Infection in patchy populations: contrasting pathogen invasion success and dispersal at varying times since host colonisation

Repeated extinction and recolonisation events generate a landscape of host populations that vary in their time since colonisation. Within this dynamic landscape, pathogens that excel at invading recently colonised host populations are not necessarily those that perform best in host populations at or near their carrying capacity, potentially giving rise to divergent selection for pathogen traits that mediate the invasion process. Rarely, however, has this contention been empirically tested. Using Daphnia magna, we explored how differences in the colonisation history of a host population influences the invasion success of different genotypes of the pathogen Pasteuria ramosa. By partitioning the pathogen invasion process into a series of individual steps, we show that each pathogen optimises invasion differently when encountering host populations that vary in their time since colonisation. All pathogen genotypes were more likely to establish successfully in recently colonised host populati...