Mechanisms and consequences of infection‐induced phenotypes

Abstract

Abstract Researchers studying animal phenotypes often overlook the potential influence of parasites hiding inside their study organisms. Yet, most wild animals host parasites, which can alter individual phenotypes (e.g. morphology, physiology, behaviour). Infection‐induced phenotypes stem from several nonmutually exclusive mechanisms (i.e. adaptive host defences, infection‐induced debilitation and host manipulation by parasites), driven by parasites and/or hosts. Changes in host phenotype can impact all levels of biological organization, from cells to communities. The nature and magnitude of these effects can vary depending on the biotic and abiotic environmental factors experienced by hosts and parasites. This special feature highlights recent insights into the ways parasites alter host phenotypes across a range of systems. Here, we contextualize how each contribution expands our knowledge of the role of parasites in driving individual variation in animal phenotypes. Looking to the future, we need to better understand how infection‐induced phenotypes fluctuate with natural variation in infection (e.g. infection intensity, coinfection) and whether studies in laboratory‐based environments provide strong proxies for host–parasite interactions in the wild. The time is ripe to acknowledge, critique and discuss the implications of infection on host phenotypes across taxonomic boundaries and biological levels of organization. Read the free Plain Language Summary for this article on the Journal blog.