The evolutionary potential of the determinants of species coexistence

"Understanding the processes that create and those that maintain biodiversity are key challenges in biological research. What is becoming clear, is that ecological and evolutionary processes can influence each other on slow as well as very rapid timescales to dictate biodiversity changes. The long-term objective of this research project is to experimentally test why evolution in response to competition sometimes promotes or hinders species coexistence. Ultimately, to address this question, my lab will conduct manipulative field evolution experiments that quantify the feedback between evolution and competition, using a theoretical framework that includes processes that both promote and hinder coexistence. Theory tells us that the outcome of species competition is determined by processes that promote coexistence (stabilizing niche differences) and those driving competitive exclusion (competitive-ability differences). Yet, before testing how these determinants of species coexistence could rapidly evolve, we must first quantify their genetic variation in natural populations. The extent and distribution of genetic variation will dictate their evolutionary potential and likely dynamics. I here request Seeding Grant funding to sample populations of duckweed, small rapidly reproducing aquatic plants, that differ in their community composition (growing alone or with a competing species). Then, I will quantify their genetic composition using molecular markers. These are critical first steps before quantifying genetic variation in niche and competitive-ability differences and ultimately conduct experimental evolution which will be supported by external funding (e.g. NSF DEB). This research project will significantly improve our understanding of fundamental interactions between community ecology and evolution. By testing the impact of genetic variance and rapid evolution, this project may profoundly change how species coexistence research views evolution from a historical process to one rapid enough to alter on-going competitive dynamics. In addition, it will help us better understand why biodiversity is lost or maintained in nature.

La transition vers la vie adulte des jeunes qui ont vécu un placement : un défi pour les organismes de protection de la jeunesse

Les adolescents qui entrent dans la vie adulte après un séjour prolongé dans un milieu substitut sont particulièrement vulnérables, en raison : de leur déficit sur les plans de la scolarisation, de l’employabilité et des habiletés de la vie quotidienne en général; d’un manque de préparation à la vie autonome; d’un déficit de liens sociaux. Les pronostics sont souvent sombres quant à leur insertion sociale et professionnelle. Pour corriger cette situation, divers programmes d’intervention visant à développer leur autonomie ou leur autosuffisance (self-sufficiency) sont mis en place. À partir d’une revue des écrits sur les programmes d’intervention visant l’autonomie fonctionnelle des jeunes en situation de placement, cet article propose de repenser la manière d’envisager la transition vers la vie adulte des jeunes placés en milieu substitut. Il s’agit d’envisager les jeunes en tant que sujets interdépendants de leur communauté en replaçant la question des relations sociales et des réseaux sociaux de soutien au coeur des préoccupations d’intervention visant à faciliter l’insertion sociale et professionnelle.Youth who have lived in residential or foster care for a long period of time are confronted with many obstacles when entering adult life, particularly in regards to their professional and social integration. In order to redress this situation, different programs are put in place to help youth develop their autonomy or self-sufficiency. Based on a literature review, this article suggests that the way the transition to adult life of youth having lived in a substitute environment has been conceptualized should be reconsidered. It is therefore recommended to envision the youth as an interdependent subject of its community by having the intervention programs aiming their social and professional integration focus on social relationships and social networks

Solutions initiales du problème de rotations d’équipages avec un modèle de programmation linéaire

