No description available.

No description available.

Climate change models predict an increase in frequency and amplitude of extreme weather events, including heat waves. To better predict how the composition and distribution of plant assemblages might respond to these changes in temperature, it is important to understand how species currently respond to these extremes. Photosynthetic thermal tolerance (T25)and photosynthetic recovery (RT25) were quantified in 27 species. We also studied the relationships between T25, RT25 and leaf mass per area (LMA). Leaf temperature was also monitored in the field. Leaves used in this study were collected from two distinct environments representing desert and montane plant assemblages. T25 and RT25 were measured using a chlorophyll fluorescence protocol incorporating sub-saturating light and short duration heat stress. Mean T25and LMA were significantly different between environments. Mean RT25 was not significantly different between environments. There was a positive relationship between T25 and LMA in both environments. The ability to recover from heat stress does not differ between two biomes that experience vastly different mean maximum temperatures during the summer months. LMA is a predictive leaf trait for thermal tolerance.

Many of the habitats occupied by fish are highly dynamic, naturally demonstrating substantial abiotic fluctuations over diurnal, tidal or seasonal cycles. It is also the case that throughout their 545 million year evolutionary history, fish have existed in aquatic environments very different to those of the present day. However, the past several decades have seen unprecedented rates of environmental change, at local and global scales, arising from human activities. The two major themes of the present thesis are: 1) Respiratory responses of fish to changes in environmental oxygen and temperature in the context of exploring intra- and inter-specific trait variation and its ecological implications 2) The effects of environmental factors (oxygen, carbon dioxide, temperature and seawater chemistry) on the intestinal precipitation and excretion of calcium carbonate by marine teleosts. In the first study (chapter two) a comprehensive database of fish critical PO2 (Pcrit) data compiled from the published literature is presented. The systematic review of this literature provided the opportunity to critically examine methodologies for determining Pcrit as well as its usefulness as an indicator of hypoxia tolerance in fish. The second study (chapter three) examines whether inter- and intra-specific variation in thermal and hypoxia tolerance in two reef snapper species (Lutjanus carponotatus and Lutjanus adetii) reflects their distributions across the contrasting biophysical environments of the reef flat and reef slope surrounding Heron Island on the Great Barrier Reef. L. carponotatus was clearly the most thermally and hypoxia tolerant of the two species, demonstrating a ~3.5 °C wider thermal tolerance zone (higher CTmax, lower CTmin) and ~26% lower Pcrit than L. adetii. These results suggest that the contrasting distribution of these species between flat and slope reef zones is reflected in their physiological tolerances. However, there was no evidence of intra-species variation in tolerance between flat and slope caught L. carponotatus individuals, indicating that this species does not form physiologically distinct subpopulations between these reef zones. The third study (chapter four) experimentally quantified the effect of hypercarbia (3000 μatm) and hypoxia (50% air saturation) on gut carbonate production by the European flounder (Platichthys flesus). Both hypercarbia and hypoxia resulted in a significant increase in carbonate excretion rate (1.5-fold and 2.4-fold, respectively) and acted synergistically when combined. In the final study (chapter five), gut carbonate production was measured in the European flounder undergoing conditions simulating the ‘calcite seas’ of the Cretaceous. The results of this study support the hypothesis that ocean conditions prevalent during the Cretaceous period resulted in piscine carbonate production rates substantially higher (~14-fold) than the present day. Ultimately, this thesis directly links the environmental physiology of fish at the individual level to wider scale implications (past, present and future), ranging from local ecological patterns all the way up to global carbon cycles.

