LOGAN, Utah, October 20 2016 – Scientists have discovered that Great Basin bristlecone pine, which has the longest lifespan of any non-clonal organism worldwide, is highly resistance to mountain pine beetle.
Mountain pine beetles, a native insect to western North America, have killed millions of trees in the last decade. Warming temperatures associated with climate change have fueled population outbreaks across western North America and caused range expansion northward in Canada and are also fueling extensive outbreaks in high-elevation forests. These outbreaks in iconic high-elevation whitebark and limber pine forests have scientists worried about other high-elevation pines, including Great Basin bristlecone pine.
Pines that have evolved with mountain pine beetle are expected to have more defenses to resist attack. Because high-elevation pines occupy areas that can get extremely cold, they may not have had to deal with mountain pine beetle in the past. As a result, the thought was that they would therefore be more susceptible as they may not have evolved many defenses against the beetles. The U.S. Forest Service Rocky Mountain Research Station and partners at Utah State University surveyed high-elevation stands across the Great Basin region in Utah, Nevada and California to determine which pine species were most vulnerable to mountain pine beetles.
The scientists discovered that not only is Great Basin bristlecone pine less susceptible than other high elevation pine species, but that mountain pine beetles are not killing this species at all, even when other pines in the same area are heavily attacked. Foxtail pine, which is a close relative of Great Basin bristlecone pine, experienced only low levels of beetle-caused mortality. By contrast, mountain pine beetles in the same areas killed large numbers of limber pines. What are the potential factors driving this unique resistance in the world’s longest living non-clonal trees? Tree sampling conducted by the scientists provides insight into this question.
Great Basin bristlecone pine had eight times the level of chemical resin defenses than limber pine, and four times more than foxtail pine. “We were very surprised to find such incredible defenses in Great Basin bristlecone pine,” said Dr. Barbara Bentz, lead scientist on the study with the U.S. Forest Service Rocky Mountain Research Station. “Great Basin bristlecone and foxtail pines were also found to have greater wood density than limber pines. High resin content and high wood density are traits that also aid in the extreme longevity of bristlecone pines, which can live to be more than 5000 years old. Extreme longevity and past evolutionary experiences have helped this species survive current pressures in a changing climate.”
Understanding resistance mechanisms in these trees will help facilitate the conservation of high-elevation keystone species and development of novel strategies for protection of other pine species from mountain pine beetle attacks.
View the publication here.
Learn more about the study in this Science Spotlight.
Citation: Bentz, Barbara J.; Hood, Sharon M.; Hansen, E. Matthew; Vandygriff, James C.; Mock, Karen E. 2016. Defense traits in the long-lived Great Basin bristlecone pine and resistance to the native herbivore mountain pine beetle. New Phytologist. doi: 10.1111/nph.14191.
Bentz, Barbara J. ; Hood, Sharon M. ; Hansen, Matt ; Vandygriff, James C. ; Mock, Karen E. , 2016