We investigated the role of spatial structure between two competing pathogens for a single host. Evolutionary outcomes depend on the ecological forces acting on a population. One of the driving ecological forces influencing evolutionary dynamics is competition. Many competition models assume that populations are well-mixed, but increasingly it has been shown that populations occur in spatially structured environments with limited dispersal abilities. For infectious diseases, theoretical studies predict that spatial host population structure impacts life-history strategies of pathogens by selecting for lower infectivity. However, we lack empirical studies that consider the distribution of multiple pathogen genotypes in spatially structured environments. Bacteriophages are an excellent model system for observing competitive dynamics. In this work, we investigated the effects of spatial structure on pathogen life-history strategies using a joint experimental and theoretical approach.
Results/Conclusions
By competing two lytic bacteriophages of the host Pseudomonas syringae in experimental microhabitats, ranging from well-mixed to spatially structured environments, we show that the weaker phage competitor is able to persist in spatially structured environments. We further developed a spatially explicit individual-based model that incorporates key aspects of phage life cycles to examine how changes in phenotype affects fitness across different environments. Our integrated approach allows us to explore the possible mechanisms underlying the differences in behavior.