The biological diversity of the planet is at great risk as a direct result of an ever-expanding human population and its associated activities. Landscape transformation to accommodate such activities leads to habitat loss and habitat fragmentation, often creating patches of relatively undisturbed habitat within a matrix of transformed areas that are often too small too support most species previously occupying the area and as a result loses its ecological integrity. A century ago the escarpment region of Mpumalanga consisted of large open plains covered with montane grassland dissected by montane forests and riparian vegetation alongside mountain streams. Today the grasslands and forests have almost disappeared from the area, the remaining patches mostly small fragments within a matrix of exotic tree plantations which have also dried up many of the rivers and streams in the area. The natural grassland areas persisting in the region are unique in habitat characteristics and floral species composition. It is also high in plant species richness, diversity and endemicity. The high degree of isolation experienced by these floral communities poses serious threats to both the floral and faunal species that currently exits within these isolated ‘islands’, many of which are endemic to the area and at great risk of extinction. These risks call for serious collaboration between the land owners (mostly forestry companies) and conservationists to assure the practical and necessary preservation and management of this unique and crucially valuable natural resource. This study aims to provide the first step into understanding the ecological principles associated with habitat fragmentation related specifically to the mountain grassland fragments within the afforestation matrix of the escarpment region of Mpumalanga, and to create a platform for the process of collaboration between land owners and conservation agencies to assess and manage these grassland patches. The aims of Chapter 2 included: 1 To determine if any marked human-induced disturbance to the plant communities in the grassland fragments has occurred. I do this in three ways: a) To compare the plant community composition of eighteen fragments with those of six control plots outside of the plantations where no marked disturbance to the grassland can be observed. b) To determine whether the plant assemblages in the fragments can be assigned to any of the natural and intact plant communities that Matthews (1993) described from a large-scale survey of undisturbed mountain areas. c) To determine the presence of any known intruder plant species within the fragments. 2 To assign conservation priorities to the remaining grassland fragments. The results obtained from the TWINSPAN analysis revealed six alliances of plant communities grouped hierarchically into four orders and two major classes of montane grassland. The DECORANA supported these results, indicating clear differences between communities 1.1 (Eriosema salignum – Loudetia simplex grassland of the wetter North region), 1.2 (Lobelia erinus – Panicum natalense grassland of the Transitional region), 2.1 (Parinari capensis – Eragrostis racemosa grassland) and 2.2 (Helichrysum rugulosum – Eragrostis racemosa grassland). Different plant communities revealed different combinations of geological characteristics, slope, aspect and elevation. The sample plots of isolated grassland fragments and those of large unfragmented areas compare well with each other - the species richness of experimental and control plots do not differ significantly. Also, the species composition of plots from the Wetter North, Transitional and Drier South regions show more variation than is evident between experimental and control plots. There was also good qualitative comparisons (quantitative comparisons were not possible as a results of sampling and analytic discrepancies) between the sample plots used in this study and the plant communities described by Graham Deall and Wayne Matthews. Some evidence of exotic invader plants was found within the sample plots, notably Pteridium aquilinum. Fortunately such species were localized in their distribution and restricted to community 1.1.2.2. The aims of Chapter 3 included the following: 1. To compare the faunal biodiversity in grassland fragments within afforested areas to that of control plots in large, relatively undisturbed grassland areas. 2. To determine to which degree the Coleoptera, Orthoptera, Lepidoptera and bird communities reflect recognized plant communities, and are restricted to specific plant communities. 3. To compare the habitat specificity (degree of stenotopy) of the different taxonomic groups and trophic levels of animals. 4. To make recommendations for the conservation of the Afromontane grassland fauna in the remaining grassland fragments in afforested areas. The sampling of 15602 beetles, grasshoppers and crickets were collected, with an average of 3900 per sampling period, revealed unique combinations of animal species linked to the different plant communities mentioned above. Significant differences were evident from the one-way analyses of similarity (ANOSIM) used to compare the faunal community structures of sample plots of the Wetter North, Transitional and Dryer South regions. The faunal community structures of the experimental and control plots of the Wetter North and Transitional regions did not differ significantly. The indexes of habitat specificity (fractions of species constricted to certain plant communities) indicated that the plants and butterflies were more habitat-specific than the Coleoptera, Orthoptera and Birds. The carnivorous insects showed a surprisingly high level of habitat specificity compared to the relatively low level of the phytophagous insects. This surprising trend was also evident in various insect families – Acrididae, Scarabaeidae and Nymphalidae had relatively high levels of habitat specificity compared to that of the Curculionidae and the Chrysomelidae. Chapter 4 has the following aims: 1. To quantify the effect of several environmental characteristics (slope, rainfall, geology, etc) on the faunal community structure of the grassland fragments. 