A multi-scale test of competition between exotic and native ambrosia beetles

Ambrosia beetles are some of the first insects to colonize stressed and dying trees. A few of these species (primarily in Scolytinae: Xyleborini) are super-invaders that have spread throughout the world, often bringing with them plant pathogens and causing economic harm. Although the negative effects of these invaders on plant health are well established, their impacts on fauna inhabiting shared resources are uncertain. No substantial evidence of competition has been found between exotic and native ambrosia beetles; yet concern is warranted due to exotics commonly outnumbering natives in trap samples. Here, we use lessons learned from plant invasions, and data integrated from multiple sources, to test a multi-scale hypothesis of competition between native and exotic ambrosia beetles. We predict that exotic and native abundance will be negatively correlated at small spatial scales (within deadwood objects) but positively correlated at large spatial scales (flight-intercept traps that sample from a ‘landscape’ of deadwood objects). This pattern would support competition within finite resources but similar habitat selection within forested landscapes, mirroring scale-dependent patterns of native and exotic plants. Results and further hypotheses regarding the ecological impacts of exotic ambrosia beetles will be discussed.