Resource Ecology of Virulence in a Planktonic Host‐Parasite System: An Explanation Using Dynamic Energy Budgets

Abstract: Parasites steal resources that a host would otherwise direct toward its own growth and reproduction. We use this fundamental notion to explain resource‐dependent virulence in a fungal parasite (Metschnikowia)–zooplankton host (Daphnia) system and in a variety of other disease systems with invertebrate hosts. In an experiment, well‐fed hosts died faster and produced more parasites than did austerely fed ones. This resource‐dependent variation in virulence and other experimental results (involving growth and reproduction rate/timing of hosts) readily emerged from a model based on dynamic energy budgets. This model follows energy flow through the host, from ingestion of food, to internal energy storage, to allocation toward growth and reproduction or to a parasite that consumes these reserves. Acting as a consumer, the parasite catalyzes its own extinction, persistence with an energetically compromised host, or death of the host. In this last case, more resources for the host inadvertently fuels fa...