2. To quantify the effects of degree of isolation on species richness, species diversity and assemblage structure of plants, insects and birds in grassland remnants. 3. To test for the effects of edges on the extant insect biodiversity in the grassland fragments inside plantations. 4. To quantify the effects of fragment size on species richness, species diversity and assemblage structure of plants, insects and birds. 5. To rank the grassland fragments in an order of conservation importance using factors such as biodiversity and uniqueness of the floral community. No clear relationship between fragment size and area sampled and species richness and/or – diversity was evident from the results. Indeed, the smallest area sampled had the fourth highest species richness and the largest area sampled had the fourth lowest species richness and species diversity. Regressions results did not show any significant effects of the geographical area sampled on the biodiversity estimates of the fragments. Therefore I assume that the estimates arrived at for the area sampled within each fragment is representative of that of the complete fragment. The Detrended correspondence analysis (DCA - using square root transformed abundance data) used, indicated the need to perform a gradient analysis using a redundancy analysis (RDA). The permutation test resulting from this analysis revealed a non-significant value for the first canonical axis, but a significant value for the first four canonical axes together. The ten species contributing the most to above-mentioned result include two Scarabs (Scarabaeidae – Aphodius sp 1 and Melolonthinae sp 2), two weevils (Curculionidae – Eudraces sp 1 and Curculionidae sp 42), one leaf beetle (Chrysomelidae – Asbecesta near capensis), one darkling beetle (Tenebrionidae – Lagria sp 1), one longhorn beetle (Cerambycidae – Anubis scalaris), one jewel beetle (Buprestidae – Buprestidae sp 1), one ladybird (Coccinellidae – Coccinellidae sp 4) and one Dor beetle (Bolboceratidae – Mimobolbus maculicollis). Of these ten beetles only three are not restricted to the Drier South Region (Anubis scalaris – Wetter North and Drier South, Lagria sp 1 – throughout and Eudraces sp 1 – throughout). The associated stepwise multivariate regression showed distance to the nearest grassland to be the only environmental characteristic to significantly influence the faunal community structure of the fragments. Slope was the environmental characteristic with the smallest effect. In contrast with the results from redundancy analysis, the analysis of similarity (ANOSIM) and t-tests did not reveal significant differences in the faunal community structure of fragments closer to – and further than one kilometre from the nearest grassland neighbour. This trend was the most evident for fragments of the Transitional region and the least obvious for the fragments of the study area as a whole. The SIMPER analysis showed that of the ten species contributing most to the dissimilarity between insect communities of fragments closer/further than one kilometre from the nearest grassland neighbour, eight were also in the group of ten species characterizing the faunal communities of either/both groups (contributing towards similarity). The insect communities found at 10, 20 and 50 metres from the edge of the grassland fragments did not differ significantly, nor did an ANOSIM performed separately for each of the three major plant communities reveal any significant edge-related differences. The ANOVA results for the individual species revealed only one (of 57 - in the Transitional region) having a distribution that differs significantly with respect to distance from the habitat edge:Eremnus sp. 2 was only found at 10 metres from the edge of the fragment, close to the plantations. Of all the groups, only bird diversity, bird richness and general faunal diversity showed significant relationships with fragment size. There was a non-significant trend for insects to biodiversity to be reduced in very small fragments. Most of the botanical data exhibited no significant relationship with fragment size. The species composition of control sites were not found to be significantly different from that of experimental fragments for all the faunal groups pooled together or for the fragments of the Transitional Region and the Wetter North Region. Using the four separate scores for birds, butterflies, beetles and grasshoppers, each fragment was assigned a total conservation score. The twenty-four fragments were then ranked in order of conservation importance. Fragments of the Wetter North had an average score of 65.3, fragments of The Transitional Region 66.6 and fragments of the Drier South 52.3. The results relating to this study has lead to the following conclusions: o It is concluded that afforestation and habitat fragmentation have not significantly impacted on the flora of the montane grassland of the study area since many of the