Department of Agricultural Sciences, University of Helsinki, Helsinki, Finland.
Biodiversity Unit, University of Turku, Turku, Finland.
J Anim Ecol. 2021 Apr;90(4):859-874. doi: 10.1111/1365-2656.13415. Epub 2021 Jan 13.
In a warming world, changes in climate may result in species-level responses as well as changes in community structure through knock-on effects on ecological interactions such as predation and herbivory. Yet, the links between these responses at different levels are still inadequately understood. Assessing how microclimatic conditions affect each of them at local scales provides information essential for understanding the consequences of macroclimatic changes projected in the future. Focusing on the rapidly changing High Arctic, we examine how a community based on a common resource species (avens, Dryas spp.), a specialist insect herbivore (Sympistis zetterstedtii) and natural enemies of lepidopteran herbivores (parasitoids) varies along a multidimensional microclimatic gradient. We ask (a) how parasitoid community composition varies with local abiotic conditions, (b) how the community-level response of parasitoids is linked to species-specific traits (koino- or idiobiont life cycle strategy and phenology) and (c) whether the effects of varying abiotic conditions extend to interaction outcomes (parasitism rates on the focal herbivore and realized herbivory rates). We recorded the local communities of parasitoids, herbivory rates on Dryas flowers and parasitism rates in Sympistis larvae at 20 sites along a mountain slope. For linking community-level responses to microclimatic conditions with parasitoid traits, we used joint species distribution modelling. We then assessed whether the same abiotic variables also affect parasitism and herbivory rates, by applying generalized linear and additive mixed models. We find that parasitism strategy and phenology explain local variation in parasitoid community structure. Parasitoids with a koinobiont strategy preferred high-elevation sites with higher summer temperatures or sites with earlier snowmelt and lower humidity. Species of earlier phenology occurred with higher incidence at sites with cooler summer temperatures or later snowmelt. Microclimatic effects also extend to parasitism and herbivory, with an increase in the parasitism rates of the main herbivore S. zetterstedtii with higher temperature and lower humidity, and a matching increase in herbivory rates. Our results show that microclimatic variation is a strong driver of local community structure, species interactions and interaction outcomes in Arctic ecosystems. In view of ongoing climate change, these results predict that macroclimatic changes will profoundly affect arctic communities.
在全球变暖的情况下，气候变化可能会通过对捕食和食草等生态相互作用产生连锁效应，导致物种层面的反应以及群落结构的变化。然而，不同层面之间的这些联系仍然没有得到充分理解。评估微观气候条件如何在当地尺度上影响它们每一个，为了解未来预测的宏观气候变化的后果提供了至关重要的信息。本研究聚焦于快速变化的北极地区，我们研究了一个基于共同资源物种（北极花属植物，Dryas spp.）、专门的昆虫食草动物（Sympistis zetterstedtii）和鳞翅目食草动物天敌（寄生蜂）的群落如何沿着多维微观气候梯度变化。我们提出了以下三个问题：（a）寄生蜂群落组成如何随当地非生物条件而变化；（b）寄生蜂的群落水平反应如何与物种特异性特征（兼性或专性生活史策略和物候）相关联；（c）不断变化的非生物条件的影响是否会扩展到相互作用的结果（对焦点食草动物的寄生率和实际食草率）。我们在山坡上的 20 个地点记录了寄生蜂的本地群落、北极花上的食草率和 Sympistis 幼虫中的寄生率。为了将群落水平的反应与微气候条件与寄生蜂特征联系起来，我们使用了联合物种分布模型。然后，我们通过应用广义线性和加性混合模型来评估相同的非生物变量是否也会影响寄生率和食草率。我们发现，寄生策略和物候解释了寄生蜂群落结构的局部变化。具有兼性生活史策略的寄生蜂更喜欢高海拔、夏季温度较高或融雪较早、湿度较低的地点。较早物候的物种在夏季温度较低或融雪较晚的地点发生的频率较高。微气候效应还延伸到寄生和食草作用，主要食草动物 S. zetterstedtii 的寄生率随着温度升高和湿度降低而增加，相应的食草率也增加。我们的研究结果表明，微观气候的变化是北极生态系统中局部群落结构、物种相互作用和相互作用结果的一个强大驱动因素。鉴于正在发生的气候变化，这些结果表明，宏观气候变化将深刻影响北极地区的社区。
