Fungal root symbionts of high-altitude vascular plants in the Himalayas

Milan Kotilínek,Inga Hiiesalu,Jan Altman,Martin Kopecký,Petr Šmilauer,Jiří Doležal,Miroslav Dvorský,Jiří Košnar,Marie Šmilauerová

doi:10.1038/s41598-017-06938-x

Abstract

Arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) form symbiotic relationships with plants influencing their productivity, diversity and ecosystem functions. Only a few studies on these fungi, however, have been conducted in extreme elevations and none over 5500 m a.s.l., although vascular plants occur up to 6150 m a.s.l. in the Himalayas. We quantified AMF and DSE in roots of 62 plant species from contrasting habitats along an elevational gradient (3400–6150 m) in the Himalayas using a combination of optical microscopy and next generation sequencing. We linked AMF and DSE communities with host plant evolutionary history, ecological preferences (elevation and habitat type) and functional traits. We detected AMF in elevations up to 5800 m, indicating it is more constrained by extreme conditions than the host plants, which ascend up to 6150 m. In contrast, DSE were found across the entire gradient up to 6150 m. AMF diversity was unimodally related to elevation and positively related to the intensity of AMF colonization. Mid-elevation steppe and alpine plants hosted more diverse AMF communities than plants from deserts and the subnival zone. Our results bring novel insights to the abiotic and biotic filters structuring AMF and DSE communities in the Himalayas.

Highlights

Arbuscular mycorrhizal fungi (AMF, sub-phylum Glomeromycotina1) are a crucial part of soil microbiota across major biomes and associate with the vast majority of terrestrial plant species[2]
Concentrated in the Alps while very few reports are from elevations above 5000 m a.s.l. from the Andes and the Himalayas. Those from Andes show a rapid decrease of AMF abundance in plant roots with increasing elevation[14, 22] while a study from an elevation gradient of 1990 to 4648 m a.s.l. in the Himalayas found no effect of elevation on AMF diversity, a significant effect on taxonomic composition and a negative effect on the abundance of AMF23
It remains unknown whether AMF and dark septate endophytes (DSE) occur in these extreme elevations and help vascular plants to cope with the harsh environmental conditions

Summary

Introduction

Arbuscular mycorrhizal fungi (AMF, sub-phylum Glomeromycotina1) are a crucial part of soil microbiota across major biomes and associate with the vast majority of terrestrial plant species[2]. Some of the most extreme conditions occur in high mountains where plants are limited by low temperature, desiccation and a short growing season[7]. The studies from the Himalayas were mainly targeted on spore populations of Glomeromycotina in the soil and showed the dominance of the Glomus[11, 23, 27] or Acaulospora[28] genera It remains unknown whether AMF and DSE occur in these extreme elevations and help vascular plants to cope with the harsh environmental conditions. We address the knowledge gap concerning AMF distribution along elevation gradients and its relation to the ecological properties of host plants by exploring the composition of mycorrhizal fungal communities associated with vascular plants growing in Ladakh, an arid high-elevation region in the NW Himalayas. A significant gap in knowledge exists about the functions of DSE in cold-stressed habitats, the phosphorus uptake is most probably enhanced by fine endophytes[31] and they could be surrogate mycorrhizas in these ecosystems[32]

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