Rethinking intraspecific diagnostics in Lymantria dispar: from traditional taxonomy to population genomics

The spongy moth, Lymantria dispar , provides a compelling example of how advances in genomic methods can reshape the practical interpretation of intraspecific taxonomy. Historically, geographic forms of this species were differentiated on the basis of morphology, geographic range, and female flight capability; subsequently, a three-subspecies framework comprising L. d. dispar, L. d. asiatica , and L. d. japonica became widely adopted. This classification has direct phytosanitary relevance because Asian forms are associated with a greater potential for dispersal and international transport. However, subspecies identity, geographic provenance, genomic ancestry, and traits associated with phytosanitary risk represent distinct types of information and require separate interpretation. Molecular studies have shown that diagnostic signals do not always coincide: RAPD, microsatellite, COI, and locus-specific markers can discriminate selected reference samples effectively, but their performance for ancestry inference and subspecies assignment depends on marker characteristics and reference coverage. Contemporary genome-wide SNP studies have identified broad patterns of genetic differentiation and admixture across Eurasia, including a pronounced Japanese component and a gradual transition between western Eurasian and East Asian populations. An additional layer of complexity is introduced by mitochondrial–nuclear discordance, whereby a maternally inherited mitochondrial lineage may not reflect an individual’s overall nuclear ancestry. This review evaluates the complementary roles of traditional taxonomy, early molecular markers, population genomics, and targeted SNP diagnostics in L. dispar identification and intraspecific characterization. We evaluate which practical aspects of diagnosis have been substantially improved, which limitations remain, and why future phytosanitary diagnostics may benefit from complementing categorical subspecies assignment with an integrative assessment of species identity, geographic provenance, genome-wide ancestry, while incorporating risk-associated traits remains a future objective requiring further validation.