Invasion of an inconspicuous ambrosia beetle and fungus may affect wood decay in southeastern North America.
Several ambrosia beetles are invasive pests able to attack and kill live trees, but most species established in non-native areas do not cause any documented impact. Here we report the recent invasion and rapid spread of Ambrosiodmus minor and its fungal associate Flavodon subulatus in the Southeastern US. We used a combination of a multi-year survey to document the increase in the beetle vector abundance, a field experiment to demonstrate the impact of the fungus on native mycoflora, data from the literature on F. subulatus competitiveness as a wood degrader, and field observations of wood colonization patterns. In less than ten years, A. minor abundance has increased several orders of magnitude in Florida. Joint colonization of wood by A. minor and F. subulatus results in extensive white rot (lignin removal) by the fungus. The presence of F. subulatus suppresses the diversity of native fungi on experimental logs by a third, and their abundance by more than two thirds. Therefore, the invasion of this symbiosis is impacting the wood decay community, an ecosystem previously considered immune to non-native ambrosia beetles. We suggest monitoring the impact of this invasion on native wood-inhabiting organisms and on biomass degradation in the region.