Multiple introductions shaped genomic diversity and demographic history of invasive box tree moth (Cydalima perspectalis) populations in North America

The box tree moth (Cydalima perspectalis) is an invasive pest of boxwood plants (Buxus spp.) that has rapidly expanded across Europe and, since its first detection in Canada in 2018, across North America. Understanding its introduction pathways and early population structure is critical for effective surveillance and management. We integrated genome-wide single nucleotide polymorphism (SNP), mitochondrial cytochrome c oxidase I (COI), and morphological data to investigate the early invasion history of C. perspectalis across North America. Genome-wide analyses revealed pronounced genetic differentiation between North American and European populations, together with substantial genetic structure within North America. Delaware was genetically distinct from other North American populations and showed greater affinity with European populations, consistent with a separate introduction history. In contrast, New York, Massachusetts, Michigan, Ohio, and Ontario showed greater genetic similarity, suggesting shared ancestry and/or regional connectivity, whereas Virginia and West Virginia exhibited additional differentiation. Mitochondrial data supported shared ancestry among most North American populations, while Delaware shared a haplotype group with the Croatian European population. D-statistic analyses identified asymmetric allele sharing among several North American and European populations, consistent with multiple introductions and subsequent admixture. Morphometric analyses revealed significant geographic variation in several body and wing traits. Together, these complementary datasets indicate that multiple introductions, regional genetic structuring, and admixture have shaped the North American invasion. These findings highlight the value of integrating genomic approaches with nursery and border surveillance to identify introduction pathways and inform targeted containment and long-term management of this emerging horticultural pest.