WorldCat Identities

Mailleret, Ludovic

Overview
Works: 17 works in 19 publications in 2 languages and 27 library holdings
Roles: Author, Thesis advisor, Other, Opponent
Publication Timeline
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Most widely held works by Ludovic Mailleret
Stabilisation globale de systèmes dynamiques positifs malconnus : applications en biologie by Ludovic Mailleret( Book )

2 editions published in 2004 in French and held by 3 WorldCat member libraries worldwide

Works presented in this thesis focus on problems related to the control of positive systems of nonlinear ordinary differential equations. Biological models that aim at describing the evolution of positive quantities do belong to this class of systems. These models often include some parts, related to the phenomenon's biology, which have unknown analytical expressions but are known in a qualitative manner. In this thesis, we propose to use these qualitative properties together with a control law, based on the measurement of the uncertain part, in order to globally stabilize any trajectory towards a single equilibrium. A brief state of the art on positive systems begins the thesis. We introduce then a control law, able to ensure the global stabilization of the considered class of systems. The introduction of an adaptive part enhances our approach, so that the control law is able to deal with some parameter uncertainties. We apply these results to some biological models : fishery management model, bioreactors exploiting microorganisms... One of our main applications concerns cascade bioreactions occurring in bioreactors some experimental tests of our approach on an anaerobic digester, an efficient but very sensitive waste water treatment plant, validate our approach
From elaborate to compact seasonal plant epidemic models and back: is competitive exclusion in the details? by Ludovic Mailleret( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

How optimal foragers should respond to habitat changes: on the consequences of habitat conversion by Vincent Calcagno( )

1 edition published in 2019 in English and held by 2 WorldCat member libraries worldwide

A Dynamic Game Approach to Uninvadable Strategies for Biotrophic Pathogens by Ivan Yegorov( )

1 edition published in 2019 in English and held by 2 WorldCat member libraries worldwide

Augmentative biocontrol when natural enemies are subject to Allee effects by Nicolas Bajeux( )

1 edition published in 2016 in English and held by 2 WorldCat member libraries worldwide

Mate Limitation in Fungal Plant Parasites Can Lead to Cyclic Epidemics in Perennial Host Populations by Virginie Ravigné( )

1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide

Role of Spatial and Temporal Refuges in the Evolution of Pest Resistance to Toxic Crops by Valérie Lemesle( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

How optimal foragers should respond to habitat changes: a reanalysis of the Marginal Value Theorem by Vincent Calcagno( )

1 edition published in 2013 in English and held by 2 WorldCat member libraries worldwide

Dos and don'ts in augmentative biological control : insights from mathematical modelling by Sapna Nundloll( Book )

2 editions published in 2010 in English and held by 2 WorldCat member libraries worldwide

This thesis presents the mathematical analysis of models in augmentative biological control, from which practical guidelines are the derived. Biological control provides a means to fight pest invertebrates that attack crops with their natural predators. It is an essential component in efforts to reduce pesticide usage in agriculture. Pesticides pose a threat to human health, both to the agricultural worker and the consumer, as well as to the environment because of their toxicity : this largely motivates the need for current biological control programs to be improved and new ones developed. In this thesis, we look in particular at augmentative biological control, which involves the periodic release of predators that are not able to establish in an ecosystem in the absence of the pest, their primary prey. We introduce a general class of models that describe the intrinsic predator-prey dynamics by a pair of ordinary differential equations and the periodic releases by a discrete equation. We study the variants of this class of models, that may arise in a biological control set-up and highlight the consequences on the strategy of releases. We analyse the effect of intrapredatory interference occurring when the predator preys the pest, the impact of cannibalism among the predators, and finally the outcome of partial harvests of crops on the biological control program. Finally, we summarise the results of our mathematical analysis into a set of practical guidelines. We also report experiments on an agronomic predator-prey system, in which the predator species exhibits interfering behaviour. The experimental results validates out mathematical predictions
Impact de la capacité de charge de l'environnement sur les dynamiques d'expansions de métapopulation : théories et applications à un système expérimental hôte-parasitoïde by Marjorie Haond( )

