Les poules pondeuses sont susceptibles d’être exposées à des polluants organiques persistants (POP) potentiellement présents dans leur environnement. Dans un contexte de sécurisation des systèmes d’élevage avicole vis-à-vis des POP, nous avons étudié les facteurs influençant le transfert des POP ingérés vers l’œuf. Ces facteurs sont liés à la nature de la matrice ingérée (sol ou aliment), aux caractéristiques de l’animal (taux de ponte, état d’engraissement) et aux caractéristiques de la molécule (lipophilicité, susceptibilité à la métabolisation). Pour cette étude, différentes approches scientifiques ont été mobilisées : l’expérimentation in vivo et la modélisation mathématique. Les expérimentations in vivo ont permis d’étudier la biodisponibilité relative des PCB d’un sol naturellement contaminé, et de renseigner les paramètres de la cinétique de transfert vers l’œuf de molécules non encore étudiées chez la poule pondeuse telles que des molécules émergentes (exemple d’un retardateur de flammes bromé, HBCD) ou les HAP. Nos résultats montrent en particulier l’importance de l’impact du degré de métabolisation de la molécule sur l’allure de la cinétique et le niveau du transfert. L’élaboration d’un modèle mathématique dynamique a permis d’explorer l’influence des caractéristiques de l’animal sur le transfert de POP vers l’œuf. Le niveau de ponte influence directement, et de façon proportionnelle, le niveau de contamination des tissus de la poule à l’état d’équilibre. Le niveau d’engraissement a un rôle de dilution en cas de période de non ponte et influence de façon marquée la vitesse de décontamination des tissus lors d’une période d’épuration suivant une exposition / Laying hens are likely to be exposed to a wide range of persistent organic pollutants (POPs) potentially present in their environment. In the context of securing poultry farming systems regarding POPs, our research has focused on identifying and grading factors likely to influence the transfer of ingested POPs to eggs. These factors are related to the nature of the ingested matrix (soil or feed), to the characteristics of the animal (laying rate, fatness) and to the properties of the molecule (lipophilicity, sensitivity to metabolism). Different scientific approaches have been implemented: in vivo experimentation and mathematical modeling. In the frame of in vivo experiments we have assessed the relative bioavailability of PCBs from one naturally contaminated soil. In addition, we have calculated parameters of the kinetics of transfer to eggs of molecules that had never been studied in laying hens, such as emerging molecules (for example a brominated flame retardant, HBCD), or PAHs. Our results point out the dominant impact of the molecule metabolism on the shape of its kinetics and on its rate of transfer to eggs.The developed dynamic mathematical model makes it possible to pilot variations with time of the size of the lipid compartments in the animal and of the frequency of laying. It was used to assess the influence of these animal characteristics on the transfer of POPs to eggs. Laying rate proportionally influences the contamination level of eggs and of animal tissues at steady state. Body fat dilutes absorbed POPs in absence of laying and significantly influences the rate of decontamination of tissues during depuration subsequent to an exposure period

Understanding the unequal distribution of life on earth is a fundamental goal of ecology and evolutionary biology. Past efforts to explain large-scale patterns in diversity have tended to focus on two broad classes of explanation, one invoking the importance of abiotic factors (i.e. climate and vegetation) and the other biotic (i.e. competition); but neither has proven entirely adequate. Parasites are a major but poorly understood component of life that may offer some answers. Yet despite widespread theoretical support and some empirical evidence, the role of parasites in explaining patterns in the diversity, distribution, and abundance of species remains largely untested in natural communities. In this thesis I use a mega-diverse elevation gradient of birds as a model system to study the role of avian malaria in explaining these macroecological patterns. In the first data chapter I tested the extent to which patterns of infection across species is predictable. I found that the effects of host ecology and environment were weakly related to infection prevalence and were not consistent across different malaria lineages. Instead, I show that hosts coexisting with many close phylogenetic relatives consistently experience higher infection than evolutionarily distinct host species. In the second chapter I tested if parasite sharing may help explain these observed relationships and show that parasite sharing among host pairs declines with the time since divergence. Spatial contiguity between host pairs was also positively associated with parasite sharing. In the third chapter I tested how infection prevalence varies across species ranges in accordance with expected variation in host abundance. I show that birds are more likely to be infected at the centre of their elevation range, where host abundance is expected to be highest. Intriguingly, I also found that the incidence of host infection is unrelated to the position within the geographic range of the parasite. In the fourth data chapter, I tested whether parasites may regulate diversity by limiting geographic ranges of their hosts through ‘apparent competition’ in which a non-lethal parasite in a primary host, may be lethal in a secondary host. In support of this, I found that more observed bird ranges end at parasite infection zones than would be expected by chance. Taken together, my results suggest that parasites may play a major role in shaping patterns in the distribution and diversity of species, over both ecological and evolutionary scales. This is likely to arise and be maintained by host parasite interactions in which distantly related hosts are less likely to be infected by local parasites than close relatives, thus promoting the build up of diversity locally. On the basis of my analyses, I conclude that across montane elevation gradients in birds, and across diversity gradients more generally, parasites are likely to play a crucial role in the origin and maintenance of high biological diversity.

