Résumé
One of the main aims of evolutionary biology is to understand the mechanisms responsible for the phenotypic variation on which natural selection can act. Maternal effects occur when a mother's phenotype or her environment influence her offspring's phenotype. Despite the importance of such effects for the ecology of host-parasite interactions, their role has been relatively neglected to date. In this thesis, we examined how mothers influence the immune defense of their young in an environment that varies in space and time. This work has primarily focused on a colonial seabird, the black-legged kittiwake (Rissa tridactyla). Using this model, we have first shown that specific maternal antibodies against parasites, commonly present in the environment (the bacterium Borrelia burgdorferi s. l. vectored by the seabird tick Ixodes uriae) were transferred from mothers to chicks via the egg yolk. Analyses of observational data in the kittiwake-tick-Borrelia system and an experimental approach using vaccination protocol allowed us to confirm the existence of a maternal effect induced by parasitism and to investigate its potential adaptive properties (immunomodulator effects). Moreover, a study examining the influence of individual factors on this transfer underlined the importance of considering the immunological history of individual and their intrinsic quality in these processes. Finally, our work has stressed the influence of local environmental factors on the general development of immune defenses. Overall, this thesis underlines the importance of maternal effects and the maternal environment in the ecology and evolution of host-parasite interactions and, in turn, suggests a role for such process in the epidemiology of infectious diseases.