Declining malaria incidence offers the opportunity to accelerate toward its elimination, which requires accurate information to target control where it is most needed and will deliver the greatest impact. The impact of environmental adaptation on vector populations, their vectorial capacity and susceptibility to control remain poorly understood. Anopheles arabiensis is common in arid areas, increasing in relative prevalence throughout sub-Saharan Africa, and is the dominant malaria-vector in Senegal. We aim to investigate how natural and anthropogenically-influenced landscape variation influences its genetic diversity, population structure and gene-flow, and how this may impact disease incidence, and aid targeting of vector control. We aim to test the hypothesis that its population structure in Senegal is impacted by both its prevailing environment and recent range expansions toward the more humid parts of the country. Furthermore, local adaptation, especially during this expansion, may have reduced genetic population sizes and genetic diversity, and gene flow between locally-adapted populations. Expected outcomes are: 1. Characterisation of An. arabiensis population structure and connectivity to provide predictions for targeted control 2. Understanding how genetic diversity, and potential adaptability/vulnerability of its populations depends on environment and range expansion 3. Investigation of how the above impact parasite diversity and vector blood feeding, and vectorial capacity. The sub-Saharan Africa region has been and still the area that carries the heaviest malaria burden. However, the incidence of malaria has been reduced significantly by the successful scaling-up of insecticide-based vector control interventions (indoor residual spraying (IRS) and long-lasting insecticide-treated nets (LLIN). The decline of malaria makes elimination a possible, especially in areas where vector populations may be particularly vulnerable such as arid regions of sub-Saharan Africa. Elimination, however, requires increasingly detailed information about the characteristics of both the vector and the parasite populations to target control optimally and to design new interventions. How the environment affects the interconnection of vector populations and their vulnerability to control is poorly understood. In this project, we propose to address this question using a combination of country-wide sampling of the major malaria vector Anopheles arabiensis in Senegal, whole genome sequencing to identify markers of local adaptation, and investigation of how environment acts as a template for population size and connectivity. The results will provide general information on vector-environment inter-relationships, and specific information on how to predict vulnerability and optimally target populations for control.