As the earth’s climate changes due to anthropogenic emissions, it has increasingly become an imperative within the ecological community to understand existing species adaptations to climate change. Much focus has been paid to how a species might react to climate change, but the role of locally adapted traits and responsible environmental mechanisms have received less attention. Quantifying how sublethal (e.g. growth rates) and lethal (e.g. thermal tolerance) trait performance vary between populations can thus improve our understanding of how populations, and the entire species, will react to climate change. Here, I quantified the spatial patterns of performance of several traits in populations of the predatory marine snail Urosalpinx cinerea from across two thermal gradients on the Pacific and Atlantic coasts of North America. In chapter 2, I quantified local adaptation and plasticity of thermal tolerance, warming tolerance, and developmental traits of Urosalpinx. I found that while low latitude populations have evolved higher thermal tolerance than their low latitude counterparts, they also demonstrate negative plasticity in response to higher acclimation temperatures. This is likely a result of low latitude population adaptation to cooler developmental conditions. Further, low latitude populations live in environments much closer to their thermal maxima than high latitude counterparts, resulting in higher climate sensitivity in low latitudes. In chapter 3, I quantified growth and consumption rates of Urosalpinx via a common garden experiment. I found evidence for a novel pattern of trait adaptation, wherein high latitude populations tended to have higher trait performance at higher thermal optima than low latitude counterparts. This can be attributed to the maximizing of growth rate during short growing seasons at high latitudes. Together, these results demonstrate that local adaptation in endemic across two traits in Urosalpinx. I demonstrate that these traits tend to be adapted to aspects of the environment directly related to aspects of Urosalpinx phenology, and not to environmental means as is commonly assumed. These insights suggest that models of organismal performance under climate change must consider not only the potential for local adaptation in populations, but also the aspects of the environment to which these populations are evolved.

Two prominent factors posing a major threat to biodiversity in marine ecosystems are climate change and the establishment of invasive species, and the interaction between these two. Because of the upwelling of cold, nutrient-rich water, the coast of Portugal is a thermal refuge and distribution edge for cold-adapted species, making it a particularly important study area from a biodiversity point of view. In this study I investigated the physiological tolerance to heat stress of six different native and co-occurring non-native marine species, red algae; C. crispus and G. turuturu, brown algae; S.polyschides  and U. pinnatifida,  and mussels ; X.securis and M.galloprovincialis,  in the intertidal  rocky coast of Portugal. Dynamic ramping assays with four different durations and intensity of thermal stress was conducted for each specie to determine a so-called thermal death time (TDT) curve and the thermal tolerance parameters CTmax (the temperature that will cause death within one min) and z (the decrease in thermal decay over time) for each specie. To compare the thermal tolerance between the native vs non-native species a linear mixed effects model was applied. This study found a significantly higher thermal tolerance to extreme temperatures expressed as the upper critical temperature CTmax in the invasive red algae G. turuturu and mussel X.securis compared to its native counterparts C.crispus and M.galloprovincialis. The study found no significant difference in the thermal tolerance expressed for the kelp species S. polyschides and U.pinnatifida which had a similar response to the heat challenge. The implication from these the findings for the coast of Portugal, could be that the invasive algae and mussel might better survive an extreme event such as a heatwave then the co-occurring native, while the invasive kelp species would respond in a similar way to the heat challenge. Hence the invasive capacity might depend more on the invasion window after a stressful event and on how well the native species recover from a heat stress. The findings from this study call for further conservation, restoration and monitoring efforts in this area given the biodiversity supported by the important intertidal marine native species. Furthermore, management to avoid spread of the invasive mussel into the Portuguese. coast and limit further increase in abundance of the invasive algae species. These results are highly relevant for projections on how further climate changes might affect the invasive and native species at the coast of Portugal.

