Phylogenetic analysis of a highly resolved insect food web

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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.