grassland fragments surrounded by plantations are still easily identifiable as natural communities, described by Matthews and Deall in broader-scale surveys in the past. Also, no obvious invader – or disturbed plant communities are discernible even though some of them have been isolated for as long as 40 years. o The plant communities of conservation importance described by Matthews coincide with the important communities recognized in this study. Rare and endangered plant species, as well as species endemic to the region, are more often than not found on the scarce Black Reef quartzite of the region, which is more evident to the Northern part of the study area. Communities 1.1 and 1.2.2 are therefore of particular conservation importance, not only as a result of their scare geological base, but also because of the high risk associated with the few grassland examples left of these communities. o The high levels of habitat specificity of many of the taxonomic and trophic faunal groups indicate that many of the invertebrate taxa are probably endemic to the region, and that the plant endemicity encountered in the Afromontane grasslands is reflected by a similar degree of animal endemicity. o The similarity in faunal assemblages and diversity between isolated fragments and large areas of grassland emphasizes the conservation importance of the fragments, even when smaller than 5 Ha in extent. o Appropriate management of the grassland fragments within the plantations is therefore important for the conservation of the plant and animal taxa encountered there. Experimental management involving grazing, mechanical cutting, grazing and burning is needed to decide on an efficient management regime, so that the grassland biodiversity can be conserved in a planned way. Such work will also allow empirical testing the efficiency of the indicator species suggested above. o Isolated grassland fragments in this study represent largely unaffected natural plant and insect communities, differing little from large unfragmented grasslands in the study area. o Fragments found within afforested areas therefore have a high conservation importance, since they represent ‘natural’ grassland areas and are often the only representative of a particular plant community left in the area. o No significant edge effects on the faunal communities 10, 20 and 50 metres from the fragments’ edges exist as a result of afforestation in the area. o Birds (and probably other vertebrates in these grasslands) are affected by fragment size, while invertebrates are much less affected and plants do not show any measurable effect of fragment size. o Fragments in the wetter northern part of the study area, characterized by high levels of plant endemicity, have a higher conservation importance as judged by faunal biodiversity. / Dissertation (MSc (Zoology and Entomology))--University of Pretoria, 2005. / Zoology and Entomology / unrestricted

Cette thèse vise à démontrer la pertinence de la chromatographie en phase supercritique (SFC) et de son couplage à la spectrométrie de masse tandem haute résolution (HRMS/MS) quant à l’étude de produits naturels en mélange complexe. Pour y parvenir trois projets ont été menés en parallèle.Une méthode d’analyse structurale ciblée sur les acétogénines d’Annonaceae a été développée. Le recours à une cationisation post-colonne par des sels de lithium a permis d’obtenir les informations structurales recherchées. Des études ont également été menées quant à l’influence de la nature du cation sur la conformation de l’adduit formé et les voies de fragmentation observées.Une séparation de composés polaires et ionisables a également été mise au point à travers l’étude des nucléosides modifiés de l’ARN. La SFC-HRMS permet la séparation et l’étude d’un grand nombre de modifications et constitue donc un nouvel outil d’analyse pour le biologiste.Pour finir, une étude en lipidomique globale a également été entreprise. Bien que préliminaires, les premiers résultats semblent très prometteurs avec pour but de développer des méthodes d’analyses non ciblées associés à des outils d’annotation automatique.Pour chaque projet, la pertinence de nos approches a été vérifiée par l’étude d’échantillons réels et complexes permettant de tirer des conclusions réalistes quant aux possibilités de la SFC-HRMS/MS pour l’étude de composés naturels. / This PhD work aims to demonstrate the relevance of supercritical fluid chromatography (SFC) and its hyphenation to high resolution tandem mass spectrometry (HRMS/MS) in the field of natural product analysis. Three different research projects were carried out.A new strategy for structural analysis of Annonaceous acetogenins was developed by SFC and targeted HRMS/MS including post-column lithium cationisation to give access to the relevant structural information. Investigations were conducted to observe the influence of cations onto the gas-phase conformation and fragmentation pathways.A separation of polar and ionisable compounds was also developed using modified nucleosides from RNA as models. The SFC-HRMS method led to the separation and analysis of several tens of modifications and demonstrated to be a new performant analytical tool for biologists.Finally, a global lipidomic approach was optimized. Preliminary results look compatible with the development of untargeted approaches using automatic annotation tools.For each project, the relevance of our work was evaluated analyzing complex samples to obtain a realistic point of view of the capabilities for SFC-HRMS/MS systems for natural product studies.

