Biogeography of plant root‐associated fungal communities in the North Atlantic region mirrors climatic variability

Abstract

Aim Polar and alpine ecosystems appear to be particularly sensitive to increasing temperatures and the altered precipitation patterns linked to climate change. However, little is currently known about how these environmental drivers may affect edaphic organisms within these ecosystems. In this study, we examined communities of plant root‐associated fungi (RAF) over large biogeographical scales and along climatic gradients in the North Atlantic region in order to gain insights into the potential effects of climate variability on these communities. We also investigated whether selected fungal traits were associated with particular climates. Locations Austria, Scotland, Mainland Norway, Iceland, Jan Mayen and Svalbard. Taxa Root fungi associated with the ectomycorrhizal and herbaceous plant Bistorta vivipara. Methods DNA metabarcoding of the ITS1 region was used to characterize the RAF of 302 whole plant root systems, which were analysed by means of ordination methods and linear modelling. Fungal spore length, width, volume and shape, as well as mycelial exploration type (ET) of ectomycorrhizal (ECM) basidiomycetes were summarized at a community level. Results The RAF communities exhibited strong biogeographical structuring, and both compositional variation as well as fungal species richness correlated with annual temperature and precipitation. In accordance with general island biogeography theory, the least species‐rich RAF communities were found on Jan Mayen, a remote and small island in the North Atlantic Ocean. Fungal spores tended to be more elongated with increasing latitude. We also observed a climate effect on which mycelial ET was dominating among the ectomycorrhizal fungi. Main conclusions Both geographical and environmental variables were important for shaping root‐associated fungal communities at a North Atlantic scale, including the High Arctic. Fungal OTU richness followed general biogeographical patterns and decreased with decreasing size and/or increasing isolation of the host plant population. The probability of possessing more elongated spores increases with latitude, which may be explained by a selection for greater dispersal capacity among more isolated host plant populations in the Arctic.

Can root-associated fungi mediate the impact of abiotic conditions on the growth of a High Arctic herb?

“…Our finding that fungal community composition did not affect plant measurements could perhaps originate from strong environmental filtering on root-associated fungal communities 36 . High physicochemical heterogeneity of arctic soils corresponds with distinct RAF community composition observed at different scales [5][6][7]37 . On the one hand, a set of physicochemical conditions that translates into ecological niches selects species that can withstand and thrive in these locality-specific combinations of factors.…”

“…On the one hand, a set of physicochemical conditions that translates into ecological niches selects species that can withstand and thrive in these locality-specific combinations of factors. Among them principally abiotic factors were shown to affect fungal parameters 37,[81][82][83] . Relationships between variables established based on the literature search (Table 3) were, in general, poorly reflected in the results of our models.…”

“…To test our hypotheses, we selected alpine bistort Bistorta vivipara (L.) Delarbre ( Polygonaceae ), a model plant to study root-associated microbial communities in alpine 6,[31][32][33][34][35] and arctic habitats 7,19,[36][37][38][39][40] . Bistorta vivipara is a common, long-lived perennial herb in the northern hemisphere.…”

Community composition of arctic root-associated fungi mirrors host plant phylogeny

“…The roots were put in 50 mL Falcon tubes with 2000 μL CTAB and homogenized and extracted as described in Botnen et al . ( 2019 ). In short, a modified CTAB protocol was used (Murray and Thompson 1980 ; Gardes and Bruns 1993 ), and the DNA extracts were further cleaned using the E.Z.N.A soil kit (Omega Bio‐Tek, Norcross, GA).…”

Mycena species can be opportunist-generalist plant root invaders

“…(2014) 272 595 sequences from Mundra et al ., (2015) 249 888 from Davey et al . (2015), and 132912 from Botnen et al . (2019), making a total of 1095997 ITS1 sequences for clustering into OTUs/ASVs.…”