Population genetic structure and demographic of <i>Spodoptera eridania</i> (Lepidoptera: Noctuidae), an emerging soybean pest in Brazil

Spodoptera eridania (Stoll) is a key pest of soybean crops in Brazil. However, information about the physiology, behavior, and ecology of S. eridania, including its genetic variability within the agricultural landscape, remains scarce. In this study, we conducted an exploratory analysis of the genetic diversity, population structure, and demographic patterns of S. eridania in Brazil. A cytochrome c oxidase I (COI) gene fragment of 866 bp was sequenced from 89 S. eridania individuals collected in Brazilian soybean macroregions. We identified 33 COI haplotypes with high haplotype diversity and moderate nucleotide diversity distributed throughout the country. The genetic relationships among COI haplotypes show a recent divergence with no evidence of distinct haplogroups. Spodoptera eridania collected on soybean crops showed a lack of population genetic structure associated with soybean macroregions or Brazilian states. Overall, our data suggest that S. eridania populations are undergoing demographic and spatial expansion in Brazil, with an increasing effective population size in the last 200 years. This study provides the first insights into the population diversity and demography of S. eridania in the Americas, shedding light on the dynamics and evolution of this species and further supporting integrated pest management strategies in Brazilian soybean crops.