1 edition published in 2019 in French and held by 1 WorldCat member library worldwide

Les équations de réaction-diffusion sont couramment utilisées pour décrire les dynamiques de propagation des populations. Elles permettent notamment de définir deux types de dynamiques : tirée et poussée. La dynamique tirée résulte d'une colonisation menée par les individus en faible effectif situés en bordure de la population, la dynamique poussée résulte d'une colonisation menée par de plus grands effectifs issus du cœur de la population. Les mécanismes biologiques à l'origine des fronts poussés sont encore peu décrits, toutefois, la présence d'un effet Allee (caractérisé par une corrélation positive entre le taux de croissance et la densité de population pour de petits effectifs) est connue pour entraîner une dynamique poussée. D'autres mécanismes générant une dépendance entre la taille de population et la probabilité de colonisation sont également susceptibles de générer des fronts poussés, mais cette généralisation reste à confirmer. Peu de travaux ont abordé les effets de facteurs de l'environnement tels que la capacité de charge sur les vitesses d'expansion des populations. Or, si pour une dynamique tirée, la colonisation des individus à l'avant du front, peu nombreux, ne devrait pas être influencée par la valeur de la capacité de charge du milieu, dans le cas poussé, les individus évoluant à des effectifs plus importants, la capacité de charge pourrait être un facteur limitant de l'expansion. Nous avons donc cherché à décrire (i) les effets de la capacité de charge sur les dynamiques d'expansion des populations notamment au travers du prisme des dynamiques tirées/poussées, et (ii) la diversité des mécanismes démographiques pouvant générer des dynamiques poussées. Pour cela nous avons utilisé des approches de modélisation individu-centrés et de l'expérimentation en microcosme sur des hyménoptères parasitoïdes, les Trichogrammes. Nous avons utilisé une espèce ayant une dispersion densité-dépendante positive entraînant un accroissement de la probabilité individuelle de migrer en grande population menant ainsi à des dynamiques de colonisation possiblement poussées. Grâce à ces deux approches, nous avons étudié dans une première partie l'impact de la capacité de charge sur la vitesse des expansions, permettant de valider nos hypothèses nous amenant à penser que la dépendance de la vitesse d'expansion à la capacité de charge pourrait être un indicateur de la nature poussée/tirée des expansions. Dans une deuxième partie nous avons étudié les phénomènes d'arrêt de colonisation ("Range pinning") décrits pour des populations soumises aux effets Allee et avons chercher à généraliser ce phénomène aux dynamiques poussées en présence de dispersion densité dépendante positive. Dans une troisième partie nous avons étudié comment une répartition hétérogène dans l'espace de différentes capacités de charges allait influencer les dynamiques d'expansions notamment poussées
Optimal resource allocation for biotrophic plant pathogens*( )

1 edition published in 2017 in English and held by 1 WorldCat member library worldwide

Abstract: A significant class of plant pathogens is constituted by biotrophic fungi. They set up long-term feeding relationships with their hosts. This kind of parasitism decreases competitive abilities of plants in natural environments and reduces yields in agricultural systems. Therefore, it is relevant to develop and validate mathematical models which can help to better understand how related disease associated traits evolve. In this paper, one-season dynamics of a within-host cohort of spore-producing biotrophic fungi is considered. Their within-host multiplication and outer transmission are implemented by the mycelial growth and free-living (spore) forms, respectively. We state and investigate a specific dynamic optimization problem in order to determine how the fungi allocate available host resources between mycelial growth and spore production. The pathogen fitness criterion is introduced as maximization of the reproductive output. The constructed optimal feedback strategy can serve as a benchmark to compare actual infection mechanisms. There is a singular control subregime which plays an important role from the biological point of view. It keeps the average mycelium size equal to a particular steady value and represents an intermediate configuration of the resource allocation. We also analyze the asymptotic behavior of this steady state when the lesion density is large
Étude des stratégies de mouvement chez les parasitoïdes du genre Trichogramma : apports des techniques d'analyse d'images automatiques by Victor Burte( )

1 edition published in 2018 in French and held by 1 WorldCat member library worldwide

