Hur påverkar skalbaggarnas och spindlarnas matvanor den biologiska bekämpningen?

Åkrar producerar inte bara livsmedel, de är också boplatser för många växter och djur som kan förse oss med viktiga ekosystemtjänster. Ett exempel på detta är de naturliga fienderna, det vill säga de nyttoinsekter som kan bidra till en effektiv skadedjursbekämpning (så kallad biologisk bekämpning). Skalbaggar och spindlar är exempelvis naturliga fiender till många skadedjur i jordbruket, såsom bladlöss i vårkorn. Dessa naturliga fiender, eller predatorer som de också kallas, är generalister. Detta innebär att de inte bara äter skadedjur, utan också äter många andra djur i åkermarkerna. Men kan de fortfarande ge en effektiv biologisk bekämpning om de äter andra bytesdjur, även dem som inte är skadedjur? Utöver detta så är intensifieringen av jordbruket - särskilt vad gäller användningen av kemiska bekämpningsmedel - ett hot mot naturliga fienders mångfald och mängd i åkrar. Men vad behövs egentligen mångfalden för

Rôles et régulation du PI(4,5)P2 dans le remodelage cortical et la morphogénèse cellulaire en mitose

La division cellulaire doit être précisément contrôlée dans le temps et dans l'espace pour permettre la formation de deux cellules filles, au contenu génétique identique à celui de la cellule mère. Ceci requiert des modifications successives de la forme des cellules, induites par un remodelage du cortex cellulaire. A ce jour, les mécanismes moléculaires du contrôle de l'organisation corticale restent mal caractérisés. Nos travaux chez la drosophile mettent en évidence que le PI(4,5)P2, un phosphoinositide de la membrane plasmique, se concentre à l'équateur des cellules dés l'entrée en anaphase. Ce PI(4,5)P2 est nécessaire à la stabilité corticale des cellules en mitose, via l'activation de la dMoésine. Celle-ci, en liant l'Actine à la membrane plasmique, joue un rôle clé dans l'organisation du cortex des cellules mitotiques et dans la régulation de ses propriétés mécaniques. Nous montrons que l'interaction PI(4,5)P2/dMoésine participe à la contraction cellulaire à l'entrée en mitose, puis à l'élongation cellulaire caractéristique des étapes plus tardives. En fin de mitose, la phosphatase Pp1-87B inactive la dMoésine. Par un crible fonctionnel systématique, nous avons mis en évidence le rôle majeur de deux voies de biosynthèse qui agissent en synergie pour produire localement du PI(4,5)P2, dépendantes de Skittles et de Pten, ainsi que le rôle d'une troisième voie nécessitant l'activité de la protéine dOcrl pour contrôler l'homéostasie du PI(4,5)P2. Ensemble, ces résultats permettent de mieux comprendre les mécanismes qui contrôlent le remodelage cortical et les modifications de forme cellulaire qui ont lieu en mitose.Cell division must be accurately controlled in time and space to permit the formation of two daughter cells whose genetic content is identical to that of the mother cell. This process requires successive modifications of cell shape, induced by cortical remodelling. Molecular mechanisms controlling cortical reorganization during mitosis remain partially uncharacterized. Our work in Drosophila cells demonstrates that PI(4,5)P2, a phosophoinositide of the plasma membrane, is enriched at the equatorial plate at the onset of anaphase. This PI(4,5)P2 is necessary for the cortical stability of mitotic cells and requires dMoesin activation. The dMoesin, linking actin to the plasma membrane, plays a critical role in the cortical organization of mitotic cells and in the regulation of its mechanical properties. We show that the interaction PI(4,5)P2/dMoesin participates in cellular contraction at the beginning of mitosis, then in cell elongation characteristic of subsequent steps. At the end of mitosis, the Pp1-87B phosphatase inactivates the dMoesin. By a systematic functional screen, we characterize the key role of two pathways acting in synergy to locally produce PI(4,5)P2, Skittles- and Pten-dependent, and the role of a third pathway requiring dOcrl activity to control PI(4,5)P2 homeostasis. Altogether, these results allow us to better understand the mechanisms controlling cortical remodelling and modifications of cell shape that occur during mitosis

Food webs in agroecosystems

The management of insect pests in modern agriculture is dominated by chemical control, despite wide recognition of its detrimental impact on the environment and human health. As a sustainable alternative, the service of biological control of insect pests is provided by a diversity of natural enemies, such as ground dwelling carabids and spiders. A better understanding of natural enemy communities and the feeding relationship between natural enemies and their prey is therefore crucial to better conserve and promote the provisioning of biological control in agricultural fields. To this end, we quantitatively summarized published studies that addressed the relationship between increased natural enemy diversity and biological control and studied moderation by biotic and abiotic factors. The results of this meta-analysis support an overall positive effect of increased natural enemy diversity on herbivore suppression, and suggest this effect is lessened by an increase of prey diversity. I then focused on communities of generalist, ground dwelling predators controlling aphids in cereal fields. I used recently developed DNA based molecular gut content analysis to study the feeding relationships between predators and their prey, i.e., food webs, and their implications for biological control. I investigated the effects and underlying mechanisms of increased predator diversity on aphid biological control in manipulative field cage experiments, and identified feeding interactions in relation to the availability of predators and prey during the growing season in field conditions. I showed that generalist predators appear to be functionally redundant in the provisioning of cereal aphid biological control, when considering short time periods. However, when the entire cropping season is considered the importance of different predators as aphid biological control agents varied, which suggests that high predator diversity may provide a more stable biological control service over time. The findings of this thesis support the design of conservation strategies that promote predator diversity and high levels of non-pest extraguild prey in order to sustain generalist ground dwelling predators and secure their contribution to biological control services in agricultural fields

Management of the broad bean weevil (Bruchus rufimanus Boh.) in faba bean (Vicia faba L.)

