Genetic and behavioural mechanisms of reproductive isolation and speciation in recently-diverged sibling species of the malaria vector Anopheles gambiae s.l.

Abstract

Anopheles gambiae s.l. species are reported as the most important vectors due to their ability to spread and exploit both temporary and man-made breeding sites. These factors combined with their capacity to transmit malaria, make them wide-open subject for researchers to find alternative different methods to control malaria disease. Historically, there were many attempts to limit or eradicate malaria disease by controlling the mosquitoes. The control methods varied between using insecticide-treated bed nets and indoor residual spraying, in addition to other methods that based on sterile insect technique (SIT) or genetic modification techniques. However, the success of any attempts to eliminate malaria depends on our understanding of the genetic diversity of the vectors in field. In this regard, two distinct sibling species Anopheles coluzzii and Anopheles gambiae s.s. were defined in An. gambiae complex based on single nucleotide polymorphisms intergenic spacer (IGS) near the centromere of the X chromosome. These species were found to mate assortatively even within mixed swarms. Moreover, genetic differences between them were limit to three regions that were 2L, 3L and X chromosome near the centromere regions. Several studies tried to explain the sympatric speciation process between the An. gambiae s.l. sibling species based on these islands of speciation and their role in assortative mating behaviour, but no full explanation was concluded so far. Therefore, two objectives were taken into consideration in this thesis. The first was genetic objective that aims to identify the islands of speciation that more likely responsible for assortative mating. The second was behavioural objective that aims to identify the mechanisms of assortative mating using recombinant and parental strains. These studies were important step for trying to explain the speciation process within An. gambiae s.l. species that in turn important for malaria control strategies.