Unravelling the role of mitochondrial DNA in hybrid incompatibility within species of the Anopheles gambiae complex

Isolation mechanisms between mosquito species of the Anopheles gambiae complex, which includes major malaria vectors, remain poorly understood. In some cases, pre-zygotic barriers have been shown to limit gene flow between species of the complex, leading to a low level of hybridisation in nature. Post-zygotic mechanisms manifest with F₁ hybrid males fully sterile and F₁ hybrid females with reduced fertility. Genetic approaches combined with DNA sequencing techniques have highlighted the involvement of genomic regions in hybrid incompatibility with a predominant role of the X chromosome. In addition, differences in the phenotype of F₁ hybrid males have been identified depending on the directionality of the parental cross used to generate them. All these studies have focused on the interaction of nuclear DNA elements in hybrid individuals. Given the role that mitochondrial DNA plays in genetic incompatibilities within other organisms and its unique inheritance pattern, commonly maternal, we conducted a genetic study that relied on the introgression of mitochondrial DNA between Anopheles gambiae and Anopheles arabiensis. The findings indicate that the mitochondrial switch does not appear to restore the fertility of F₁ hybrid males, suggesting that mitochondrial DNA may not play a role in hybrid incompatibilities in these Anopheles species.