an expanded sampling in the second part.
In the second part of the dissertation, I expanded the sampling based on the results of part one. I collected bark surface samples from the three regions of the Biodiversity Exploratories covering large spatial and environmental gradients representative for Central European forests. The collection included composite samples from 150 plots and over 750 trees. Utilizing measurements of climatic and forest structure variables provided by the Biodiversity Exploratories, as well as my own community data, I identified the biotic and abiotic drivers behind alpha and beta diversity of the bark surface microbiome.
In the third part, I studied the differences between the bark surface as an unexplored and the soil as an example of a well characterized forest microbiome. Using only the fungal part of the large sampling campaign and soil samples obtained from the same plots at the same time, I assessed the commonalities and differences of the micro-communities of these distinct forest niches. Furthermore, I included two coniferous and one deciduous tree species to examine, if the effect of tree species, previously shown for soil microbiomes, also holds true for the bark surface.
In the last part of my dissertation, I used eDNA in a more applied way as a tool in biodiversity assessments of lichenized fungi. I compared the results from eDNA metabarcoding to an expert floristic mapping conducted in the same plots in 2007/2008. I assigned functional guilds to the fungal taxa obtained in the large sampling campaign and used a subset that was assigned as lichenized fungi.
In conclusion, I showed that eDNA metabarcoding is a valuable tool to reveal the unknown diversity of microorganisms in forest ecosystems. In particular, my results advance our understanding of the bark surface microbiome, an underexplored habitat within forests. The tightly linked interactions of the three major microbial groups underline that studies need to take holistic approaches across multiple taxonomic groups to deepen our understanding of processes governing the assembly of microbiomes. Results from my dissertation may serve as a foundation to inform hypotheses addressing the functions of forest microbiomes. The massive diversity data collected may also contribute to closing the gap in our understanding of macro-organisms and micro-organisms with respect to diversity distributions and patterns of richness, and serve as a baseline for predictions of biodiversity responses under future anthropogenic change.
Im Rahmen dieser Dissertation wurden unterschiedliche Aspekte der Verbreitung der Vertreter des Pseudoterranova decipiens Komplexes betrachtet und Fragestellungen zur Ökologie und Humanpathogenität der Parasiten bearbeitet. Sie basiert auf drei (ISI-) Fachartikeln, in denen die Nutzung von Fischparasitengemeinschaften als ökologische Indikatoren für entlegene Ökosysteme des Südpolarmeeres (I), die Modellierung geeigneter Verbreitungsgebiete für Arten mit geringen Vorkommensdaten am Beispiel des P. decipiens Komplexes (II) und das Vorkommen potentiell humanpathogener P. bulbosa in unterschiedlichen Mikrohabitaten in Atlantischem Kabeljau (III) thematisiert wurde.
Die Parasitengemeinschaften der in Studie I untersuchten, nahverwandten Antarktisdorsche (Nototheniinae) Nototheniops larseni (n=40), N. nudifrons (n=40) und Lepidonotothen squamifrons (n=49) unterschieden sich hauptsächlich hinsichtlich seltener Parasitenarten. Pseudoterranova decipiens E zählte zu den häufigsten Parasiten der drei betrachteten Wirtsarten. Die Analyse der Wirtsspektren der auf Artebene bestimmten Parasiten zeigte eine geringe Spezifität antarktischer Fischparasiten im Larven- (z.B. Pseudoterranova decipiens E) und Adultstadium (z.B. Elytrophalloides oatesi). Für eine Nutzung als Bioindikatoren ergibt sich die Empfehlung, nicht auf einzelne Parasitenarten, sondern die Zusammensetzung von Parasitenfaunen zurückzugreifen und Parameter wie Abundanz oder Intensität zu berücksichtigen. Vergleiche mit Literaturdaten legten nahe, dass ein Studiendesign, das den periodischen Vergleich der Parasitierungsmuster von Nototheniinae ermöglichen soll, Standorteffekte berücksichtigen sollte. Da es sich bei der Probennahme demersaler Fische um ein aufwändiges und einschneidendes Verfahren handelt, sollten alternative Samplingmethoden vorangetrieben und eine Datenbasis dafür geschaffen werden.
