Molecular and morphological insights into the taxonomic classification and introduction pathways of Vespa crabro

The classification of the European hornet, Vespa crabro, into subspecies based on thoracic and abdominal color patterns remains controversial. This study combined morphological assessments and mitochondrial genetic analyses to critically evaluate subspecies delimitation and introduction pathways of V. crabro, focusing on two traditionally recognized subspecies in Korea: V. c. crabroniformis and V. c. flavofasciata. Morphological examination of 163 Korean specimens identified 27 distinct color patterns. Furthermore, thoracic and abdominal characters exhibited weak correlation, thus limiting their utility as diagnostic markers. Genetic analysis using mitochondrial CO1 sequences revealed nine haplotypes among Korean populations that showed weak correspondence to the previously defined morphological subspecies. Furthermore, comparative genetic analyses demonstrated that Korean haplotypes are genetically distinct from both Japanese and European populations, indicating previously underappreciated geographic genetic diversity. Additionally, mitochondrial DNA analyses identified multiple independent invasion events into North America, originating from both European and Korean lineages. Collectively, our findings strongly challenge the validity of subspecies classifications relying solely on color patterns. Considering both morphological and genetic evidence, we conclude that V. crabro does not comprise clearly defined subspecies. Nonetheless, CO1 analysis effectively revealed provisional mitochondrial lineages, providing new insights into the invasion history and biogeographic structure of V. crabro.