Les écosystèmes sub-Antarctiques sont particulièrement vulnérables aux perturbations environnementales et notamment aux invasions biologiques. L'introduction du Chat (Felis silvestris catus) sur la Grande Terre de l'archipel des Kerguelen a eu des effets désastreux sur les communautés d'oiseaux marins. Ce prédateur doit sa survie dans cet environnement à la présence d'une proie introduite, le Lapin (Oryctolagus cuniculus), qui constitue sa ressource principale pendant l'hiver lorsque les oiseaux marins sont repartis en mer. L'éradication du chat n'apparaît pas être une solution réaliste compte tenu de la taille de l'île (6675 km2) et son inaccessibilité. De plus elle serait susceptible de conduire à des résultats non souhaités comme par exemple une explosion démographique des populations de lapins. La mise en place d'une politique de gestion adaptée nécessite d'améliorer notre connaissance des facteurs qui conditionnent la dynamique spatio-temporelle des populations de chats. Au cours de cette thèse, j'ai cherché à identi_er les mécanismes des interactions entre le chat, le lapin et la végétation, car elles sont attendues conditionner celles existantes entre le chat et les oiseaux marins. J'ai analysé la dynamique spatio-temporelle de quatre populations de chats sur la Grande Terre et j'ai en particulier recherché si des conditions environnementales spatialement corrélées (effet Moran) pouvaient, en se propageant dans la chaine alimentaire, synchroniser les variations temporelles d'abondance des populations de chats. Enfin, j'ai étudié l'impact des variations spatio-temporelles d'abondance des populations de chats sur les variations spatio-temporelles de la structure génétique des populations de chats.

Oil and gas exploration conducted in the 1970s left behind a legacy of abandoned well sites in the Mackenzie Delta region of northern Canada, including several in the Kendall Island Migratory Bird Sanctuary and surrounding areas. Evidence of 30 year-old well sites is present in the form of drilling mud sumps, which are mounds of disturbed tundra that contain frozen drilling-wastes. One to two years after the wells were decommissioned some of the sites were seeded with non-native grass species and fertilized to test whether these treatments could accelerate vegetation recovery and prevent erosion. The main objective of this research was to examine the long-term impact of post-disturbance seeding treatments on the vegetation recovery of drilling mud sumps.<p> Surveys of vegetation composition and environmental conditions at 12 sump sites (6 seeded and 6 unseeded) showed that, after over 30 years of recovery, seeded sumps in the Mackenzie Delta did not significantly differ from those left for natural recovery. However, seeded and previously introduced grasses <i>Festuca rubra</i> and <i>Poa pratensis</i> were found on both seeded and unseeded sumps. The undisturbed surrounding tundra seems to be resistant to invasion by these introduced grasses. However, these species could become invasive in the future, particularly in the context of warming in the North and increasing anthropogenic disturbance. The results of this study contribute valuable information on the long-term effects of revegetation treatments that is critical for making informed management decisions about the rehabilitation of industrial disturbances in the Arctic.

