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Environmental DNA data provides taxa-specific insights into community differences across Reunion Island back-reef depressions
No full textInternational audienceReunion Island’s coral reefs host complex biological communities, making comprehensive monitoring essential for detecting shifts in species presence as markers of reef health. Biodiversity monitoring, traditionally based upon visual censuses, can be enhanced through environmental DNA (eDNA) surveys that expand species detection. A recent eDNA metabarcoding study used 12S, 18S, and COI gene markers to screen water samples from four back-reef depressions (or ‘lagoons’) in Reunion Island, revealing distinctive communities across five different sites. This study offers new insight by identifying species and families driving community distinctiveness, and providing a preliminary glimpse into how single time-point eDNA data align with multi-year observational surveys from the Global Coral Reef Monitoring Network (GCRMN) in evaluating its effectiveness for detecting local fish species. The 12S marker detected 52 fish families across all sites, while COI and 18S, targeting mainly invertebrates, identified 262 and 414 families, respectively. Further analyses revealed strong contrasts among all sites, including two within the same lagoon. At the Planch’Alizé site, analyses indicated lower sequence read representation of corals, hydrozoans and several coral-associated fish species. Spatially proximate GCRMN surveys, aggregated over several years, recorded 149 fish species, compared to 213 detected by eDNA. Further, the GCRMN dataset recorded higher proportions of herbivores and omnivores, while eDNA detected a higher proportion of piscivores and captured more nocturnal and/or cryptic species. These results highlight the strength of eDNA for revealing fine-scale community differences, while emphasizing the importance of combining different survey types to gain a more comprehensive understanding of reef systems for supporting long term monitoring efforts
Flood pulse monitoring in wetlands with multi-temporal Sentinel-1 interferometric coherence data: Application to the Okavango Delta (Botswana)
No full textInternational audienceFlood-pulsed wetlands are characterized by significant seasonal water fluctuations, which play a critical role in the dynamics of these sensitive ecosystems. Among the growing number of existing remote sensing products, we explore the potential of interferometric (InSAR) coherence time series, derived from Sentinel-1 synthetic-aperture radar images, to characterize the hydrological dynamics of the Okavango Delta, a vast flood-pulsed wetland. Interferometric coherence reflects changes in surface conditions, making it a powerful tool for detecting flood propagation. By fitting harmonic functions, we produce parameters that quantify the seasonality of coherence time series with short isotemporal baselines (12 days). In particular, we developed a normalized seasonal index based on the ratio between the seasonal amplitude and the root-mean-square error of the fitted harmonic function, to map the seasonality of the coherence time series. A multi-annual analysis of coherence time series reveals a strong relationship between their seasonality, land cover, and flood frequency. Unsupervised clustering applied to statistical and seasonal metrics of coherence time series yields consistent classifications that map the variability of flood frequencies across wetland areas and clearly distinguish wetlands from dry zones. Similarly thresholds applied to normalized seasonal indices delineate the year-to-year extent of flood pulses with accuracy around 79 %. We show that coherence time series in never flooded areas exhibit a pronounced seasonal pattern driven by rainfall cycle, whereas this seasonality is disrupted by flood pulses in wetlands. Building on this, developed a change-detection approach to map the floods by identifying the date when coherence time series diverge from their seasonal pattern. The resulting flood arrival dates achieve 74–83 % accuracy compared to a reference dataset derived from optical data. Our results highlight the potential of coherence time series as a robust indicator of seasonal variations in inundation extent in flood-pulsed wetlands
Democratic Control Over Tax Treaties: A Comparative Constitutional Perspective
No full textInternational audienceThe article asks a fundamental constitutional question: who democratically controls tax treaty policy? Using a functional, lifecycle-based comparative method, it examines four pivotal moments at which representative consent may shape or limit tax treaty commitments: entry (negotiation and approval), clarification (reservations, subsequent agreements, interpretative practice), operation (domestic implementation and application, including override), and exit (termination). Although tax treaties reallocate taxing right, reshape tax bases and affect public revenue, the comparative analysis of selected civil-law and common-law jurisdictions reveals a recurring pattern of executive dominance. Parliaments play a central but temporarily compressed role at approval or implementation, but they are only weakly integrated into the management and evolution of treaty commitments. The article maps emerging best practices and advances a reform agenda aimed at re-embedding tax treaties within domestic chains of democratic legitimacy, so that the principle of “no taxation without representation” applies coherently to both international tax commitment and ordinary tax legislation