Les alcaloïdes sont parmi les molécules naturelles les plus intéressantes pour leurs propriétés biologiques et médicinales. Parmi ceux-ci, les amaryllidacés et notamment la clivonine et ses analogues présentent de nombreuses propriétés peu étudiées et la synthèse de molécules de cette famille permettra des avancées dans ces études. Notre équipe s’intéresse particulièrement à cette molécule car sa synthèse pourrait se faire à partir d’une réaction de nitroso Diels-Alder énantiosélective qui est un sujet majeur de recherche dans notre laboratoire. Dans la suite de la synthèse, une deuxième étape clé doit faire intervenir une insertion C-H intramoléculaire. La réaction de nitroso Diels-Alder a été réalisée avec un excès énantiomérique de 96% et la synthèse a été poursuivie pour accéder à l’intermédiaire diazo clé, substrat de départ de l’insertion C-H. Cette dernière réaction n’a pas permis d’obtenir les produits escomptés en utilisant des catalyseurs commerciaux et une collaboration a été entamée avec le Pr Huw Davies pour pouvoir utiliser des catalyseurs plus élaborés. Les résultats de cette collaboration ne sont pas encore définitifs. Parallèlement, trois autres voies de synthèse de la clivonine ont été conçues et expérimentées, des variations de la synthèse originale, mais aucune n’a abouti. En revanche, une de ces synthèses nous a permis de découvrir une réactivité nouvelle des cycloadduits de nitroso Diels-Alder : en présence d’organolithiens, une réaction de β-fragmentation a lieu, suivie d’une addition, qui permet d’obtenir des composés monocycliques très fonctionnalisés avec une très bonne stéréosélectivité. Cette réaction et son étendue doivent encore être étudiées mais pourraient avoir des applications en synthèse totale. / Alkaloids are among the most interesting natural compounds because of their biological and medicinal properties. Among them amaryllidaceae alkaloids and especially clivonine and its analogues bear many under-studied properties and the synthesis of members of this family should allow more advances in this field. Our team is particularly interested in this target since its synthesis could be achieved starting from an enantioselective nitroso Diels-Alder reaction which is a major research topic of our group. Later in the synthesis a second key step would involve an intramolecular C-H insertion. The nitroso Diels-Alder reaction was performed with an enantiomeric excess of 96% and the synthesis was continued to access the key diazo intermediate, starting material for the C-H insertion step. This last reaction did not allow to access the desired products using commercially available catalysts and a collaboration was started with Pr Huw Davies in order to use more advanced catalysts. The final results of this collaboration are not available yet. Meanwhile three other synthetic routes for clivonine were designed and investigated as variants of the original strategy but none of them allowed access to clivonine. However one of those syntheses led to the discovery of a new reactivity of nitroso Diels-Alder cycloadducts: when exposed to organolithium reagents, a β-fragmentation occurs followed by an addition leading to highly fonctionnalized monocyclic products with high diastereoselectivity. This reaction and its scope need to be investigated further but may have applications in total synthesis.

La sylviculture intensive modifie la composition, la structure et la dynamique des peuplements, réduisant notamment la densité et la diversité des attributs forestiers caractéristiques des stades de sénescence (bois mort et micro-habitats portés par les arbres). Ces éléments représentent des habitats essentiels pour les espèces lignicoles. A l’échelle du massif, la planification des opérations sylvicoles va créer une discontinuité spatiale de ces micro-habitats, pouvant être perçue comme une source de fragmentation pour de nombreuses espèces. Cependant, les effets ont été peu explorés au sein des forêts tempérées exploitées. L’objectif de cette thèse est d’évaluer l’effet de la disponibilité des micro-habitats (quantité et configuration) à de multiples échelles spatiales sur les communautés et les populations d’espèces lignicoles, afin de fournir in fine des connaissances pour la spatialisation des stratégies de conservation. Nous avons proposé une méthodologie statistique permettant de prédire la distribution des micro-habitats au sein du massif de Compiègne (France). En s’appuyant sur cette cartographie prédictive, nous avons montré que différentes guildes de coléoptères saproxyliques, définies en fonction de traits d’histoire de vie liés aux capacités de dispersion, répondaient à la structure du paysage à différentes échelles spatiales. La modélisation de la dynamique des métapopulations d’une bryophyte épixylique (Dicranum viride) nous a permis de mettre en évidence l’importance de la dispersion sur les processus de colonisation/extinction qui sous-tendent les patrons d’occurrence des espèces observés à l’échelle du massif. Nos résultats soulignent le rôle central du bois mort et des micro-habitats, qui peuvent être considérés comme un levier de gestion pertinent. Augmenter leur quantité et optimiser leur arrangement spatial intra et inter-peuplement apparaît essentiel pour assurer la persistance des espèces lignicoles au sein des massifs forestiers gérés. / Intensive forestry induces a simplification of forest stand structure, composition, and dynamics, resulting in a decrease of density and diversity of old-growth forest attributes (deadwood and tree-related microhabitats). These elements represent critical habitats for lignicolous species. At the landscape scale, forest management planning create a spatial discontinuity of these microhabitats, which can be perceived as a fragmentation process for many species. Although habitat fragmentation is currently recognized as one of the major threats to biodiversity, its impact on species in managed temperate forest are still poorly understood. The objective of this work was to evaluate the effect of microhabitat availability (quantity and configuration) on species communities and populations, at multiple spatial scales, in order to provide evidence-based recommendations regarding the spatial arrangement of conservation strategies. We proposed a statistical methodology to predict the microhabitats distribution within the complex of the Compiègne forest (France). Based on this predictive mapping, we showed that different guilds of saproxylic beetles, defined according to their life history traits related to dispersal abilities, respond to the landscape structure at different spatial scales. Modelling metapopulation dynamics of an epixylic bryophyte (Dicranum viride) has highlighted the importance of dispersal on colonization/extinction processes that underlie the species’ occurrence patterns observed at the forest scale. Our results emphasize the key role of deadwood and tree-related microhabitats, which can be considered as relevant management leverage. Increase their quantity and optimize their spatial arrangement within and between forest stands, appears to be essential for persistence of the lignicolous species within managed forests.

