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Semer la biodiversité, Récolter la durabilité
No full textL’agriculture, la foresterie, l’aquaculture et les pêcheries font face à de nombreux défis : une demande alimentaire croissante, des malnutritions persistantes et une dégradation des ressources naturelles. Les changements climatiques rendent encore plus complexe la tâche d’assurer la sécurité alimentaire de 9.7 milliards de personnes d’ici 2050, tout en maintenant les moyens de subsistance des sociétés et en respectant l’environnement. Le rythme de ces changements et l’ampleur de leurs impacts et coûts humains rendent urgent la recherche de solutions pour renforcer la résilience des systèmes alimentaires. Mes recherches évaluent le potentiel d’une solution basée sur la biodiversité, sauvage et cultivée.Dans ce cadre, mes travaux visent à améliorer la compréhension des liens entre les activités agricoles, la biodiversité, le fonctionnement et les contributions de la nature aux sociétés par une approche interdisciplinaire, multi-échelles et dans une démarche finalisée en agroécologie. Deux thématiques se dégagent :1. Mes recherches évaluent les effets de la biodiversité sur le fonctionnement d’écosystèmes naturels et cultivés, anciens et actuels. Depuis 2016, je m’intéresse particulièrement à la diversité des plantes cultivées comme levier pour stabiliser les rendements agricoles face aux variations climatiques. Je contribue à avancer les connaissances sur les mécanismes des liens diversité-stabilité et les échelles spatiales—de l’exploitation au pays—auxquelles ces liens s’articulent. Cette recherche soutien une vision dynamique des agroécosystèmes (stabilité vs rendements annuels, variabilité climatique) et dépasse l’étude des espèces dominantes (riz, blé, maïs, soja) pour intégrer la diversité et composition en espèces et variétés cultivées par les agriculteurs·rices.2. Fruit d’un rapprochement avec l’ethnoécologie, mes travaux s’appuient sur les savoirs locaux des agriculteurs·rices pour retracer les changements passés de la diversité cultivée et mettre en lumière l’articulation entre les valeurs des agriculteurs·rices à l’égard des plantes qu’ils cultivent et les facteurs externes (i.e., les changements climatiques) dans le processus de choix des plantes. Ces recherches soutiennent une meilleure reconnaissance du rôle central des agriculteurs·rices, de leurs perceptions, connaissances et valeurs multiples dans les décisions politiques pour l’adaptation, notamment aux changements climatiques.Mon projet ambitionne d’identifier plus concrètement les échelles spatiales et les combinaisons d’espèces cultivées qui maximisent l’effet d’assurance biologique et stabilise ainsi la production alimentaire (axe1). Je souhaite ensuite dépasser les limites d’une approche monodisciplinaire et monofonctionnelle pour construire une vision plus holistique des multiples fonctions—agronomiques, écologiques et socio-culturelles—soutenues par l’agrobiodiversité. Je propose ainsi de (i) construire et caractériser la géométrie de l’espace multifonctionnel occupé par les espèces de plantes cultivées, (ii) suivre les dynamiques interannuelles et la stabilité de cet espace et (iii) évaluer sa vulnérabilité aux changements climatiques (axe 2)
Root application of Bisphenol A (BPA) and di(2-ethylhexyl) phthalate (DEHP) at environmental doses impacts tomato growth and production
No full textInternational audienceThe escalating decline in biodiversity in agroecosystems is a growing concern. Chemical pollutants such as plasticizers are increasingly implicated in this decline, with potential implications for both food production and quality. Among these pollutants, the endocrine-disrupting compounds (EDC) bisphenol A (BPA) and di(2-ethylhexyl) phthalate (DEHP) are particularly widespread and well documented in agricultural environments. Previous studies have reported the bioaccumulation of BPA and DEHP in crop plants, resulting in impaired growth and productivity. However, these findings were based on contaminant concentrations thousands of times exceeding those typically found in the environment. This raised critical questions about the real effects of BPA and DEHP on crop plants at environmentally relevant doses, particularly under conditions of single or combined exposure. This study investigated the effects of environmental doses of BPA and DEHP on tomato plants (Solanum lycopersicum), one of the most important crops in the world. Plants were exposed via root application to low and intermediate environmental concentrations (0.05 µg.L-1 BPA and 0.5 µg.L-1 DEHP or 50 µg.L-1 BPA and 10 µg.L-1 DEHP, respectively), under both mono- and co-exposure. The results revealed disruption in plant growth and productivity, which varied based on the specific EDC, concentration and exposure conditions
Descendre de l’échelle. Pour une approche multidimensionnelle du projet ethnographique
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A re-evaluation of the notosuchian crocodyliform Eremosuchus elkoholicus from the lower Eocene of Algeria and the evolutionary and biogeographic history of sebecids