En España se diagnostican cada año unos 12.000 nuevos casos de carcinoma urotelial (CU). Más concretamente, en Cataluña este tumor representa entre un 9,9 y un 11,7% del total de tumores malignos, dando lugar a una mortalidad cáncer específica del 5,2% en el sexo masculino. Aunque en la mayoría de casos la enfermedad se acaba detectando en su fase más inicial, la alta frecuencia de recidivas y la posibilidad de progresión y diseminación debido a la agresividad de algunas formas limitarán la supervivencia del paciente.El método estándar para la detección y seguimiento del CU se basa en la combinación de la citología urinaria y la cistoscopia. Sin embargo, la primera de estas técnicas presenta baja sensibilidad en la detección de tumores de estadio inical y bajo grado, mientras que la segunda es una técnica invasiva que además no es lo suficientemente sensible para detectar todas las lesiones de crecimiento plano.Por otro lado, las técnicas histológicas convencionales para el diagnóstico de la diseminación linfática del CU no son lo suficientemente sensibles ya que alrededor del 50% de pacientes sometidos a cirugía radical con linfadenectomía N0, fallecen antes de los 5 años post-cirugía. Estos datos sugieren que existe una diseminación tumoral antes de la cirugía que no es detectada mediante estas técnicas histológicas.Debido a la elevada prevalencia y gravedad de la enfermedad, a la invasividad de las pautas utilizadas en su diagnóstico y a la falta de métodos de estadiaje refinados, el desarrollo de nuevos sistemas diagnósticos que permitan una detección temprana tanto del CU inicial como de sus recidivas y de su diseminación es esencial para mejorar la calidad de vida y el pronóstico de los pacientes con esta enfermedad.En el presente trabajo se ha evaluado la utilidad de la técnica "fluorescence in situ hibridization" (FISH) en el diagnóstico no invasivo del Cu de bajo estadio, en el diagnóstico no invasivo del CU localizado en el tracto urnario superior (TUS) y en el pronóstico de pacientes con CU de alto riesgo de recurrencia y progresión, tratados mediante inmunoterapia con el bacilo de Calmette Guérin (BCG). Por otro lado se ha intentado detectar la presencia de micrometástasis linfáticas así como de diseminación sanguínea del CU, mediante marcadores moleculares en pacientes sometidos a cistectomía y linfadenectomía radical.Los resultados obtenidos indican que la técnica FISH basada en los cromosomas 3, 7, 9 y 17 presenta mayor sensibilidad que la citología urinaria, y una similar especificidad equivalente en la detección del CU no músculo-infiltrante, así como en la detección del CU localizado en el TUS. La naturaleza no invasiva de este ensayo así como su elevada sensibilidad y especificidad podrían contribuir a mejorar el actual diagnóstico/seguimiento del CU en estas localizaciones. Otro resultado interesante fue que los pacientes con un resultado positivo de FISH tras la terapia BCG tienen mayor probabilidad de presentar una recurrencia del tumor. Así, la técnica FISH parece ser útil en el seguimiento de los pacientes con un tumor no músculo-infiltrante de alto riesgo de recurrencia y progresión sometidos a terapia BCG. Finalmente, se observó que la utilización de marcadores moleculares permite mejorar la sensibilidad del análisis histopatológico en la detección de la diseminación linfática tumoral y que la linfadenectomía juega un importante papel curativo eliminando la enfermedad microdiseminada. Sin embargo, el análisis de la expresión génica en muestras de sangre periférica no es adecuado para seleccionar a aquellos pacientes que desarrollarán metástasis detectables clínicamente, aunque sí permite distinguir entre pacientes con CU de controles sanos. / Cystoscopy and cytology are the standard methods to detect and monitor urothelial carcinoma (UC). Cystoscopy is an invasive technique (especially to visualize the upper urinary tract or UUT) that has a high sensitivity, except in flat malignancies. Cytology has the advantage of being non-invasive with a high specificity, but it lacks sensitivity and produces high rates of suspicious cases, especially for low-stage and low-grade tumors. Another weak point in the clinical management of UC is the fact that current methodologies to detect disseminated UC lack sensitivity.The aims of this study were: (1) to evaluate the performance of a multiprobe FISH (fluorescence in situ hybridization) assay for non-invasive detection of superficial UC in the bladder, in comparison to urinary cytology, (2) to assess the clinical utility of FISH as a non-invasive method for diagnosing and monitoring UC in UUT, (3) to evaluate the use of FISH for determining the response of patients with high-risk superficial bladder tumour (HRSBT) to bacillus Calmette-Guérin (BCG) therapy, (4) to identify and test potential mRNA markers of UC dissemination in lymph nodes, and to compare the performance of selected markers with patients' clinical outcome, and (5) to test the efficiency of such mRNA markers in detecting and monitoring UC haematogenous dissemination.According to our results, FISH assay for chromosomes 3, 7, 9, and 17 has higher sensitivity than cytology and a similar specificity in the detection of superficial UC and UC at UUT, which could be useful for reducing some cystoscopies in the follow-up of these patients. Moreover, a high percentage of positive pre-BCG FISH results were obtained, suggesting the need for adjuvant therapy in patients with HRSBT after the transurethral resection. In addition, patients with a positive post-BCG FISH result were more likely to relapse after therapy. Thus, FISH appears to be useful for the surveillance of patients with HRSBT following BCG therapy.Finally, using molecular markers it was possible to improve the sensitivity of LN histologic analysis. Also this methodology allowed distinguishing between UC patients and controls. However, despite its high sensitivity, it was not possible to monitor UC haematogenous dissemination.