Summary Bruchus rufimanus Boh. is a common pest on faba beans (Vicia faba L.) all over Europe and worldwide. The area of faba bean production is increasing in Sweden and in Europe, partly encouraged by the CAP subsidies for legume crops and diversified crop rotations. At the same time, number of the insecticides commonly used against B. rufimanus have been removed from the market as pollinators risk to be harmed as the treatment timing corresponds to crop flowering. In Sweden, only one insecticide is available and its efficacy against B. rufimanus is not well established. The pest pressure is likely to increase if no measures are taken to reduce the population. This has increased the interest in alternative management methods in Europe, particularly so in the UK and in France where faba beans is extensively grown. This report presents an overview of B. rufimanus biology and management strategies. This report is the result of a literature search including scientific literature and other available documentations (e.g., grower organizations, technical institutes). Additionally, contacts with technicians, referring advisors and researchers across Europe involved in research projects related to B. rufimanus management, enabled me to obtain an up-to-date overview of the advancement of their projects that I present in this report. In conclusion I suggest further investigations that would clarify the risks for faba bean production and help identify measures both in term of field management and direct control that could be recommended in Sweden

Connectivity-consistent mapping method for 2-D discrete fracture networks

International audienceWe present a new flow computation method in 2-D discrete fracture networks (DFN) intermediary between the classical DFN flow simulation method and the projection onto continuous grids. The method divides the simulation complexity by solving for flows successively at a local mesh scale and at the global domain scale. At the local mesh scale, flows are determined by classical DFN flow simulations and approximated by an equivalent hydraulic matrix (EHM) relating heads and flow rates discretized on the mesh borders. Assembling the equivalent hydraulic matrices provides for a domain-scale discretization of the flow equation. The equivalent hydraulic matrices transfer the connectivity and flow structure complexities from the local mesh scale to the domain scale. Compared to existing geometrical mapping or equivalent tensor methods, the EHM method broadens the simulation range of flow to all types of 2-D fracture networks both below and above the representative elementary volume (REV). Additional computation linked to the derivation of the local mesh-scale equivalent hydraulic matrices increases the accuracy and reliability of the method. Compared to DFN methods, the EHM method first provides a simpler domain-scale alternative permeability model. Second, it enhances the simulation capacities to larger fracture networks where flow discretization on the DFN structure yields system sizes too large to be solved using the most advanced multigrid and multifrontal methods. We show that the EHM method continuously moves from the DFN method to the tensor representation as a function of the local mesh-scale discretization. The balance between accuracy and model simplification can be optimally controlled by adjusting the domain-scale and local mesh-scale discretizations

Réflexions sur le rôle du langage en éducation morale

Conversion therapies have been classified as inhuman treatment or torture on several instances, including by the UN Special rapporteur on torture and other cruel, inhuman or degrading treatment or punishment, and are explicitly prohibited by several professional bodies around the world such as the World Medical Association and the World Professional Association for Transgender Health. They have been defined as “any treatment, practice or sustained effort that aims to change, repress and, or eliminate a person’s sexual orientation, gender identity and, or gender expression” (Malta, 2016).However, based on its functional definition, the concept of “conversion therapy” can be successfully used as a broader analytical framework to describe carceral practices that regulate gender identity and expression and, in particular, those implemented by sex-segregated detention facilities.This paper argues that, coupled with often restrictive and sometimes impossible means for accessing legal gender recognition to change one’s identity documents, single-sex detention acts as a form of conversion therapy for trans and gender diverse people at least in two ways by coercing detainees into adopting gender expression modes that do not align with their gender identity. In that sense, it can be said that sex-segregated detention acts to change the gender identity or expression of gender diverse detainees and, therefore, can amount to inhuman treatment or torture

Semi-analytical solutions for solute transport and exchange in fractured porous media

International audienceFracture-matrix interactions can significantly affect solute transport in fractured porous media and rocks, even when fractures are major (or sole) conduits of flow. We develop a semi-analytical solution for transport of conservative solutes in a single fracture. Our solution accounts for two-dimensional dispersion in the fracture, two-dimensional diffusion in the ambient matrix, and fully coupled fracture-matrix exchange, without resorting to simplifying assumptions regarding any of these transport mechanisms. It also enables one to deal with arbitrary initial and boundary conditions, as well as with distributed and point sources. We investigate the impact of transverse dispersion in a fracture and longitudinal diffusion in the ambient matrix on the fracture-matrix exchange, both of which are neglected in standard models of transport in fractured media