Um die Belastung von Speisefischen mit potentiell humanpathogenen Parasiten in bestimmten Fanggebieten abzuschätzen, kann anhand von Vorkommens- und Umweltdaten mittels statistischer Modelle die Habitateignung für den Parasiten bestimmt werden. Eine Voraussetzung für eine verlässliche Modellierung bilden die Wahl eines geeigneten Algorithmus und die Qualität der Eingangsdaten. Für die Modellierung geeigneter Verbreitungsgebiete für die sechs Arten des P. decipiens Komplexes wurde im Rahmen von Studie II erstmalig ein biotischer Deskriptor herangezogen. Dem Ansatz lag die Annahme zugrunde, dass das Vorkommen geeigneter Endwirte der entscheidende, limitierende Faktor für die Verbreitung eines Parasiten ist, da nur so der Lebenszyklus geschlossen werden kann. Als Hypothesentest dienten Vergleiche der ökologischen Nischen von Parasiten und ihren spezifischen Endwirten im Nischenraum. Anhand der Endwirtdistanz wurde eine Verbesserung der Modellierungsergebnisse mit MaxEnt, gegenüber der ausschließlich auf abiotischen Prädiktoren basierenden Modellierung, für alle Pseudoterranova Arten, insbesondere jene mit einer geringen Anzahl Fundpunkte, erzielt. Grundsätzlich ist der Ansatz auf marine Parasitenarten, deren spezifische Endwirte verlässliche Vorkommensdaten aufweisen, übertragbar. Die Methode stellt jedoch keinen Ersatz für die Erhebung von Vorkommensdaten dar, weshalb die genetische Bestimmung schwer zu identifizierender Taxa sowie die Angabe von Metadaten in jeder parasitologischen Studie obligatorisch sein sollten.
Die Verteilung potentiell humanpathogener Parasitenstadien in für den menschlichen Verzehr vorgesehenen Fischen kann ein entscheidender Faktor für die Übertragung sein. Im Rahmen von Studie III wurde mit dem Referenztranskriptom von P. bulbosa das erste Transkriptom für eine Art den P. decipiens Komplexes erstellt. Anhand einer differentiellen Genexpressionsanalyse wurde untersucht, was die Verteilung der Parasiten auf unterschiedliche Mikrohabitate beeinflusst haben könnte. Dabei wurden siebzig differentiell exprimierte Gene identifiziert, die in aus Leber (32 Gene) und Viscera (38 Gene) von Atlantischem Kabeljau (Gadus morhua) isolierten Proben von P. bulbosa hochreguliert waren. Eine Erklärung für diesen subtilen Unterschied könnte ein Dauerstadium der P. bulbosa Larven zum Zeitpunkt der Probennahmen sein. Ob sich bestimmte Mikrohabitate innerhalb des Wirtes begünstigend auf den Parasiten auswirken, muss mit Hilfe experimenteller Studien gezeigt werden. Erste in Studie III erhobene Daten zum allergenen Potential von P. bulbosa sollten in serologischen Studien getestet werden. Als Grundlage für die Bewertung des pathogenen Potentials von P. bulbosa, sowie der weiteren Arten des P. decipiens Komplexes, sollten in experimentellen Studien NGS-Daten erhoben werden.
Im Rahmen dieser Dissertation wurde in drei methodisch unterschiedlichen Studien ein Bedarf besserer Referenzdaten aufgezeigt. Bestreben diese Datenlücken zu schließen, um das Potential der Methoden besser ausschöpfen zu können, müssen zukünftig noch weiter verstärkt werden.
Auf den Einsatz von Tieren im Rahmen der (Umwelt-)Risikobewertung von Stoffen kann nach wie vor nicht verzichtet werden. Dabei führen die Überprüfungen einer zunehmenden Anzahl neu entwickelter Stoffe, aber auch die gestiegenen Anforderungen der Gesetzgebungen zu einem hohen Verbrauch von Versuchstieren. Diese Untersuchungen sind wichtig, da viele der in Gebrauch befindlichen und in allen Bereichen genutzten Chemikalien potentiell endokrin wirksam sind, auf unterschiedlichen Wegen in die Umwelt gelangen und sich potentiell negativ auf die Gesundheit von Mensch und Tier auswirken können.
