# Divergent Selection Promotes Intraspecific Genomic Differentiation in Spodoptera littoralis With Possible Involvement in Detoxification

## TL;DR

The cotton leafworm shows genetic differences between populations due to natural selection on detoxification genes, which could impact pest management strategies.

## Contribution

This study identifies divergent selection on detoxification genes as a driver of genomic differentiation in Spodoptera littoralis populations.

## Key findings

- Genomic differentiation exists between populations of Spodoptera littoralis based on geographic origin.
- Detoxification genes are enriched in loci with restricted gene flow, suggesting divergent natural selection.
- Phylogenetic analysis shows sub-Saharan and southern European populations share a common ancestor distinct from northern African populations.

## Abstract

The cotton leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae), is a major agricultural pest affecting crops like cotton, maize, tomatoes, and wheat across southern Europe, Africa, the Middle East, and western Asia. Whole genome analyses have revealed adaptive evolution in chemosensation and detoxification genes in
S. littoralis
. However, the extent of intraspecific diversity influenced by recent adaptive evolutionary forces remains unclear. In this study, we conducted a population genomics analysis using 31 
S. littoralis
individuals from sub‐Saharan Africa, northern Africa, and southern Europe to assess the existence of intraspecific population divergence and identify the underlying evolutionary forces. We show whole genome differentiation between populations based on geographic origin from the analyzed samples. Phylogenetic analyses indicate that sub‐Saharan and southern European populations share a common ancestor, distinct from several northern African populations. FST and dXY statistics along the chromosomes reveal loci with restricted gene flow among populations. These loci are associated with population‐specific selective sweeps, indicating the role of divergent natural selection in limiting gene flow. Notably, these loci are enriched with detoxification genes, including cytochrome P450, multidrug resistance, and xanthine dehydrogenase genes, all of which are potentially associated with detoxification. These results demonstrate that divergent selection limits gene flow among geographically distinct populations with the possibility of the involvement of detoxification as a key trait. We argue that this genetic heterogeneity can be considered in pest monitoring and management, as strategies tailored to specific populations may not be relevant for others.

Population genomics analysis of Spodoptera littoralis reveals whole genome differentiation based on geographic sampling in Egypt, sub‐Saharan Africa, and Southern Europe. We showed that this differentiation is driven by divergent selection on genes potentially involved in detoxification.