Species interactions under global change: can ecosystem processes be maintained in species assemblages with altered species composition?

据预测，全球变化将改变物种的分布。这也将不可避免地改变当地物种组合的物种组成。然而，我们目前缺乏对物种组成改变对维持当地物种组合生态过程的影响的了解，许多关键的生态过程，如捕食、种子传播或授粉，都涉及物种之间的相互作用，在给定的生态过程中，每个物种都履行一定的功能角色。当地物种组合中物种组成的变化可能会破坏物种之间的相互作用，例如由于当地的排斥，这可能最终导致独特功能作用的丧失。然而，这些损失的程度取决于当地相互作用网络可以重新连接的程度，即剩余和/或新到达的物种是否可以接管当地灭绝物种的功能角色。在我的项目中，我建议调查物种组成的变化如何影响当地物种组合中功能角色的多样性，利用一个区域性种子传播系统中植物-鸟类互惠互动的数据集。首先，我将评估食果鸟类物种在当前的本地互动网络的功能作用，使用最近建立的方法，通过其觅食生态位的功能作用的物种的特点。然后，我将模拟所有食果鸟类物种的区域物种库的潜在未来分布，并评估这如何影响当地物种组合的物种组成。然后，我将模拟潜在的物种之间的相互作用，在未来的物种组合的基础上物种的觅食生态位。最后，我将研究物种组成的预期未来变化如何影响局部相互作用网络中功能角色的多样性，以评估种子传播互利共生将受到物种分布的预期未来变化影响的程度。相互作用网络的布线是一个相对较新的研究方向，其方法仍在开发中。因此，我的研究也涉及方法的一部分，因为我的目标是完善的方法，从物种的内在属性，即它们的功能特征来模拟个体的相互作用。我最近开发的方法框架的基础上，我的目标是得到一个模型的相互作用的物种群体的性状之间的一般关系。一旦建立，这样的模型将有助于独立于经验数据和跨空间尺度的相互作用的建模，具有广泛的潜在应用，例如，将物种相互作用纳入未来物种分布的模型，以及在大空间尺度上研究生态过程中的功能作用。

Global changes are predicted to alter the distribution of species. This will inevitably also change the species composition of local species assemblages. However, we currently lack an understanding of the consequences of altered species compositions for the maintenance of ecological processes in local species assemblages.Many key ecological processes, e.g. predation, seed-dispersal or pollination, involve species interactions, and within a given ecological process, each species fulfills a certain functional role. Changes in the species composition in local species assemblages might disrupt interactions between species, e.g. due to local extinctions, which could ultimately lead to the loss of distinct functional roles. The magnitude of these losses, however, depends on the degree to which a local interaction network can be re-wired, that is whether the remaining and/or newly arriving species can take over the functional roles of locally extinct species.In my project I propose to investigate how changes in species composition affect the diversity of functional roles in local species assemblages, using a dataset on mutualistic plant-bird interactions from a regional seed-dispersal system. First, I will assess the functional roles of frugivorous bird species in the current local interaction networks, using a recently established method that characterizes the functional role of species via their foraging niche. I will then model the potential future distribution of all frugivorous bird species from the regional species pool and assess how this affects the species composition in the local species assemblages. I will then model potential interactions between the species in the future species assemblages based on species' foraging niches. Finally, I will investigate how the expected future changes in species compositions affect the diversity of functional roles in the local interaction networks in order to assess the degree to which the seed-dispersal mutualism is going to be affected by the expected future changes in species distributions.The modeling of species interactions and the re-wiring of interaction networks is a relatively new line of research and the methodology is still being developed. My study therefore also involves a methodological part, as I aim to refine the methodology to model individual interactions from species intrinsic properties, i.e. their functional traits. Building upon a methodological framework that I recently developed, I aim to derive a model for general relationships between the traits of interacting species groups. Once established, such a model would facilitate the modeling of interactions independent of empirical data and across spatial scales, with a wide range of potential applications, for instance, the incorporation of species interactions into models of future species distributions and the study of functional roles in ecological processes on large spatial scales.