Phylogenetic analysis of a highly resolved insect food web

自然生态系统由复杂的物种网络组成，这些物种通过相互取食联系在一起。这些网络的描述被称为食物网。就像其他网络（如互联网、国家电网）一样，我们可以分析食物网的特性，并深入了解生态系统的功能和恢复能力。为了能够预测这些复杂的系统将如何应对气候变化和其他形式的人类影响，我们需要了解决定食物网结构的生物机制。如果我们能回答是什么决定谁吃谁？为什么有些物种受到许多捕食者的攻击，而有些物种受到少数捕食者的攻击？是什么决定了物种是否共享资源？是什么决定了它们是否有共同的天敌？等等，然后我们得到负责馈送链接分发的流程的处理。食物网的结构将是当前生态过程的结果，也是过去进化的结果。尽管我们的兴趣可能是在当前的生态过程中，但我们只有在控制了进化的限制条件后才能测试它们的影响。例如，两个物种在食物网中有相似位置的原因可能是因为它们的大小相似（生态效应），但也可能是因为它们共享最近的进化历史，即它们是密切相关的。为了区分这些可能性，我们需要知道网络中物种之间的进化关系，就像系统发育（家谱）所代表的那样。到目前为止，还没有对食物网进行详细的系统发育分析，因为没有必要的数据。在这个项目中，我建议从一个已经收集了10年的非常有特征的食物网中构建蚜虫、它们的初级寄生蜂和攻击初级寄生蜂的次级寄生蜂的分子系统发育学（总共约100种昆虫）。我们将使用DNA序列来解决系统发育问题，我们将用这些来测试关于这个食物网组织的假设。在未来，我们可以对这个群落如何应对扰动（如新物种的入侵）提出假设，并设计实验来测试这些预测。

Natural ecosystems consist of complex networks of species that are linked via feeding interactions. Descriptions of these networks are called food webs. Just like other networks (e.g. internet, national grid) we can analyse the properties of food webs and gain an insight into the functioning and the resilience of ecosystems. In order to be able to predict how these complex systems will respond to climate change and other form of human impact we need to gain an understanding of the biological mechanisms that determine the structure of food webs. If we can answer questions like what determines who eats whom? why are some species attacked by many predators and some by few? what determines whether species share resources? what determines whether they share natural enemies? etc., then we get a handle on the processes that are responsible for the distribution of feeding links. The structure of food webs will be the result of current ecological processes but also of the evolutionary past. Even though our interest may be in the current ecological processes we can only test for their effects if we control for the constraints of evolution. For example, the reason that two species have a similar place in a food web maybe because they are a similar size (ecological effect) but it may also be because they share a recent evolutionary past, ie they are closely related. In order to distinguish between these possibilities we need to know the evolutionary relations among the species in the web as represented in a phylogeny (family tree). So far detailed phylogenetic analyses of food webs have not been carried out simply because the necessary data is not available. In this project I propose to construct molecular phylogenies of aphids, their primary parasitoid wasps and the secondary parasitoid wasps that attack the primary parasitoids (~100 insect species in all) from an exceptionally well characterised food web that has been collected over a period of 10 years. We will use DNA sequences to resolve the phylogenies and we will use these to test hypotheses on the organisation of this food web. In the future we can then formulate hypotheses on how this community will respond to perturbations such as the invasion by a new species and design experiments to test these predictions.