Disease-initiated trophic cascades are modulated by genetic variation in plant enemy resistance

Background/Question/Methods

Disease-causing pathogens can have profound impacts on communities and ecosystems, especially when their hosts are foundation species.  Host genotype influences resistance to pathogens, but its role in modulating pathogens’ indirect effects on associated communities has not been studied. 

Results/Conclusions

Under experimental field conditions, we found that leaf pathogens caused a 50% decline in the richness and abundance of insect herbivores and their predators on tree genotypes susceptible to disease compared to tree genotypes resistant to disease.  Furthermore, in the presence of pathogens, associated declines in herbivory were greater on insect susceptible tree genotypes relative to insect resistant tree genotypes.  We conclude that genetic-based interactions among highly interactive species (plants, pathogens and herbivores) can produce trophic cascades that redefine community structure and food webs.