Nutrient deposition is a pervasive global change that is altering plant biodiversity and ecosystem function across the globe. The response of plant-associated symbiont communities, like leaf fungal endophytes, to nutrient deposition may be mediated by the simultaneous loss of plant biodiversity, increases in plant productivity, and shifts in plant community composition. Here, we use a decade-long experiment manipulating nitrogen, phosphorus, and potassium + micronutrients to investigate how nutrient-induced changes to plant diversity, productivity, and community composition mediate leaf fungal endophyte diversity response of focal host, Andropogon gerardii.
Results/Conclusions
The effects of nutrients on endophyte diversity (Inverse Simpson’s Index) were mediated by plant diversity but unaffected by plant productivity, and plant composition. Specifically, we found that nitrogen addition reduced plant diversity by 40% and resulted in an 11% decrease in endophyte diversity. Although we observed increased productivity with phosphorus addition and reduced Andropogon cover and productivity with potassium addition, phosphorus and potassium + micronutrients did not impact plant diversity or endophyte diversity. Thus, our results suggest that fungal endophyte diversity within a focal host is maintained by dispersal and successful colonization of fungi from the plants in the local neighborhood of a focal individual, independent of plant productivity, a surrogate for potential propagule pressure and the abundance of focal host Andropogon. However, plant neighborhood diversity explained only ~16% of the variation in endophyte diversity, suggesting that much of the variability in the leaf endophyte community may be driven by stochastic long-distance colonization events, environmental variability, or genetic variability in Andropogon hosts in addition to neighborhood colonization processes. Our results reinforce the need to integrate plant community context within studies exploring symbiont response to global change.