Recent extreme events of drought and heat have been associated with insect-driven tree mortality. However, there is substantial uncertainty about the impact of climate variability and extreme climatic episodes on insect–host dynamics, especially over species biogeographical ranges. Here, we use climatic suitability indices derived from species distribution models to analyze the spruce beetle (Dendroctonus rufipennis) outbreak dynamics in spruce-fir forests across the Southern Rocky Mountains (USA) during a warm and dry episode (2000–2013). We estimated the historical climatic suitability of the host tree (1969–1998), its inter-annual variability, and the climatic suitability during the 2000–2013 episode for both beetle and host tree. Overall, outbreak was more likely to occur in host tree populations inhabiting areas with historically suitable climatic conditions that were also characterized by loss of suitability during the episode. Specifically, the outbreak initiation was located in areas with suitable climatic conditions for the beetle and high historical suitability for the host. However, the year-to-year analysis revealed that low–moderate amounts of outbreak initiation and spread were also determined by high host historical climatic suitability, with high historical inter-annual variability, and a modest reduction of suitability during the episode. Years with high amounts of outbreak initiation and spread mostly occurred in dense forests with large trees and were promoted by suitable climate conditions for the beetle. This study highlights the importance of considering the climatic suitability of the insect–host system to understand and anticipate outbreak dynamics at different temporal scales.

最近发生的干旱和高温极端事件与昆虫驱动的树木死亡率有关。但是，关于气候多变性和极端气候事件对昆虫寄主动态的影响，尤其是在物种生物地理范围内，存在很大的不确定性。在这里，我们使用从物种分布模型得出的气候适宜性指数来分析云杉甲虫（Dendroctonus rufipennis），在温暖干燥的季节（2000年至2013年），整个落基山脉（美国）的云杉杉林爆发动态。我们估计了寄主树（1969–1998）的历史气候适应性，年际变化以及甲虫和寄主树在2000–2013年间的气候适应性。总体而言，暴发更可能发生在寄居树种群中，这些寄居树种群具有历史上适宜的气候条件，其特征还在于发作期间的适应性下降。具体而言，爆发的起始地点位于甲虫的气候条件适宜且寄主寄居地的历史适应性较高的地区。但是，按年进行的分析表明，爆发的低度适度爆发也取决于寄主的历史气候适宜性，具有较高的历史年度间变异性，并且在发作期间适度降低了适应性。爆发爆发和传播数量很高的年份大多发生在茂密的森林中，树木茂密，并且由于甲虫的适宜气候条件而得到促进。这项研究强调了考虑昆虫寄主系统的气候适应性以了解和预测不同时间尺度上的暴发动态的重要性。