Data from: Transient synchrony among populations of five foliage-feeding Lepidoptera

1. Studies of transient population dynamics have largely focused on temporal changes in dynamical behavior, such as the transition between periods of stability and instability. The present study explores a related dynamic pattern, namely transient synchrony during a 49-year period among populations of five sympatric species of forest insects that share host tree resources. The long time-series allows a more comprehensive exploration of transient synchrony patterns than most previous studies. Considerable variation existed in the dynamics of individual species, ranging from periodic to aperiodic.
2. We used time-averaged methods to investigate long-term patterns of synchrony and time-localized methods to detect transient synchrony. We investigated transient patterns of synchrony between species and related these to the species’ varying density dependence structures; even species with very different density dependence exhibited at least temporary periods of synchrony. Observed periods of interspecific synchrony may arise from interactions with host trees (e.g. induced host defenses), interactions with shared natural enemies, or shared impacts of environmental stochasticity.
3. The transient nature of synchrony observed here raises questions both about the identity of synchronizing mechanisms and how these mechanisms interact with the endogenous dynamics of each species. We conclude that these patterns are the result of interspecific interactions that act only temporarily to synchronize populations, after which differences in the endogenous population dynamics among the species acts to desynchronize their dynamics.

1. 暂态种群动态（transient population dynamics）的相关研究多聚焦于种群动态行为的时序变化，例如稳定期与不稳定期之间的动态转换。本研究探讨了一类相关动态模式：共享寄主树木资源的5种同域森林昆虫种群，在长达49年的监测周期内呈现出的暂态同步性（transient synchrony）。相较于多数既往研究，本研究依托的长时序数据集能够更全面地解析暂态同步性模式。各物种种群的动态存在显著差异，涵盖周期性与非周期性两类行为。
2. 本研究采用时间平均法探究同步性的长期模式，并借助时间局域化方法检测暂态同步性。我们分析了物种种群间的暂态同步模式，并将其与各物种各异的密度依赖结构进行关联分析；结果显示，即便密度依赖特征差异显著的物种，也至少存在短暂的同步周期。观测到的种间同步现象，可能源于与寄主树木的相互作用（如诱导寄主防御反应）、与共有天敌的种间相互作用，或环境随机性的共同影响。
3. 本次研究中观测到的同步性具有暂态特征，这引发了两个核心学术问题：一是同步驱动机制的具体类型，二是这些机制如何与各物种种群的内源性动态相互作用。本研究结论表明，此类同步模式源于仅能短暂实现种群同步的种间相互作用；后续各物种种群内源性动态的差异，则会重新使种群动态去同步化。