Bei den bisher verwendeten Methoden werden vor allem juvenile oder adulte Tiere, aber auch Tiere zur Untersuchung des kompletten Lebenszyklus über eine oder mehrere Generationen für die Beurteilung von Substanzen eingesetzt. Dabei ist bekannt, dass die Entstehung reproduktiver Störungen in der Embryonalphase der jeweiligen Individuen auftritt. Um den Tierverbrauch zu reduzieren, werden teilweise In-vitro-Testsysteme angewendet. Es zeigt sich aber, dass diese Tests lediglich einen bestimmten Zelltyp in einem bestimmten Entwicklungsstadium abbilden können, was die Aussagekraft über die tatsächliche Wirkung auf ein komplexes Gewebe und dessen Entwicklung, erst Recht für den kompletten Organismus, stark einschränkt. Die Aussagekraft dieser Methoden ist daher in bestimmten eingeschränkten Grenzen zu sehen. In der vorliegenden Arbeit wird eine alternative Ersatzmethode vorgestellt mit dem Ziel einer stärkeren Aussagekraft bei toxikologisch und ökotoxikologisch relevanten Endpunkten. Im Fokus stehen hierbei die Effekte von androgenen und estrogenen Substanzen auf die Geschlechtsentwicklung von Hühnerembryonen (Gallus gallus domesticus) auf Ebene der Expression der mRNA, vereint mit Effekten auf Ebene der Organhistologie und – morphologie, verglichen mit den Normalzuständen unbehandelter Individuen. Die neu entwickelte Methode zur Beurteilung solcher Substanzen kann im Rahmen der human- und umwelttoxikologischen Risikobewertung von Stoffen eingesetzt werden und ist ein geeignetes Werkzeug, um die notwendigen Untersuchungen mit der gefordert hohen Beurteilungsqualität durchzuführen. Gleichzeitig kann mit dieser Tierversuchsersatzmethode bei hoher Aussagekraft auch der Verbrauch an weiter und höher entwickelten Versuchstieren verringert werden, was auch einem gesellschaftlich-ethischen Bedürfnis gerecht wird.
In the light of emerging resistances against common drugs, new drug leads are required. In the past natural sources have been more yielding in this respect than synthetic strategies. Fungi synthesize many natural products with biological activities and pharmacological relevance. However, only a fraction of the estimated fungal diversity has been evaluated for biological activity, and much of the Fungi’s natural chemical diversity awaits discovery. Especially promising in this context are lichenized fungi. Lichens are well known for their particularly rich and characteristic secondary chemistry which allows them to withstand intense UV radiation, protects them against herbivory, and prevents them from being overgrown. The slow growth rates of lichens and difficulties and infeasibility of large scale cultivations in the laboratory render lichens inaccessible for applied purposes. These experimental challenges have led to a poor understanding of the molecular mechanisms underlying the biosynthesis of characteristic lichen secondary metabolites. The recent development of improved sequencing techniques has enabled new strategies to address multi-species assemblages directly through metagenome sequencing and survey their biosynthetic potential through genome mining. However, whole genome sequencing of entire lichen thalli to metagenomically assess the lichen-forming fungus without the need of cultivation has not been evaluated for lichens before. This approach will enable the reconstruction of fungal genomes from mixed DNA from lichen thalli and allow the exploration of biosynthetic gene content.
My thesis was conducted in two parts: a methodological evaluation of a metagenomic strategy to reconstruct genomes and gene sets of lichen-forming fungi, and the exploration of biosynthetic gene content with the help of comparative genomics and phylogenetics. For the first part, I evaluated the quality of metagenome-derived genome assemblies and gene sets by direct comparison to culture-derived reference assemblies and gene sets of the same species. I showed that metagenome-derived fungal assemblies are comparable to culture-derived references genomes and have a similar total genome size and fungal genome completeness. The quality of assemblies was affected strongly by the choice of assembler, but not by the method of taxonomic assignment or inference of non-mycobiont DNA sequences. The fungal gene space is well covered in metagenome-derived and culture-derived fungal gene sets and overlaps to 88-90 %. Finally, the metagenome-derived assemblies reliably recover gene families of secondary metabolism. This shows the suitability of metagenomically derived genomes for mining biosynthetic genes, and potentially also other gene families. Overall, the method validation showed a high similarity between metagenome- and culture-derived genome assemblies.
