Abstract
Since their discovery and the establishment of their role as vectors of Plasmodium responsible for human malaria, the sibling species An. gambiae and An. coluzzii have been challenging the human community in general and the scientific community in particular. Firstly, due to their strong involvement in the malaria burden on the African continent, which is mainly the result of a very pronounced anthropophilic behavior. And secondly, their adaptation capacity, enabling them not only to evade the existing control tools, but also to thrive in a variety of environments. In spite of this eco-plasticity, the presence of An. gambiae and An. coluzzii has always been linked to the presence of man. This thesis was prompted by the observation of these vectors, heretofore regarded as exclusively anthropophilic, in sylvatic settings. The aim of my thesis was to characterize and better understand the adaptive traits of sylvatic populations of An. gambiae s.l. in La Lopé National Park, Gabon. To conduct this research, we carried out intensive fieldwork to assess in situ trophic behavior and population dynamics. In addition, we used molecular biology approaches to study the genetic diversity and population structure, and assess the risk of Plasmodium transfer by these vectors. Our results indicate that sylvatic populations of An. gambiae and An. coluzzii have a similar feeding preference to domestic populations. However, with no human host available in the park, these sylvatic Anopheles show phenotypic plasticity by feeding on alternative animal hosts. Furthermore, despite the presence of indications of local adaptation, our results indicate significant gene flow between domestic and sylvatic populations. We reported a seasonal effect on vector population dynamics, with higher densities in sylvatic environments during dry seasons, suggesting the possibility of the use of this habitat as a refuge. In addition, An. gambiae and An. coluzzii were found to be infected in sylvatic environments by both human and non-human Plasmodium. These vectors could therefore be potential bridge vectors of malaria parasites from non-human animals to humans, and vice versa.Taken together, these results suggest an expansion of the ecological niche of An. gambiae and An. coluzzii in sylvatic environments through adaptation to local resources and conditions. These results could have epidemiological implications in areas with similar ecological configurations to La Lopé. In addition, the results of this study point to new research perspectives on the ecological and evolutionary dynamics of the major malaria vectors An. gambiae and An. coluzzii.