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Abstract Foliar fungal endophytes are ubiquitous plant symbionts that can affect plant growth and reproduction via their roles in pathogen and stress tolerance, as well as plant hormonal signaling. Despite their importance, we have a limited understanding of how foliar fungal endophytes respond to varying environmental conditions such as nutrient inputs. The responses of foliar fungal endophyte communities to increased nutrient deposition may be mediated by the simultaneous effects on within‐host competition as well as the indirect impacts of altered host population size, plant productivity, and plant community diversity and composition. Here, we leveraged a 7‐yr experiment manipulating nitrogen, phosphorus, potassium, and micronutrients to investigate how nutrient‐induced changes to plant diversity, plant productivity, and plant community composition relate to changes in foliar fungal endophyte diversity and richness in a focal native grass host,Andropogon gerardii. We found limited evidence of direct effects of nutrients on endophyte diversity. Instead, the effects of nutrients on endophyte diversity appeared to be mediated by accumulation of plant litter and plant diversity loss. Specifically, nitrogen addition is associated with a 40% decrease in plant diversity and an 11% decrease in endophyte richness. Although nitrogen, phosphorus, and potassium addition increased aboveground live biomass and decreased relativeAndropogoncover, endophyte diversity did not covary with live plant biomass orAndropogoncover. Our results suggest that fungal endophyte diversity within this focal host is determined in part by the diversity of the surrounding plant community and its potential impact on immigrant propagules and dispersal dynamics. Our results suggest that elemental nutrients reduce endophyte diversity indirectly via impacts on the local plant community, not direct response to nutrient addition. Thus, the effects of global change drivers, such as nutrient deposition, on characteristics of host populations and the diversity of their local communities are important for predicting the response of symbiont communities in a changing global environment.
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Species diversity of fungal endophytes across a stress gradient for plants
Summary Foliar fungal endophytes are one of the most diverse guilds of symbiotic fungi found in the photosynthetic tissues of every plant lineage, but it is unclear how plant environments and leaf resource availability shape their diversity.We explored correlations between leaf nutrient availability and endophyte diversity amongPinus muricataandVaccinium ovatumplants growing across a soil nutrient gradient spanning a series of coastal terraces in Mendocino, California.Endophyte richness decreased in plants with higher leaf nitrogen‐to‐phosphorus ratios for both host species, but increased with sodium, which may be toxic to fungi at high concentrations. Isolation frequency, a proxy of fungal biomass, was not significantly predicted by any of the same leaf constituents in the two plant species.We propose that stressed plants can exhibit both low foliar nutrients or high levels of toxic compounds, and that both of these stress responses predict endophyte species richness. Stressful conditions that limit growth of fungi may increase their diversity due to the suppression of otherwise dominating species. Differences between the host species in their endophyte communities may be explained by host specificity, leaf phenology, or microclimates.
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- Award ID(s):
- 1725797
- PAR ID:
- 10452649
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- New Phytologist
- Volume:
- 228
- Issue:
- 1
- ISSN:
- 0028-646X
- Page Range / eLocation ID:
- p. 210-225
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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