Genetically-based trait variation within a foundation tree species influences a dominant bark lichen

Lichens frequently exhibit preference for tree species, however, tree traits that influence preference also vary intraspecifically. We hypothesized that genetically-based trait variation within Populus angustifolia affects bark lichens. To test this hypothesis, we quantified the lichen Xanthomendoza galericulata, and factors that could influence its distribution, including photosynthetically active radiation, bark roughness, bark condensed tannins, bark nitrogen and bole circumference on replicated P. angustifolia genotypes in a common garden. Several key findings emerged: (1) Tree genotype explained one-third of the variation in X. galericulata cover (broad-sense heritability: H2 = 0.32); (2) Bark roughness, condensed tannins and bole circumference varied among tree genotypes (H2 = 0.25–0.35); (3) Structural equation modelling suggested that bark roughness is the genetically-based trait that positively influences X. galericulata, and that bark roughness is positively influenced by bole circumference. This is the first study to link genetically-based trait variation in a foundation tree species to variation in the cover of a dominant lichen.