Mozambique is to fifty percent covered by forest, most of which belongs to the biodiverse miombo woodlands. The last decades, Mozambique has been suffering from rapid deforestation. The once continuous forest cover has turned into a mosaic of forest patches, farmland, settlements etc. The remaining forest patches are in many cases very isolated. These forests have distinct edges towards the neighbouring land, which means that the edge zones have different environmental conditions (more light, higher temperatures etc.) and tree species composition than the interior. In order to examine how the forests of Mozambique are affected by edge effects, the highly isolated Nhamacoa forest was studied. An additional aim of the project was to make a floristic inventory of the forest in order to further assess its conservation status. Specimens were collected, pressed and photographed for identification. Edge effects were studied in plots at the edge and in the interior of the forest in a paired design. Trees inside the plots were identified, counted and measured (dbh (diameter at breast height) and height) to search for differences in species richness, diversity, biomass and height-to-dbh ratios. Environmental parameters (air temp., soil temp., light and slope) were also measured. In total, 76 species of trees were sampled and 44 (35 in the interior and 32 at the edge) of these were found inside the plots. The interior plots harboured significantly more individuals and species of trees than their paired edge plots. Additionally, biomass and height-to-dbh ratios were higher in the interior plots than in the edge plots. These differences strongly suggest that the Nhamacoa forest is affected by edge effects, although none of the measured environmental parameters could explain why. That the Nhamacoa forest is affected by edge effects goes in line with the research hypothesis and shows that it is important to maintain large and intact pieces of forest in order to preserve the Mozambican miombo forests. For future studies, additional environmental parameters (wind speed, humidity etc.) could be examined in order to better explain the presence of edge effects in the Nhamacoa forest.

Plast påverkar vårt samhälle i stor utsträckning och har hjälpt till att utveckla nya förbättringar och redskap i vår vardag. Trots alla bra egenskaper med plaster har några oönskade effekter kommit till ytan med negativ påverkan på miljön. Detta examensarbete undersökte hur plastmaterial bryts ned av vittring utanför den svenska västkusten. Plastmaterialen undersöktes med hjälp av Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) och Scanning Electron Microscopy (SEM) för att fastställa om kemisk nedbrytning sker efter 12 månader. Följande frågor stod i fokus: Vilka plaster har brutits ned, och i vilken utsträckning? Hur har plastens egenskaper förändrats? Vilka förutsättningar har de olika plastmaterialen för nedbrytning på stränder, och vilka faktorer påverkar nedbrytningen? Resultatet indikerade att liten eller ingen detekterbar nedbrytning skett på proverna efter 12 månaders vittring genom FTIR analys. Några prover visade dock tecken på förändring i de fysiska egenskaperna vid DSC analys, vilket kan beror på nedbrytning. Trots detta resultat fanns det synliga tecken på fragmentering, fysisk skada från stress och yttre krafter, såsom sand- och vågtumling för EPS (Styrofoam), LD-PE (Candy Paper) och PP (Blårep). Fragmenteringens påverkan på havlsmiljön kunde dock inte bevisas i denna studie eftersom prover på sand eller vatten från området inte genomfördes. Detta gör att endast synliga indikationer på fragmentering var identifierbara, men inte bevisa att det bidragit till makro- eller mikroplaster i närmiljön. Samtliga plastmaterial i studien innehöll någon form av tillsatts så som stabilisatorer. Eftersom endast små variationer förekommer i analysen av plastmateralen kunde det antas att tillsatserna och stabilisatorerna i materialen var effektiva i att hindra polymererna från nedbrytning under 12-månaders vittring. / Plastic has greatly impacted our society today and helped develop new improvements and implements in the daily lives. Despite all the good things, some undesirable impacts have also been discovered, which have been shown to impact the climate negatively. This thesis was to investigte how plastic degrades when weathered outside the  Swedish West Coast. The plastic materials were analysed using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM) to determine whether degradation had occurred after 12 months. The following questions were at focus: What plastics have been degraded, and if so, which to the greatest extent? How have the properties of the plastic changed? What were theprerequisites for the different plastic materials for degradation on the shoreline, and what factors are affecting the degradation? The results indicated that the samples had little to no detectable degradation regarding the FTIR analysis after 12 months of weathering. Some of the samples showed a change in the physical properties from the DSC analysis, which could indicate degradation. Despite the result of degradation extent, there were clear signs of fragmentation, physical damage from stress, and external forces, such as rock and wave tumbling for EPS (Styrofoam), LD-PE(Candy Paper) and PP (Blue Rope). Fragmentation was not proven since no soil or water samples were made at the wethering site. This made the fragmentation only a visible parameter based on the samples after weathering, not proving that micro- or macro-plastic has been washed out in the ocean. All of the plastic materials used in the study were produced with some sort of additive, such as stabilisers. Since only small variations were shown in the analysis of the plastic materials, it can be assumed that additives and stabilisers were effective because there was no clear sign of degradation after 12 months of weathering.