Réactivité institutionnelle et qualité de réponses aux réclamations de la clientèle sur l'utilisation des services bancaires en période de crise sécuritaire à Goma (R.D. Congo) : Clients en détresse, Banques à l'épreuve
No full textInternational audienceAbstract This paper has examined the institutional responsiveness of commercial banks operating in Goma (Democratic Republic of Congo), in a context marked by prolonged security instability affecting service quality. It has aimed to identify the factors that have influenced user satisfaction in the face of service disruptions, particularly regarding complaint procedures. A mixed-methods approach has been employed, combining a quantitative survey of 412 users with semi-structured interviews conducted with bank officials. The data have been analyzed using a binary logistic regression model to assess the impact of explanatory variables on reported satisfaction. The findings have shown that the clarity of procedures and the accessibility of institutional channels have had a significant effect (p < 0.05), whereas the speed of resolution has not demonstrated statistical significance (p = 0.106). These results have suggested that perceived responsiveness depends more on transparency and proximity than on speed. The study has recommended strengthening customer relationship governance through accessible, readable, and resilient mechanisms adapted to unstable environments. Keywords: «Institutional responsiveness; User satisfaction; complaint management; banking Services; Security Crisis » Classification JEL : D12, G21, L15, M31, O17Résumé Ce papier a examiné la réactivité institutionnelle des banques commerciales à Goma (RDC), dans un contexte de crise sécuritaire prolongée affectant la qualité des services. Il a visé à identifier les facteurs influençant la satisfaction des usagers confrontés à des dysfonctionnements, notamment dans les procédures de réclamation. Une approche méthodologique mixte a été mobilisée : une enquête quantitative auprès de 412 usagers et des entretiens semi-directifs avec des responsables bancaires. Les données ont été analysées par régression logistique binaire afin d’évaluer l’effet des variables explicatives sur la satisfaction déclarée. Les résultats ont montré que la clarté des procédures et l’accessibilité des canaux institutionnels ont eu un effet significatif (p < 0,05), contrairement à la vitesse de résolution (p = 0,106). La perception de réactivité repose ainsi davantage sur la transparence et la proximité. L’étude recommande de renforcer la gouvernance de la relation client par des dispositifs accessibles, lisibles et résilients, adaptés aux zones d’instabilité. Mots-clés : « Réactivité institutionnelle ; Satisfaction des usagers ; Gestion des réclamations ; Services bancaires ; Crise sécuritaire » JEL Classification : D12, G21, L15, M31, O1
Short note: on the determination of the relaxation time distributions using Bézier curves
No full textInternational audienceFor the interpretation of spectral induced polarization spectra, the determination of the relaxation time distributions (RTD) can be useful, for instance to extract the grain size distribution. However, this is an ill-posed problem, and retrieving the RTD often requires regularization during the inversion process. In this note, we use Bézier curves and simulated annealing to determine the RTD. The procedure that does not require any regularization nor smoothing, by reducing the number of parameters thanks to Bézier curves which are intrinsically continuous and infinitely derivable. We successfully applied our methodology to three examples (Cole–Cole model, Davidson–Cole model, and an experimental spectrum), demonstrating its interest and efficiency
: Histoire évolutive de l'invasion du mildiou du tournesol en France
No full textInternational audienceUnderstanding the genetic diversity and evolutionary history of plant pathogens is crucial for effective disease management strategies. Sunflower downy mildew, caused by the oomycete Plasmopara halstedii , is a worldwide threat to the sunflower oil crop. We aimed to explain through phylogenomic studies how downy mildew resistance breakdown occurred recurrently in the last decades in France, leading to new virulence profiles. We assembled high‐quality genomes of three founder pathotypes of Pl. halstedii . Performing comparative genomic analyses, population genetics, and phylogenomic analyses, we studied the genomic structure among the 16 reference French pathotypes of Pl. halstedii . We revealed a conserved genomic organisation among pathotypes and a strong synteny with other Peronosporales species. The history of Pl. halstedii invasion in France over