The few Antarctic studies to date to have applied metabarcoding in Antarctica have primarily focused on microorganisms. In this study, for the first time, we apply high-throughput sequencing of environmental DNA to investigate the diversity of Embryophyta (Viridiplantae) DNA present in soil samples from two contrasting locations on Deception Island. The first was a relatively undisturbed site within an Antarctic Specially Protected Area at Crater Lake, and the second was a heavily human-impacted site in Whalers Bay. In samples obtained at Crater Lake, 84% of DNA reads represented fungi, 14% represented Chlorophyta and 2% represented Streptophyta, while at Whalers Bay, 79% of reads represented fungi, 20% represented Chlorophyta and < 1% represented Streptophyta, with ~1% of reads being unassigned. Among the Embryophyta we found 16 plant operational taxonomic units from three Divisions, including one Marchantiophyta, eight Bryophyta and seven Magnoliophyta. Sequences of six taxa were detected at both sampling sites, eight only at Whalers Bay and two only at Crater Lake. All of the Magnoliophyta sequences (flowering plants) represent species that are exotic to Antarctica, with most being plausibly linked to human food sources originating from local national research operator and tourism facilities.

Molecular phylogenetic reconstructions support the monophyly of Pylaisiaceae. The family includes Calliergonella Loeske, Homomallium (Schimp.) Loeske, Pseudohygrohypnum Kanda, Pylaisia Schimp., 2 further genera formerly placed in Hypnaceae, Ectropothecium Mitt. and Vesicularia (Müll.Hal.) Müll.Hal., as well as several species of Hypnum Hedw. recently considered to belong to Stereodon (Brid.) Rchb. Calliergonella, Ectropothecium, Pylaisia, Pseudohygrohypnum and Vesicularia, are monophyletic based on the present data, whereas Homomallium is resolved as a paraphyletic sister group to Pylaisia. Stereodon is excluded from Pylaisiaceae since its type species, S. callichrous (Brid.) Lindb., is resolved outside the Pylaisiaceae clade. Based on morphological and molecular evidence 2 new genera, Roaldia and Buckia, are described to accommodate the former Hypnum (Stereodon) species H. revolutum (Mitt.) Lindb. and H. vaucheri Lesq. respectively. The genus Pseudostereodon (Broth.) M.Fleisch. is re-established to accommodate Hypnum procerrimum Molendo. Morphological descriptions and illustrations of distinctive characters in these 3 taxa are provided and lectotypes for 2 names are designated. New distributional data is also provided for Roaldia new to Guatemala. A key to the genera of Pylaisiaceae is presented.

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.