CONICET | Buscador de Institutos y Recursos Humanos

Many host-plants exhibit genetic variation in resistance to pathogens; however,little is known about the extent to which genetic variation in pathogen resistance influencesother members of the host-plant community, especially arthropods at higher trophic levels. Weaddressed this knowledge gap by using a common garden experiment to examine whether gen-otypes of Populus trichocarpa varied in resistance to a leaf-blistering pathogen, Taphrina sp.,and in the density of web-building spiders, the dominant group of predatory arthropods. Inaddition, we examined whether variation in spider density was explained by variation in thedensity and size of leaf blisters caused by Taphrina. We found that P. trichocarpa genotypesexhibited strong differences in their resistance to Taphrina and that P. trichocarpa genotypesthat were more susceptible to Taphrina supported more web-building spiders, the dominantgroup of predatory arthropods. We suspect that this result is caused by blisters increasing theavailability of suitable habitat for predators, and not due to variation in herbivores becauseincluding herbivore density as a covariate did not affect our models. Our study highlights anovel pathway by which genetic variation in pathogen resistance may affect higher trophiclevels in arthropod communities.