Data from: Population dynamics of an Arctiid caterpillar-tachinid parasitoid system using state-space models

1. Population dynamics of insect host–parasitoid systems are important in many natural and managed ecosystems and have inspired much ecological theory. However, ecologists have a limited knowledge about the relative strengths of species interactions, abiotic effects and density dependence in natural host–parasitoid dynamics. Statistical time-series analyses would be more informative by incorporating multiple factors, measurement error and noisy dynamics. 2. We use a novel maximum likelihood and model-selection analysis of a state-space model for host–parasitoid dynamics to examine 21 years of annual census data for woolly bear caterpillars (Platyprepia virginalis) and their locally host-specific tachinid parasitoids (Thelaira americana). 3. Caterpillar densities varied by three orders of magnitude and were driven by density dependence and precipitation from the previous March but not detectably by parasitoids, despite variable and sometimes high (>50%) parasitism. 4. Fly fluctuations, as estimated from per cent parasitism, were affected by density dependence and precipitation from the previous July. There was marginal evidence that host abundance drives fly fluctuations as a generic linear effect but no evidence for classical Nicholson–Bailey coupling. 5. The state-space model analysis includes new methods for likelihood calculation and allows a balanced consideration of effect magnitude and statistical significance in a nonlinear model with multiple alternative explanatory variables.1. 昆虫寄主-拟寄生蜂（host–parasitoid）系统的种群动态在众多自然与人工管护的生态系统中均具有重要研究价值，同时催生了大量生态学理论成果。然而，生态学界对于自然寄主-拟寄生蜂动态中物种相互作用、非生物因子效应以及密度制约的相对强度仍认知有限。若在统计时序分析中纳入多因子变量、测量误差与嘈杂动态，将能获得更具信息量的研究结论。 2. 本研究针对寄主-拟寄生蜂动态构建状态空间模型（state-space model），采用全新的极大似然（maximum likelihood）与模型选择（model-selection）分析方法，对21年的年度普查数据（census data）展开实证研究，研究对象为星灯蛾毛虫（*Platyprepia virginalis*）及其本地寄主专一性寄蝇类拟寄生者（tachinid parasitoids）*Thelaira americana*。 3. 毛虫种群密度的变化幅度达三个数量级，其动态由密度制约与前一年3月的降水量共同驱动；尽管寄生率存在波动且有时高达50%以上，却未检测到寄蝇类拟寄生者的显著调控作用。 4. 基于寄生率百分比估算的寄蝇种群波动，受到密度制约与前一年7月降水量的影响。存在边际显著的证据表明，寄主丰度以通用线性效应的方式驱动寄蝇种群波动，但未发现经典尼科尔森-贝利（Nicholson–Bailey）耦合效应的相关实证支持。 5. 本次状态空间模型分析引入了全新的似然值计算方法，能够在包含多个备选解释变量的非线性模型中，均衡考量效应量与统计显著性。