For the second part of my thesis, I explored the biosynthetic gene content in two different systems: Between two sister-species with different ecological requirements but similar chemical profile, and between two species which are metabolite-rich and economically relevant in the perfume industry. I compared the diversity of biosynthetic gene clusters between the species and in the broader context of other lichenized and non-lichenized fungi. Overall, the whole genome mining revealed a large number of uncharacterised secondary metabolite gene clusters in fifteen genomes of lichen-forming fungi compared to other fungal classes. Their number highly outweighs the number of known synthesized metabolites and highlights the hidden biosynthetic potential in lichen-forming fungi. Many biosynthetic gene clusters in the ecological distinct sister-species showed a high homology in accordance with the high synteny in gene content and order in both genomes. These clusters represent ideal candidates for secondary metabolites synthesized by both species, while the remaining clusters may encode for metabolites relevant for the different ecological requirements of both species. The metabolite-rich species used in the perfume industry showed a particularly high number of biosynthetic gene clusters. An in-depth characterization of architecture and gene content of homologous gene clusters together with hints from phylogenetic relatedness to functional characterized metabolites provides promising insights into the biosynthetic gene content of these lichen-forming fungi.
In conclusion, I showed that metagenome sequencing of natural lichen thalli is a feasible approach to reconstruct the fungal mycobiont genome of lichens and circumvent time-consuming and in some cases impossible cultivation of individuals. The genome mining for secondary metabolite gene clusters in lichen-forming fungi revealed a high biosynthetic potential for the discovery of new natural products. One of the focal species, Evernia prunastri, contained the highest ever reported number (80) of biosynthetic clusters in lichenized fungi. The comprehensive cluster characterizations through annotation, comparative mapping and phylogenetics provide first valuable hints for linking metabolites to genes in these lichen-forming fungi. My results pave the way for biotechnological strategies to unlock the vast richness of natural products from lichens for applied purposes.
Antagonistic and mutualistic species interactions provide important ecosystem functions affecting plant population dynamics and distribution. Many of these functions are important for the regeneration of plants, either by limiting or facilitating successful transition between life stages. Interactions can occur across the whole geographical range of a species and thereby encompass different environmental gradients, such as changes in temperature or water availability. Understanding the joint effects of species interactions and environmental factors on the regeneration of plants is key for understanding plant population dynamics under global change and could provide important recommendations for managing and conservation efforts.
My thesis aimed at advancing the knowledge of how species interactions depend on environmental conditions and jointly affect plant recruitment along the elevational distribution of plants. This thesis includes three chapters in which I studied the effects of animal seed deposition, seed predation, mycorrhizal and pathogenic fungi occurrences as well as abiotic and biotic environmental factors on the recruitment of Swiss stone pine (Pinus cembra). I conducted fieldwork in the Swiss Alps across the entire elevational distribution of the pine (1850 – 2250 m a.s.l). Over a period of three years, I recorded animal seed deposition by spotted nutcrackers (Nucifraga caryocatactes) and conducted seed translocation experiments. Further, I assessed fungal communities using DNA metabarcoding. I measured abiotic environmental factors such as temperature, water and light availability, pH, as well as biotic environmental factors such as distance to conspecific adults and ground vegetation cover. In my thesis, I used a broad range of community ecology approaches, from seed dispersal ecology to experimental plant ecology and microbial ecology.
First, I investigated the effects of environmental factors on four recruitment processes (i.e. seed deposition, seed predation, seed germination, seedling survival) of Swiss stone pine. Further, I aimed at identifying the most important recruitment processes potentially limiting pine regeneration across its elevational range. To investigate pine recruitment, I firstly tested how seed deposition, seed predation, seed germination and seedling survival were affected by the microhabitat characteristics ultimately determining where a seed arrives in the environment (i.e. canopy cover & ground vegetation cover). Secondly, I applied a sensitivity analysis to investigate which of the four recruitment processes poses limitation to the pines’ regeneration across its range. My results reveal that the importance of particular recruitment processes varies along the pines’ elevational range. I found that at the lower range margin and the distribution centre seed germination and seedling survival were the main limiting factors, whereas animal-mediated seed dispersal became especially important at the upper range margin. My study contributes to the field with a new approach for disentangling the relative importance of recruitment processes across environmental gradients and thereby could help to project how plant recruitment might respond to future changes in environmental conditions.