La variabilité phénotypique a tendance à augmenter lorsque l'environnement est variable dans le temps ou l'espace. Cette thèse traite plus précisément de la variabilité des traits d'histoire de vie dans le cadre de populations fragmentées. En région Méditerranéenne, le Pélodyte ponctué, Pelodytes punctatus, se reproduit à la fois au printemps et en automne, en réponse aux variations temporelles de l'environnement. J'ai cherché à comprendre l'origine et les conséquences évolutives de ces stratégies de reproduction. Les deux périodes de reproduction produisent efficacement des descendants (plus en automne) et les têtards de printemps semblent souffrir de la compétition avec les têtards d'automne. Ces derniers se métamorphosent plus tôt et à une plus grande taille. Ces différences de développement ne s'expliquent pas par des différences génétiques entre des populations saisonnières. Au contraire, elles sont liées à la plasticité phénotypique et répondent à des conditions environnementales drastiquement différentes. Il semble plus favorable de se reproduire en automne. Le maintien des deux stratégies correspond à du bet-hedging ou un simple opportunisme. Par ailleurs, la fragmentation, phénomène croissant lié à l'anthropisation des milieux, diminue la taille des populations et augmente l'hétérogénéité génétique au sein d'une population. Il n'y a cependant pas de consanguinité au sein des populations étudiées mais une forte structuration en familles qui induit des associations allèles/phénotypes.Ce travail éclaire les variations de traits d'histoire de vie du Pélodyte et indique une grande plasticité phénotypique face aux variations de l'environnement. / Phenotypic variability tends to increase in temporally and spatially variable environments. This thesis deals with the variability of life-history traits in fragmented populations. In Mediterranean regions, Parsley frog, Pelodytes punctatus, breeds both in spring and in autumn, in response to temporal variations of its environment. I studied the origin and evolutionary consequences of its breeding strategies.Both breeding periods produce offspring (much more in autumn, though) and spring tadpoles suffer from intraspecific competition with older autumn tadpoles. Autumn laid juveniles are bigger and emerged sooner from the ponds. These developmental differences are not due to genetic differences between seasonal populations. They are explained by phenotypic plasticity in response to drastically different conditions. Even if it seems more favourable to breed in autumn, both strategies are maintained either by bet-hedging or pure opportunism.Besides, fragmentation, which increases with global changes, tends to reduce population effective size and increase genetic heterogeneity within populations. However, no inbreeding was found in the studied populations but a high family structure induced alleles/fitness correlations.Together, these results enlighten the variability of breeding strategies and larval traits in Parsley frog and indicate a high phenotypic plasticity in response to environmental variations.