Oil and gas exploration conducted in the 1970s left behind a legacy of abandoned well sites in the Mackenzie Delta region of northern Canada, including several in the Kendall Island Migratory Bird Sanctuary and surrounding areas. Evidence of 30 year-old well sites is present in the form of drilling mud sumps, which are mounds of disturbed tundra that contain frozen drilling-wastes. One to two years after the wells were decommissioned some of the sites were seeded with non-native grass species and fertilized to test whether these treatments could accelerate vegetation recovery and prevent erosion. The main objective of this research was to examine the long-term impact of post-disturbance seeding treatments on the vegetation recovery of drilling mud sumps.<p> Surveys of vegetation composition and environmental conditions at 12 sump sites (6 seeded and 6 unseeded) showed that, after over 30 years of recovery, seeded sumps in the Mackenzie Delta did not significantly differ from those left for natural recovery. However, seeded and previously introduced grasses <i>Festuca rubra</i> and <i>Poa pratensis</i> were found on both seeded and unseeded sumps. The undisturbed surrounding tundra seems to be resistant to invasion by these introduced grasses. However, these species could become invasive in the future, particularly in the context of warming in the North and increasing anthropogenic disturbance. The results of this study contribute valuable information on the long-term effects of revegetation treatments that is critical for making informed management decisions about the rehabilitation of industrial disturbances in the Arctic.

La maladie de Crohn (MC) est une maladie inflammatoire chronique intestinale (MICI). Son incidence et sa prévalence ont augmenté en Europe au cours des dix dernières années (150 pour 100000 habitants) constituant ainsi un problème de santé majeur. L’inflammation chronique dans la MC favorise la mise en place d’une angiogenèse pathophysiologique. Inflammation et angiogenèse sont deux réponses cellulaires suspectées dans la survenue des cancers coliques associés au MICI. Même si les facteurs favorisant la mise en place de la MC restent non élucidés, la contribution des bactéries exogènes est fortement suspectée. Parmi ces bactéries, les E.coli adhérentes et invasives (AIEC), isolées à partir de la muqueuse iléale de patients porteurs de la MC, sont un bon candidat. Les objectifs de mon projet de thèse étaient de caractériser les mécanismes moléculaires induits par les AIEC et impliqués dans la mise en place des réponses pro inflammatoire et pro angiogénique des cellules intestinales épithéliales. Le facteur de transcription hypoxique (HIF-1) est au cœur de l’immunité innée et de l’angiogenèse. J’ai émis l’hypothèse que les AIEC pouvaient moduler le niveau d’expression de HIF-1α et ainsi contrôler les réponses pro inflammatoire et pro angiogénique. Dans mon premier article, j’ai montré que HIF-1α est maximalement exprimé au niveau de l’épithélium iléal des patients porteurs de la MC. Ensuite, j’ai montré sur un modèle murin compétent pour l’infection par les AIEC, les souris CEABAC10, que les bactéries induisent l’augmentation du niveau protéique de HIF-1 α ainsi que l’activation de la voie de signalisation du VEGF, le facteur angiogénique le plus puissant. / Non communiqué.

