Immune defences are an important component of fitness. Yet susceptibility to pathogens is common, suggesting the presence of ecological and evolutionary limitations on immune defences. Here, we use structural equation modelling to quantify the direct effects of resource quality and selection history, and their indirect effects mediated via body condition prior to an immune challenge on encapsul...

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 auste...

Over the past four decades, several authors have stressed that it is not just good performance, on the average, that matters in evolution but that variation in performance also plays an important role in determining long-term evolutionary trends. Several independent lines of research have arisen from considering different kinds of variation. Dempster (1955) introduced a model in which temporal ...