Temperature‐mediated local adaptation alters the symbiotic function in arbuscular mycorrhiza

Abstract

Variation in the symbiotic function of arbuscular mycorrhizal fungi (AM fungi) has been demonstrated among distinct biotic and abiotic interactions. However, there is little knowledge on how local temperature conditions influence the functional divergence of AM symbionts in alpine ecosystems. Here, we conduct a reciprocal inoculation experiment to explore the three-way interactions among plants, AM fungal inoculum and temperature at sites of contrasting elevation. Evidence of local adaptation of plant growth was found only under low temperature conditions, with no consistent local versus foreign effect found in AM fungal performance. The origin of either the plant or the inoculum relative to the temperature was important in explaining symbiotic function. Specifically, when inoculum and temperature were sympatric but allopatric to the plant, poor adaptation by the plant to the novel environment was clearly found under both temperature conditions. Further analysis found that the symbiotic function was inversely related to fungal diversity under high temperature conditions. These results suggest that local adaptation represents a powerful factor in the establishment of novel combinations of plant, inoculum and temperature, and confirms the importance of taking into account both biotic and abiotic interactions in the prediction of the response of symbionts to global environmental change.

Temperature‐mediated phylogenetic assemblage of fungal communities and local adaptation in mycorrhizal symbioses

“…Although no local adaptation was found in plant performance, plant fitness and mycorrhizal growth response did vary with temperature conditions and the geographical origin of the symbiotic partner in the present study. Similar results were found in our studies (Yang et al, ) on local adaptation of AM associations with Deyeuxia rosea in response to contrasting climate. These findings suggest that climate have altered the function of these plant symbionts, although the function differentiation was not imposed by local condition.…”

“…This divergence in fungal community composition may reflect interspecific variation in tolerance to the novel environment (Ji et al, ). Similar results were also found in some previous studies (Uibopuu et al, ; Ji et al, ; Yang et al, ). These findings support the assumption that plants are not passive participants in the colonization process, but rather they select AM fungal partners in response to different environmental conditions and plant requirements (Reinhardt, ).…”

“…MGR was negative in all the inoculation treatments in the present study. Both positive and negative effects were found in our previous studies in Tibet (Shi et al, ; Yang et al, ). The high phosphorus content of the soil substrate might largely account for the negative effect in the present study.…”

“…Response of AM fungi symbionts was usually defined by plant performance, AM fungal performance and symbiotic function. Total dry weights were used as surrogate measures of plant performance, root colonization (involving colonization by arbuscules and hyphae) and soil colonization (hyphal length density) as measures of AM fungal performance, and plant response to inoculation was defined by mycorrhizal growth responses (MGR) as a measure of symbiotic function (Smith and Smith, ; Yang et al, ). MGR values were calculated in terms of plant growth as 100[(AM‐NM)/NM], where AM is the total dry weight in an inoculated treatment and NM is mean total dry biomass of the corresponding uninoculated control (Cavagnaro et al, ).…”

“…Specifically, temperature is a strong selective pressure for many species (Hochachka and Somero, ; Bennett et al, ) and is an ecological variable that affects AM fungi (Helgason and Fitter, ). Some evidence for functional divergence was found in AM fungi from contrasting climatic origins that consistently and differentially altered plant growth (Antunes et al, ; Yang et al, ). However, more evidence is needed to identify how temperature can mediate functional outcomes in mycorrhizal symbioses and the phylogenetic relatedness of coexisting AM fungi in natural ecosystems.…”