Parmi les diverses techniques utilisées pour analyser les pigments sur les peintures de chevalet, l'étude s'intéresse aux techniques optiques, en particulier la spectrophotométrie, l'imagerie hyperspectrale, la photographie et la spectrométrie infrarouge. Toutes présentent l'intérêt d'être non invasives : sans contact, non-destructives et aucune ne nécessite de prélèvement sur les œuvres d'art.Une étude comparative des performances des différents appareils a dans un premier temps été réalisée, puis nous avons testé l'efficacité des méthodes utilisées en routine pour la caractérisation des pigments : identification des pigments purs, en mélange, quantification des pigments en mélange. L'étude fut délibérément circonscrite aux pigments historiques avant le XVIIIème siècle, période où la palette des peintres se réduit à un nombre relativement limité de pigments et où les mélanges restent assez simples.L'imagerie hyperspectrale s'est développée ces dernières années pour l'analyse du patrimoine culturel et génère des quantités importantes de données dont le traitement est complexe. Nous avons traité cette technique à part, pour proposer une utilisation simple et accessible. Notre méthodologie d'exploitation des données d'imagerie hyperspectrale s'inspire de la photographie traditionnelle en fausses couleurs et est ouverte à des développements futurs. En effet, il s'agit de générer trois composites en fausses couleurs, en choisissant les bandes spectrales appropriées puis en les combinant afin de mettre en évidence des différences spectrales entre les pigments d'une même catégorie (bleu, vert, jaune ou rouge).Les méthodes optiques ont été testées dans un premier temps sur des échantillons de pigments purs et de mélanges expérimentaux, puis sur des peintures d'Eustache Le Sueur, peintre français du XVIIème siècle. La méthodologie des composites variables a été appliquée aux œuvres, puis confrontée aux techniques traditionnelles d'analyse des pigments, dont l'analyse par fluorescence X et l'examen à la loupe binoculaire.Les résultats sont cohérents et encourageants ; ils permettent d'envisager dans un proche futur le recours à une utilisation de l'imagerie hyperspectrale, avec un protocole simplifié. / Various techniques are currently used to characterize pigments on easel paintings. The present study focuses on optical techniques, especially spectrophotometry, hyperspectral imaging, photography and infrared spectrometry. These techniques are non-invasive, without contact, non-destructive and request no sampling.A technical comparison of the different devices is given before testing the efficiency of the commonly used methods for pigment characterization – pigment identification (pure or in a mixture) and pigment quantification in mixtures. With respect to the pigments themselves, the pre-18th century period was chosen in particular, as the number of pigments was limited and the mixtures quite simple.Analysis of cultural heritage by hyperspectral imaging has been developing fast over the past few years. This technique generates large amounts of data that are complex to process. A simplified method was developed to process the data. An evolutionary approach was chosen to extract image data and this methodology used takes its roots in false color traditional photography. Indeed, three false-color composites were generated by choosing a composition of spectral bands in order to maximize the spectral differences between the pigments of a same color category (blue, red, yellow or green).In a first step, optical techniques were tested on pigment mock-ups (pure or mixed). The variable composite methodology was applied on paintings by Eustache Le Sueur, a French painter from the 17th century. Finally the results were compared to those achieved by classical analytical tools currently used for cultural heritage such as X-ray fluorescence and optical microscopy. The results are quite consistent and very promising in favor of a more regular use of the hyperspectral imaging method.