Native and non-native ambrosia beetles compete for deadwood resources

Abstract A consequence of biological invasion is competition between native and non-native species. Ambrosia beetles (Curculionidae: Scolytinae, Platypodinae) are among the most successful insect invaders, but their impact in natural settings is poorly understood. Across the United States, non-native ambrosia beetles numerically dominate their native counterparts, creating concern of competitive displacement. We compile one new and three published datasets to test for competition between native and non-native ambrosia beetles within their breeding resources. For each dataset, deadwood objects were created in the field, left to be naturally colonized by insects and then sampled for emergent insects using identical methods. Within 356 objects, native and non-native ambrosia beetles preferentially inhabited the same resources in space and time. Within 141 inhabited objects, native ambrosia beetle abundance declined with increasing abundance of non-natives (and vice versa). Furthermore, the probability of an emerging beetle being native was impacted by wood properties. Thus, we find that native and non-native ambrosia beetles compete, most likely in an exploitative manner, and that certain conditions provide competitive advantages for both groups. Given the importance of ambrosia beetles in forest ecosystem processes, further research is needed to understand the consequences of ambrosia beetle invasion in natural settings.