Résumé Ce mémoire traite du problème de rotations d’équipages d’une compagnie aérienne. Le problème de rotations d’équipages est important pour les transporteurs aériens, car il doit être résolu lors de la confection des horaires mensuels des membres d’équipages. En effet, la masse salariale constitue le plus gros chapitre des dépenses après celui des coûts du carburant. De surcroît, il s’agit d’un problème majeur qui est également très difficile à résoudre. Le projet porte sur le problème de rotations d’équipages affectant le personnel technique. Pour les exemplaires étudiés, ce problème concerne environ 2000 vols par semaine, réalisés par de court et moyen-courrier. L’objectif principal du projet est de trouver une solution initiale de qualité au problème de rotations d’équipages. L’objectif secondaire du projet est de définir les vols qui ont de fortes chances de se trouver dans une même rotation d’équipage de la solution optimale, et ce, afin de les regrouper. On cherchera donc les meilleures agrégations de l’ensemble des segments de vol à couvrir, ce qui permettra de guider les algorithmes de résolution du problème de rotations d’équipages de notre partenaire industriel afin de trouver plus rapidement des solutions proches de l’optimum. Dans un premier temps, le problème de rotations d’équipages est modélisé à l’aide d’un programme linéaire, lequel a été développé en tenant compte des contraintes imposées par le problème de rotations d’équipages. Le programme linéaire est similaire `a un problème de flot ce qui permettra de tirer avantage de la forte structure de flot du problème de rotations d’équipages. Pour obtenir des temps de calcul raisonnables, le programme linéaire est résolu en nombres réels et la résolution de ce programme est réalisée avec CPLEX. Dans un deuxième temps, la solution optimale du programme linéaire en nombres réels est utilisée pour trouver de bonnes solutions initiales au problème de rotations d’équipages ainsi qu’une agrégation de l’ensemble des segments de vol à couvrir.----------Abstract This masters’ project is about crew scheduling in the airline industry. More specifically, the problem at hand is the crew pairing problem, which is of crucial importance for the airline industry as the payroll expenses are second only to fuel cost. Additionally, the crew pairing problem is a huge and extremely complex problem to solve. The project is about solving weekly crew pairing instances. The instances come from the airline industry and deal more precisely with the technical crews. There are on average 2000 flight segments in the different instances and they are composed of short and medium haul flights. The main objective is to find a good initial solution to the crew pairing problem. The secondary objective is to find legs that are likely to be found in the same rotation in the optimal solution, in order to find an aggregation that is as close as possible to those clusters. Both the initial solution and the aggregation will be used to speed up our industrial partner algorithm used to solve the crew pairing problem. First, the crew pairing problem is modeled as a linear program. This program takes into account the main constraints of the crew pairing problem and is close to a network flow problem in order to take advantage of the strong underlying network structure of the crew pairing problem. In order to have low computation times, the linear program is solved without the integer constraints on the variables and CPLEX is used to solve the linear program. Second, the linear program optimal solution is used to compute an initial solution for the crew pairing problem as well as an aggregation of the flight legs to cove

CD73 : cible thérapeutique dans le cancer de l'ovaire et le cancer du sein HER2+

Plusieurs mécanismes sont mis en place dans le microenvironnement tumoral pour restreindre l’activité anti-tumorale médiée par les composantes du système immunitaire. L’identification de nouvelles cibles moléculaires impliquées dans le phénomène de redondance des mécanismes d’immunosuppression est nécessaire dans le développement de stratégies d’immunothérapies permettant de rétablir un système immunitaire anti-tumorale efficace. L’un des facteurs responsables du microenvironnement immunosuppressif tumoral est l’adénosine extracellulaire générée par l’enzyme membranaire CD73. Dans le but d’évaluer le rôle de l’axe CD73 / adénosine dans un contexte d’immunothérapie, des corrélations ont été effectuées sur des cohortes de patientes. Ces résultats ont été confirmés par le biais de modèles de cancer de souris syngéniques et knockouts ainsi que par des modèles in vitro de cancers de souris et humains déficients ou compétents en CD73. Dans le cancer séreux de haut grade, cette thèse démontre que CD73 agit en tant que biomarqueur pronostique en association avec les lymphocytes T CD8+ et favorise la prolifération tumorale in vitro et in vivo. Les résultats démontrent également que l’expression de CD73 sur les cellules fibroblastiques favorise l’échappement immunitaire et la croissance tumorale. Dans le cancer du sein HER2+, cette thèse présente CD73 comme mécanisme de résistance où l’expression de cette enzyme par les cellules tumorales ou les cellules de l’hôte diminuent la réponse immunitaire anti-tumorale médiée par un anti-ErbB2. Les résultats démontrent également que l’inhibition de cette enzyme augmente l’efficacité thérapeutique d’un anti-ErbB2 dans un modèle greffé, un modèle spontané et un modèle de métastases pulmonaires. Les travaux présentés dans cette thèse démontrent l’importance de l’axe adénosinergique dans deux types de cancers où le microenvironnement tumoral immunosuppressif est un frein à une thérapie optimale. Cette thèse explore les propriétés de CD73 en tant que nouvelle cible en immunothérapie du cancer.Many mechanisms are laid in the tumor microenvironment to restrict the anti-tumor activity by the immune system. Identification of novel molecular targets responsible of redundancy phenomenon is necessary for developing innovative immunotherapy strategies that will restore the anti-tumor immune system efficacy. One of the factors responsible for the immunosuppressive tumor microenvironment is the extracellular adenosine generated by the ectoenzyme CD73. This thesis explores the properties of CD73 as a novel target in cancer immunotherapy. To evaluate the role of CD73 / adenosine axis in an immunotherapy context, correlations has been made on patient cohorts. These results have been confirming with relevant syngeneic and knockout mouse models. In vitro models of mouse and human cancer deficient or proficient in CD73 has also been using. In the high-grade serous ovarian cancer, this thesis shows that CD73 acts as a prognostic marker associated with intraepithelial CD8+ cells and promote in vitro and in vivo tumor proliferation. Results from this thesis also show CD73 expression on fibroblasts that promote immune escape and tumor proliferation. In the HER2+ breast cancer, this thesis investigates CD73 as a resistance mechanism where this enzyme expression on tumor cells and host cells decrease the anti-tumor immune response mediated by anti-ErbB2 mAb therapy. Results from this thesis also show that anti-CD73 mAb enhances anti-ErbB2 activity to treat engrafted and spontaneous tumors as well as lung metastasis. This work highlights the adenosinergic pathway in two types of cancers where the immunosuppressive tumor microenvironment is a brake for an optimal therapy. CD73 is presented as a novel target candidate in cancer immunotherapy

