| Autor: |
Hager HA; Department of Biology, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada. hhager@uoguelph.ca., Roloson JL; Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada., Shukla K; Department of Chemistry and Biology, Ryerson University, Toronto, ON, M5B 2K3, Canada., Yurkonis KA; Department of Biology, University of North Dakota, Grand Forks, ND, 58202-9019, USA., Newman JA; Department of Biology, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada. |
| Abstrakt: |
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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