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O processo de introdução de espécies é reconhecido como a segunda causa mais importante de erosão da diversidade biológica em muitos ambientes no Brasil e no mundo. As espécies invasoras possuem não apenas o poder de sobrevivência e adaptação em outros ambientes, mas a capacidade de dominar a diversidade biológica nativa através da alteração das características básicas dos processos ecológicos naturais e das interações. A jaqueira, Artocarpus heterophyllus Lamarck (Moraceae), tem sua origem nas florestas tropicais da Índia, tendo sido introduzida no Brasil ainda no período Colonial e atualmente é invasora em áreas de Mata Atlântica. Este estudo fornece os primeiros dados sobre a influência da espécie exótica invasora Artocarpus heterophyllus sobre comunidades de anuros de folhiço. As amostragens foram realizadas em uma área de Mata Atlântica, no litoral sudoeste do estado do Rio de Janeiro, incluindo informações sobre riqueza de espécies, densidades específicas e parâmetros ambientais. Nosso estudo foi realizado no Parque Estadual da Ilha Grande entre janeiro de 2009 e março de 2011. Para amostrar a comunidade de anuros de folhiço usamos 154 parcelas de 5 x 5 m, sendo 77 delas em áreas com jaqueiras e 77 em áreas sem jaqueiras, totalizando 3.850 m de chão de floresta amostrados. Nós amostramos um total de 613 anuros habitando o chão da floresta, pertencentes a dez espécies: Brachycephalus didactylus; Chiasmocleis sp.; Haddadus binotatus; Ischnocnema guentheri; Ischnocnema octavioi; Ischnocnema parva; Leptodactylus marmoratus; Physalaemus signifer; Rhinnela ornata e Zachaenus parvulus. Seis das dez espécies foram comuns às áreas com e sem jaqueiras, sendo a similaridade entre as duas áreas de 60%. As áreas com jaqueiras tiveram o dobro (N = 18) de parcelas sem nenhum anfíbio. O número de anfíbios registrados nas parcelas com jaqueiras (38%) foi menor do que o encontrado nas áreas sem jaqueiras (62%). O anfíbio predominante no folhiço em ambas às condições foi Ischnocnema parva, tendo abundancia maior nas parcelas sem jaqueiras. A densidade total de anuros vivendo no chão da floresta nas áreas com jaqueiras (12,2 ind/100 m) foi menor que nas áreas sem jaqueiras (19,7 ind/100 m). Entre os parâmetros ambientais analisados os que possuíram maior influência sobre a abundância de anfíbios foram a profundidade do folhiço e o pH do solo. Os dados sugerem que a jaqueira, além de ocupar o habitat de espécies nativas, é capaz de promover alterações na estrutura desses habitats que irão intervir na fauna do local. / The process of species introduction is recognized as the second most important cause of biological diversity erosion in many environments in Brazil and worldwide. Invasive species have not only the power to survive and adapt in other environments, but also the ability to master the native biodiversity by altering the basic characteristics of natural ecological processes and interactions. The jackfruit tree, Artocarpus heterophyllus Lamarck (Moraceae), has its origin in the tropical forests of India, being introduced in Brazil during the Colonial period and is currently invading the Atlantic Forest. In this study we provide the first data about the influence of the invasive alien species Artocarpus heterophyllus on anuran communities. Samples were taken in an area of Atlantic Forest, on the Southwest coast of the State of Rio de Janeiro, and included information on species richness, density and environmental parameters. Our study was conducted at the Ilha Grande State Park, between January 2009 and March 2011. To sample the community of litter anurans we constructed 154 plots of 5 x 5 m, being 77 of them in areas with jackfruit and 77 in areas with no jackfruit, totaling 3.850m of forest floor sampled. We collected a total of 613 frogs inhabiting the forest floor, being distributed within ten species: Brachycephalus didactylus; Chiasmocleis sp.; Haddadus binotatus; Ischnocnema guentheri; Ischnocnema otavioi; Ischnocnema parva; Leptodactylus marmoratus; Physalaemus signifer; Rhinnela ornata and Zachaenus parvulus. Six of this species were common to areas with and without jackfruit, and the similarity between the two areas was 60%. Areas with jackfruit had the double (N = 18) of plots with no amphibian. The number of amphibians recorded in plots with jackfruit (38%) was lower than the number found in areas without jackfruit (62%). The predominant amphibian species in both conditions was Ischnocnema parva, which had greater abundance in plots without jackfruit. The total density of frogs living on the forest floor in areas with jackfruit (12.2 ind/100 m) was lower than in areas without jackfruit (19.7 ind/100 m). Among the environmental parameters analyzed those with greater influence on the abundance of amphibians were the depth of leaf litter and soil pH. The data suggested that the addition of jackfruit, besides occupying the habitat of native species, is able to promote changes in the structure of these habitats that may intervene in the local fauna.