No full textInternational audienceNotosuchian systematics have been highly debated in recent decades, particularly the placement of sebecids and closely related species. As the only notosuchian lineage to have survived the Cretaceous–Paleogene mass extinction, reconciliation of conflicting views on the group’s relationships is required to better understand extinction selectivity. Here, we redescribe and newly diagnose Eremosuchus elkoholicus from the Lower Eocene El Kohol Formation of Algeria, known from the holotypic dentary and several referred remains. A new, smaller dentary is also considered to represent an immature individual of this species, providing a rare notosuchian ontogenetic series. Eremosuchus is incorporated into one of the largest notosuchian-focused character-taxon matrices yet to be compiled, comprising 450 characters and 130 taxa. Focus is placed on improved sampling of mandibular characters and putative sebecids, especially frequently neglected taxa from Europe and Africa. Phylogenetic analyses, incorporating continuous characters, consistently recover Eremosuchus elkoholicus as a sebecid, though its precise position within this clade is uncertain. Under equal weighting, Sebecidae is recovered as the sister taxon to all other notosuchians, whereas a monophyletic Sebecosuchia is retrieved using extended implied weighting. The latter weighting approach finds the early Paleogene South American species, Lorosuchus nodosus and Sahitisuchus fluminensis, within Peirosauria, which would indicate the survival of a second notosuchian lineage across the Cretaceous/Paleogene boundary. The taxonomic and spatiotemporal expansion of Sebecidae via the inclusion of fragmentary material from Africa and Europe hints at a more complicated biogeographic and evolutionary history of the clade, and it remains unclear whether sebecids originated in Gondwana or Europe
New insights into global biogeographic distribution patterns of oceanic tintinnids: a species-level approach
No full textInternational audienceTintinnids are key components of the marine microbial food web. Previous studies classified the global biogeography of oceanic tintinnids into three broad Regions at the genus level, but a finer resolution is needed to improve both taxonomic and spatial understanding, especially when compared with the well-established nine-belt framework of epipelagic plankton. Drawing on recent advances in studies of cross-water mass distributions over the past decade, this review refines the biogeography of oceanic tintinnid at the species level. We propose that oceanic tintinnids can be delineated into fourteen biogeographical belts: the Arctic Belt, the Subarctic-Arctic Transition Belt, the Subarctic Belt, two Tropical Submergence Belts, two Subtropical Belts, two Subsurface Maximum Belts, the Equatorial Belt, the Subantarctic Belt, the Subantarctic-Antarctic Transition Belt, the Antarctic Belt and the Antarctic Slope Belt. Each belt had a variable number of endemic species. Oceanic tintinnid biogeography comprised more belts than that of other plankton, with the presence of a Northern-Southern Hemisphere asymmetry. Oceanic tintinnid abundances in different belts had characteristic vertical distributions. More field surveys are needed in future studies to fill the existing knowledge gaps in tintinnid biogeography such as differences between Pacific, Atlantic and Indian Oceans, seasonal variations, poleward expansions
Asymmetric flow field-flow fractionation coupled with inductively coupled plasma mass spectrometry for quality control of the grafting state of polystyrene on gold nanoparticles
No full textInternational audienceNanoplastics are omnipresent not only in the environment, but can also be transmitted to humans, mainly via the food chain and by contaminating respiratory air. These pollutants have the ability to cross biological barriers, carried into the bloodstream and reach different organs. In order to better understand the mechanisms of their uptake and transport into human cells and better assess their potential risks, the ability to localize and quantify nanoplastics in biological material is crucial. Electron microscopy (EM) represents a common method to study the uptake and intracellular fate of nanoparticles. However, polymeric materials are more difficult to visualize in cells due to the low contrast with cellular components. In this work, approximately 20 nm gold nanoparticles grafted onto polystyrene were synthesized as a model of metal-polymer hybrid nanoparticles in order to resolve the problem of low contrast and visualize nanoplastic-like particles in cells. A multi-technique approach has been developed to characterize those particles. Asymmetric flow field flow fractionation coupled with inductively coupled plasma mass spectrometry (AF4-ICP-MS) is presented as a control quality technique to characterize the grafting percentage of polystyrene onto gold nanoparticles as well as the grafting distribution and the concentration of the synthetized nanoparticles. Thus, grafting percentage of (57 ± 2)% and (100 ± 1)% were obtained for the two samples of Au@PS nanoparticles, respectively synthesized initially and after optimization of the synthesis process. Complementarily, Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) were used jointly with AF4-ICP-MS in order to determine the particles size and get complementary information about the grafting state. Thus, hydrodynamic diameters of (26 ± 1) nm and (35 ± 3) nm were found for the synthesized Au@PS nanoparticle samples
