Oral Presentation Society for Molecular Biology and Evolution Conference 2016

High resolution populations genomics reveals an extremely complex dynamics of early speciation in Afrotropical malaria vectors. (#279)

Giordano Botta 1 , Alistair Miles 2 , Beniamino Caputo 1 , Nick Harding 2 , Alessandra della Torre 1 , Dominic Kwiatkowski 2
  1. University of Rome La Sapienza, Roma, RM, Italy
  2. Wellcome Trust Centre for Human genetics, University of Oxford, Oxford, Select State/Province, United Kingdom

Genomes of natural populations are continually exposed to a number of evolutionary forces, driving them towards either divergence, homogenisation, or a mosaicism of the two. Our ability to detect and describe genomic signatures left by these processes depends upon the level of resolution available in terms of loci, individuals and populations sequenced. The Anopheles gambiae complex is an established model system to study evolutionary dynamics between recently diverged species. The Anopheles gambiae 1000 Genomes Consortium made recently available an extraordinary genomic data resource consisting of 765 genomes sequenced at high coverage from  8 countries spanning Sub-Saharan Africa of the main malaria vectors An. gambiae and An. coluzzii. Here we describe at a very fine scale level complex dynamics of early speciation forging the genomes in contrasting way, leading to various levels of reproductive isolation and to the establishment of two new hybrid forms at the opposite edges of the species range. We virtually described all possible directions a geographically non-homogenised speciation process can take: i) local genomic divergence surrounded by remarkable homogeneity due to gene flow, ii) adaptive introgression events followed by the reestablishment of reproductive barriers, iii) reinforcement of reproductive barriers in sympatry after populations expansions, iv) origins of hybrid forms with local complete replacement of pure individuals. An. coluzzii experienced stronger overall selective pressure than An. gambiae, consistent with a recent speciation process driven by niche expansion in marginal habitats. Moreover, we identified candidate genes and described mutations under divergent selection between An. gambiae and An. coluzzii giving the first molecular support to previous hypothesis on mechanisms for the onset and maintenance of reproductive isolation necessary to species formation.