Comparative analysis of the mitochondrial protein-coding genes within genus Spodoptera (Lepidoptera: Noctuidae)

The mitochondrial genome is a powerful tool for elucidating evolutionary relationships and molecular diversity in insects. In this study, mitochondrial protein-coding genes (PCGs) of Spodoptera species were comparatively analyzed to investigate nucleotide composition, strand asymmetry, and phylogenetic relationships. The results revealed a consistently high A+T content across all species, a hallmark of insect mitochondrial genomes, although the extent of this bias varied among genes. Differences in nucleotide frequencies, AT and GC skew, and codon usage patterns indicate the presence of species-specific evolutionary pressures and mutational biases. Phylogenetic analysis based on concatenated PCGs produced a well-supported topology, demonstrating that genetic divergence is congruent with evolutionary relationships. Closely related species, such as Spodoptera frugiperda and Spodoptera litura, exhibited greater similarity in mitochondrial genome composition, whereas more distantly related taxa, including Helicoverpa species, showed increased divergence. Variation in branch lengths further reflects the accumulation of mutations over evolutionary time. These findings underscore the utility of mitochondrial genome analysis in reconstructing evolutionary histories and identifying lineage-specific molecular adaptations. Overall, this study provides valuable insights into mitochondrial genome evolution within Spodoptera and highlights the relevance of comparative mitogenomics in improving molecular systematics and pest management strategies in Lepidoptera.