Genetic diversity in epichloid endophytes ofHordelymus europaeussuggests repeated host jumps and interspecific hybridizations

Abstract

Epichloid fungal endophytes (Epichloë and Neotyphodium spp.) are excellent model systems for studying speciation processes because of their variable life history traits that are linked to host grass fitness. Presumed jumps to new hosts and subsequent somatic hybridizations appear to be common among epichloid endophytes resulting in increased genetic variation upon which selection can act and speciation be initiated. In this study, we explored the endophyte diversity of a rare European native woodland grass species, Hordelymus europaeus, along a latitudinal transect covering the entire distribution range of H. europaeus. From 28 populations in six countries, isolates were sampled and molecularly characterized. Based on the sequences of tubB and tefA, six distinct epichloid taxa (interspecific hybrid or cryptic haploid species) were found, of which four were novel and two have been previously reported from this host. Of the novel endophytes, two were presumed to be interspecific hybrids and two of nonhybrid origin. While previously known endophytes of H. europaeus are seed-born and strictly asexual, one of the novel nonhybrid endophytes found in the glacial refugium of the Apennine peninsula reproduced sexually in cultured plants. This is the first case of a seed-borne, but sexually reproducing endophyte of this host. We discuss the origin, and possible ancestral species, of the six epichloid taxa using phylogenetic analyses. Repeated host jumps and somatic hybridizations characterize the diversity of the endophytes. To date, no other grass species is known to host a larger diversity of endophytes than H. europaeus.

Mutualistic fungal endophytes in theTriticeae- survey and description

“…), and therefore, no formal identification was ever achieved. More recently, however, Oberhofer and Leuchtmann () have described the genetic diversity of endophytes from Hordelymus europaeus after isolating a number of strains of the fungus. We are also aware of the report of an epichloid endophyte of the South American grass, H. comosum (Wilson et al ., ).…”

“…(Leuchtmann & Clay, ), Hordelymus sp. (Leyronas & Raynal, ; Moon et al ., ; Oberhofer & Leuchtmann, ), Hordeum spp. (Wilson et al ., , b, c; Mahmood et al ., ; Clement et al ., ; Youssef & Dugan, ; Nan & Li, ; Moon et al ., ; Wilson, ), Leymus sp.…”

Advances in Research on Epichloë endophytes in Chinese Native Grasses

“…Fortunately, DNA sequencing can help resolve this problem. To date, all putative Epichloë hybrids contain more than one copy of tubB and can be detected by allozyme analysis (Moon et al, 2004; Oberhofer and Leuchtmann, 2012; Leuchtmann et al, 2014; Iannone et al, 2015). For example, E. chisosa and E. coenophiala each have three copies (Leuchtmann et al, 2014), indicating they experienced multiple ancient hybridization events or subsequent gene duplication.…”

“…For example, E. chisosa and E. coenophiala each have three copies (Leuchtmann et al, 2014), indicating they experienced multiple ancient hybridization events or subsequent gene duplication. Oberhofer and Leuchtmann (2012) found four new Epichloë species in Hordelymus europaeus using five enzymes; two were interspecific hybrids and the others were of nonhybrid origin.…”

Bottom–up regulates top–down: the effects of hybridization of grass endophytes on an aphid herbivore and its generalist predator

“…In general, increased resistance to herbivores is viewed as the major mechanism by which systemic endophytes such as Neotyphodium and Epichloë provide benefits to their host grasses (Cheplick and Faeth 2009). That more than two thirds of Neotyphodium endophytes within and among grass species are hybrids has been used as de facto evidence that hybrid Neotyphodium are better adapted than non‐hybrid species and strains (Schardl and Craven 2003, Oberhofer and Leuchtmann 2012).…”