Institute of Botany, Chinese Academy of Sciences, Xiangshan, Beijing, China.
Glob Chang Biol. 2013 Sep;19(9):2867-77. doi: 10.1111/gcb.12245. Epub 2013 Jul 15.
Ongoing global climate change is predicted to increase the frequency and magnitude of extreme weather events, impacting population dynamics and community structure. There is, however, a critical lack of case studies considering how climatic perturbations affect biotic interactions. Here, we document how an obligate seed dispersal mutualism was disrupted by a temporally anomalous and meteorologically extreme interlude of unseasonably frigid weather, with accompanying snowstorms, in subtropical China, during January-February 2008. Based on the analysis of 5892 fecal samples (representing six mammalian seed dispersers), this event caused a substantial disruption to the relative seed dispersal function for the raisin tree Hovenia dulcis from prestorm 6.29 (2006) and 11.47 (2007), down to 0.35 during the storm (2008). Crucially, this was due to impacts on mammalian seed dispersers and not due to a paucity of fruit, where 4.63 fruit per branch were available in January 2008, vs. 3.73 in 2006 and 3.58 in 2007. An induced dietary shift occurred among omnivorous carnivores during this event, from the consumption fruit to small mammals and birds, reducing their role in seed dispersal substantially. Induced range shift extinguished the functionality of herbivorous mammals completely, however, seed dispersal function was compensated in part by three omnivorous carnivores during poststorm years, and thus while the mutualism remained intact it was enacted by a narrower assemblage of species, rendering the system more vulnerable to extrinsic perturbations. The storm's extended effects also had anthropogenic corollaries - migrating ungulates becoming exposed to heightened levels of illegal hunting - causing long-term modification to the seed dispersal community and mutualism dynamics. Furthermore, degraded forests proved especially vulnerable to the storm's effects. Considering increasing climate variability and anthropogenic disturbance, the impacts of such massive, aberrant events warrant conservation concern, while affording unique insights into the stability of mutualisms and the processes that structure biodiversity and mediate ecosystem dynamics.
持续的全球气候变化预计将增加极端天气事件的频率和强度，从而影响人口动态和群落结构。然而，目前非常缺乏研究案例来探讨气候波动如何影响生物相互作用。在这里，我们记录了在中国亚热带地区，2008 年 1 月至 2 月期间，一场异常且极端的天气暂态过程（包括异常寒冷的天气和暴风雪）如何扰乱了一种强制性的种子传播共生关系。基于对 5892 个粪便样本（代表六种哺乳动物种子传播者）的分析，这次事件导致了中国亚热带地区的忍冬属葡萄干树（Hovenia dulcis）的相对种子传播功能从风暴前的 6.29（2006 年）和 11.47（2007 年）显著下降到风暴期间的 0.35（2008 年）。至关重要的是，这是由于哺乳动物种子传播者受到的影响，而不是由于果实缺乏，2008 年 1 月每根树枝上有 4.63 个果实，而 2006 年和 2007 年分别有 3.73 个和 3.58 个。在这次事件中，杂食性肉食动物发生了饮食诱导性转变，从食用果实转变为小型哺乳动物和鸟类，从而大大降低了它们在种子传播中的作用。然而，食草哺乳动物的范围转移完全消除了它们的种子传播功能，但是在风暴后的几年中，三种杂食性肉食动物在一定程度上补偿了种子传播功能，因此，尽管共生关系保持完整，但它是由更窄的物种组合执行的，从而使系统更容易受到外部干扰。风暴的长期影响也具有人为的影响——迁移的有蹄类动物暴露在更高水平的非法狩猎下——导致种子传播群落和共生关系动态的长期改变。此外，退化的森林尤其容易受到风暴的影响。考虑到气候变化的可变性和人为干扰的增加，这种大规模、异常事件的影响值得关注，同时为共生关系的稳定性以及生物多样性的结构和调节生态系统动态的过程提供了独特的见解。