Parasitoids of the genus Trichogramma are oophagous micro-hymenoptera widely used as biological control agents. My PhD is about the phenotypic characterization of this auxiliary's movement strategies, specifically the movements involved in the exploration of space and the search for host eggs. These phenotypes have great importance in the life cycle of trichogramma, and also of characters of interest to evaluate their effectiveness in biological control program. Trichogramma being very small organisms (less than 0.5 mm), difficult to observe, the study of their movement can take advantage of technological advances in the acquisition and automatic analysis of images. This is the strategy I followed by combining a methodological development component and an experimental component. In a first methodological part, I present three main types of image analysis methods that I used and helped to develop during my thesis. In a second time, I present three applications of these methods to the study of the movement of Trichogramma. First, we characterized in the laboratory the orientation preferences (phototaxis, geotaxis and their interaction) during egg laying in 22 trichogram strains belonging to 6 species. This type of study requires the counting of a large number of eggs (healthy and parasitized), it was developed a new dedicated tool in the form of an ImageJ / FIJI plugin made available to the community. This flexible plugin automates and makes more productive the tasks of counting and evaluation of parasitism rate, making possible screenings of greater magnitude. A great variability could be highlighted within the genus, including between strains of the same species. This suggests that depending on the plant layer to be protected (grass, shrub, tree), it would be possible to select trichogramma's strains to optimize their exploitation of the targeted area. In a second time, we characterized the exploration strategies (velocities, trajectories, ...) of a set of 22 strains from 7 trichogramma species to look for traits specific to each strain or species. I implemented a method for tracking a trichogramma group on video recorded on short time scales using the Ctrax software and R scripts. The aim was to develop a protocol for high-throughput characterization of trichogramma strains movement and to study the variability of these traits within the genus. Finally, we conducted a study of the propagation dynamics in trichogramma group from the species T. cacoeciae, by developing an innovative experimental device to cover scales of time and space greater than those usually imposed by laboratory constraints. Through the use of pictures taken at very high resolution / low frequency and a dedicated analysis pipeline, the diffusion of individuals can be followed in a tunnel longer than 6 meters during a whole day. In particular, I was able to identify the effect of the population density as well as the distribution of resources on the propagation dynamics (diffusion coefficient) and the parasitism efficiency of the tested strain
The highs and lows of dispersal: how connectivity and initial population size jointly shape establishment dynamics in discrete landscapes( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

Abstract : Identifying the main factors driving introduced populations to establishment is a major challenge of invasion biology. Due to their small initial size, introduced populations are most vulnerable to extinction because of demographic stochasticity or Allee effects. While an increase in initial population size is known to increase establishment success, much remains to be understood regarding its interplay with connectivity in spatially structured environments. In order to better understand how demographic mechanisms interact at such spatial scale, we developed a stochastic model of population dynamics in discrete space to investigate the effect of connectivity and initial population size on establishment. The predictions derived from the model were then tested using experimental introductions of an insect parasitoid (Trichogramma chilonis) in spatially structured laboratory microcosms. Both theoretical and experimental results demonstrated that the connectivity of the introduction site had 1) a deleterious effect in the first generation when the introduced population was small and 2) a beneficial impact brought about by metapopulation effects in the subsequent generations. Interestingly, populations displayed a weakly pushed invasion pattern promoting early establishment, which was mainly underpinned by dispersal stochasticity and the discrete nature of the landscape. These results shed light on the critical influence of landscape connectivity on establishment dynamics
Des interactions indirectes entre les proies : modélisation et influence du comportement du prédateur commun by Mickael Teixeira Alves( )

1 edition published in 2013 in French and held by 1 WorldCat member library worldwide

