Periodic and spatially synchronous outbreaks of insect pests have dramatic consequences for boreal and sub-boreal forests. Within these multitrophic systems, parasitoids can be stabilizing agents by dispersing toward patches containing higher host density (the so-called birdfeeder effect). However, we know little about the dispersal abilities of parasitoids in continuous forested landscapes, limiting our understanding of the spatiotemporal dynamics of host–parasitoid systems, and constraining our ability to predict forest resilience in the context of global changes. In this study, we investigate the spatial genetic structure and spatial variation in genetic diversity of two important species of spruce budworm larval parasitoids during outbreaks: Apanteles fumiferanae Viereck (Braconidae) and Glypta fumiferanae (Viereck) (Ichneumonidae). Using parasitoids sampled in 2014 from 26 and 29 locations across a study area of 350,000 km², we identified 1,012 and 992 neutral SNP loci for A. fumiferanae (N = 279 individuals) and G. fumiferanae (N = 382), respectively. Using DAPC, PCA, AMOVA, and IBD analyses, we found evidence for panmixia and high genetic connectivity for both species, matching the previously described genetic structure of the spruce budworm within the same context, suggesting similar effective dispersal during outbreaks and high parasitoid population densities between outbreaks. We also found a significant negative relationship between genetic diversity and latitude for A. fumiferanae but not for G. fumiferanae, suggesting that northern range limits may vary by species within the spruce budworm parasitoid community. These spatial dynamics should be considered when predicting future insect outbreak severities in boreal landscapes.

中文翻译：

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与云杉芽虫相关的两种寄生蜂物种的景观规模种群连通性：使用遗传数据测试喂鸟器效应

虫害的周期性和空间同步爆发对北方和亚北方森林产生了巨大的影响。在这些多营养系统中，寄生蜂可以通过向宿主密度较高的斑块分散（所谓的喂鸟器效应）而成为稳定剂。然而，我们对寄生蜂在连续森林景观中的传播能力知之甚少，限制了我们对寄主-寄生蜂系统时空动态的理解，并限制了我们在全球变化背景下预测森林恢复力的能力。在这项研究中，我们调查了两种重要的云杉芽虫幼虫寄生蜂在爆发期间的空间遗传结构和遗传多样性的空间变异：Apananteles fumiferanae Viereck (Braconidae) 和Glypta fumiferanae (Viereck) (Ichneumonidae)。^{使用 2014 年从 350,000 km 2}研究区域内的 26 和 29 个地点采集的寄生蜂，我们确定了A 的1,012 和 992 个中性 SNP 位点。fumiferanae ( N  = 279 个体)和 G. 烟曲霉( N = 382），分别。使用 DAPC、PCA、AMOVA 和 IBD 分析，我们发现了两个物种的泛混合和高遗传连通性的证据，与先前描述的云杉芽虫在相同背景下的遗传结构相匹配，表明在爆发和高寄生蜂种群密度期间类似的有效分散爆发之间。我们还发现A的遗传多样性与纬度之间存在显着的负相关关系。fumiferanae但不适用于G。fumiferanae，表明北部范围限制可能因云杉芽虫寄生蜂群落中的物种而异。在预测北方地区未来昆虫爆发的严重程度时，应考虑这些空间动态。