Host Manipulation by Parasites: A Look Back Before Moving Forward.

The ability to manipulate host behaviour is among the most fascinating and best-studied adaptations of parasites. In this opinion article, we highlight trends and biases in the study of this phenomenon that may cloud or limit our understanding of its evolution. For instance, reviews and theoretical studies have shown a disproportionately sharp increase in the past decade relative to empirical studies. We also discuss taxonomic biases in the host-parasite systems investigated, as well as recent declines in the use of experimental infections and in the proportion of these systems in which fitness benefits for the parasites have been confirmed. We finish this opinion article by offering recommendations for the continued success of research in this area.