Environmental factors affect the distribution of two Epichloë fungal endophyte species inhabiting a common host grove bluegrass (Poa alsodes)

Abstract

Aim The endophyte Epichloë alsodes, with known insecticidal properties, is found in a majority of Poa alsodes populations across a latitudinal gradient from North Carolina to New York. A second endophyte, E. schardlii var. pennsylvanica, with known insect‐deterring effects, is limited to a few populations in Pennsylvania. We explored whether such disparate differences in distributions could be explained by selection from biotic and abiotic environmental factors. Location Along the Appalachian Mountains from North Carolina to New York, USA. Taxon Fungi. Methods Studied correlations of infection frequencies with abiotic and biotic environmental factors. Checked endophyte vertical transmission rates and effects on overwintering survival. With artificial inoculations for two host populations with two isolates per endophyte species, tested endophyte–host compatibility. Studied effects of isolates on host performances in greenhouse experiment with four water‐nutrients treatments. Results Correlation analysis revealed positive associations of E. alsodes frequency with July Max temperatures, July precipitation, and soil nitrogen and phosphorous and negative associations with insect damage and soil magnesium and potassium. Plants infected with E. alsodes had increased overwintering survival compared to plants infected with E. schardlii or uninfected (E−) plants. Artificial inoculations indicated that E. alsodes had better compatibility with a variety of host genotypes than did E. schardlii. The experiment with reciprocally inoculated plants grown under different treatments revealed a complexity of interactions among hosts, endophyte species, isolate within species, host plant origin, and environmental factors. Neither of the endophyte species increased plant biomass, but some of the isolates within each species had other effects on plant growth such as increased root:shoot ratio, number of tillers, and changes in plant height that might affect host fitness. Main conclusion In the absence of clear and consistent effects of the endophytes on host growth, the differences in endophyte‐mediated protection against herbivores may be the key factor determining distribution differences of the two endophyte species.

Epichloë Fungal Endophytes—From a Biological Curiosity in Wild Grasses to an Essential Component of Resilient High Performing Ryegrass and Fescue Pastures

“…Hybrids are likely to contain more genetic variation, which may lead to improved adaptation to biotic and abiotic stresses of their host plants [ 10 , 29 , 30 , 56 , 61 ]. There is also a general hypothesis that interspecific hybridisation provides greater genetic variation and hence, a wider adaptation range in stressful environments than intraspecific hybridisation [ 56 , 62 ]. However, when comparing hybrid and non-hybrid Epichloë strains on controlled environments, there is no evidence of niche expansion of Epichloë hybrid-infected plants [ 63 ].…”

Ontogenetic and trans‐generational dynamics of a vertically transmitted fungal symbiont in an annual host plant in ozone‐polluted settings

“…Comparing the performance of endophyte-colonized plants with endophyte-free plants has been the most common experimental approach to understand the mechanisms influencing the endophyte incidence in plant populations. Very few studies have focused on underlying factors that affect the transmission process and persistence of the endophyte (Gundel et al, 2008;Gundel, Rudgers, & Ghersa, 2011;Ravel et al, 1997;Shymanovich & Faeth, 2019). Inefficiencies in the vertical transmission process mean that a host plant can produce a variable proportion of both endophyte-colonized and endophyte-free offspring (Afkhami & Rudgers, 2008;Gibert & Hazard, 2013;Gundel, Rudgers, et al, 2011).…”

Ecotype‐specific effects of fungal endophytes on germination responses of seeds of the South American wild forage grass Bromus auleticus

“…Our results show that the presence of fungal endophytes affected germination parameters of B. auleticus seeds in response to temperature and water availability but more importantly, these effects depended on the population origin and seemed to be related with the environmental characteristics of collection site. Considering that endophyte‐specific effects may result from partners' co‐adaptation to the prevailing environmental conditions (Shymanovich & Faeth, 2019), our results suggest that these differential effects associated to population origin and site of collection are the expression of an endophyte‐mediated ecotypic response.…”

“…For several indigenous grasses from Argentina (i.e., B. auleticus , Bromus pictus ) it has been reported that endophytes can promote plant growth (Iannone & Cabral, 2006; Iannone, Pinget, et al, 2012; Novas et al, 2003), mycorrhizal colonisation (Novas et al, 2005, 2009, 2011; Vignale et al, 2016, 2018), and to confer resistance to pathogens in B. auleticus (Iannone et al, 2017; Vignale et al, 2013). Despite these overall benefits, it is unclear if endophyte mediated effects on grasses of South America can vary in different populations and contribute to plant adaptation to the local environmental conditions as reported in Festuca arizonica (Sullivan & Faeth, 2008) and Poa alsodes (Shymanovich & Faeth, 2019).…”