Phytochemicals as mediators for host range expansion of a native invasive forest insect herbivore.

  • Are novel plant chemicals friends or foes of native invasive insect herbivores?

  • Author(s) / Creator(s)
  • Mountain pine beetle (MPB, Dendroctonus ponderosae) has recently breached the geo-climatic barrier of the northern Rocky Mountains and invaded novel jack pine (Pinus banksiana) forests in western Canada. This breach signifies an unprecedented climate change-induced invasion of a new plant biome by a native insect. The mechanism underlying this host range expansion is unknown, but likely involves phytochemicals that play critical roles in the MPB biology. Thus far, studies have investigated jack pine suitability to MPB as a host and examined compatibility of its chemicals with beetles and their microbial symbionts. Based on these studies, I have identified five phytochemical mechanisms that have likely facilitated the host expansion of MPB. First, relative to the historical host of MPB (lodgepole pine, P. contorta), jack pine not only
    quantitatively lacks toxic defense chemicals, but also contains large amounts of chemicals that promote MPB host colonization. Second, prior to the arrival to naïve jack pine forests, invasion of a zone of hybrids of jack and lodgepole pines by beetles likely improved their success in the jack pine as hybrids show chemical characteristics of both novel and historical hosts. Third, jack pine chemistry is compatible for beetle pheromone production, aggregation on the host trees, and larval
    development. Fourth, compatibility of jack pine chemistry with the microbial symbionts of MPB maintains beneficial interactions with their host. Finally, jack pine contains low amounts of defense and attraction inhibitory compounds, and high amounts of pheromone precursor and synergistic compounds that make historical hosts susceptible to MPB. I conclude that compatibility of chemicals of jack pine to MPB and its symbionts has likely facilitated the biological invasion.

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    Article (Draft / Submitted)
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    Attribution-NonCommercial 4.0 International
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  • Citation for previous publication
    • Erbilgin, N. 2019. Phytochemicals as mediators for host range expansion of a native invasive forest insect herbivore. New Phytologist 221(3): 1268-1278.