The worldwide invasion history of a pest ambrosia beetle inferred using population genomics

Individual RAD sequences files are available in a fq.gz format at the Sequence Read Archive (SRA) (https://www.ncbi.nlm.nih.gov/sra/PRJNA771401). The VCF files Xylosandruscrassiusculus.vcf as well as the popmap used in STACKS' population module and specimens' metadata (e.g. GPS coordinates) are available on Portail Data INRAE (https://doi.org/10.57745/JMT4KD). The Genbank accession numbers for the mitochondrial haplotypes reported in this paper are OK489329 to OK489334.International audienceXylosandrus crassiusculus, a fungus-farming wood borer native to Southeastern Asia, is the most rapidly spreading invasive ambrosia species worldwide. Previous studies focusing on its genetic structure suggested the existence of cryptic genetic variation in this species. Yet, these studies used different genetic markers, focused on different geographical areas, and did not include Europe. Our first goal was to determine the worldwide genetic structure of this species based on both mitochondrial and genomic markers. Our second goal was to study X. crassiusculus' invasion history on a global level and identify the origins of the invasion in Europe. We used a COI and RAD sequencing design to characterize 188 and 206 specimens worldwide, building the most comprehensive genetic dataset for any ambrosia beetle to date. The results were largely consistent between markers. Two differentiated genetic clusters were invasive, albeit in different regions of the world. The two markers were inconsistent only for a few specimens found exclusively in Japan. Mainland USA could have acted as a source for further expansion to Canada and Argentina through stepping-stone expansion and bridgehead events. We showed that Europe was only colonized by Cluster 2 through a complex invasion history including several arrivals from multiple origins in the native area, and possibly including bridgehead from the USA. Our results also suggested that Spain