Defence syndromes in lodgepole – whitebark pine ecosystems relate to degree of historical exposure to mountain pine beetles |
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| Authors: | Kenneth F Raffa Charles J Mason Pierluigi Bonello Stephen Cook Nadir Erbilgin Ken Keefover‐Ring Jennifer G Klutsch Caterina Villari Philip A Townsend |
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| Affiliation: | 1. Department of Entomology, University of Wisconsin – Madison, Madison, WI, USA;2. Department of Entomology, Pennsylvania State University, State College, PA, USA;3. Department of Plant Pathology, The Ohio State University, Columbus, OH, USA;4. Department of Plant, Soil and Entomological Science, University of Idaho, Moscow, ID, USA;5. Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada;6. Departments of Botany and Geography, University of Wisconsin – Madison, Madison, WI, USA;7. Warnell School of Forestry and Natural Resources, University of Georgia – Athens, Athens, GA, USA;8. Department of Forest and Wildlife Ecology, University of Wisconsin – Madison, Madison, WI, USA |
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| Abstract: | Warming climate is allowing tree‐killing bark beetles to expand their ranges and access naïve and semi‐naïve conifers. Conifers respond to attack using complex mixtures of chemical defences that can impede beetle success, but beetles exploit some compounds for host location and communication. Outcomes of changing relationships will depend on concentrations and compositions of multiple host compounds, which are largely unknown. We analysed constitutive and induced chemistries of Dendroctonus ponderosae's primary historical host, Pinus contorta, and Pinus albicaulis, a high‐elevation species whose encounters with this beetle are transitioning from intermittent to continuous. We quantified multiple classes of terpenes, phenolics, carbohydrates and minerals. Pinus contorta had higher constitutive allocation to, and generally stronger inducibility of, compounds that resist these beetle–fungal complexes. Pinus albicaulis contained higher proportions of specific monoterpenes that enhance pheromone communication, and lower induction of pheromone inhibitors. Induced P. contorta increased insecticidal and fungicidal compounds simultaneously, whereas P. albicaulis responses against these agents were inverse. Induced terpene accumulation was accompanied by decreased non‐structural carbohydrates, primarily sugars, in P. contorta, but not P. albicaulis, which contained primarily starches. These results show some host species with continuous exposure to bark beetles have more thoroughly integrated defence syndromes than less‐continuously exposed host species. |
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| Keywords: | Bark beetles carbohydrates climate change conifers defence fungi induction ophiostomatoid phenolics terpenes |
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