Phylogeny and divergence of Aedini mosquitoes: evolutionary scenarios and genomic perspectives

Mosquitoes are the indirect cause of more morbidity and mortality among humans than any other group of organisms. One-third of all mosquitoes species belong to the Aedini, a tribe comprising common vectors of viral zoonoses. In order to improve our understanding of their evolution, we present a detailed multigene estimate of their phylogeny and divergence based on relaxed clocks and fossil calibrations. Our phylogenies using different replacement models and statistical frameworks recover some recognized clades such as Stegomyia, Ochlerotatus, clades A and B but also indicate unstable supports at many nodes: this is likely due to fast radiation events which should be investigated in future using whole genome data. Our divergence estimates point toward mosquito radiation in the mid-Jurassic and Aedini radiation from the mid-Cretaceous on: this is compatible with a paleo-ecological scenario in which first lineages of mosquitoes co-radiated with reptiles, followed by diversification of Aedini in a more modern ecosystem characterized by mammals, birds, and angiosperms. We observe both topological and chronological incongruence when comparing nuclear and mitochondrial data: this may be explained by either peculiar evolutionary events such as hybridization and/or by wrong taxa assignment in samples collections. Our divergence estimates indicate that emerging model Aedes albopictus can be currently compared from a genomic point of view only against distantly related A. aegypti: genome data from its sister species A. flavopictus would more than half the time from common ancestor increasing resolution of comparative genome studies. Overall, our results provide an updated view of Aedini molecular phylogeny and suggest paleo- ecological scenarios for their evolution; it also reveals some methodological issues which may be of help in setting the research agenda for future genome studies.