The second aim of my study was to investigate how abiotic and biotic environmental factors affect the occurrence of Swiss stone pine-associated pathogenic and mutualistic fungi by combining field measurements of environmental factors with a DNA metabarcoding approach. I identified potentially important fungal interaction partners of the pine and determined drivers shaping their occurrences. My results reveal that generalist fungi were not affected by abiotic and biotic environmental factors. However, specialist pathogens showed patterns according to the Janzen-Connell framework (i.e. accumulation of pathogen close to adult plants). Interestingly, I found evidence for an “inverse” Janzen-Connell effect, i.e. high abundance of a specialist mutualist close to adult plants, potentially mitigating effects of soil pathogens close to parent trees. Further, I found that pine-associated fungi are distributed widely within and beyond the range of their host plant, adding knowledge on how mutualisms and antagonisms might be affected when plants move their distributional range upwards.
Finally, I investigated how known and unknown plant-associated fungi affect the regeneration of Swiss stone pine in an environmental context. My results suggest that seedling establishment was most strongly affected by abiotic environmental factors, such as light availability and maximum summer temperature. Further, the results indicate that seedling survival was affected by biotic environmental factors, i.e. fungal agents, with high abundances of a known fungal pathogen co-occurring with low seedling survival rates. My results also reveal that known mycorrhizal partners as well as a large number of unknown fungal operational taxonomic units (OTUs) were associated with the survival of seedlings. My findings highlight the importance of plant-fungal interactions for plant recruitment and offer a feasible approach for the identification of hidden plant-fungal associations in highly complex DNA metabarcoding datasets. This approach offers a valuable tool for investigating plant-microbe interactions, ultimately helping to understand plant population dynamics.
My dissertation adds to a deeper understanding on the linkage between plant regeneration and species interactions, especially on how plant-animal and plant-fungal interactions in concert with environmental factors shape plant recruitment. My study reveals the importance of animal-mediated seed dispersal and fungal pathogens in plant recruitment with consequences for potential range shifts of plant species. My thesis has important implications for conservation and management efforts by informing on key species interactions under environmental change.
Algae as primary producers are highly important in aquatic ecosystems and provide a variety of environmental and anthropogenic services. In small lotic ecosystems in agriculturally influenced landscapes, algae are often the main constituent of the base of the food web and they contribute considerably to biodiversity. Within these small lotic ecosystems, algae are influenced by both natural stressors, such as flow regime and dry-out events, and anthropogenic factors. Agricultural practices especially influence algal communities by introducing plant protection products (PPP) and fertilizers into the water. The impacts of these exposures and how they affect planktonic algae in particular are not yet well studied in small lotic ecosystems. However, the protection of algae as primary producers is of high relevance and was thus included in official biomonitoring programs such as the European Water Framework Directive (WFD) or in risk assessment of e.g. PPPs. Hence, this thesis addresses this knowledge gap and links new information on algal communities in small lotic ecosystems with biomonitoring and risk assessment.
Data was gathered from small ditches and streams in central Germany as well as from laboratory algal assays. A technique to rapidly classify and quantify planktonic and benthic algae based on their photopigment concentration (measured via delayed fluorescence - DF) in ecological and ecotoxicological studies was assessed, both in the laboratory and in the field. This research provides insight into planktonic and benthic algal communities in small streams and ditches in order to improve management and protection strategies in the face of increased agricultural chemical input. ...
Gallery forests (GFs) are floristically and functionally distinct forests along rivers and watercourses. The GFs of the West African savannas form thin stripes with a particular, species-rich flora differing significantly from the surrounding vegetation. Due to their relative isolation in the savannas and their dependence on rivers, GFs are particularly endangered by the expected global climate changes in the 21st century. Despite their high diversity, little is known about the ecology and biogeography of GFs in West Africa. Especially, their response to climate changes and their vegetation dynamics remain largely unknown. This thesis combines floristic, phylo-geographic and ecological data to investigate the biodiversity, historical and recent biogeography and conservation status of GF species in Burkina Faso (BFA) as a model for West Africa.