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O processo de introdução de espécies é reconhecido como a segunda causa mais importante de erosão da diversidade biológica em muitos ambientes no Brasil e no mundo. As espécies invasoras possuem não apenas o poder de sobrevivência e adaptação em outros ambientes, mas a capacidade de dominar a diversidade biológica nativa através da alteração das características básicas dos processos ecológicos naturais e das interações. A jaqueira, Artocarpus heterophyllus Lamarck (Moraceae), tem sua origem nas florestas tropicais da Índia, tendo sido introduzida no Brasil ainda no período Colonial e atualmente é invasora em áreas de Mata Atlântica. Este estudo fornece os primeiros dados sobre a influência da espécie exótica invasora Artocarpus heterophyllus sobre comunidades de anuros de folhiço. As amostragens foram realizadas em uma área de Mata Atlântica, no litoral sudoeste do estado do Rio de Janeiro, incluindo informações sobre riqueza de espécies, densidades específicas e parâmetros ambientais. Nosso estudo foi realizado no Parque Estadual da Ilha Grande entre janeiro de 2009 e março de 2011. Para amostrar a comunidade de anuros de folhiço usamos 154 parcelas de 5 x 5 m, sendo 77 delas em áreas com jaqueiras e 77 em áreas sem jaqueiras, totalizando 3.850 m de chão de floresta amostrados. Nós amostramos um total de 613 anuros habitando o chão da floresta, pertencentes a dez espécies: Brachycephalus didactylus; Chiasmocleis sp.; Haddadus binotatus; Ischnocnema guentheri; Ischnocnema octavioi; Ischnocnema parva; Leptodactylus marmoratus; Physalaemus signifer; Rhinnela ornata e Zachaenus parvulus. Seis das dez espécies foram comuns às áreas com e sem jaqueiras, sendo a similaridade entre as duas áreas de 60%. As áreas com jaqueiras tiveram o dobro (N = 18) de parcelas sem nenhum anfíbio. O número de anfíbios registrados nas parcelas com jaqueiras (38%) foi menor do que o encontrado nas áreas sem jaqueiras (62%). O anfíbio predominante no folhiço em ambas às condições foi Ischnocnema parva, tendo abundancia maior nas parcelas sem jaqueiras. A densidade total de anuros vivendo no chão da floresta nas áreas com jaqueiras (12,2 ind/100 m) foi menor que nas áreas sem jaqueiras (19,7 ind/100 m). Entre os parâmetros ambientais analisados os que possuíram maior influência sobre a abundância de anfíbios foram a profundidade do folhiço e o pH do solo. Os dados sugerem que a jaqueira, além de ocupar o habitat de espécies nativas, é capaz de promover alterações na estrutura desses habitats que irão intervir na fauna do local. / The process of species introduction is recognized as the second most important cause of biological diversity erosion in many environments in Brazil and worldwide. Invasive species have not only the power to survive and adapt in other environments, but also the ability to master the native biodiversity by altering the basic characteristics of natural ecological processes and interactions. The jackfruit tree, Artocarpus heterophyllus Lamarck (Moraceae), has its origin in the tropical forests of India, being introduced in Brazil during the Colonial period and is currently invading the Atlantic Forest. In this study we provide the first data about the influence of the invasive alien species Artocarpus heterophyllus on anuran communities. Samples were taken in an area of Atlantic Forest, on the Southwest coast of the State of Rio de Janeiro, and included information on species richness, density and environmental parameters. Our study was conducted at the Ilha Grande State Park, between January 2009 and March 2011. To sample the community of litter anurans we constructed 154 plots of 5 x 5 m, being 77 of them in areas with jackfruit and 77 in areas with no jackfruit, totaling 3.850m of forest floor sampled. We collected a total of 613 frogs inhabiting the forest floor, being distributed within ten species: Brachycephalus didactylus; Chiasmocleis sp.; Haddadus binotatus; Ischnocnema guentheri; Ischnocnema otavioi; Ischnocnema parva; Leptodactylus marmoratus; Physalaemus signifer; Rhinnela ornata and Zachaenus parvulus. Six of this species were common to areas with and without jackfruit, and the similarity between the two areas was 60%. Areas with jackfruit had the double (N = 18) of plots with no amphibian. The number of amphibians recorded in plots with jackfruit (38%) was lower than the number found in areas without jackfruit (62%). The predominant amphibian species in both conditions was Ischnocnema parva, which had greater abundance in plots without jackfruit. The total density of frogs living on the forest floor in areas with jackfruit (12.2 ind/100 m) was lower than in areas without jackfruit (19.7 ind/100 m). Among the environmental parameters analyzed those with greater influence on the abundance of amphibians were the depth of leaf litter and soil pH. The data suggested that the addition of jackfruit, besides occupying the habitat of native species, is able to promote changes in the structure of these habitats that may intervene in the local fauna.

