Loss of fungal symbionts at the arid limit of the distribution range in a native Patagonian grass ? resource ecophysiological relations

CASAS, C; GUNDEL, P; DELIENS, E; IANNONE, L. J; GARCIA MARTINEZ, G; VIGNALE, M V; SCHNYDER, H

FUNCTIONAL ECOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2021

0269-8463

1. Crucial to our understanding of plant ecology is the consideration of the ecophysiological responses and constraints of plant-fungal symbioses throughout thenative distribution range of their host.2. We examined key eco-physiological roles of two co-occurring fungal symbionts[Epichloë endophytes and arbuscular mycorrhizal fungi (AMF)] in the endemic grassHordeum comosum across a wide bioclimatic gradient and contrasting grazingseverity. We sampled H. comosum plants along four humid-to-arid transects inPatagonia, Argentina, covering its entire distribution range and determined Epichloëpresence, AMF root colonization, nitrogen and phosphorus concentration, intrinsicwater use-efficiency (iWUE, the ratio of photosynthesis to stomatal conductance) and18O-enrichment of cellulose in shoots.3. Root colonization by AMF increased with Epichloë-presence. All plants hostedEpichloë in the humid range of the gradient, but symbioses occurrence decreasedtowards arid sites which also displayed severe grazing symptoms at site level.4. Symbiosis with Epichloë correlated positively with shoot nitrogen concentration inthe centre of the distribution range, and with shoot phosphorus concentration acrossthe entire distribution range.5. The site-level relationship of AMF colonization with 18O-enrichment and iWUEsuggested that mycorrhiza boosted stomatal conductance in humid environments butcurbed it in arid environments.6. While the interpretation of interactions and potential causalities from observationalstudies should be done with caution, this study demonstrates distinct correlations This article is protected by copyright. All rights reservedbetween plant-fungal symbiont associations and key resource parameters(phosphorus, nitrogen, and iWUE vs 18O-enrichment). Such correlations may suggestparticular functional roles for these symbionts in the ecology of their host plant.