The best for the guest: high Andean nurse cushions of Azorella madreporica enhance arbuscular mycorrhizal status in associated plant species

Abstract

Positive interactions between cushion plant and associated plants species in the high Andes of central Chile should also include the effects of fungal root symbionts. We hypothesized that higher colonization by arbuscular mycorrhizal (AM) fungi exists in cushion-associated (nursling) plants compared with conspecific individuals growing on bare ground. We assessed the AM status of Andean plants at two sites at different altitudes (3,200 and 3,600 ma.s.l.) in 23 species, particularly in cushions of Azorella madreporica and five associated plants; additionally, AM fungal spores were retrieved from soil outside and beneath cushions. 18 of the 23 examined plant species presented diagnostic structures of arbuscular mycorrhiza; most of them were also colonized by dark-septate endophytes. Mycorrhization of A. madreporica cushions showed differences between both sites (68% and 32%, respectively). In the native species Hordeum comosum, Nastanthus agglomeratus, and Phacelia secunda associated to A. madreporica, mycorrhization was six times higher than in the same species growing dispersed on bare ground at 3,600 ma.s.l., but mycorrhiza development was less cushion dependent in the alien plants Cerastium arvense and Taraxacum officinale at both sites. The ratio of AM fungal spores beneath versus outside cushions was also 6:1. The common and abundant presence of AM in cushion communities at high altitudes emphasizes the importance of the fungal root symbionts in such situations where plant species benefit from the microclimatic conditions generated by the cushion and also from well-developed mycorrhizal networks.

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

“…Even if high-altitude mountain regions harbour relatively diverse AMF communities, it remains unclear exactly which host plants are colonized and which AMF taxa are able to persist in extreme environments. In addition to AMF, dark-septate endophytes (DSE) are often recorded in the roots of high-elevation plants 14, 15 , where they can partially or completely replace AMF 16 . DSE comprises a miscellaneous group of root-inhabiting fungi with notoriously obscure taxonomic and functional affinities.…”

Size-Mediated Interaction between a Cushion Species and Other Non-cushion Species at High Elevations of the Hengduan Mountains, SW China

“…Cushion species can provide a thermal buffer, hydric refuge, islands of fertility and microorganism associations for establishment and recruitment of other non-cushion species (e.g., Cavieres et al, 2006; Yang et al, 2010; Casanova-Katny et al, 2011; Molina-Montenegro et al, 2015). Thus, by increasing species richness, cushion species play an important role in enhancing the diversity of harsh alpine environments at community level both globally and regionally (Cavieres and Badano, 2009; Cavieres et al, 2014; Chen et al, 2015).…”

Communities of Putative Ericoid Mycorrhizal Fungi Isolated from Alpine Dwarf Shrubs in Japan: Effects of Host Identity and Microhabitat

“…The structure of ERM is characterized by hyphal coils formed in the epidermal cells of the extremely thin “hair roots” of hosts. While ERM is widespread in temperate regions, it is particularly dominant in the dwarf shrub vegetation of alpine and arctic regions (7, 16, 39, 59). Mineralization and decomposition rates in these regions are extremely low due to low temperatures, and, thus, most of the nitrogen in soil exists in organic forms that are unavailable to most plants (33).…”