Petrogenesis of Volcanogenic Sedimentary Lithium Ore in the Neogene Macusani Volcanic Field, Puno, Peru
No full textInternational audienceThe recently discovered Falchani volcanogenic sedimentary lithium deposit, situated within the Neogene Macusani Volcanic Field in SE Peru, represents one of the world’s most significant resources of this metal. The Li ore is mainly hosted in the so-called lithium-rich tuff, a tuffaceous mudstone that is sandwiched between two Li-rich volcaniclastic units (Upper and Lower Breccia). The major and trace element composition of the Li-ore units differs from that of previously reported ash-flow tuff in the Macusani Volcanic Field. Rather, it approximates the chemistry of highly evolved peraluminous obsidian glasses, known as macusanite, and exhibits the characteristic geochemical fingerprint of peraluminous rare-metal granites and Li-Cs-Ta pegmatites. The parental magmas of the Li-ore units have been modeled as containing <25% of a mantle component with the isotopic signature of potassic to ultra-potassic basaltic melts. The remaining is attributed to partial melts of Proterozoic and Paleozoic paragneiss and metapelites. High fluorine activity in the melt lowered the solidus and delayed fluid-melt immiscibility, promoting high degrees of differentiation through fractional crystallization. Pre-eruptive metasomatic processes in the upper part of the crystal mush could have increased the concentration of Li and other fluid-mobile elements. Contrary to many volcanogenic sedimentary lithium deposits worldwide, in situ post-depositional metasomatic processes associated with the formation of secondary clay and zeolite assemblages did not result in lithium enrichment, but in its partial leaching. Falchani represents a first documentation of a volcanogenic sedimentary deposit where the primary lithium enrichment to economic grades was related to pre-eruptive magmatic processes
Identifying mosquito plant hosts from ingested nectar secondary metabolites
No full textInternational audienceAbstract Establishing how plants contribute food and refuge to insects can be challenging for small species that are difficult to observe in their natural habitat, such as disease vectoring mosquitoes. Currently indirect methods of plant-host identification rely on DNA sequencing of ingested plant material but are often unsuccessful for small insects that feed primarily on plant sugars or have little contact with plant cells. Here we developed an innovative approach to determine species-specific phytophagy by detecting taxon-specific plant secondary metabolites (PSMs) in nectar. Two mosquito species were exposed to three PSMs, each present in the nectar of a known plant host, firstly from dosed sucrose solutions and secondly from flowers. Both experiments yielded high rates of PSM detection in mosquitoes using liquid chromatography-mass spectrometry (LC-MS). PSMs were consistently detected in mosquitoes up to 8 h post-ingestion. In experiments consisting of two or three plant species, multiple PSMs from different host plants could be detected. These positive results demonstrate that PSMs could be useful indicators of insect plant-hosts selection in the wild. With expanded knowledge of nectar-based PSMs across a landscape, improved knowledge of plant-host relationships could be achieved where direct observations in their natural habitat are lacking. Increasing understanding of vector insect ecology will have an important role in tackling vector-borne disease
Towards a New Industrial Revolution? Entropy and its Challenges
No full textInternational audienceMarie Chollat-Namy and I were members of the Association, students of the life sciences and humanities</div
Phenotypic and dispersal plasticity are not alternative strategies for organisms to face thermal changes
No full textInternational audienceTo buffer the effects of local environmental changes, organisms may modify their phenotypic traits (i.e. phenotypic plasticity) or disperse towards other potential habitats (i.e. dispersal plasticity). Despite extensive work studying either ‘local phenotypic plasticity’ or ‘dispersal plasticity’ independently, little is known about their potential covariation and interplay. These strategies are classically viewed as alternatives. However, this expectation has been challenged by theoretical work suggesting that they may instead evolve together under some environmental contexts. Here, we experimentally quantified morphological, movement and dispersal plasticity in response to thermal changes in 12 strains of the ciliate Tetrahymena thermophila . We showed that phenotypic and dispersal plasticity are not alternative strategies, with half of the strains expressing simultaneously all dimensions of plasticity in response to thermal changes. Furthermore, the extent of morphological and movement plasticity weakly but significantly differed between residents and dispersers. Interestingly, we found no covariation between these different plasticity dimensions, suggesting that they may evolve independently, which pleads for studying which environmental contexts favour the evolution of each. The fact that phenotypic and dispersal plasticity are not alternative strategies and may affect the expression of one another opens interesting perspectives about their joint evolution and the potential consequences of their interplay