Dans ce document, serons détaillées les résultats de mes travaux de recherche d’études doctorales. Tout d’abord, nous discuterons de la synthèse totale de la lépadine B, la plus courte à paraître dans la littérature à ce jour. Cette synthèse, en plus de valoriser la synthèse asymétrique de pipéridines poly-substituées développée par l’équipe du professeur Charette, mettra à profit une utilisation originale d’une séquence de fermeture-ouverture de cycle par la réaction de métathèse d’alcènes. De plus, nous détaillerons une brève étude mécanistique de cette dernière nous ayant permis la proposition d’un mécanisme peu commun de ce type de séquence réactionnel et dont les conséquences expérimentales sont impressionnantes. Au cours de cette synthèse, nous avons identifié un synthon d’une grande valeur synthétique. En effet, ne comportant pas moins que quatre centres chiraux, ce synthon pouvait être obtenu énantiopure en seulement trois étapes à partir de la pyridine. Ainsi, nous avons effectué une analyse structurale de ce synthon et avons envisagé une valorisation supplémentaire par une utilisation originale de la fragmentation de Grob. Dans ce contexte, nous avons développé une toute nouvelle synthèse de pipéridines 2,3,6-trisubstituées hautement régio- et diastéréosélective. Afin de pouvoir réaliser la précédente méthodologie, nous avons dû étudier la réduction d’une amide en présence de groupements fonctionnels sensibles dans les conditions usuelles. Heureusement, l’année précédente nous avions développée une réaction hautement chimiosélective d’amides tertaires. Cette nouvelle réaction, qui a été fondamentalement inspiré par une méthodologie du professeur Charette sur l’activation d’amides, a permis la réduction d’amides tertiaires en présence de fonctions telles les cétone, ester, nitrile, époxyde, insaturations, etc. Enfin, l’ensemble des connaissances acquises au cours de ces projets a permis l’élaboration d’une toute nouvelle stratégie de synthèse pour la préparation d’indolizidines et quinolizidines. Plus spécifiquement, nous avons développé la première séquence d’activation intramoléculaire et déaromatization asymétrique de la pyridine. Ceci permet d’avoir un accès aux squelettes indolizidine et quinolizidine avec des stéréosélectivités élevées, la nature insaturée de ces derniers laissant également place à une grande flexibilité synthétique. Dans ce contexte, nous allons détailler une très courte synthèse de trans-indolizidines. / In this document, the results of Ph.D. thesis will be detailed. First, we will discuss the synthesis of alkaloid lepadin B, the shortest to appear in the literature to date. This synthesis, in addition to validating the asymmetric synthesis of polysubstituted piperidines developed earlier by the group of Professor Charette, will highlight an original use of a ring-closing ring-opening alkene metathesis sequence. Also, a brief mechanistic study of the latter reaction will be detailed, a study which led us to propose an unusual mechanism for this reaction sequence and for which the experimental concequences are impressive. During the total synthesis of lepadin B, we identified a synthon of great synthetic value. Indeed, containing not less than four chiral centres, that synthon could be obtained enantiopure through a short three-step synthesis from pyridine. We performed a structural analysis of this synthon and we envisaged an additional validating through an original use of the Grob fragmentation. Consequently, we developed a new highly regio- and diastereoselective synthesis of 2,3,6-trisubstituted piperidines. To succesfully realize the latter methodology, it was required to perform an amide reduction in the presence of sensitive functionnalities under usual reduction conditions. Fortunatly, we had recently developed a set of conditions for the highly chemoselective reduction of tertiary amides. This new reaction, fundamentaly inspired by an amide activation methodology from Charette’s group, allowed the reduction of amides in the presence of functionalities such as ketone, ester, nitrile, epoxide, unsaturations, etc. Finaly, the knowledge acquired by conducting this research allowed for the elaboration of a new methodology for the synthesis of indolizidines and quinolizidines. Specifically, we developed the first intramolecular pyridine activation-asymmetric dearomatization reaction of the pyridine. This led us to the highly stereoselective access to indolizidine and quinolizidine backbone, the unsaturated nature of which permitting a good degree of synthetic flexibility. In that context, we will detail a short synthesis of trans-indolizidines.

RésuméEn raison des bouleversements qui ont eu lieu dans la seconde moitié du XXe siècle, le monde a connu une accélération notable de l'histoire. Cette accélération s'est manifestée sur plusieurs fronts – l'historique, le scientifique, le technologique – mais aussi sur le front littéraire, changeant à jamais la façon dont nous représentons notre monde et notre passé. Cette thèse porte sur les nouveaux modes de représentation ou mimesis dans l'œuvre d'art. Comment les événements, qui se déroulent en dehors du roman, ont-ils affecté la forme même, la technique et la langue du roman contemporain ? Comment la violence qui a été infligée au monde extérieur s'est-elle reflétée dans le récit littéraire ? Du fait que la forme narrative est en soi un moyen de « rassembler » les événements dispersés et les incohérences de la réalité, la forme traditionnelle manipule violemment cette réalité dans le but de lui donner un sens, quand elle est souvent inexplicable. En mettant en question les conventions naturelles et données du récit, les romans expérimentaux du XXe siècle ont tenté de mettre en place des formes originales, en mesure de représenter des expériences différentes. Notre thèse traite principalement de ces nouvelles conceptions de la représentation dans le roman contemporain et de la manière dont, en dépit de leur fragmentation, de l'expérimentation et de la rupture violente avec les traditions du passé, ces romans innovants ont néanmoins réussi à produire des «représentations» de la réalité qui captent fidèlement notre