Lahr Eleanor C, Sala Anna
Division of Biological Sciences, The University of Montana, 32 Campus Drive, 104 Health Sciences, Missoula, MT 59812 (
Current address: Department of Entomology, North Carolina State University, 100 Derieux Place, 2301 Gardner Hall, Raleigh, NC 27695.
Environ Entomol. 2016 Dec;45(6):1463-1475. doi: 10.1093/ee/nvw138. Epub 2016 Oct 7.
Recent outbreaks of forest insects have been directly linked to climate change-induced warming and drought, but effects of tree stored resources on insects have received less attention. We asked whether tree stored resources changed following mountain pine beetle (Dendroctonus ponderosae Hopkins) attack and whether they affected beetle development. We compared initial concentrations of stored resources in the sapwood of whitebark pine (Pinus albicaulis Engelmann) and lodgepole pine (Pinus contorta Douglas ex. Louden) with resource concentrations one year later, in trees that were naturally attacked by beetles and trees that remained unattacked. Beetles did not select host trees based on sapwood resources-there were no consistent a priori differences between attacked versus unattacked trees-but concentrations of nonstructural carbohydrate (NSC), lipids, and phosphorus declined in attacked trees, relative to initial concentrations and unattacked trees. Whitebark pine experienced greater resource declines than lodgepole pine; however, sapwood resources were not correlated with beetle success in either species. Experimental manipulation confirmed that the negative effect of beetles on sapwood and phloem NSC was not due to girdling. Instead, changes in sapwood resources were related to the percentage of sapwood with fungal blue-stain. Overall, mountain pine beetle attack affected sapwood resources, but sapwood resources did not contribute directly to beetle success; instead, sapwood resources may support colonization by beetle-vectored fungi that potentially accelerate tree mortality. Closer attention to stored resource dynamics will improve our understanding of the interaction between mountain pine beetles, fungi, and host trees, an issue that is relevant to our understanding of insect range expansion under climate change.
近期森林昆虫的爆发与气候变化导致的变暖和干旱直接相关，但树木储存资源对昆虫的影响却较少受到关注。我们研究了在山地松甲虫（Dendroctonus ponderosae Hopkins）攻击后树木储存资源是否发生变化，以及这些变化是否会影响甲虫的发育。我们比较了白皮松（Pinus albicaulis Engelmann）和黑松（Pinus contorta Douglas ex. Louden）边材中储存资源的初始浓度与一年后的资源浓度，这些树木有的是自然受到甲虫攻击的，有的则未受到攻击。甲虫不会根据边材资源来选择寄主树木——受攻击树木和未受攻击树木之间事先没有一致的差异——但相对于初始浓度和未受攻击的树木，受攻击树木中非结构性碳水化合物（NSC）、脂质和磷的浓度有所下降。白皮松的资源下降幅度比黑松更大；然而，边材资源与这两个物种中甲虫的成功与否均无关联。实验操作证实，甲虫对边材和韧皮部NSC的负面影响并非由于环剥造成。相反，边材资源的变化与有真菌蓝变的边材百分比有关。总体而言，山地松甲虫的攻击影响了边材资源，但边材资源并未直接促成甲虫的成功；相反，边材资源可能支持由甲虫传播的真菌的定殖，而这些真菌可能会加速树木死亡。更密切地关注储存资源动态将增进我们对山地松甲虫、真菌和寄主树木之间相互作用的理解，这一问题对于我们理解气候变化下昆虫的分布范围扩张具有重要意义。
