In this laboratory study, the role of juvenile hormone (JH) and ecdysone in regulating wing polyphenism was investigated in the non-model organism Gerris buenoi. Topical application of the JH analog methoprene elicited reduced pronotum, wing defects, and nymphal-adult intermediates but no changes to wing morph. Similarly, while microinjection of the ecdysone derivative 20-hydroxyecdysone (20E) elicited aberrant phenotypes there was again no influence on the wing morph. Using data from a transcriptomics experiment, RNAi knockdown of the differentially expressed 20E induced receptor gene, Hr4, caused high mortality rates (> 90 %) which resulted in a sample size too small to draw any inferences of Hr4’s involvement in G. buenoi wing polyphenism. My results indicate that both JH and ecdysone are involved in several developmental processes including wing development, but they do not seem to be important for determining wing polyphenism. However, several factors are important to consider in future research which means that the potential role of JH and ecdysone in G. buenoi wing polyphenism should not be dismissed at this stage.

Phenotypic plasticity plays an important role in organisms’ adaptability to environmental change such as global warming caused by greenhouse-gas emissions. One plastic response to increased temperatures is for organisms to shift their phenology. It is of great concern that the phenologies of interacting species, such as plants and pollinators, may be shifting at different rates, causing temporal mismatches, which for plants can lead to unsuccessful reproduction. The “reproductive assurance hypothesis” states that plants capable of self-pollination should be under high selection to employ this as their main reproductive strategy in the event of pollinator scarcity to ensure reproduction, and consequently invest less in attracting pollinators. This study examines how soil warming in the Hengill geothermal area in Iceland affects the flowering phenology, reproductive strategy and investment in attractiveness to pollinators in the self-compatible herb Cerastium fontanum (Caryophyllaceae), when grown in a common garden in Stockholm, Sweden. Previous research showed that C. fontanum from warmed soils flowered earlier in situ than plants from colder soils, and later when grown in a common environment. In this study, C. fontanum plants collected along a temperature gradient followed the same counter-gradient pattern, where plants from warmer soils flowered later than plants from colder soils. Soil temperature at site of origin positively affected flower number but had no effect on flower size, seed production from autogamous self-pollination or visitation rate. Based on my findings it does not appear that C. fontanum, despite having an earlier flowering phenology in situ, is under any selection to alter its reproductive strategy or investment in attractiveness to pollinators when grown in a common temperature, and therefore it seems unlikely that plants are experiencing a temporal mismatch with insect pollinators. However, it would be worthwhile to conduct a similar experiment in Iceland to better understand how an earlier flowering affects pollination systems.

Crop wild relatives (CWR) are an indispensable and at the same time threatened genetic resources for plant breeding. The study uses wild species related to celery to demonstrate how genetic resources of CWRs can be actively maintained in their natural surroundings (in-situ). Genetic reserves should be designated for long term conservation of selected occurrences. The study presents the selection procedure in detail, aiming at the identification of occurrences and sites suitable for the designation of genetic reserves, the spatial model of a genetic reserve and first practical results of the project. The overall aim of the project is the establishment of a nationwide network of genetic reserves for Apium graveolens, Helosciadium repens, H. nodiflorum and H. inundatum, the four wild celery species native to Germany. Helosciadum repens (Jacq.) W.D.J.Koch is threatened by genetic erosion due to a decline in population numbers and sizes. The loss of any population is an irretrievable loss of diversity and opportunity to enhance crops in the future. Genetic reserves are one way to conserve these populations and their genetic potential. Twenty-seven populations were selected for the analysis in a decision process based on site information. Microsatellites (SSR) were used to elucidate the genetic diversity of German populations. A cluster analysis was performed to see if the individuals form clusters of similarity. For that, a discriminate analysis of principal components (DAPC) was conducted, as the inbreeding index indicated a high number of inbreeding events in the populations and thus discordance with HWE (Hardy-Weinberg equilibrium). The analysis identified six genetic groups, which coincide well with the geographic origin of the analysed plants. The allelic richness (mean counts of alleles per individual per population) was higher in the southern populations compared to the northern ones. This North-South discrepancy was also visible as a high heterogeneity in the cluster assignments in the DAPC analysis. These differences in genetic diversity might be a result of the biogeographic history of Europe, especially the last glacial maximum. For the establishment of genetic reserves, two populations were considered as most important: The population that differs the most from the average genetic composition and the population that represents the average genetic composition of a population the best. The two extremes of differentiation were interpreted as such that the former has a specific adaptation to its local environment, and the latter represents all populations the best. DifferInt was used to analyse the SSR data and validate the differentiation of all populations compared to a pool of populations. However, SSRs are not capable of detecting adaptive traits. Populations were additionally chosen from different eco-geographic units (EGU), to increase the chance of capturing different traits. EGUs (Naturräume) are areas of specific abiotic and biotic features. These features may influence selection pressures and induce local adaptations. Based on site parameters and genetic data, 14 most appropriate wild populations (MAWP) were identified for genetic reserves establishment. For H. repens, two eco-forms are known and described in the literature. Besides their different habitats (terrestrial/semi-terrestrial and aquatic) they can be differentiated by morphological traits. Leave and stolon sizes and flowering behaviour differ significantly. Furthermore, the roots of the aquatic forms do not anchor in soil but on other aquatic plants, wood or roots of trees, while the terrestrial form exhibits a shallow root system network similar to other perennial species. To this end, no genetic analysis was conducted to clarify the phylogenetic status of the putative forms and authors avoided the usage of any specific noun rather than form. The SSR data from the previous study was evaluated, particularly with regards to the two forms. Additionally, an ISSR analysis was conducted, and the data was used to perform a PCA. There was no genetic clustering regarding the two forms neither in the SSR nor in the ISSR data. Nonetheless, the North-South discrepancy in the genetic diversity that was visible in the DAPC plot was confirmed in the PCA of the ISSR data. However, markers may fail to detect quantitative variation for adaptively important traits. As the most obvious difference in the two habitats was the water availability, the adaptation of both forms to drought stress was studied by measuring the relative water content of leaves, system water content and water loss during drought stress conditions. The stomatal index was measured for different water treatment levels. The results indicate that phenotypic plasticity rather than genotypic adaptation is responsible for different H. repens phenotypes.