Cette thèse a pour objet la modélisation de systèmes multi-proies-prédateurs. Elle s'intéresse particulièrement à l'influence du comportement d'un prédateur sur les interactions indirectes entre ses proies, i.e. l'effet de l'ajout d'une proie sur la densité des autres. La théorie classique prédit l'occurrence d'effets indirects négatifs entre les proies, ou compétition apparente, résultant de l'interaction avec un prédateur commun ; des résultats plus récents identifient certains mécanismes à même d'atténuer ces effets négatifs. Nos travaux revisitent les hypothèses autour de ces mécanismes dans des systèmes composés de deux proies et de leur prédateur commun. Après avoir fixé le cadre écologique en rappelant les principaux types d'interactions directes et indirectes, nous introduisons les modèles proies-prédateurs classiques. Les travaux se concentrent ensuite sur une famille de modèles présentant de la densité-dépendance négative chez les prédateurs couplés à différentes modélisations du comportement des prédateurs lorsqu'ils sont confrontés à plusieurs types de proies. Nous montrons notamment que les interactions entre ces mécanismes peuvent inverser la compétition apparente et, contre intuitivement, accroître la densité des proies par l'intermédiaire d'un prédateur commun. Nos résultats trouvent pour partie application en lutte biologique, où il est courant de chercher à favoriser les auxiliaires en aménageant leur environnement (apport de nourriture alternative, refuge, ...). Ils suggèrent que de telles pratiques peuvent se révéler contre-productives, le contrôle des ravageurs pouvant être affaibli du fait d'une distraction de leurs prédateurs
Gestion durable des nématodes à galles en culture maraîchère par la modélisation et l'optimisation du déploiement de variétés résistantes by Samuel Nilusmas( )

1 edition published in 2020 in French and held by 1 WorldCat member library worldwide

Root-knot nematodes are obligate soil-borne endoparasites of plant roots that cause major yield losses throughout the world. Environmentally-friendly plant protection methods against root-knot nematodes are mainly based on the use of resistant plant cultivars. These cultivars efficiently control nematode populations naturally present in the field, but they favour the emergence of virulent variants that circumvent the resistance genes carried by these cultivars. Since virulence is associated with fitness costs, which limit the virulent nematode ability to infest plant roots or reproduce, susceptible crops counter-select virulent nematodes. The aim of this thesis is to identify effective and sustainable resistance deployment strategies to control root-knot nematodes in horticultural crops. To this end, we developed a semi-discrete epidemiological model describing the nematode dynamics in the soil and in the roots of a resistant or susceptible plant during its growing season, as well as the survival of nematodes in the soil between cropping seasons. The model was fitted to experimental data of within-season infestation of susceptible tomato roots. It was used to determine the rotation strategies alternating susceptible and resistant plants that maximise an average yield proxy, over different time horizons and for different combinations of epidemiological intensity and genetic parameters (mutation rate and virulence costs). Moreover, sensitivity analyses were performed to assess the robustness of the plant resistance deployment strategies. Our results show that carefully designed rotation strategies would not only increase crop yield, but also preserve the sustainability of resistance genes. Sensitivity analyses were performed to evaluate the robustness of our results. This thesis opens both experimental and modelling perspectives for a better control of root-knot nematodes
Temporal niche differentiation of parasites sharing the same planthost: oak powdery mildew as a case study( )

1 edition published in 2016 in English and held by 1 WorldCat member library worldwide

Abstract: Plant diseases are often caused by complexes of closely related parasite species. The coexistence of species sharing the same niche challenges the competitive exclusion principle. Here, we performed the mathematical analysis of a generic model of sibling parasite species coexistence based on seasonality. We showed that coexistence through temporal niche partitioning is biologically plausible as it occurred in a significant part of the parameter space of the model. Moreover, the reversal of species relative frequencies (i.e., the most frequent species at the beginning of the season becoming the last frequent at the end) can occur without compromising the long-term coexistence of the two species. We provided data showing that this reversal pattern does repeat over years in the case of two sibling species responsible for oak powdery mildew (Erysiphe alphitoides and Erysiphe quercicola) in Europe. Last, the model was fitted to the data and satisfactorily described the population dynamics of oak powdery mildew species. The seasonal succession of these two plant pathogen species provides one of the few examples of coexistence by temporal niche partitioning at the scale of the season caused by exploitative competition. We discuss whether evolutionary branching may have led to temporal niche differentiation in this system
 
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Alternative Names
Ludovic Mailleret researcher

Ludovic Mailleret wetenschapper

Languages
English (12)

French (6)