Mountain pine beetle (MPB) is a native tree-killer of the western United States, and all pine species have been considered susceptible to attack. Great Basin bristlecone pine is not attacked by MPB due to stimuli that repel attacking beetles. This knowledge provides new avenues for identifying deterrent compounds to protect susceptible pine species. Over the last two decades, warming temperatures have resulted in epidemic levels of mountain pine beetle populations across much of western North America, killing millions of trees. Many high-elevation pine species are susceptible hosts and have experienced high levels of mortality in the recent outbreaks, but co-occurring Great Basin bristlecone pines were not attacked. Using no-choice attack box experiments, we compared Great Basin bristlecone pine resistance to mountain pine beetle with that of limber pine, a well-documented mountain pine beetle host. We confined sets of mountain pine beetles onto pairs of living Great Basin bristlecone and limber pines and recorded beetle status after 48 hours. Beetles placed on Great Basin bristlecone pine rarely initiated attacks relative to those placed on limber pine. Also, more beetles on Great Basin bristlecone pine retreated to the exit jar, indicating an aversion to the tree bole. Our results indicate that Great Basin bristlecone pine has a high level of resistance to mountain pine beetle due at least in part to stimuli that repel pioneering beetles from initiating attacks. Great Basin bristlecone pine is a keystone species and has the longest lifespan of any non-clonal organism worldwide. Research to identify the repellant compounds in Great Basin bristlecone is ongoing.
1. Great Basin bristlecone pine has a high level of resistance to mountain pine beetle due to repellant stimuli against attacking beetles.
2. Although climate change-driven increases in mountain pine beetle activity are expected to continue at high elevations, Great Basin bristlecone pine has low vulnerability to attack.
3. Ongoing research is testing if mountain pine beetle can produce offspring in Great Basin bristlecone, in addition to evaluating potential repellant compounds found in Great Basin bristlecone that could be used to protect susceptible pine species.