Abstract
Strictly vertically transmitted (hereditary) Epichloë spp. fungal endophytes are symbionts with cool-season pooid host grasses. Such endophytes may increase host invasiveness in the non-native, introduced ranges. However, because costs and benefits for the host can vary with the growing conditions, the endophyte may become locally or temporally extinct when costs outweigh benefits. Our long-term field experiment involved the introduction of seven Schedonorus pratensis (meadow fescue) cultivars hosting Epichloë uncinata endophyte, which represent host-grass populations differing in genetic backgrounds and Epichloë infection frequencies, to an unmanaged old field. In the first 6 years, the host grasses persisted but did not become invasive in the plant community, regardless of their endophyte infection frequency. Subsequently, we hypothesized that increasing nutrient availability would decrease endophyte costs and thus increase the host’s success and abundance. We fertilized half of the plots for four additional years and re-examined S. pratensis invasiveness. We predicted that increased nutrient availability would increase S. pratensis abundance and E. uncinata frequency and concentration, as well as decrease plant community diversity, relative to unfertilized plots. Fertilization increased endophyte concentrations in three low-endophyte host populations. However, E. uncinata did not enable S. pratensis populations to achieve high abundance or to reduce plant community diversity in the old field, with or without fertilization. Thus, nutrient availabililty and host invasiveness appear to be decoupled in this study system.
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Our complete curated raw data are publicly archived in the Scholars Portal Dataverse (Hager et al. 2021). https://doi.org/10.5683/SP2/QJUUCN
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Acknowledgements
We gratefully acknowledge the assistance of K. Bolton, A. Patchett, Newman lab field crews, P. Purvis, and the Guelph Turfgrass Institute field maintenance crew. We thank S. Saari for providing the Schedonorus pratensis seed used to establish the experiment, and two reviewers for providing constructive comments on the manuscript.
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This research was funded by the Natural Sciences and Engineering Research Council of Canada (303775), Canada Foundation for Innovation (32598), and the Ontario Ministry of Agriculture, Food, and Rural Affairs.
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Designed the experiment: JAN, KAY, HAH; performed fieldwork: HAH, KS, JLR; performed qPCR: JLR; analysed data: HAH, JLR; wrote the manuscript: HAH, JLR; edited manuscript: all authors.
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Hager, H.A., Roloson, J.L., Shukla, K. et al. Effects of nutrient addition on endophyte-associated grass invasion in a long-term, old-field community experiment. Oecologia 196, 469–482 (2021). https://doi.org/10.1007/s00442-021-04933-8
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DOI: https://doi.org/10.1007/s00442-021-04933-8