The Influence of Variation in Host Tree Monoterpene Composition on Secondary Attraction by an Invasive Bark Beetle: Implications for Range Expansion and Potential Host Shift by the Mountain Pine Beetle
Forest Ecology and Management
The range of mountain pine beetle (Dendroctonus ponderosae) has expanded in recent years to include many evolutionarily naïve forests in western Canada. These forests include novel populations of the principal host species, lodgepole pine (Pinus contorta), the novel species jack pine (Pinus banksiana), and their hybrids (P. contorta × P. banksiana). These novel forests are chemically and physically different than native forests, and recent studies have shown beetle reproductive performance is enhanced in these novel habitats. We conducted a field experiment to determine the effect of differing host chemistry, specifically α-pinene content, on secondary attraction by foraging mountain pine beetles. Alpha-pinene is the precursor molecule for the production of trans-verbenol, the main aggregation pheromone for this beetle species. We found that elevated relative concentrations of α-pinene in bolts significantly increased their attractiveness to in situ mountain pine beetles. Seventy-five percent of attacks were found on infested bolts with the most α-pinene relative to other monoterpenes. Other measures of terpene chemistry between bolt types could not explain the pattern of attacks. This result suggests that elevated concentrations of α-pinene could increase the rate of aggregation and attack success by the mountain pine beetle in novel pine forests. Newly invaded hybrid and jack pine in the western boreal forest are reported to contain 3–4 times the relative concentration of α-pinene than lodgepole pines in forests in which the beetle has coevolved. These elevated concentrations may help the mountain pine beetle overcome some of the potential restraints for establishment and spread in the boreal forest, such as low pine volume and connectivity, and continue expanding its range.
Burke, Jordan L.; Carroll, Allan L. 2016. The Influence of Variation in Host Tree Monoterpene Composition on Secondary Attraction by an Invasive Bark Beetle: Implications for Range Expansion and Potential Host Shift by the Mountain Pine Beetle. Forest Ecology and Management 359: 59-64.