La destruction de l'habitat, les invasions biologiques et leur interaction sont des menaces majeures pour la biodiversité. La Nouvelle-Calédonie est menacée à la fois par des feux d'origine humaine, et par des fourmis invasives : il est important de comprendre leur impact sur ce biotope unique. Pour ce faire, une approche hiérarchique intégrant différents aspects de la biodiversité (composition, structure et fonction) a été adoptée. Les fourmis ont une grande importance écologique, en particulier en milieu tropical, et leur classification en groupes fonctionnels facilite l'interprétation de leur réponse aux perturbations environnementales. Les objectifs de cette étude étaient donc d'évaluer les impacts des feux, des fourmis invasives, et de leur interaction, sur les fourmis natives de Nouvelle-Calédonie, et ce à différentes échelles spatiales (globale, régionale, locale) et temporelles (court et long terme), ainsi qu'à divers niveaux d'organisation biologique (communautés, espèces, gènes). L'étude contribue à une meilleure connaissance de la myrmécofaune calédonienne, en révélant l'absence de fourmis souterraines spécialisées, et en documentant la distribution et composition des communautés de fourmis à l'échelle de l'île, en lien avec l'habitat et les fourmis exotiques. Les mécanismes par lesquels les feux impactent les fourmis natives, y compris en association avec les fourmis invasives, sont révélés. Le feu, en créant les conditions de micro- et macrohabitat favorisées par les fourmis invasives, facilite l'invasion, qui cause ensuite d'avantage de perte de diversité, soit quelques années après un incendie ou dans le contexte de la fragmentation à long terme. L'approche hiérarchique a permis de détecter des réponses contrastées au niveau des espèces et de la génétique, liées à différents traits d'histoire de vie, en plus des réponses mesurées au niveau des communautés. Cette étude souligne l'avantage d'une approche holistique pour adresser des problèmes liés à la biodiversité. / Habitat destruction, biological invasions and their interaction are global drivers of biodiversity loss. The New Caledonian hotspot of biodiversity is threatened by both anthropogenic fires and invasive ants: it is important to understand their impacts on its biota. Because biodiversity spans several levels of organisation (from genes to communities) and relates to different attributes (compositional, structural and functional), this thesis takes a hierarchical approach to address this issue. Ants are of great ecological importance, especially in tropical biomes, and their classification into functional groups provides a global framework for analysing their response to disturbance. My aims were therefore to investigate the impacts of anthropogenic fires and invasive ants, and their interaction, on the native New Caledonian ant fauna at different spatial (global, regional, local) and temporal (short and long term) scales, and at different levels of biological organisation (community, species, genes). The study contributes to an improved knowledge of the New Caledonian ants, by revealing the lack of specialised subterranean species, and by investigating island-scale patterns of ant communities, in relation to habitat and invasion. The mechanisms by which fire impacts native ants, either as a standalone process or in association with invasion could be identified. In particular, I show that fire, by creating macro- and microhabitats favoured by invasive ants, facilitates invasion, which then causes further diversity declines, either in the short- (post-burning) or long-term (forest fragmentation). The hierarchical approach used enabled the detection of contrasting trait-derived responses at the species and genetic level, in addition to responses measured at the community level. This study highlights the advantage of a holistic approach to investigating biodiversity-related issues.

