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- Westerlund, Tina, 1972
(författare)
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Trädgårdsmästarens förökningsmetoder – schema och katalog över förökningsdelar vid vegetativ förökning av fleråriga örtartade växter
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this licentiate thesis is to gather and classify information about traditional vegetative propagation of perennial herbaceous plants. This thesis is the first, self-contained part of a survey of propagation methods used by horticulturists. The overarching issue concerns horticultural craft practice and knowledge as explanations, understanding and skills in the conditions, processes, and procedures in plant propagation practices. Knowledge of plant propagation is based on a long tradition of horticultural activities in which the transfer of knowledge has mainly been restricted to the working process. However, in recent decades, the number of professional propagators has decreased. As a consequence, there is an increasing risk that some aspects of this knowledge will be lost to future generations. Admittedly, written information about plant propagation is scattered in various sources, but it is difficult to find instructions that clearly describe the various procedures and action steps, and the variants of the same, included in the propagation process. In order to determine and evaluate the relationship between instructions of how work is (or ought to be) performed and plants of various kinds requires either that you have extensive practical experience, or that you have a clear method for organizing, analysing and drawing conclusions about performance in propagation practices. One part of this method is structuring of information. Therefore the question to be considered in this study is: What is the best way to organize collected information on vegetative propagation methods in order for it to function as instructions for the practical work? Information is obtained by observations in nurseries, in dialogue with professional growers and an examination of instructions in written sources. Part of the methodology was that the investigator was involved as an active participant. A key part of the inquiry has therefore been my own propagation trials and experiments carried out with students. The result is a model for sorting and structuring propagation methods based on the plant parts used for vegetative propagation. The model is presented as a scheme and a catalogue. In addition to the aim of constructing the scheme and the catalogue, an additional purpose is to take the first steps towards the propagation instructions in focus in the second part of the study. The paper concludes with a discussion of possible model expansions, as well as how the model can be related to various growth habits. The underlying idea is that the link between reproduction and growth habit may reveal untested combinations of propagation techniques and plant species. It should also be possible to provide answers to why and how the various methods of vegetative propagation work, and how they might evolve.
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| 2. |
- Faust, Ellika
(författare)
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Genetic Identification of Corkwing Wrasse Cleaner Fish Escaping from Norwegian Aquaculture
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The genetic impact of farmed fish escaping aquaculture is a highly debated issue. However, non-target species, such as cleaner fish that are used in fish farms to remove parasitic sea lice, are rarely considered. Here, we report that wild corkwing wrasse (Symphodus melops), which are transported long distances to be used as cleaner fish in salmon farms, escape and hybridize with local wrasse populations. Recently, increasing numbers of corkwing wrasse have been reported north of its described distribution range, in Flatanger in Trøndelag in Norway, an area heavily relying on the import of cleaner fish from Skagerrak. Using a high number of nuclear genetic markers identified with 2bRAD sequencing, we show that, although the Flatanger population is largely a result of a northward range expansion, there is also evidence of considerable gene flow from southern populations in Skagerrak. Of the 40 corkwing wrasses first sampled in Flatanger, we discovered two individuals with clear southern genotypes, one first-generation hybrid, and 12 potential second-generation hybrids. Thus, we found clear evidence of gene flow from source populations of translocated cleaner fish at the edge of an ongoing northwards range expansion. To better understand the extent of gene flow we then greatly expanded our sampling. Based on patterns of genetic divergence and homogeneity, we identified a smaller battery of 84 SNPs which is able to detect escapees with a Skagerrak origin as well as first and secondgeneration hybrids with high accuracy and power. We then used these SNPs to investigate the magnitude and geographic extent of escaping and hybridizing cleaner fish along the Norwegian coast. We found that escapees and hybrids may constitute up to 20 % of the local populations at the northern edge of the species distribution. In other parts of the Norwegian coast where salmon farming is also common, we found surprisingly few escapees and hybrids. Possible causes for few escapees and hybrids found in these areas are difficult to evaluate with the current lack of reporting of translocations by aquaculture operators. Overall, these findings provide critical information both for aquaculture management and conservation of wild populations of non-target species, and have implications for the increasing use of cleaner fish as parasite control in fish farms, that is both poorly documented and regulated. Moving genetic material between isolated populations could drastically alter the genetic composition and erode population structure, potentially resulting in loss of local adaptation and hampering natural range expansion. Although the ecological and evolutionary significance of escapees warrant further investigation, these results should be taken into consideration in the use of translocated cleaner fish.