the last 60 years was documented by identifying founder strains and their admixture patterns. The emergence of pathotypes with broader virulence spectra and therefore capable of overcoming host resistance was associated with genomic reshuffling. We highlighted genomic mosaicism in admixed pathotypes and identified regions associated with the breakdown of host resistance genes harbouring putative effector genes. Our findings provide insights into evolutionary mechanisms underlying plant pathogen host adaptation, which has implications for a sustainable deployment of multiple resistance genes.RÉSUMÉ Comprendre la diversité génétique et l'histoire évolutive des agents phytopathogènes est crucial pour l'élaboration de stratégies efficaces de gestion des maladies. Le mildiou du tournesol, causé par l'oomycète Plasmopara halstedii, représente une menace mondiale pour la culture du tournesol oléagineux. Notre objectif était d'expliquer, par des études phylogénomiques, la réapparition récurrente du contournement de la résistance au mildiou au cours des dernières décennies en France, conduisant à de nouveaux profils de virulence de l'agent pathogène. Nous avons assemblé les génomes de haute qualité de trois pathotypes fondateurs de Pl. halstedii. Grâce à des analyses de génomique comparative, de génétique des populations et de phylogénomique, nous avons étudié la structure génomique des 16 pathotypes français de référence de Pl. halstedii. Nous avons mis en évidence une organisation génomique conservée parmi les pathotypes et une forte synthénie avec d'autres espèces d'oomycètes Peronosporales. L'histoire de l'invasion de Pl. halstedii en France au cours des 60 dernières années a été documentée par l'identification des souches fondatrices et de leurs schémas d'introgression. L'émergence de pathotypes présentant un spectre de virulence plus large et capables, de ce fait, de contourner la résistance de l'hôte tournesol, a été associée à des remaniements génomiques. Nous avons mis en évidence un mosaïcisme génomique chez des pathotypes admixés et identifié des régions associées au contournement des gènes de résistance de l'hôte, abritant des gènes effecteurs putatifs. Nos résultats éclairent les mécanismes évolutifs sous-jacents à l'adaptation des pathogènes végétaux à leurs hôtes, ce qui a des implications pour un déploiement durable des gènes de résistance
Revisiting the meanings of the Critical Zone through the OZCAR research infrastructure example, definitions and evolutions
No full textOZCARInternational audienceSince its first definition by the National Research Council in 2001, the concept of Critical Zone has known undeniable success over the last quarter of a century. A success that is often reflected by the evolution and diversification of its meanings. Recently, Lee et al. (2023) proposed a review that literally focuses on “the meanings of the Critical Zone”. Through an extensive review of the literature across the disciplines and journals, they have identified three loosely overlapping meanings. An ontological meaning, where the Critical Zone is mostly seen as the Earth’s spatial interface where geochemical and biological activity sustains life. An epistemic meaning, where the Critical Zone is considered a product of collaborative efforts between scientific communities to build a whole-system knowledge data-base and library. And finally, an anthropocenic meaning, where the Critical Zone is the vulnerable home of the human species. In this contribution, we aim at revisiting these three meanings through the creation and development of the French network OZCAR (Critical Zone Observatories: Research and Application).Created in 2015 to enhance the collaborations between Critical Zone observatories (Gaillardet et al., 2018), OZCAR is a French Research Infrastructure that gathers 23 national observation services and +120 study sites in metropolitan France and on 5 continents. If most observation services existed prior to the creation of OZCAR, we have seen major evolutions over the last decade as the OZCAR community developed and bloomed. Originally conceived as a spatial definition (ontological meaning), the “Critical Zone” words in OZCAR became a vast collaborative effort to develop the whole system approach and data base (epistemic meaning). It is now also fostering transformative research aimed at preserving our planet’s habitability, i.e., the giant spaceship in which we all live together (anthropocenic meaning).References:Lee, R. M., Shoshitaishvili, B., Wood, R. L., Bekker, J., & Abbott, B. W. (2023). The meanings of the Critical Zone. Anthropocene, 42, 100377.,doi:10.1016/j.ancene.2023.100377. Gaillardet, J., Braud, I., Hankard, F., Anquetin, S., Bour, O., Dorfliger, N., et al. (2018). OZCAR: The French network of critical zone observatories. Vadose Zone Journal, 17(1), 1-24, doi:10.2136/vzj2018.04.0067
Modélisation, analyse et contrôle d'un ravageur du chou : cas de Plutella xylostella