La fibrillation atriale affecte 2-3% des européens et nord-américains, les tachycardies ventriculaires sont liées à un risque important de mort subite. Les approches minimalement invasives comme l’Ablation par Cathéter Radiofréquence (RFCA) ont révolutionné le traitement de ces maladies, mais le taux de réussite de la RFCA est limité par le manque de techniques d’imagerie pour contrôler cette ablation thermique.Le but de cette thèse est de proposer de nouvelles approches ultrasonores pour des traitements cardiaques minimalement invasifs guidés par échographie.Pour cela nous avons d’abord validé la précision et la viabilité clinique de l’Élastographie par Ondes de Cisaillement (SWE) en tant que modalité d’imagerie quantitative et temps réel pour l’ablation thermique in vivo. Ensuite nous avons implémenté la SWE sur un transducteur intracardiaque et validé la faisabilité d’évaluer l’ablation thermique in vitro et in vivo sur cœur battant de gros animal. Puis nous avons développé un transducteur intracardiaque dual-mode pour effectuer l’ablation et l’imagerie ultrasonores avec les mêmes éléments, sur le même dispositif. Les lésions thermiques induites par Ultrasons Focalisés de Haute Intensité (HIFU) et contrôlées par la SWE ont été réalisées avec succès in vivo dans les oreillettes et les ventricules chez le gros animal. Finalement la SWE a été implémentée sur un dispositif d’imagerie et thérapie ultrasonores transœsophagien et la faisabilité de cette approche a été démontrée in vitro et in vivo. Ces approches originales pourraient conduire à de nouveaux dispositifs cliniques pour des traitements plus sûrs et contrôlés d’un large éventail d’arythmies et maladies cardiaques. / Atrial fibrillation (AF) affects 2-3% of the European and North-American population, whereas ventricular tachyarrhythmia (VT) is related to an important risk of sudden death. AF and VT originate from dysfunctional electrical activity in cardiac tissues. Minimally-invasive approaches such as Radio-Frequency Catheter Ablation (RFCA) have revolutionized the treatment of these diseases; however the success rate of RFCA is currently limited by the lack of monitoring techniques to precisely control the extent of thermally ablated tissue.The aim of this thesis is to propose novel ultrasound-based approaches for minimally invasive cardiac ablation under guidance of ultrasound imaging. For this, first, we validated the accuracy and clinical viability of Shear-Wave Elastography (SWE) as a real-time quantitative imaging modality for thermal ablation monitoring in vivo. Second we implemented SWE on an intracardiac transducer and validated the feasibility of evaluating thermal ablation in vitro and in vivo on beating hearts of a large animal model. Third, a dual-mode intracardiac transducer was developed to perform both ultrasound therapy and imaging with the same elements, on the same device. SWE-controlled High-Intensity-Focused-Ultrasound thermal lesions were successfully performed in vivo in the atria and the ventricles of a large animal model. At last, SWE was implemented on a transesophageal ultrasound imaging and therapy device and the feasibility of transesophageal approach was demonstrated in vitro and in vivo. These novel approaches may lead to new clinical devices for a safer and controlled treatment of a wide variety of cardiac arrhythmias and diseases.