Prédire les réponses de la biodiversité aux changements climatiques anthropiques est devenu un champ de recherche avec des enjeux scientifiques et sociétaux majeurs. Mon travail de thèse a consisté à évaluer les impacts du réchauffement climatique sur un parasitoïde de drosophiles, Leptopilina boulardi, à une petite échelle géographique, le sud-est de la France. L'objectif était non seulement d'examiner l'évolution de la distribution du parasitoïde en réponse à une hausse des températures qu'il fallait préciser à cette échelle géographique, mais aussi d'appréhender les adaptations mises en place dans la zone de progression de l'espèce. Dans un premier temps, l'analyse de données d'échantillonnages et de données météorologiques m'ont permis de mettre en évidence une rapide expansion de l'aire de répartition du parasitoïde vers le nord, à un taux moyen de 90km/décennie, simultanément à une augmentation moyenne de la température de 1,57°C ces 30 dernières années, dans l'aire d'étude. Après avoir identifié les principaux facteurs environnementaux, structurant la répartition spatiale de L. boulardi, j'ai modélisé sa distribution potentielle dans le sud-est de la France, sous conditions climatiques actuelles et pour 2050, pour deux scénarios d'émission de CO2. En 2050, la distribution géographique de L. boulardi devrait considérablement s'étendre vers le nord sous l'effet des changements climatiques. Ensuite, en mesurant plusieurs traits d'histoire de vie selon 4 régimes thermiques fluctuants, j'ai montré que les populations de L. boulardi situées en limite d'aire de répartition sont génétiquement différenciées de celles situées dans l'aire centrale de répartition. Le fait que les populations marginales aient une valeur sélective plus importante à faible température suggère une adaptation locale des parasitoïdes dans la zone de progression de l'aire de répartition. La dernière partie de ce travail de thèse a pour objectif de mieux comprendre le processus de colonisation de L. boulardi. Pour cela, j'ai entrepris le développement de marqueurs RAD-sequencing sur 15 populations de cette espèce, distribuées le long d'un cline de latitude dans le sud-est de la France. Les nombreuses données issues du séquençage Illumina me permettront de connaître la structuration génétique de ces populations. L'ensemble de ces résultats obtenus au cours de ma thèse révèlent la force avec laquelle les changements climatiques peuvent impacter les espèces, principalement celles de haut niveau trophique, en provoquant des changements très rapide de distribution et des modifications génotypiques et phénotypiques permettant une meilleure adaptation locale / Predicting biodiversity responses to anthropogenic climate change has become a field of research with major scientific and societal issues. The main goal of my thesis was to evaluate the impacts of global warming on a Drosophila parasitoid, Leptopilina boulardi, at a small geographical scale, the South-East of France. The aim was not only to examine the change in the distribution of the parasitoid in response to rising temperatures, but also to understand the adaptations associated with this change. First, the analysis of insect sampling and meteorological data allowed me to demonstrate a rapid expansion of the parasitoid range to the north with an average rate of 90km/decade as well as a simultaneous temperature increase of 1.57°C on average over the past 30 years in the studied area. Following the identification of the main environmental factors structuring the spatial distribution of L. boulardi, I fitted a model predicting its potential distribution in the south-east of France, under the current climate and in 2050, for two CO2 emission scenarios. In 2050, the geographical distribution of L. boulardi should significantly extend northward as a result of climate change. Then, by measuring several life history traits under four fluctuating temperature regimes, I have shown that populations of L. boulardi located on the border of the range are genetically differentiated from those in the central range. The fact that marginal populations have a greater fitness at low temperature suggests local adaptation of parasitoids in the area of progression of range. The last part of this thesis aimed to better understand the process of colonization of L. boulardi. For this, I undertook the development of RAD-sequencing markers to genotype 15 populations of this species distributed along a cline of latitude in the southeast of France. Numerous data from Illumina sequencing will allow me to characterize the genetic structure of the populations. All the results obtained in my thesis highlight the force with which climate change may impact species, in particular those of high trophic level, causing rapid changes in distribution along with genotypic and phenotypic changes underlying local adaptation

Human activities have substantially increased the atmospheric concentrations of greenhouse gases, resulting in warmer ocean temperatures that are having a negative impact on reef corals, which are highly susceptible to changes in temperature. Understanding the degree to which species vary in their tolerance to elevated temperatures and whether this variation is heritable is important in determining their ability to adapt to climate change. In order to address this, Acropora cervicornis fragments from 20 genetically distinct colonies were kept at either ambient or elevated temperatures, and mortality was monitored for 26 days. Heritability of thermal tolerance was estimated using a clonal method comparing the difference in lifespan within and among clones in a one-way ANOVA, as well as a marker based method using the program MARK (Ritland 1996) to estimate relatedness between colonies. To understand the physiological basis of thermal tolerance, tissue samples from both treatments were taken after 12 hours to investigate gene expression associated with sub-lethal temperature stress at both the mRNA and the protein level. The results revealed that this population of A. cervicornis has a relatively high amount of total genetic variation in thermal tolerance (H2 = 0.528), but low additive genetic variation for this trait (h2 = 0.032). In addition, both gene expression and protein expression among colonies were highly variable and did not show consistent patterns related to differences in thermal tolerance among colonies. These results reveal that this population of A. cervicornis may have a limited capacity to respond to projected increases in ocean temperatures. In addition, the results suggest that the molecular basis of thermal tolerance in this species is complex and that there are potentially many genotypic combinations that can result in a heat-tolerant phenotype.

