Data from: Life-stage differences in spatial genetic structure in an irruptive forest insect: implications for dispersal and spatial synchrony

Dispersal determines the flux of individuals, energy, and information and is therefore a key determinant of ecological and evolutionary dynamics. Yet, it remains difficult to quantify its importance relative to other factors. This is particularly true in cyclic populations in which demography, drift, and dispersal contribute to spatio-temporal variability in genetic structure. Improved understanding of how dispersal influences spatial genetic structure is needed to disentangle the multiple processes that give rise to spatial synchrony in irruptive species. In this study, we examined spatial genetic structure in an economically important irruptive forest insect, the spruce budworm (Choristoneura fumiferana) to better characterize how dispersal, demography, and ecological context interact to influence spatial synchrony in a localized outbreak. We characterized spatial variation in microsatellite allele frequencies using 231 individuals and 7 geographic locations. We show that: (1) gene flow among populations is likely very high (Fst ≈ 0); (2) despite an overall low level of genetic structure, important differences exist between adult (moth) and juvenile (larvae) life-stages; and (3) the localized outbreak is the likely source of moths captured elsewhere in our study area. This study demonstrates the potential of using molecular methods to distinguish residents from migrants and for understanding how dispersal contributes to spatial synchronization. In irruptive populations, the strength of genetic structure depends on the timing of data collection (e.g., trough vs. peak), location, and dispersal. Taking into account this ecological context allows us to make more general characterizations of how dispersal can affect spatial synchrony in irruptive populations.

扩散（Dispersal）决定了个体、能量与信息的通量，因此是生态与进化动态的关键调控因子。然而，相较于其他生态过程，量化扩散的相对重要性仍颇具挑战。这一困境在循环种群系统中尤为凸显——此类种群中，种群统计学、遗传漂变与扩散共同驱动了遗传结构的时空变异。

学界亟需深化对扩散如何影响空间遗传结构的认知，以此厘清驱动暴发物种空间同步性的多重过程。本研究针对一种具有重要经济价值的暴发性森林昆虫——云杉芽卷蛾（Choristoneura fumiferana）展开空间遗传结构分析，旨在系统刻画扩散、种群统计特征与生态背景如何相互作用，影响局域暴发种群的空间同步性。

研究依托231个采样个体与7个地理采样位点，对微卫星（microsatellite）等位基因频率的空间变异进行了定量表征。结果显示：（1）种群间基因流水平极高（遗传分化系数Fst≈0）；（2）尽管整体遗传结构水平较低，但成虫（蛾）与幼体（幼虫）两个生活史阶段间存在显著遗传差异；（3）本研究区域内捕获的成虫，其大概率起源于该局域暴发种群。

本研究证实了利用分子手段区分本地定居种群与迁入个体的可行性，并增进了我们对扩散如何推动空间同步性的理解。在暴发种群中，遗传结构的强弱取决于数据采集时机（如种群低谷期与暴发高峰期）、采样点位以及扩散模式。结合此类生态背景开展研究，能够让我们对扩散如何影响暴发物种种群空间同步性做出更具普适性的刻画。