The global invasion and the spread of insecticide resistance mutations in the fall armyworm (Spodoptera frugiperda).
Yainna, S*; d’Alençon, E; Brévault, T; Nam, K
The fall armyworm (Lepidoptera; FAW) is native to the Americas and is one of the major agricultural pests against corns causing millions of dollars annually lost. The first reported invasion of the FAW was in West Africa in 2016. Following this report, FAW quickly spread into Africa, Asia and Oceania (detected in New Zealand in 2022) . We performed population genomics analyses to uncover evolutionary process of invasion using globally sampled 177 FAW individuals. Principal component analysis, ancestry coefficient, and phylogenetic analysis show that invasive FAWs originated from corn strain in the FAW. The composite likelihood approach demonstrates selective sweep specific to invasive FAWs, and the targeted loci include genes associated with host-plant adaptation and insecticide resistance. Interestingly, invasive populations exhibited an increased copy number of detoxification genes and an increased allele frequency conferring target-site mutation. From these results, we concluded that invasive FAWs originated from a genetically admixed population of the corn strain (sfC) which could have contributed to adaptive evolution in the FAW, and that the FAW evolved resistance to insecticides could have helped with its’ successful invasions by the spread of these resistance mutations.
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