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| 3. |
- Lund, David, 1994
(författare)
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Computational discovery of antibiotic resistance genes and their horizontal transfer
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Antibiotic resistance is increasing among clinical infections and represents one of the most serious threats to public health. Pathogens often become resistant by acquiring mobile antibiotic resistance genes (ARGs) via horizontal gene transfer (HGT). To limit the spread of new ARGs, it is important that we identify emerging threats early, and that we improve our understanding of what drives the HGT of ARGs. The three papers encompassing this thesis aim to increase our knowledge about ARGs and their mobility. In paper I, computational screening of large genomic datasets was used to identify new resistance genes for macrolide antibiotics, and to clarify their evolution. A large diversity of new erm and mph genes was identified, including six new families of mobile ARGs carried by pathogens, that showed varied phylogenetic origins. Of the tested genes, 70% induced resistance in Escherichia coli . In paper II, we identified previously undiscovered mobile genes giving resistance to aminoglycoside antibiotics in pathogens, further demonstrating how computational methods can discover potential emerging ARGs. Close to one million bacterial genomes were screened for aac and aph genes, and the mobility of each predicted gene was evaluated. A total of 50 families of new mobile ARGs were identified in pathogens. When new ARGs were tested in E. coli . 86% were functional, with 39% giving clinical resistance. In paper III, the factors influencing the HGT of ARGs were investigated. Phylogenetic analysis was used to identify HGT events from a large set of ARGs. For each event, the genetic compatibility of the involved gene(s) and genomes, as well as the co-occurrence of donor and recipient in different environments, were computed and used as input to train random forest classifiers. The resulting models suggested that the most important factor for determining if a mobile ARG successfully undergoes horizontal transfer is the genetic compatibility between the gene and the recipient genome. The findings presented in this thesis increase our knowledge about new genes giving resistance to two important classes of antibiotics. Furthermore, the results provide new insights into the horizontal transfer of resistance genes.
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| 4. |
- Abadikhah, Marie, 1992
(författare)
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Influence of electrode material and stochastic factors on the performance and microbial community assembly in microbial electrochemical systems
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Microbial electrolysis cells (MECs) are systems with microbial communities in the form of biofilms on electrode surfaces. The electrogenic bacteria in the anode biofilm act as catalysts for the oxidization of organic compounds, leading to release of electrons, generation of electrical current, and production of hydrogen and methane at the cathode. In addition to production of energy carriers, MECs can be used for other applications as well; for example, as biosensors to monitor biochemical oxygen demand or toxicity. The performance of MECs is determined by both deterministic and stochastic factors influencing the microbial communities on the electrode surfaces, most of which as still poorly understood. In this thesis, the effects of electrode materials on microbial community assembly and MEC performance was investigated. Two experiments were carried out. In the first, three cathode materials (carbon nanoparticles, titanium, and steel) were compared. In the second, three anode materials (carbon cloth, graphene, and nickel) were compared. The cathode materials had no significant effect on the performance of the MECs, as opposed to the anode materials where carbon cloth MECs had the highest current density and the shortest lag time during startup. The differences seen in lag time of replicate systems at the start of the experiment indicated a stochastic initial attachment of the electrogenic bacteria on the anode. Different microbial communities develop in the biofilms on the anodes and cathodes. Electrogens from the Desulfobacterota phylum dominated the anode, while various hydrogenotrophic methanogens, e.g., Methanobacterium, were found to dominate on the cathodes. Diversity and null model analysis of the electrode communities highlighted stochasticity and not electrode material as the important factor in the community assembly. Network analysis showed that the cathode communities had fewer negative interactions between taxa in comparison to the anode. Since hydrogen gas generated at the cathode surface can diffuse through the biofilm, all microorganisms on the cathode have access to the substrate, reducing the need for competition between species. In contrast, electrogens require a short distance to the anode to be able to use it as electron acceptor. Limited space on the anode and competition between electrogens shaped the anode communities and explain the higher number of negative interactions observed. Based on the findings in this thesis, it is suggested that stochastic factors have more influence than electrode material on the anode community even though there is a selective pressure for electrogenic bacteria.
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| 5. |
- Rydh Stenström, Jenny
(författare)
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Mixture toxicity of pesticides and biological effects in agricultural streams : field and laboratory studies
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main objective of this thesis was to examine pesticide mixture toxicity and its effects on aquatic biota in agricultural streams. This was accomplished by (1) calculating the ΣTUs for algae and Daphnia magna and a pesticide toxicity index (PTI) based on water quality standards (WQS) for long-term monitoring data (2002-2010), (2) by performing algal inhibition tests with Pseudokirchneriella subcapitata, using both collected in situ water samples and reconstituted water spiked with field-observed pesticide mixtures, and (3) by studying seasonal changes in macroinvertebrate and diatom communities during 2008 in four agricultural streams and determine a set of community-based metrics such as species richness, diversity, ASPT, SPEAR and IPS. Partial Least Squares (PLS) regression was used to analyse community changes. Long-term data showed that collected stream water samples had peaks of estimated pesticide toxicity, mainly due to herbicides though insecticides and fungicides also contributed. ∑TUalgae, based on weekly average concentrations, exceeded 0.1 on 28 out of 902 occasions, and 8 of these were higher than 0.2. Only one or a few pesticides contributed to a major part of estimated mixture toxicity in the streams. The algal growth inhibition studies in spiked water showed negative effects at pesticide concentrations corresponding to those found in stream water samples, indicating that pesticide effects on algae occur under in situ conditions. The field study also showed effects of pesticides, suggesting diatom diversity as a sensitive indicator of pesticide effects. Macroinvertebrate community changes were primarily explained by physiochemical conditions, though some non-insect invertebrates decreased (Asellus aquaticus) or increased (Oligochaeta) with pesticide exposure. Somewhat surprisingly, the SPEARpesticides index, specifically developed to detect pesticide effects of macro-invertebrate communities in streams, was not related to pesticide toxicity. The SPEAR index may need to be modified to better fit to Swedish conditions. A combination of chemical and biological monitoring is needed to increase our understanding of the relationship between pesticide stress and the biological diversity of agricultural streams. Specific endpoints and analysis methods are also needed to separate effects of pesticides from effects of other stressors.
