How species of malaria vector mosquitoes emerged and evolved in the Anopheles gambiae complex in face of widespread introgressive hybridization: Theoretical and empirical approaches

Evidence of introgressive hybridization is widespread in the tree of life, occurring especially among closely related species in various clades such as hominids, Anopheline mosquitoes and Heliconius butterflies. High-resolution genomic-data have recently been produced and enabled scientists to perform in-depth investigation of the extent and evolutionary consequences of introgression on the adaptation and speciation processes. However, major challenges remain to redefine key biological concepts and our understating of speciation: How can species diverge and adapt to distinct ecological niches if their reproductive barriers are porous? What genomic features and processes keep species as separate entities if their genomes are a blend of private genomic sequences that have evolved within the species and genomic information borrowed from related organisms but with an independent evolutionary past? What are the adaptive implications of introgression and how to quantify them? This project explores the genetic architecture of divergence, adaptation and speciation with gene-flow in the medically important A. gambiae species complex, mosquito vectors of the deadly Plasmodium sp. parasite causing malaria. We will use state-of-the-art population genetic approaches to analyse mosquitoes’ genetic diversity using new comprehensive genomic data about the species complex. From a theoretical perspective, we will use mechanistic models to simulate conditions under which species of A. gambiae complex diverged and specialize ecologically in face of gene flow; we will also simulate introgression occurring between individuals to analyse the resilience of allele networks occurring in nature and, using agent-based models, we will aim to understand how patterns of gene flow can become established and be affected by changes in the environment. Finally, we will try to integrate the results produced in the previous three approaches in a definitive theory of speciation that incorporates the concept of gene exchange and porous reproductive barriers.