Different cottonwood genotypes support different aboveground fungal communities: A genetic basis to community structure

Understanding the factors influencing the distributions of species and composition of communities is a major focus in ecology.  There is an emerging body of evidence indicating that intraspecific genetic variation in foundation plant species can affect the distribution of associated species, communities and ecosystem processes.  Many of these communities and ecosystem processes correlate with tree traits such phytochemistry, suggesting potential mechanisms connecting tree genes to their community phenotypes.  Here we utilize a common garden containing replicated genotypes of narrowleaf cottonwood (Populus angustifolia) to measure the influence of genetics on the associated fungal community, including lichen, a leaf pathogen (Marssonina) and twig endophytes.  We also measured twig condensed tannin, leaf condensed tannin, and leaf phenolic glycoside concentrations as potential links between cottonwood genes and associated fungi.  Our results demonstrate 1) lichen cover, Marssonina abundance, and endophyte abundance differ significantly among tree genotypes, 2) endophyte community composition varies significantly among tree genotypes, and 3) phytochemistry does not predict fungal abundance or community composition, indicating that it is not a significant link between tree genes and fungi.  These findings demonstrate a significant genetic component to fungal community structure that appears to be unrelated to two major types of cottonwood phytochemicals.  Tree genetics could prove to be a major overlooked factor structuring a wide range of fungal communities.  Although covariance between plant genetics and fungal pathogens is well documented, no studies have incorporated the taxonomic and functional diversity of fungi reported here.