Global, asynchronous partial sweeps at multiple insecticide resistance genes in Aedes mosquitoes

Aedes aegypti (yellow fever mosquito) and Ae. albopictus (Asian tiger mosquito) are globally invasive pests that confer the worlds dengue burden. Insecticide-based man-agement has led to the evolution of insecticide resistance in both species, though the genetic architecture and geographical spread of resistance remains incompletely un-derstood. This study investigates partial selective sweeps at resistance genes on two chromosomes and characterises their spread across populations. Sweeps at the volt-age-sensitive sodium channel gene (VSSC) on chromosome 3 correspond to one nu-cleotide substitution in Ae. albopictus and three substitutions in Ae. aegypti, including two at the same nucleotide position (F1534C) that have evolved and spread independently. In Ae. aegypti, we also identified partial sweeps at a second locus on chromosome 2. This locus contained 15 glutathione S-transferase (GST) epsilon class genes with significant copy number variation among populations and where three distinct genetic backgrounds have spread across the Indo-Pacific region, the Americas, and Australia. Local geographical patterns and linkage networks indicate VSSC and GST backgrounds probably spread at different times and interact locally with different genes to produce resistance phenotypes. These findings highlight the rapid spread of resistance genes globally and are evidence for the critical importance of GST genes in resistance evolution.