Species sensitivity and community structure: an integrated approach to understanding how one affects the other

人们对动植物物种的未来表示了很大的担忧，例如农田鸟类的减少或许多植物和昆虫的日益稀少。然而，每个物种都不是孤立存在的。相反，一个物种与其他物种相互作用，这些物种反过来又与其他物种相互作用，因此它们形成了高度复杂的生态网络，例如食物网。通常研究集中在物种或整个网络上，但我将采取综合的方法，考虑两者，例如，通过研究物种在生态网络中的位置（它们与网络的连接程度）的生物学和敏感性。我将通过提出以下问题来解决这一问题：（1）最不好地连接到网络中的物种是否对环境变化（如栖息地破碎化）最敏感？（2）联系最少的物种最有可能稀少和减少吗？然而，物种丰度的变化以及它们在网络中的连接程度反过来又会影响整个网络的结构。因此，了解网络中个体物种的身份将有助于我们更好地理解生态网络，即使在许多以前的研究中物种的身份没有被考虑。在这项研究中，我将调查林地斑块的生态网络。林地曾经覆盖了英国的大部分地区，但我将研究的斑块是保留下来的碎片，它们的大小和与其他斑块的距离都不同。我将同时研究这些林地斑块中两种不同的生态网络：一种是花朵和访问并授粉的昆虫的网络，另一种是植物，蚜虫和蚜虫捕食者的网络。我将测量每个物种在网络中的连接程度，并将其与（1）其对林地破碎化的敏感性，（2）其国家稀有性和衰退以及（3）物种的生物学特征，例如它的寿命有多长，繁殖速度有多快，或者移动的有多快。我也会问栖息地破碎化如何影响整个网络，以及它是否会使它们对物种灭绝的适应力降低。在这两个网络中，都有食蚜蝇，因为成虫是访花者，许多物种的幼虫以蚜虫为食。因此，我会问，一个与其食物网连接良好的幼虫是否会产生一个与其植物-传粉者网络连接良好的成虫。这两个网络将通过它们共享的物种（食蚜蝇和植物）连接起来，从而提高了网络中灭绝“漩涡”的可能性，其中一个物种的损失导致依赖于它的其他物种的损失，以及依赖于这些物种的更多物种的损失，等等，通过两个连接的网络循环。研究环境变化对生物多样性的影响的研究通常只考虑个别物种或整个网络。通过采取综合的方法，我将提供一个新的理解物种和生态网络如何相互影响，影响生物多样性作为一个整体。

There is, quite rightly, much concern expressed over the future of animal and plant species; for example the decline in farmland birds or the increasing rarity of many plants and insects. However, each species does not exist in isolation. Instead, one species interacts with other species, and those species, in turn, interact with yet others and so they form highly complex ecological networks, such as food webs. Usually studies are focussed on either species or whole networks, but I will take an integrated approach by considering both, for example, by examining the biology and sensitivity of species in the context of their place in ecological networks (how well connected they are into the network). I will address this in asking the following questions: (1) are the species that are least well connected into networks those that are most sensitive to changes to the environment, such as habitat fragmentation?, and (2) are the least well connected species the most likely to be rare and declining? However, changes in the abundance of species and how well connected they are in networks in turn affect the structure of whole networks. Therefore knowing the identity of individual species in the networks will help us to understand ecological networks better, even though in many previous studies species' identity has not been considered. In this study I will investigate ecological networks in woodland patches. Woodland used to cover most of Britain, but the patches I will study are the fragments that remain, and they vary both in their size and how close they are to other patches. I will simultaneously study two different ecological networks in these woodland patches: one is the network of flowers and the insects that visit and pollinate them, and the other is the network of plants, aphids and aphid predators. I will measure how well connected each species is in a network and relate this to (1) its sensitivity to woodland fragmentation, (2) its national rarity and decline and (3) biological characteristics of the species, such as how long it lives, how quickly it reproduces, or how mobile it is. I will also ask how habitat fragmentation affects whole networks and whether it makes them less resilient to the extinction of species. Hoverflies feature in both these networks since adults are flower visitors and the larvae of many species feed on aphids. Therefore I will ask whether a larva that is well connected into its food web gives rise to an adult that is well connected into its plant-pollinator network. The two networks will be linked through their shared species (hoverflies and plants) raising the possibility of extinction 'vortices' in the networks, where the loss of one species causes the loss of others that are dependent on it, and the loss of yet more species dependent on those, and so on cycling through the two linked networks. Often studies examining the effects of environmental change on biodiversity consider only individual species or whole networks. By taking an integrated approach I will provide a novel understanding of how species and ecological networks influence each other to affect biodiversity as a whole.