histoire contemporaine, caractérisée par l'accélération et la fragmentation. Pour justifier cet argument, nous avons comparé les récits de fiction avec ceux des deux autres domaines à partir desquels nous tirons la connaissance de notre passé, à savoir l'histoire et la mémoire. Où est la place de la fiction aux côtés de ces deux piliers de connaissance souvent totalisants et totalitaires ? Enfin, que peut faire la littérature pour ces sujets de l'histoire, systématiquement exclus de l'écriture de l’histoire dominante ? En prenant la plume pour écrire leur version de l'histoire, ces «autres» du document historique dominant ont inscrit leur histoire particulière sur le palimpseste existant de l'histoire dominante et ont également obligé les canons littéraires, auxquels ils appartiennent, à développer leurs limites esthétiques et éthiques. / SummaryAs a result of the changes that have occurred in the latter half of the twentieth century, the world has witnessed a noticeable acceleration of history. This acceleration has manifested itself on many fronts – the historic, the scientific, the technological – but also on the literary front changing forever the way we represent our world and our place in it. This paper deals with the new modes of representation or mimesis in the work of art. How have the events happening outside the novel affected the very form, technique and the language of the contemporary novel? How has the violence that has been inflicted on the outside world being replicated and perhaps resolved in the literary narrative? Because narrative form is in itself a way of ordering and “bringing together” the fragmented events and incoherencies of reality, the very traditional form often violently manipulates this reality with the aim of giving meaning to an often inexplicable reality. By bringing into question the natural and given conventions of narrative, the experimental novels of the twentieth century have tried to realize original and unique forms that are able to represent different experiences. Our paper deals with primarily with these new conventions of representing reality and how, despite their fragmentation, experimentation, and violent rupture with the traditions of the past, they have nonetheless successfully produced “representations” of reality that faithfully capture our contemporary history characterized by acceleration as well as fragmentation. In order to justify this argument, we have compared narratives of fiction with the other two domains from which we derive the knowledge of our past, namely history and memory. Where is the place of fiction alongside these two often totalizing and totalitarian pillars of knowledge? Finally, what can literature do to those subjects of history who have systematically excluded from the writing of their dominant History? By taking the pen to write their side of the story, these “others” of the dominant historical document have both inscribed their particular stories on the existing palimpsest of dominant history, but have also forced the literary canons in which they belong to expand both their aesthetic and ethical boundaries.

Les rayonnements ionisants (RI) traversent les tissus humains, y déposent de l'énergie et la dissipent en fragmentant des molécules. Les fragments obtenus peuvent être mis en évidence par spectrométrie de masse. Malgré la quantité d'informations obtenue expérimentalement à partir du spectre de masse, l'expérience seule ne peut pas répondre à toutes les questions concernant les mécanismes de fragmentation des bases de l'ADN/ARN, et l'étude issue des méthodes quantiques est un complément précieux à ces informations. L'étude théorique permet de connaître les liaisons moléculaires rendues faibles dans chaque base par ionisation et ainsi de prévoir les mécanismes de fragmentation et les fragments produits. Le but de ce travail est d'étudier l'ionisation et les mécanismes de fragmentation de bases de l'ADN/ARN (Uracile, Cytosine, Adénine et Guanine) et d'identifier les cations correspondants à chaque pic des spectres de masse. Nous avons effectué nos calculs en utilisant la DFT avec la fonctionnelle PBE. Dans cette thèse, pour toutes les bases d'ARN, la réaction de rétro Diels-Alder est une des voies principales de dissociation (élimination de HNCO ou de NCO•) à l'exception de l'adénine qui n'a pas d'atome d'oxygène. La perte d'une molécule NH3 (NH2•) est aussi un chemin commun à toutes les bases contenant un ou plusieurs groupes amine. Egalement, la possibilité de la perte d'un hydrogène à partir des cations est également envisagée, ainsi que la dissociation de ces cations déshydrogénés et des bases protonées, en se limitant à l'uracile. Ce travail montre tout l'intérêt de l'apport de calcul (DFT) à l'interprétation des spectres de masse de bases de l'ADN / Ionizing radiation (IR) cross human tissue, deposit energy and dissipate fragmenting molecules. The resulting fragments may be highlighted by mass spectrometry. Despite the amount of information obtained experimentally by the interpretation of the mass spectrum, experience alone cannot answer all the questions of the mechanism of fragmentation of DNA/RNA bases and a theoretical study is a complement to this information. A theoretical study allows us to know the weakest bonds in the molecule during ionization and thus may help to provide mechanisms of dissociation and produced fragments. The purpose of this work, using the DFT with the PBE functional, is to study the ionization and fragmentation mechanisms of DNA/RNA bases (Uracil, Cytosine, Adenine and Guanine) and to identify the cations corresponding to each peak in mass spectra. For all RNA bases, the retro Diels-Alder reaction (elimination of HNCO or NCO•) is a major route for dissociating, with the exception of adenine for which there is no atom oxygen in its structure. Loss of NH3 (NH2•) molecule is another common way to all bases that contain amine group. The possibility of the loss of hydrogen from the cations is also investigated, as well as the dissociation of dehydrogenated cations and protonated uracil. This work shows the interest of providing DFT calculation in the interpretation of mass spectra of DNA bases