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This thesis assesses climate change during the Hypsithermal Climatic Interval through the analysis of freshwater mussel remains from archaeological sites in Eastern North America. Modern climate data was used as a model to test the mosaic consequences of climate change. Freshwater mussels: can be used as indicators of precipitation by examining changes in overall size through time: larger mussels are found in larger streams, while smaller mussels are found in smaller streams. This study combines morphometric and isotopic data from archaeological freshwater mussels at Modoc Rock Shelter, Watson Brake, Plum Creek, Owens site, and Landerneau mounds to assess past climatic conditions. At Modoc Rock Shelter, oxygen isotopic data corroborate morphometric data and show that climate was fluctuating with a period of stability at the onset of the Hypsithermal. The oxygen isotopic data sets from the Louisiana sites show that the mid-Holocene was much warmer than the late-Holocene.

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Stressful experiences in early life can have profound and lasting impacts on phenotypic development. In anthropogenic environments, organisms are increasingly exposed to evolutionarily novel stressors that may play a major role in shaping the phenotypic variation upon which natural selection acts. For instance, ionizing radiation persists in areas affected by nuclear reactor accidents, nuclear weapons testing, and the nuclear power production process. This thesis explored the dose-response effects of early life ionizing radiation exposure on life- history traits in the cricket (Acheta domesticus L.). Specifically, this work had two goals: (1) to examine the effects of early life radiation stress on the potential tradeoff between growth and self-maintenance, and (2) to explore the dose-dependent effects of juvenile radiation exposure on adult trait expression (particularly fecundity, offspring investment, and offspring fitness). It was found that exposure to moderate doses of radiation in early development resulted in a slower juvenile growth rate but increased survival in early adulthood, suggesting that self- maintenance was prioritized over growth. Despite the strong inhibitory effects of early life radiation on adult female body mass, age-specific fecundity was negatively impacted only at relatively high radiation doses. Crickets exposed to moderate radiation doses in early development laid larger eggs in adulthood relative to controls and these eggs had a greater hatching success, suggesting that radiation exposure had transgenerational effects on offspring performance. No noticeable effects of early life radiation exposure were detected on total and non-enzymatic antioxidant capacity or hydrogen peroxide levels in adult females. Together, this research indicates that a single, acute exposure to ionizing radiation in early life can affect phenotypic development in a complex, dose-dependent manner and that rather than being purely negative, phenotypic responses can be sustained or even enhanced. / Thesis / Master of Science (MSc) / Stressful experiences in early life can have lasting impacts on organismal development, but the extent to which early life stress is harmful is unclear. In human-dominated environments, pollutants such as ionizing radiation can be a significant form of developmental stress. This thesis explores the fitness-related effects of early life ionizing radiation exposure in the cricket, Acheta domesticus. Impacts on growth, longevity, fecundity, and offspring fitness are explored. This research indicates that early life stress can affect phenotypic development in a complex, dose-dependent manner and that rather than being purely negative, responses can be sustained or even enhanced.