Abstract
<jats:p>Growth in international trade has contributed to increasing numbers of forest insect invasions, many of which have had substantial ecological and economic impacts. Improving our understanding of the geographic structure and dynamics of introduction pathways is a central challenge for the development of biosecurity strategies aimed at mitigating invasion risk. Data on species intercepted during biosecurity inspections at ports provides a useful proxy for species propagule pressure and is indicative of the importance of various invasion routes. We conducted a multi-continental analysis of historical bark and ambrosia beetle (Coleoptera: Curculionidae: Scolytinae, Platypodinae) interception records from import inspections in five recipient countries (Canada, Chile, Japan, New Zealand and USA). Here, we (1) identified principal source countries and biogeographic regions of origin, (2) quantified the effects of trade value and geographical distance on intercepted species richness, and (3) evaluated the frequency and magnitude of apparent bridgehead effects. Propagule pressure was highly uneven, with interceptions originating from a limited set of source regions that differed among recipient countries and reflected region-specific trade connectivity. Import value had a strong positive association with intercepted species richness, while geographical distance showed a weaker effect. Although secondary interceptions with imports from non-native regions were recorded for 62% of species, primary interceptions from native regions dominated overall with 86% of records, indicating that native source regions remain the main contributors to introduction pressure. However, the relative importance of bridgehead invasions varied among recipient countries and biogeographic regions, with the Palearctic and nearby geographic areas being prominent contributors. Our results show that introduction invasion risk in bark and ambrosia beetles is shaped by trade intensity, historical trade linkages, and emerging indirect invasion routes. These findings demonstrate how integrating multi-country interception data provides insights for improving pathway-based risk assessments and strengthening proactive biosecurity strategies amid expanding global trade.</jats:p>