The evolution of juvenile susceptibility to infectious disease. Issue 1881 (20th June 2018)

• Record Type: Journal Article
• Authors: Ashby, Ben; Bruns, Emily
• Is Part Of: Proceedings. Volume 285:Issue 1881(2018)
• Publication Date: 2018-06-20
• Subjects: host–parasite -- age structure -- trade-off -- susceptibility -- development -- eco-evolutionary theory; Biology -- Periodicals; 570.5
• DOI: 10.1098/rspb.2018.0844
• Languages: English
• ISSNs: 0962-8452

Abstract

Abstract : Infection prior to reproduction usually carries greater fitness costs for hosts than infection later in life, suggesting selection should tend to favour juvenile resistance. Yet, juveniles are generally more susceptible than adults across a wide spectrum of host taxa. While physiological constraints and a lack of prior exposure can explain some of this pattern, studies in plants and insects suggest that hosts may trade off juvenile susceptibility against other life-history traits. However, it is unclear precisely how trade-offs shape the evolution of juvenile susceptibility. Here, we theoretically explore the evolution of juvenile susceptibility subject to trade-offs with maturation or reproduction, which could realistically occur due to resource allocation during development (e.g. prioritizing growth over immune defence). We show how host lifespan, the probability of maturation (i.e. of reaching the adult stage) and transmission mode affect the results. Our key finding is that elevated juvenile susceptibility is expected to evolve over a wide range of conditions, but should be lowest when hosts have moderate lifespans and an intermediate probability of reaching the adult stage. Our results elucidate how interactions between trade-offs and the epidemiological-demographic structure of the population can lead to the evolution of elevated juvenile susceptibility.