Species traits shape the intercontinental introduction patterns of bark and ambrosia beetles

Abstract

O_LIA negative consequence of international trade is the accidental transport of non-native insect species to non-native regions, but our understanding of how this risk varies among species and how it relates to species traits remains incomplete. C_LIO_LIWe conducted a multi-continental analysis of historical border interception records for bark and ambrosia beetles (Coleoptera: Curculionidae: Scolytinae and Platypodinae), integrating 13,124 interception events (353 species) from Canada, Chile, Japan, New Zealand, and the United States. We estimated an intercontinental propagule pressure index and tested how species characteristics influence transport likelihood. C_LIO_LIInterception assemblages showed low similarity among countries, with 64% of species recorded in only one nation, indicating strong geographic structuring linked to trade pathways. Interceptions were taxonomically and biogeographically non-random: species native to the Palearctic Nearctic and Indo-Malayan regions were overrepresented, whereas Neotropical, Austro-Pacific and Afrotropical taxa were underrepresented. C_LIO_LIHost tree taxa emerged as the strongest predictor of propagule pressure. Species associated with conifers--particularly Pinaceae--exhibited approximately twice the propagule pressure of species restricted to broadleaved hosts. Ambrosia beetles showed higher propagule pressure than bark and twig/seed feeders. Propagule pressure also increased with the number of regions where species have already invaded, consistent with bridgehead dynamics. C_LIO_LISynthesis and applications: Our findings demonstrate that intercontinental transport of bark and ambrosia beetles is strongly structured by host associations, feeding guild, and biogeographic origin, reflecting the composition of traded commodities and historical trade networks. Identifying taxa with consistently high propagule pressure provides a basis for prioritizing surveillance and strengthening global forest biosecurity. C_LI