Host-pathogen interactions and variation in disease prevalence: Implications for host demography

1) Background/Question/Methods: Given that pathogens are prevalent across all ecosystems, an individual’s reproductive success and survival will depend on its ability to resist infection. Natural populations have been shown to support considerable diversity in resistance, and theory predicts that under pathogen-imposed selection variation in resistance is maintained by allocation costs with susceptible individuals having higher fitness in the absence of disease.  Thus far the empirical evidence supporting costs of resistance as a mechanism that maintains resistance variation has remained mixed. Environmental variation across the landscape and variable rates of gene flow may play a key role in how variation in resistance is maintained, and hence on host demography. Here, my aim is to understand how host evolutionary potential and pathogen imposed selection vary across the landscape and what the consequences are for host demography. For this purpose, I’ve analyzed long term data on host population size and disease prevalence in the Plantaga lanceolata-Podosphaera plantagins interaction in the Åland Islands, SW Finland.

2) Results/Conclusions The results show that the strength of pathogen imposed selection varies across the landscape, in a spatially structured manner, suggesting that environmental variation plays a key role in mediating host-pathogen interactions. The results highlight the importance of studying host-pathogen dynamics across multiple populations to truly understand what the consequences of infection are for the host.