Bickerstaff, J. R.; Walsh, T.; Court, L.; Pandey, G.; Ireland, K.; Cousins, D.; Caron, V.; Wallenius, T.; Slipinski, A.; Rane, R.; Escalona, H.

Background: Bark and ambrosia beetles are among the most ecologically and economically damaging introduced plant pests worldwide, with life history traits including polyphagy, haplodiploidy, inbreeding polygyny and symbiosis with fungi contributing to their dispersal. Species vary in host tree ecologies, with many species attacking stressed or recently dead trees, such as the globally distributed E. similis (Ferrari). At the other end of the spectrum, the Polyphagous Shot Hole Borer (PSHB), Euwallacea fornicatus (Eichhoff), attacks over 680 host plants and is causing considerable economic damage in several countries worldwide. Despite their notoriety, publicly accessible genomic resources for Euwallacea Hopkins species are scarce, hampering better understanding of their invasive capabilities as well as modern control measures, surveillance and management. Findings: Using a combination of long read and short read sequencing we assembled and annotated high quality (BUSCO > 98% complete) chromosome level genomes for these species. Comparative macro-synteny analysis showed that chromosome number increases in haplodiploid inbreeding species of Euwallacea due to fission events, reducing synteny with outbred diploid species. This suggests that life history traits can impact chromosome structure. Further, the genome of E. fornicatus had a higher relative proportion of repetitive elements, up to 17% more, than E. similis. We used the genome assemblies to identify the haplotype of the invasive population in Perth, Western Australia. Additionally, metagenomic analyses identified microbiota associated with both species, with fewer taxa found in association with E. fornicatus compared to E. similis. Conclusions: Comparative analyses between closely related species with varying host tree ecologies and invasive capabilities will shed light into the molecular underpinning of species invasion. Moreover, these haplodiploid genomes will also contribute to the understanding of how life history traits contribute to their genome evolution.