Soil Fungal Diversity and Ecology Assessed Using DNA Metabarcoding along a Deglaciated Chronosequence at Clearwater Mesa, James Ross Island, Antarctic Peninsula

Abstract

We studied the fungal diversity present in soils sampled along a deglaciated chronosequence from para- to periglacial conditions on James Ross Island, north-east Antarctic Peninsula, using DNA metabarcoding. A total of 88 amplicon sequence variants (ASVs) were detected, dominated by the phyla Ascomycota, Basidiomycota and Mortierellomycota. The uncommon phyla Chytridiomycota, Rozellomycota, Monoblepharomycota, Zoopagomycota and Basidiobolomycota were detected. Unknown fungi identified at higher hierarchical taxonomic levels (Fungal sp. 1, Fungal sp. 2, Spizellomycetales sp. and Rozellomycotina sp.) and taxa identified at generic and specific levels (Mortierella sp., Pseudogymnoascus sp., Mortierella alpina, M. turficola, Neoascochyta paspali, Penicillium sp. and Betamyces sp.) dominated the assemblages. In general, the assemblages displayed high diversity and richness, and moderate dominance. Only 12 of the fungal ASVs were detected in all chronosequence soils sampled. Sequences representing saprophytic, pathogenic and symbiotic fungi were detected. Based on the sequence diversity obtained, Clearwater Mesa soils contain a complex fungal community, including the presence of fungal groups generally considered rare in Antarctica, with dominant taxa recognized as cold-adapted cosmopolitan, endemic, saprotrophic and phytopathogenic fungi. Clearwater Mesa ecosystems are impacted by the effects of regional climatic changes, and may provide a natural observatory to understand climate change effects over time.

Keywords: Antarctica; environmental DNA; extremophiles; fungi; metabarcoding; taxonomy.

Figure 1

Satellite images (a,b) (obtained in Google Earth Pro, 2019). (a) Antarctica with the northern Antarctic Peninsula inside the red rectangle; (b) The western part of James Ross Island inside the red rectangle; (c) Clearwater Mesa with colored stars representing Site 1 (64°01′16.5″ S; 57°43′49.6″ W), site 2 (64°01′53.5″ S; 57°40′47.0″ W), Site 3 (64°02′03.6″ S; 57°40′05.9″ W) and Site 4 (64°02′09.5″ S; 57°39′22.1″ W) on James Ross Island. Photo c taken by Natacha Lopez. Yellow line represents the distances between the sites sampled: a = 650 m, b = 2700 m, c = 640 m, d = 730 m and e = 50 m.

Figure 2

Venn diagram showing the distribution of fungal amplicon sequence variants (ASVs) across the four soil samples obtained at Clearwater Mesa, James Ross Island, north-east Antarctic Peninsula. In the key: green represents the dominant taxa, blue those of intermediate abundance and orange the rare taxa.