Reconstructing the invasion pathways of the bark beetles Orthotomicus erosus and Cyrtogenius luteus (Coleoptera, Curculionidae, Scolytinae) in South America

Global trade and the spread of non-native host plants are driving the introduction of forest insects to new regions, often causing substantial ecological and economic damage in forests. Understanding invasion pathways is essential to tracking and preventing these introductions. This study investigates invasion pathways of two pine bark beetle species ( Orthotomicus erosus and Cyrtogenius luteus ) in South America using mitochondrial DNA analysis. We collected samples from native ranges (Europe/Asia) and invaded areas (Argentina/Uruguay) to understand genetic diversity and likely invasion routes. For O. erosus , results revealed two main genetic clusters in its native range, with South American populations closely related to western European populations. The presence of shared haplotypes between Argentina and Uruguay and the invasion timeline, suggest a single introduction event, likely through Uruguay first. For C. luteus , one widespread haplotype was found across all populations, indicating China as a possible source, though multiple introductions may have occurred given the presence of unique haplotypes in South America. Both species show similar invasion patterns in Argentina and Uruguay, suggesting connected populations facilitated by extensive pine plantations and regional trade. This study highlights the importance of understanding invasion pathways for implementing effective biosecurity measures, particularly given the expected increase in pine pest invasions in South America over coming decades.