Chromosomal inversions and ecotypic differentiation in Anopheles gambiae: the perspective from whole-genome sequencing

The molecular mechanisms and genetic architecture that facilitate adaptive radiation of lineages remain elusive. Polymorphic chromosomal inversions, due to their recombination-reducing effect, are proposed instruments of ecotypic differentiation. Here we study an ecologically diversifying lineage of An. gambiae, known as the Bamako chromosomal form based on its unique complement of three chromosomal inversions, to explore the impact of these inversions on ecotypic differentiation. We used pooled and individual genome sequencing of Bamako, typical (non-Bamako) An. gambiae, and the sister species An. coluzzii to investigate evolutionary relationships and genome-wide patterns of nucleotide diversity and differentiation among lineages. Despite extensive shared polymorphism and limited differentiation from the other taxa, Bamako clusters apart from the other taxa, and forms a maximally supported clade in neighbor-joining trees based on whole genome data (including inversions) or solely on co...