Subcellular spatial resolution achieved for deep-brain imaging in vivo using a minimally invasive multimode fiber

Achieving intravital optical imaging with diffraction-limited spatial resolution of deep-brain structures represents an important step toward the goal of understanding the mammalian central nervous system1,2,3,4. Advances in wavefront-shaping methods and computational power have recently allowed for a novel approach to high-resolution imaging, utilizing deterministic light propagation through optically complex media and, of particular importance for this work, multimode optical fibers (MMFs)5,6,7. We report a compact and highly optimized approach for minimally invasive in vivo brain imaging applications. The volume of tissue lesion was reduced by more than 100-fold, while preserving diffraction-limited imaging performance utilizing wavefront control of light propagation through a single 50-μm-core MMF. Here, we demonstrated high-resolution fluorescence imaging of subcellular neuronal structures, dendrites and synaptic specializations, in deep-brain regions of living mice, as well as monitored stimulus-driven functional Ca2+ responses. These results represent a major breakthrough in the compromise between high-resolution imaging and tissue damage, heralding new possibilities for deep-brain imaging in vivo

Choosing an Adequate Pesticide Delivery System for Managing Pathogens with Difficult Biologies: Case Studies on <em>Diplodia corticola, Venturia inaequalis</em> and <em>Erwinia amylovora</em>

With the challenges that negatively impact tree-based agriculture, landscapes and forests, such as climate change, plant pathogen and insect range expansion, invasive species and limited new pesticides, it is important to introduce new and effective tree protection options. In the last 20 years, pathogens that invade wood i.e. vascular tissues of trees causing wilt, yellowing, premature defoliation, cankers and tree death, have been on the rise. Diplodia corticola causes Bot canker of oak species which can kill trees diminishing the valuable ecological services they provide and reducing profits from wood and cork production. Since this and similar pathogens have difficult biologies because they reside in wood and cause severe internal damage and tree death, their management is difficult or inefficient with classical pesticide application methods that cannot reach and distribute the active ingredient in vascular wood tissues. As practical management options for this and other vascular tissue pathogens of trees are limited, we evaluated efficacy of several trunk injected fungicides in control of D. corticola and compared it with the efficacy of trunk injection of similar compounds for control of Venturia inaequalis and Erwinia amylovora, as two well-studied apple tree pathogens with different or partially similar lifestyles to D. corticola, respectively

Active compensation of extrinsic polarization errors using adaptive optics

We present a scheme for active compensation of complex extrinsic polarization perturbations introduced into an optical system. Imaging polarimeter is used to measure the polarization state across a beam profile and a liquid crystal spatial light modulator controls the polarization of the input beam. A sequence of measurements permits determination of the birefringence properties of a perturbing specimen. The necessary correction is calculated and fed back to the polarization modulator to compensate for the polarization perturbation. The system capabilities are demonstrated on a range of birefringent specimens