Does hybridization of endophytic symbionts in a native grass increase fitness in resource‐limited environments?

Abstract

Hybridization is common among plants, animals and microbes. However, the ecological consequences of hybridization for microbes are far less understood than for plants and animals. For symbiotic Epichloë fungi, hybridization is widespread and may augment the well-known benefits of the endophytes to their grass hosts, especially in stressful environments. We tested the hybrid fitness hypothesis (HFH) that hybrid endophytes enhance fitness in stressful environments relative to non-hybrid endophytes. In a long-term field experiment, we monitored growth and reproduction of hybrid-infected (H+), non-hybrid infected (NH+), naturally endophyte free (E-) plants and those plants from which the endophyte had been experimentally removed (H- and NH-) in resource-rich and resource-poor environments. Infection by both endophyte species enhanced growth and reproduction. H+ plants outperformed NH+ plants in terms of growth by the end of the experiment, supporting HFH. However, H+ plants only outperformed NH+ plants in the resource-rich treatment, contrary to HFH. Plant genotypes associated with each endophyte species had strong effects on growth and reproduction. Our results provide some support the HFH hypothesis but not based upon adaptation to stressful environments. Our results reinforce the notion of a complex interplay between endophyte and plant genotype and environmental factors that determine fitness of the symbiotum.

Fungal endophyte infection increases tall fescue's survival, growth, and flowering in a reconstructed prairie

“…Grass‐endophyte symbioses, similar to the one in tall fescue, occur in 20–30% of grass species globally, including both native and other agronomic grasses, across diverse ecological habitats (Leuchtmann ; Clay ). Though endophyte effects may be more variable in native species of cool‐season grasses compared to agronomic species (Saikkonen et al ; Saikkonen ; Faeth ; Malinowski & Belesky ), similar symbiotic benefits are sometimes observed, including increased fitness, abiotic stress tolerance, negative effects on competitors, and herbivore deterrence (Malinowski & Belesky ; Crawford et al ; Vázquez‐de‐Aldana et al , ; Santangelo et al ; Casas et al ; Faeth et al ). Therefore, grass‐fungal endophyte symbioses may play a role in determining reconstruction and restoration success across a wide range of grassland types.…”

Alkaloid Contents in Epichloë Endophyte-Infected Elymus tangutorum Sampled along an Elevation Gradient on the Qinghai-Tibetan Plateau

“…The association between cool-season grasses and Epichloё endophytes can promote host plant growth [10,11], increase plant nutrient uptake [12,13], inhibit plant pathogen growth [14][15][16], increase host fitness and improve host tolerance to biotic (e.g., pests, disease, animal grazing) [15][16][17][18], and abiotic factors (e.g., waterlogging, drought, cold, soil acidity, mineral imbalance stresses) [13,[19][20][21][22]. There are four major classes of alkaloids produced by this symbiosis; indole-diterpenoids (e.g., lolitrem B), pyrrolizidine (e.g., lolines), pyrrolopyrazine (e.g., peramine) and ergot alkaloids [23].…”