Living organisms are exposed to environmental fluctuations (including temperature) at the daily, seasonal or annual scale. In ectotherms, environmental temperature directly affects body temperature and thus the physiology, locomotory performance, activity and ultimately the fitness of individuals. Embryonic development is a very sensitive step to thermal fluctuations and ectotherms have deployed a variety of means to buffer its effects. In annual multiple clutches species, reproduction spread over an extended period during which the seasonal thermal conditions vary widely. These fluctuations can profoundly constrain the activity of the individuals and affect developmental trajectories. Determinants of reproductive success thus involve the consideration of environmental constraints as well as ontogéniques trajectories. Indeed, in indeterminate growth species, the nature of allocation trade-offs should strongly depends on the size and age of the individuals. Ontogenetic changes in strategies for resource allocation are expected to optimize reproductive success. In this thesis, we examined the reproductive strategies in a species with multiple clutches, the wall lizard (Podarcis muralis) in a thermally challenging context (oceanic climate, Central West of France). Using an experimental approach, we demonstrated the strong impact of thermal conditions on the quality of embryonic development and the importance of phenology (laying date) on individual trajectories. Early laying dates and incubation temperatures promote high survival of juveniles. The population monitoring initiated in 2006 has highlighted the importance of age and body size of females in the allocation trade-offs. Thus older individuals cease to allocate their resources in growth and encourage the capitalization of energy. This ontogenic shift supports a higher reproductive effort and a earlier engagement in reproduction. Energy constraints induced by reproduction have also been revealed by studying the seasonal variations in levels of corticosteroids and ectoparasites. Finally the study of multipaternity emphasizes the influence of female size and laying sequence on the reproductive strategy.
