Parallel evolution in mosquito vectors – a duplicated esterase locus is associated with resistance to pirimiphos-methyl inAn. gambiae

Abstract

AbstractThe primary control methods for the African malaria mosquito,Anopheles gambiae, are based on insecticidal interventions. Emerging resistance to these compounds is therefore of major concern to malaria control programmes. The organophosphate, pirimiphos-methyl, is a relatively new chemical in the vector control armoury but is now widely used in indoor residual spray campaigns. Whilst generally effective, phenotypic resistance has developed in some areas in malaria vectors. Here, we used a population genomic approach to identify novel mechanisms of resistance to pirimiphos-methyl inAnopheles gambiae s.lmosquitoes. In multiple populations, we found large and repeated signals of selection at a locus containing a cluster of detoxification enzymes, some of whose orthologs are known to confer resistance to organophosphates inCulex pipiens. Close examination revealed a pair of alpha-esterases,Coeae1fandCoeae2f, and a complex and diverse pattern of haplotypes under selection inAn. gambiae, An. coluzziiandAn. arabiensis. As inCx. pipiens, copy number variation seems to play a role in the evolution of insecticide resistance at this locus. We used diplotype clustering to examine whether these signals arise from parallel evolution or adaptive introgression. Using whole-genome sequenced phenotyped samples, we found that in West Africa, a copy number variant inAnopheles gambiaeis associated with resistance to pirimiphos-methyl. Overall, we demonstrate a striking example of contemporary parallel evolution which has important implications for malaria control programmes.