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Aim of the study: The aim of this study is to provide information on species-specific basic wood density (g cm-3) and moisture content (%) in Mediterranean shrublands. Area of study: The study covers two sites of the sclerophyllous shrubland in central Chile, Cortaderal (34°35’S 71°29’W) and Miraflores (34°08’S 70°37’W), characterized by different climatic and topographic conditions. Material and methods: The sampling area covers 4,000 m2 over four plots at two sites. Shrub species were identified and size-related attributes such as height and crown size measured. A total of 322 shrubs were sampled at 0.3 m aboveground to determine basic wood density and moisture content. Species-specific differences and similarities were analyzed by multiple pairwise comparisons (post-hoc tests) and by ordination and hierarchical clustering. Main results: We found high variation across species in wood density (0.46-0.77 g cm-3) and moisture content (41.6-113.1%), with many significant differences among species in wood density and among sites in moisture content. Because intraspecific variability could not be explained by shrub size and pronounced differences in wood density (0.49-0.64 g cm-3) also occurred between species of the same genus (e.g., Baccharis linearis and Baccharis macraei), our results suggested that phylogenetic affinity may be less important than adaptation to local conditions. Research highlights: The values presented here were variable according to the type of species and environmental conditions, necessitating the determination of basic wood density (BWD) and moisture content at site – and species-specific level. The provided BWD estimates allow converting green volume to aboveground biomass in shrubland areas and are an essential source of information for estimating the carbon stocks.

Plasmids providing antibiotic resistance to their host bacteria pose a major threat to society, as antibiotics are often the only way to treat infectious diseases. Here the existence conditions of plasmids are investigated in an ecological framework with mathematical methods such as ordinary differential equations and individual-based models. It is shown how (i) the arise of different kinds of compensatory mutation, (ii) intra- and intercellular interactions of plasmids representing opposing plasmid lifestyles as well as (iii) a diverse plasmid community affect plasmid dynamics, community composition and persistence. The results indicate that evolutionary modifications and interactions between plasmids broaden the existence conditions of plasmids in a way that has not been recognized before, but explains their occurrence in nature. This includes that biotic interactions could maintain costly plasmid-encoded antibiotic resistance despite the absence of abiotic selection. These findings open a way to study remaining research questions related to the complexity of natural environments.:1. Introduction 2. Article I (published) – Mobile compensatory mutations promote plasmid survival 3. Article II (published) – Conjugative plasmids enable the maintenance of low cost non-transmissible plasmids 4. Article III (submitted) – The autopoiesis of plasmid diversity 5. Supervised Master thesis I – The propagation of antibiotic resistances considering migration between microhabitats 6. Supervised Master thesis II – Estimation of the pB10 conjugation rate in Escherichia coli combining laboratory experiments and modelling 7. Supervised research internship – Plasmid population dynamics considering individual plasmid copy numbers 8. Discussion Plasmide, die Antibiotikaresistenzen an ihre Wirtsbakterien vermitteln, stellen eine große Bedrohung füur die Gesellschaft dar, weil Antibiotika oft die einzige Möglichkeit sind Infektionskrankheiten zu behandeln. In dieser Arbeit werden die Existenzbedingungen von Plasmiden aus einer ökologischen Perspektive mit mathematischen Methoden wie gewöhnlichen Differentialgleichungen und Individuen-basierten Modellen untersucht. Es wird gezeigt, wie (i) das Aufkommen verschiedener Kosten-kompensierender Mutationen, (ii) intra- und interzelluläre Wechselwirkungen von Plasmiden, die gegensätzliche Plasmidlebensstile repräsentieren, sowie (iii) eine vielfältige Plasmidgemeinschaft einen Einfluss auf die Dynamik, Gemeinschaftszusammensetzung und Persistenz von Plasmiden ausüben. Die Ergebnisse deuten darauf hin, dass evolutionäre Modifikationen und Wechselwirkungen zwischen Plasmiden die Existenzbedingungen von Plasmiden in einer Weise erweitern, die bisher nicht erkannt wurde, aber ihr Auftreten in der Natur erklärt. Dazu gehört auch, dass biotische Wechselwirkungen trotz fehlender abiotischer Selektion eine kostspielige Plasmid-vermittelte Antibiotikaresistenz aufrechterhalten könnten. Die Erkentnisse dieser Arbeit können dazu genutzt werden verbleibende Forschungsfragen anzugehen, die im Zusammenhang mit der Komplexität der natürlichen Umwelt stehen.:1. Introduction 2. Article I (published) – Mobile compensatory mutations promote plasmid survival 3. Article II (published) – Conjugative plasmids enable the maintenance of low cost non-transmissible plasmids 4. Article III (submitted) – The autopoiesis of plasmid diversity 5. Supervised Master thesis I – The propagation of antibiotic resistances considering migration between microhabitats 6. Supervised Master thesis II – Estimation of the pB10 conjugation rate in Escherichia coli combining laboratory experiments and modelling 7. Supervised research internship – Plasmid population dynamics considering individual plasmid copy numbers 8. Discussion

Understanding the evolutionary forces that maintain antibiotic resistance genes in a population, especially when antibiotics are not used, is an important problem for human health and society. The most common platform for the dissemination of antibiotic resistance genes is conjugative plasmids. Experimental studies showed that mutations located on the plasmid or the bacterial chromosome can reduce the costs plasmids impose on their hosts, resulting in antibiotic resistance plasmids being maintained even in the absence of antibiotics. While chromosomal mutations are only vertically inherited by the daughter cells, plasmid mutations are also provided to bacteria that acquire the plasmid through conjugation. Here we demonstrate how the mode of inheritance of a compensatory mutation crucially influences the ability of plasmids to spread and persist in a bacterial population., The global dissemination of plasmids encoding antibiotic resistance represents an urgent issue for human health and society. While the fitness costs for host cells associated with plasmid acquisition are expected to limit plasmid dissemination in the absence of positive selection of plasmid traits, compensatory evolution can reduce this burden. Experimental data suggest that compensatory mutations can be located on either the chromosome or the plasmid, and these are likely to have contrasting effects on plasmid dynamics. Whereas chromosomal mutations are inherited vertically through bacterial fission, plasmid mutations can be inherited both vertically and horizontally and potentially reduce the initial cost of the plasmid in new host cells. Here we show using mathematical models and simulations that the dynamics of plasmids depends critically on the genomic location of the compensatory mutation. We demonstrate that plasmid-located compensatory evolution is better at enhancing plasmid persistence, even when its effects are smaller than those provided by chromosomal compensation. Moreover, either type of compensatory evolution facilitates the survival of resistance plasmids at low drug concentrations. These insights contribute to an improved understanding of the conditions and mechanisms driving the spread and the evolution of antibiotic resistance plasmids. IMPORTANCE Understanding the evolutionary forces that maintain antibiotic resistance genes in a population, especially when antibiotics are not used, is an important problem for human health and society. The most common platform for the dissemination of antibiotic resistance genes is conjugative plasmids. Experimental studies showed that mutations located on the plasmid or the bacterial chromosome can reduce the costs plasmids impose on their hosts, resulting in antibiotic resistance plasmids being maintained even in the absence of antibiotics. While chromosomal mutations are only vertically inherited by the daughter cells, plasmid mutations are also provided to bacteria that acquire the plasmid through conjugation. Here we demonstrate how the mode of inheritance of a compensatory mutation crucially influences the ability of plasmids to spread and persist in a bacterial population.