DNA barcoding-assisted classification of the genus Actias (Lepidoptera: Saturniidae)

The classification of the species in the genus Actias Leach, 1815 (Lepidoptera: Saturniidae) is challenging because many species have a highly similar morphology, while differences in database classification standards also provoke identification problems. To help resolve these issues, we conducted an integrative analysis of 741 cytochrome oxidase subunit I (COI) barcode sequences available by combining phylogenetic reconstruction, population genetic (Fst) metrics, and biogeographic data. This approach delineated 44 molecular operational taxonomic units (MOTUs) and established a genus-specific, empirical genetic distance threshold of 2.05% from a baseline of 29 morphologically validated MOTUs. These 29 MOTUs/morphospecies were then utilized to assess the interspecific genetic distance gap of this genus and further used as the species-level genetic distance to delimit the remaining morphospecies. Applying this multi-evidence framework allowed us to propose a significant re-evaluation of species boundaries, including several taxonomic reclassifications, and to generate the molecular inventory for Actias. Our study illustrates the power of an integrated molecular approach to resolve complex taxonomic issues and provides a robust, data-driven foundation for future research on Actias.