Spatial determinants of food web structure and function, from landscape to global scales

食物网是如何在空间中变化的？一方面，由于当地环境的差异或有限的扩散，遥远的食物网可能包含不同的物种。当它们相距很远，以至于从不同的物种池中聚集时，食物网的这种差异可能是极端的。另一方面，尽管物种组成不同，但物种的特征可能保持不变，这样食物网就会以同样的方式发挥作用。解决空间对食物网结构和功能的影响对于理解大规模应激源(如气候变化、森林碎片化)如何影响食物网至关重要。为了解决空间如何影响食物网，我们需要(A)在景观和大陆尺度上重复实验，以确定扩散或生物地理如何改变物种或特征；(B)将这种复制的食物网暴露在环境变化中，如气候变化，减少扩散，如在孤立的森林碎片中发生的情况；以及(C)在不同地点之间移植物种，甚至食物网，以将物种特征的地点差异与环境分开。*在这个建议中，我提出了这样一个研究计划，基于在热带菠萝充满水的腋下发现的大型无脊椎动物(主要是未成熟的昆虫)。这些小系统(通常为1L)密度很高，因此是热带森林碳收支和生物多样性的重要贡献者。对于这项提议来说，菠萝科植物广泛存在于各个地区和大洲(北美、中美洲和南美洲)。我协调了一个由45名研究人员组成的网络，他们在这个系统的整个范围内工作。*我的研究项目考虑了气候变化、森林碎片化、扩散和物种池如何影响从景观到大陆的菠萝食物网的结构和功能。为了研究气候变化，我们首先将海拔作为一个指标，因为预计今天的中等海拔气候将是未来的高海拔气候。我们还将重点关注降雨，预计降雨将改变的不仅仅是新热带地区的温度，以及它对菠萝食物网的影响。为了研究碎裂，我们将使用树洞-一个非常类似于菠萝的系统，因为我们碎片中的菠萝密度太小了。为了研究扩散，我们将把种群遗传学的方法应用于食物链中的许多物种。为了研究物种库的影响，我们将在哥斯达黎加、波多黎各、法属圭亚那和巴西进行重复实验，并比较11个国家(在两种情况下都利用研究网络)汇编的食物网络数据。最后，我们还将操纵食物网顶部(捕食者)和底部食物网(枯叶)的特征，以帮助理解食物网是如何工作的。*总而言之，这项研究建议为理解食物网如何在地貌和全球范围内发挥作用，以及环境变化可能如何扰乱这种作用提供了一张蓝图。**

How do food webs change over space? One the one hand, distant food webs may contain different species because of differences in the local environment or limited dispersal. Such differences in food webs may be extreme when they are so far apart as to draw from different species pools. On the other hand, even though species composition differs, the traits of the species may remain the same, such that food webs “work” the same way. Resolving the effects of space on the structure and functioning of food webs is critical for understanding how large-scale stressors (e.g. climate change, forest fragmentation) affect food webs. To resolve how space affects food webs, we need to (a) replicate experiments over landscape and continental scales, to determine how dispersal or biogeography changes species or traits; (b) expose such replicated food webs to environmental change, like altered climate, and reduced dispersal, such as occurs in isolated forest fragments; and (c) transplant species or even food webs between sites, to separate site-differences in species traits from the environment.******In this proposal I present such a research program, based on the macroinvertebrates (largely immature insects) found in the water-filled axils of tropical bromeliads. These small systems (typically <1L) can occur at high density and are therefore important contributors to the carbon budget and biodiversity of tropical forests. Importantly for this proposal, bromeliads occur widely across landscapes and continents (North, Central and South America). I co-ordinate a network of 45 researchers who work on this system throughout its range. ******My research program considers how climate change, forest fragmentation, dispersal and the species pool affect the structure and functioning of bromeliad food webs at landscape to continental scales. To study climate change, we will first use elevation as a proxy, as today's mid-elevation climate is expected to be the future's high-elevation climate. We will also focus on rainfall, expected to change more than temperature in the Neotropics, and its impact on bromeliad food webs. To study fragmentation, we will use treeholes - a system very similar to bromeliads as bromeliad densities in our fragments are too spotty. To study dispersal, we will apply methods from population genetics to many species in the food web. To study effects of the species pool, we will conduct replicated experiments in Costa Rica, Puerto Rico, French Guiana and Brazil and compare compiled food web data over 11 countries (in both cases making use of the research network). Finally, we will also manipulate the traits at the top of food webs (predators) and at the bottom of food webs (dead leaves) to help understand how the food web functions. ******In sum, this research proposal provides a blueprint for understanding how food webs function at landscape and global scales, and how environmental change may disrupt that functioning. **