Abstract
Coevolution is the evolutionary process that involves an interaction between two parties, where adaptation in one party leads to a changed selection regime for the other party and vice versa. Coevolution is one of the major processes in many types of interactions and therefore implicated in the formation and maintenance of biodiversity. Although the importance of coevolution is potentially very large, only few experimental studies have investigated this process. In this project, we aim to explore the coevolutionary process between the specialist predatory mite Phytoseiulus persimilis and its herbivorous prey, the two-spotted spider mite Tetranychus urticae. The latter is known for its prolific production of protein-rich silk webs as a defence against predators. We will focus on the key question how the defensive ability of a prey species depends on other life-history traits via an energetic and/or genetic trade-off. The main defensive trait in spider mites, silk production for webbing, is known to involve investment of essential amino acids. We intend to assess the relation between silk production and other fitness components, such as egg production and detoxification of secondary plant compounds, using selection experiments on silk production. These trade-offs will be studied in more detail by investigating their physiological basis by measuring investment of essential amino acids in silk or egg production in the various selection lines. In addition, we investigate how differences in silk investment affect predation risk and predator-prey dynamics, as well as how these depend on host plant quality. Based on these experimentally established relations we generate predictions for silk investment levels in the field and test these predictions in population experiments, using natural predator-prey populations in Sicily and in Turkey, in which predator densities and host plant quality will be manipulated. In this way, our project aims to provide much-needed insights by studying coevolution in a simple and well-known experimental system, focusing on the role of trade-offs and in particular its physiological basis, and extrapolating these insights to population-level tests in the field.
Netherlands