Species diversity and host plant associations of ambrosia beetles in Southeast Asian forests of Laos and Vietnam revealed by DNA barcoding

1. The weevil subfamilies Scolytinae and Platypodinae (Curculionidae) represent a highly diverse group of beetles, comprising over 6,000 described species classified into 26 tribes and 246 genera.2. Despite their economic and ecological importance, knowledge of their host plant diversity remains limited. Accurate host plant data are essential for pest risk assessment, monitoring invasive species, and mitigating their introduction through international plant and wood trade.3. We developed an integrative DNA barcoding framework to elucidate the host plant diversity associated with ambrosia beetle diversity, sampled directly from their host trees in the tropical forests of Laos and Vietnam.4. We obtained mitochondrial cytochrome oxidase I (COI) gene sequences for 130 ambrosia samples representing 27 species in 16 genera. We also analyzed 30 host plant species representing 17 different plant families using nuclear ribosomal internal transcribed spacer (ITS) and the chloroplast maturase K (matK) sequences.5. We observed substantial variation in host specificity and dominance among ambrosia beetle taxa. Xylosandrus crassiusculus emerged as the most frequently recorded and dominant generalist species, associated with 19 host plant species across 12 families, accounting for 63% of all host plant records. Most of the host plant associations documented in this study represent the first recorded hosts in tropical forests of Asia, as well as several novel host associations were uncovered.6. Our findings reveal high, previously undocumented host range, emphasizing the ecological importance of diverse forest tree communities. Furthermore, the newly identified host associations highlight potential pathways for beetle movement through regional and international plant trade.