Ein Ziel dieser Arbeit war die Entwicklung und biologische Evaluierung einer Sensorik zur Verbesserung der Prognose des Apfelschorfs. Als Grundlage für die Schorfprognose dient nach dem Modell von Mills die Länge der Blattnässedauer in Abhängigkeit von der Lufttemperatur. Es wurden mehrjährige Vergleiche verschiedener käuflicher Blattnässesensoren durchgeführt und in Zusammenarbeit mit der Firma THIES Clima ein Sensor für Wasserbenetzung entwickelt. Der Vergleich der käuflichen Sensoren zeigte deutliche Unterschiede in der Anzeige der Nässedauer zwischen den verschiedenen getesteten Sensoren. Die Eignung dieser Sensoren für die Prognose war sehr verschieden. Der im Rahmen des Verbundprojektes entwickelte Sensor ist zuverlässig, wetterfest, korrosionsbeständig und wartungsarm. Die einzelnen Prototypen wurden nach der Evaluierung in der Klimakammer im Freiland getestet und die Einstellungen anhand von Bioassays auf ihre Eignung zur Prognose überprüft. Der marktreife Prototyp kann ohne weitere Modellierung zur Erfassung der Blattnässe von Apfelblättern in die Prognose eingebunden werden.
Ein weiteres Ziel der vorliegenden Arbeit war es, die Zusammenhänge der diurnalen Rhythmik der Sporenausschleuderung von Venturia inaequalis zu untersuchen. Im Freiland wurden die Ascosporenflüge unter natürlichen Bedingungen und mit Störlicht registriert. Im Labor wurde der Sporenausstoß unter dem Einfluss der Beleuchtungsstärke und Wellenlängen-Zusammensetzung untersucht. Sowohl im Freiland als auch im Labor konnte eine Aufhebung der Dunkelhemmung des Sporenausstoßes erreicht werden. Der sichtbare Anteil des Lichts konnte auch bei Helligkeiten von über 10000 Lux als Auslöser des Sporenausstoßes ausgeschlossen werden. Durch die Bestrahlung der Pseudothecien tragenden Blätter mit nicht sichtbaren infraroten Lichtanteilen wurde eine Freisetzung der Ascosporen auch im Dunkeln erreicht und die diurnale Rhythmik der Sporenausschleuderung im Freiland wurde aufgelöst.
Invasive non-native species are key components of human-induced global environmen-tal change and lead to a loss of biodiversity, alterations of species interactions and changes of ecosystem services. Freshwater ecosystems in particular are strongly affect-ed by biological invasions, since they are spatially restricted environments and often already heavily impacted by anthropogenic activities. Recent human-induced species invasions are often characterized by long-distance dispersal, with many species having extended their native distribution range within a very short time frame. However, a long term view into the past shows that biological invasions are common phenomena in nature—representing the arrival of a species into a location in which it did not originally evolve—as a result of climatic changes, geotectonic activity or other natural events. Once a species arrives in a new habitat, it may experience an array of novel selection pressures resulting from abiotic and biotic environmental factors and simultaneously act as a novel selective agent on the native fauna. Consequences of species invasions are manifold. My thesis, which combines seven studies on different aspects of biological invasions, aims to explore the influence of abiotic stressors and biotic interactions during species introductions and range expansions, as well as the consequences of biological invasions on evolutionary and ecosystem processes.
The first part of my thesis examines human-induced biological invasions, dealing with basic ecological characteristics of invaded ecosystems, novel predator-prey interactions, functional consequences of species invasions and certain behavioral traits that may contribute to the invasiveness of some species. The second part of my thesis examined distribution patterns and phenotypic trait divergence in species that historically invaded new geographical areas. I investigated variation of abiotic and biotic selection factors along a stream gradient as well as ecological and evolutionary consequences of species invasions to extreme habitats. The results highlight the importance of simultaneously considering processes involved in natural invasions and during human-induced invasions to understand the success of invading species.
We often lack detailed information on the impacts of historical biological inva-sions. Also, we are currently lacking crucial knowledge about the time scales during which different mechanisms (behavioral flexibility, plastic phenotypic changes, and ge-netic adaptation) play a role during biological invasions and affect species exchange and establishment. Comparative analyses of historical, natural invasion and recent (man-made) invasions can provide insights into the relative importance of the processes governing adaptation to abiotic stressors and selection resulting from biotic interactions. Beyond their negative effects, the establishment of invasive species and the subsequent range expansion represent “natural experiments” to investigate fundamental questions in ecology and evolution. My comparison of natural and human-induced biological invasions revealed that in many cases preadaptation to altered abiotic conditions plays a key role during early stages of invasions and range expansions. Considering the evolutionary history of invasive species and the evolutionary history of the recipient native fauna might therefore help predict the consequences of biological invasions for the ecosystem under consideration and the future success of the invading species. This knowledge can also be implemented when formulating conservation strategies, including methods to mitigate and manage human-induced biological invasions.