No full textEnsuring positive economic results for smallholder farms is a major issue for the development and promotion of sustainable agriculture. This is not always easy, since pests destroy crops and considerably reduce farm yields. In addition, there are high costs related to pest management, which can be both environmentally damaging and ineffective. In the face of all these difficulties, smallholders have to find ways of generating enough profit not only to sustain their farm activities, but also to meet their own needs, as access to external finance is difficult. The main objective of this thesis is to study the long-term economic sustainability of a self-financing cabbage farm by proposing bioeconomic models. Two control strategies are implemented: chemical control using bio-insecticide and parasitoid-based biological control. Based on biological considerations, the baseline model combines the dynamics of the cabbage and the diamondback moth, a bio-insecticide and the current balance of the plantation. The first analysis confirms that the use of bioinsecticide as a pest control is effective, less expensive and suitable to the concept of self-financing. The best operating points for subsystems were defined in order to maximise the farmer's income. In addition, the thesis compares three different techniques of releasing parasitoids and we indicate the best technique based on the characteristics of the parasitoid involved and the number of releases. Hence this work presents novel results in crop protection, mathematical modelling, and dynamical systems analysis.Garantir des résultats économiques positifs aux petites exploitations agricoles est un enjeu majeur pour le développement et la promotion d'une agriculture durable. Cela n'est pas toujours facile, car les ravageurs détruisent les cultures et réduisent considérablement les rendements agricoles. De plus, la lutte contre les ravageurs engendre des coûts élevés et elle peut s'avérer à la fois néfaste pour l'environnement et inefficace. Face à toutes ces difficultés, les petits agriculteurs doivent trouver des moyens pour générer suffisamment de profit non seulement pour maintenir leurs activités agricoles, mais aussi pour subvenir à leurs propres besoins, car l'accès à des financements externes est difficile. L'objectif principal de cette thèse est d'étudier la viabilité économique à long terme d'une exploitation de choux autofinancée en proposant des modèles bio-économiques. Deux stratégies de lutte sont mises en œuvre : la lutte chimique à l'aide d'un bio-insecticide et la lutte biologique à base de parasitoïdes. Sur la base de considérations biologiques, le modèle de référence combine la dynamique du chou et de la teigne du chou, un bio-insecticide et le solde courant de la plantation. La première analyse confirme que l'utilisation d'un bio-insecticide comme moyen de lutte contre les ravageurs est efficace, moins coûteuse et adaptée au concept d'autofinancement. Les meilleurs points de fonctionnement des sous-systèmes ont été définis afin de maximiser les revenus de l'agriculteur. De plus, la thèse compare trois techniques différentes de lâchers de parasitoïdes et nous indiquons la meilleure technique en fonction des caractéristiques du parasitoïde concerné et du nombre de lâchers. Ce travail présente donc des résultats novateurs dans les domaines de la protection des cultures, de la modélisation mathématique et de l'analyse des systèmes dynamiques
A GasPak-Based Ischemia Model for Studying ER Stress–Ischemia Interactions in Human Endothelial Cells
No full textInternational audienceDuring ischemia, endothelial cell integrity is compromised, as a consequence, blood barrier homeostasis is disrupted. Therefore, the structural and functional preservation of endothelial cells is paramount when trying to improve outcomes after ischemic injury. Endoplasmic reticulum (ER) stress is increasingly recognized as a key player in ischemic injury through unfolded protein response (UPR) signalling, and its crosstalk with mitochondrial death pathways. This study provides a cost-effective and straightforward method to delve into the relationship between ER stress and ischemia in human microvascular endothelial cells-1 (HMEC-1). HMEC-1 was exposed to 8 h of oxygen-glucose deprivation (OGD) in glucose-free medium with rapidly induced hypoxia. Hypoxia, oxygen consumption, cell viability, apoptosis, and ER stress markers (BiP/GRP78, PERK, ATF6, IRE1/XBP1s, CHOP) were assessed by RT-qPCR and Western blot. Cell viability decreased by approximately 33% following OGD, while CHOP expression increased ~4-fold, indicating significant ER stress induction. The model enables quantification of metabolic stress (OCR), as well as evaluation of viability loss, membrane integrity, apoptotic commitment, and discrimination between ER stress resolution versus maladaptation. Overall, GasPak EZ Pouch Systems provide a reproducible and practical in vitro platform to study ischemic injury down to the mechanistic details of ER-mitochondria signalling. They give the opportunity to evaluate therapeutic approaches that target ER homeostasis to limit apoptosis and/or recovery of metabolic function after ischemia. This method could allow rapid screening of ER stress-modulating interventions aimed at preserving endothelial barrier function, in various ischemic contexts