Invasion Biology, Genetic Diversity, and Rapid Adaptation of Spodoptera frugiperda Populations in West African Maize Agroecosystems: A Nigerian Multi-Zone Investigation

Spodoptera frugiperda colonized sub-Saharan Africa in 2016 and rapidly established across Nigerian maize agroecosystems, yet the invasion genetics, population structure, and evidence of rapid local adaptation in Nigerian populations have not been comprehensively investigated. Understanding whether the invading population originated from North America or the Caribbean, and whether rapid adaptation is occurring to local host plants and climates, is fundamental to predicting the long-term evolution of this pest in West Africa. This study investigates the invasion biology, genetic diversity, and signatures of rapid adaptation in S. frugiperda collected across five agroecological zones in Nigeria over three years. Specimens from over 200 field collections across 15 states will be genotyped using genome-wide SNPs derived from restriction-site associated DNA sequencing. Phylogenomic analysis will determine haplotype identity, invasion source region, and colonization route. Tests of admixture, selection scans using XP-EHH and SweeD, and latitudinal genetic variation analyses will identify candidate loci under local adaptation. Phenotypic assays measuring larval performance on local maize varieties versus standard laboratory diets will test for genotype-by-environment interactions consistent with host plant adaptation. This study makes a major original scientific contribution to the invasion biology of a globally significant agricultural pest, generating fundamental insights applicable beyond Nigeria to all of West Africa's affected maize production systems. Keywords: Spodoptera frugiperda, invasion genetics, rapid adaptation, population genomics, Nigerian agroecosystems