Effects of theEpichloëfungal endophyte symbiosis withSchedonorus pratensison host grass invasiveness

Abstract

Initial studies of grass–endophyte mutualisms using Schedonorus arundinaceus cultivar Kentucky-31 infected with the vertically transmitted endophyte Epichloë coenophiala found strong, positive endophyte effects on host-grass invasion success. However, more recent work using different cultivars of S. arundinaceus has cast doubt on the ubiquity of this effect, at least as it pertains to S. arundinaceus–E. coenophiala. We investigated the generality of previous work on vertically transmitted Epichloë-associated grass invasiveness by studying a pair of very closely related species: S. pratensis and E. uncinata. Seven cultivars of S. pratensis and two cultivars of S. arundinaceus that were developed with high- or low-endophyte infection rate were broadcast seeded into 2 × 2-m plots in a tilled, old-field grassland community in a completely randomized block design. Schedonorus abundance, endophyte infection rate, and co-occurring vegetation were sampled 3, 4, 5, and 6 years after establishment, and the aboveground invertebrate community was sampled in S. pratensis plots 3 and 4 years after establishment. Endophyte infection did not enable the host grass to achieve high abundance in the plant community. Contrary to expectations, high-endophyte S. pratensis increased plant richness relative to low-endophyte cultivars. However, as expected, high-endophyte S. pratensis marginally decreased invertebrate taxon richness. Endophyte effects on vegetation and invertebrate community composition were inconsistent among cultivars and were weaker than temporal effects. The effect of the grass–Epichloë symbiosis on diversity is not generalizable, but rather specific to species, cultivar, infection, and potentially site. Examining grass–endophyte systems using multiple cultivars and species replicated among sites will be important to determine the range of conditions in which endophyte associations benefit host grass performance and have subsequent effects on co-occurring biotic communities.

Seeding tallgrass prairie in monospecific patches promotes native species establishment and cover

“…The site was treated twice with glyphosate herbicide (Roundup, St. Louis, MO, U.S.A.) and cultivated and leveled with a Blecavator (Specialized Turf Equipment Company, Anderson, SC, U.S.A.) to create homogeneous bare soil conditions prior to seeding. Mean daily growing season temperatures (17.03 ± 0.21 ∘ C [SE]) and mean weekly total precipitation (15.86 ± 1.40 mm [SE]) for the area were similar among all study years (Shukla et al 2015).…”

Costs, Benefits, Parasites and Mutualists: The Use and Abuse of the Mutualism–Parasitism Continuum Concept forEpichloëFungi

“…However, it is not uncommon to see the same authors’ positions shifting through time (e.g. mutualism : Newman et al, 2003, Ryan et al, 2014, Shukla et al, 2015, Bastías et al, 2018), ( unclear/continuum/admits possibility : Hunt and Newman, 2005, Rasmussen et al, 2007, Antunes et al, 2008).…”

Direct and indirect effects of the fungal endophyte Epichloë uncinatum on litter decomposition of the host grass, Schedonorus pratensis

“…At the time the meta-analysis was performed, the preponderant hypothesis was that fungal alkaloids produced by endophyte symbionts which have shown deterrent effects on herbivores (see e.g., Clay 1988;Schardl et al 2007), would have a direct inhibitory effect on litter decomposition. However, as observed for the effects of endophytes on plant-herbivore interactions (Saikkonen et al 2010(Saikkonen et al , 2013aUeno et al 2016;Shukla et al 2015), effects on decomposition have proven to be highly variable with negative, neutral, or positive results depending on host species, partners' genotypes, and ecological conditions (Omacini et al 2004;Lemons et al 2005;Siegrist et al 2010;Gundel et al 2016;Mikola et al 2016). Apart from the alkaloids, endophytes have been associated with changes in plant biomass quality that could be also linked to litter decomposition.…”

“…With the same grass species, Lemons et al (2005) found that the exclusion of meso-invertebrates shifted the endophyte effect from decreasing to increasing the rate of litter decomposition. However, endophyte influence on invertebrates (although not necessarily involved in decomposition) associated to host plants has been variable depending on grass species and genotype, and the ecological conditions (see e.g., Rudgers and Clay 2008;Vesterlund et al 2011;Popay and Jensen 2005;Shukla et al 2015). Studies have revealed that symbiosis with leaf fungal endophytes affects abundance and structure of the soil microbial community associated with the rhizosphere of tall fescue plants (Buyer et al 2011;Rojas et al 2016).…”