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| 7. |
- Hentati-Sundberg, Jonas, 1983-
(författare)
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Social-ecological dynamics in a highly regulated fisheries system - Sources of resilience and limits to command-and-control management
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sustainable governance of natural resources is challenged by the poor understanding of complex human-nature couplings. Major advancements in resilience theory, acknowledging the importance of social-ecological linkages and the self-organizing capacity of social-ecological systems, provides a new perspective on research in sustainability science. Yet, limitations in methods and data for integrated studies of social-ecological systems limit progress in science and management. This PhD project aims to generate and test specific hypotheses building on social-ecological systems theory using a variety of methods and a long-term, multidimensional empirical dataset of the Baltic Sea social-ecological fisheries system.In paper 1, we ask which factors have impacted change in fisheries patterns in the Baltic Sea over a 15 year period, 1995-2009. We conclude that the responses of fishers are largely driven by top-down management regulations, which has favoured increasing scale of operations and specialization, and that the capacity of fishers to engage in ecosystem stewardship is low. Resilience could be enhanced through an increased focus on governance actions that can stimulate the self-organising capacity of the systemPaper 2 focuses on one particular fishery, whose long-term dynamics have been strongly driven by an ecological regime-shift in the Baltic Sea. High potential profits and weak control has raised suspicions of widespread misreporting in this fishery. By developing a new method for reconstructing catches, we suggest that under-reporting has been significant, and likely driven by high economic incentives created by ill-designed policy. This misreporting risks contributing to a negative feed-back that substantially alters the management cycle, and thereby constitutes a part of a social-ecological trap in this fishery.The research within this project so far indicates that there are good prospects for using the Baltic Sea as case for integrated social-ecological studies, aiming at informing resilience theory. Some ideas on future direction of the research are outlined.
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| 8. |
- Thyberg, Annika
(författare)
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Students’ meaning-making of epigenetic visual representations : An exploration within and between levels of biological organization
- 2024
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis explores lower secondary students’ meaning-making of epigenetic visual representations within and between biological organization levels. Data obtained from five focus group discussions where students indicated and reasoned about eight epigenetic visual representations were explored. By analyzing students’ interactions with multiple visual representations, and the impact of linking and reasoning patterns on their meaning-making, the research contributes insights to the learning of epigenetics. Epigenetics, which is gaining rapid importance in emerging biology curricula, is communicated at different biological organization levels, and serves as the meaning-making context explored in the thesis. A compelling biology didactics context, where students are required to reason with multiple representations depicted within and between organizational levels to make meaning about epigenetics.The thesis uncovers three primary findings. First, four linking patterns in students’ meaning-making across and between organizational levels using various visual representations are illuminated. Second, five visual characteristics that influence students’ linking within and between levels were discerned. Third, students’ meaning-making processes were observed to emerge through four phases, which involved form and function attributes of the visual representations, and the transfer of scientific ideas across representations.
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| 9. |
- Bergsten, Arvid, 1981-
(författare)
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Fragmented landscapes : Assessment and communication of landscape connectivity in human-dominated landscapes
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis summarizes the first half of my PhD on the theme of management of fragmented landscapes. The thesis applies – and reflects on the use of – network analysis of connectivity in relation to landscape planning. Relevant theory on knowledge management and spatial ecology is summarized and discussed in connection with two papers.Paper I centers on municipal ecologists and environmental planners in the Stockholm region. They state that connectivity is rarely considered enough in planning and that assessment tools are lacking. Paper I studies the benefits and difficulties of using network analysis to manage connectivity in land-use planning. Among the main difficulties was the choice of model species and access to input data. The main strengths were the graphical and quantitative results, the potential for social learning, identification of critical sites and to relate local planning and ecology to the regional landscape.Paper II applies network methodology to quantify habitat availability of fragmented lichen-type forests in protected areas in northern Sweden. It studies a dynamic landscape that is continuously rearranged by forestry, with consequences that depend on species’ abilities to compete for resources in protected habitats, and to disperse through unprotected mature forest stands. We discuss the results with reference to the planning of forestry and protected areas, and to the resilience of species to patchy disturbance regimes.To end I propose a continuation of research, including a methodological development of network analysis; a sociological study of the acceptance of ecological advice in urban planning; and an integration of social and ecological network analysis to compare patterns of cross-municipal collaboration with landscape connectivity.
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