No description available.

Ziel dieser Arbeit war die Erhöhung der Temperaturtoleranz des Cyanobakteriums Synechocystis sp. PCC 6803 mittels ungerichteter Mutagenese und adaptiver Evolution. Trotz des erneuten Interesses an Cyanobakterien und Mikroalgen in den letzten Jahren, gibt es nur relativ wenige aktuelle Studien zum Einsatz dieser Methoden an Cyanobakterien. Zur Analyse eines mittels Mutagenese erzeugten Gemischs an Stämmen, ist es von großem Vorteil Hochdurchsatz-Methoden zur Kultivierung und zum Screening einsetzen zu können. Auf Basis eines Pipettierroboters wurde solch eine Plattform für phototrophe Mikroorganismen neu entwickelt und folgend stetig verbessert. Die Kultivierung erfolgt in 2,2ml Deepwell-Mikrotiterplatten innerhalb einer speziell angefertigten Kultivierungskammer. Schüttelbedingungen, Beleuchtung, Temperatur und CO2-Atmosphäre sind hierbei vollständig einstellbar.Die Plattform erlaubt semi-kontinuierliche Kultivierungen mit automatisierten Verdünnungen von hunderten Kulturen gleichzeitig. Automatisierte Messungen des Wachstums, des Absorptionsspektrums, der Chlorophyllkonzentration, MALDI-TOF-MS sowie eines neu entwickelten Vitalitätsassays wurden etabliert. Für die Mutagenese wurden die Letalität- und die nicht-letale Punktmutationsrate von ultravioletter Strahlung und Methylmethansulfonat für Synechocystis charakterisiert. Synechocystis wurde mit den so ermittelten optimalen Dosen mehrfach behandelt und anschließend einer in vivo Selektion unterzogen. Somit wurde dessen Temperaturtoleranz um bis zu 3°C erhöht. Über die Screeningplattform wurden die thermotolerantesten monoklonalen Stämme identifiziert. Nach einer Validierung wurde das vollständige Genom der Stämme sequenziert. Hierdurch wurden erstmals Mutationen in verschiedenen Genen mit der Langzeittemperaturtoleranz von Synechocystis in Verbindung gebracht. Bei einigen dieser Gene ist es sehr unwahrscheinlich, dass sie mittels anderer Verfahren hätten identifiziert werden können. / The goal of this work was the increase of the thermal tolerance of the cyanobacteria Synechocystis sp. PCC 6803 via random mutagenesis and adaptive evolution. Even with the renewed interest in cyanobacteria in the recent years, there is relatively limited current research available on the application of these methods on cyanobacteria. To analyse a mixture of various strains typically obtained through random mutagenesis, a method allowing high-throughput miniaturized cultivation and screening is of great advantage. Based on a pipetting robot a novel high-throughput screening system suitable for phototrophic microorganisms was developed and then constantly improved. The cultivation was performed in 2,2 ml deepwell microtiter plates within a cultivation chamber outfitted with programmable shaking conditions, variable illumination, variable temperature, and an adjustable CO2 atmosphere. The platform allows semi-continuous cultivation of hundreds of cultures in parallel. Automated measurements of growth, full absorption spectrum, chlorophyll concentration, MALDI-TOF-MS, as well as a novel vitality measurement protocol, have been established. Prior to the mutagenesis, the lethality and rate of non-lethal point mutations of ultraviolet radiation and methyl-methanesulphonate were characterized for Synechocystis. The thus determined optimal dosages were applied to Synechocystis followed by in vivo selection in four rounds of mutagenesis, thereby raising its temperature tolerance by 3°C. The screening platform was used to identify the most thermotolerant monoclonal strains. After validation, their whole genomes were sequenced. Thus mutations in various genes were identified which promote the strains'' thermal tolerance. For some of the genes it is very unlikely that their link to high thermal tolerance could have been identified by other approaches.