Prominent intra-specific genetic divergence within Anopheles gambiae sibling species triggered by habitat discontinuities across a riverine landscape

The Anopheles gambiae complex of mosquitoes includes malaria vectors at different stages of speciation, whose study enables a better understanding of how adaptation to divergent environmental conditions leads to evolution of reproductive isolation. We investigated the population genetic structure of closely-related sympatric taxa that have recently been proposed as separate species (An. coluzzii and An. gambiae), sampled from diverse habitats along the Gambia River in West Africa. We characterised putatively neutral microsatellite loci as well as chromosomal inversion polymorphisms known to be associated with ecological adaptation. The results revealed strong ecologically-associated population subdivisions within both species. Microsatellite loci at chromosome-3L revealed a clear differentiation between coastal and inland populations, which in An. coluzzii is reinforced by a peculiar inversion polymorphism pattern, supporting the hypothesis of genetic divergence driven by adaptation to ...