Keele Research Repository

Malaria is a leading cause of death, killing thousands every year. Sub-Saharan Africa has the highest mortality rate, with pregnant women and children under the age of five most affected. The culprits responsible for transmission of the disease are mosquitoes of the genus Anopheles. Preventative measures using vector control are mainly insecticide based, however, resistance threatens the efficacy of these methods. The spreading of transgenes is considered an alternative vector control method but the success of this depends on knowledge of the Anopheles population and cryptic taxa in the wild. The genetic and ecological differences that exist between the populations and how reproductive isolation occurs between the vectors is of great importance in prospective vector control programs which rely on the release of transgenic mosquitoes.
Focusing on Anopheles coluzzii and Anopheles gambiae, the recently diverged members of the Anopheles gambiae complex, morphological and molecular techniques were used to study genetic and ecological differences between the sibling species. Egg morphological differences facilitated by ecological divergences between the two sibling species were studied. Results showed a difference in egg shape and size between the two species and populations within species.
The genetic studies focused on the identification of assortative mating genes. In order to identify candidate mate choice genes, expression levels in 27 putative genes located on the X-island of speciation were investigated. A majority of the genes were over-expressed in virgin males in the samples. An attempt to silence the two top candidate putative assortative mating genes through RNAI using injection as the method of dsRNA delivery led to a surprising outcome, as the mechanical impact of the injections appeared to disrupt the assortative mating pattern.