L’hexabromocyclododécane (HBCD) a été utilisé comme additif dans des polystyrènes (PS). En 2013, l’HBCD a été inclus à la Convention de Stockholm comme Polluant Organique Persistant. Les denrées alimentaires d’origine animale (DAOA) constituent la source principale d’exposition de la population générale à ce polluant. Le niveau moyen d’exposition du consommateur ne représente pas un risque majeur pour la sécurité sanitaire des aliments (EFSA, 2011). Malgré des concentrations moyennes généralement proches d’un ng g-1 lipides dans les DAOA, des concentrations maximales supérieures à 2000 ng g-1 lipides dans certains échantillons d’œuf ont été rapportées. Plusieurs sources potentielles d’exposition orale des volailles existent. Les poules pondeuses pourraient être exposées majoritairement à l’isomère α-HBCD. Au vu de l’absence d’informations dans la littérature sur le devenir de l’α-HBCD chez la poule pondeuse, une expérimentation in vivo a été réalisée et a permis d’estimer la plupart des paramètres cinétiques du devenir de l’α-HBCD ingéré chez la poule pondeuse. Un modèle pharmacocinétique basé sur la physiologie (PBPK) de transfert de l’α-HBCD chez la poule pondeuse a été développé, calibré par des données de la littérature, soumis à analyse de sensibilité et plusieurs paramètres ont été ajustés sur des résultats in vivo. Une validation du modèle a été testée. Ce modèle a permis de déterminer l’influence des caractéristiques physiologiques de la poule pondeuse sur le devenir de l’α-HBCD en cas d’exposition à la molécule. Parmi les caractéristiques d’intérêt, le poids vif (PV) est celle qui influence le plus la concentration d’α-HBCD dans les tissus et les œufs. Un PV bas et des performances de ponte réduites prédisposent à une concentration plus élevée dans ces matrices. La mue produit une augmentation de la charge corporelle de la molécule. Ce modèle peut être extrapolé à d’autres animaux et molécules lipophiles après modification de certains paramètres / Hexabromocyclododecane (HBCD) has been used as an additive in polystyrene (PS). In 2013, HBCD was included in the Stockholm Convention as a Persistent Organic Pollutant. The foodstuffs of animal origin are the main source of exposure of the general population to this pollutant. The mean exposure level of the consumers to HBCD doesn’t represent a major risk to the food safety (EFSA, 2011). In spite of mean concentrations generally close to 1 ng g-1 lipids in the foodstuffs of animal origin, maximal concentrations higher than 2000 ng g-1 lipids have been reported in some egg samples. There are several potential sources of oral exposure of the hens to this pollutant. The hens could be exposed mainly to the α-HBCD isomer. Since the bibliographic synthesis highlights the absence of information about the α-HBCD kinetics in the laying hen, an in vivo experience has been realized and has allowed the estimation of the majority of the α-HBCD kinetic parameters in the laying hen. A physiologically based pharmacokinetic (PBPK) model has been developed, calibrated by literature data, submit to a sensitivity analysis and some parameters have been adjusted on the basis of experimental data. A validation of the model has been attempted. This model has allowed to determine the influence of the main physiological characteristics of the laying hen exposed to the molecule on the α-HBCD accumulation in tissues and transfer to eggs. Among the physiological characteristics of concern, the body weight (BW) is the main feature influencing the α-HBCD kinetics. If the hen is exposed to the α-HBCD, a low BW and low laying performances predispose the hen to have higher concentrations of the molecule in all the matrices. The molting stage raises the body charge of the molecule. This model can be extrapolated to other animals and lipophilic molecules after modification of some parameters