Abstract
We report a metabarcoding study documenting the fungal taxa in 29 barren fellfield soils sampled from along a 1,650 km transect encompassing almost the entire maritime Antarctic (60–72°S) and the environmental factors structuring the richness, relative abundance, and taxonomic composition of three guilds and growth forms. The richness of the lichenised fungal guild, which accounted for 19% of the total fungal community, was positively associated with mean annual surface air temperature (MASAT), with an increase of 1.7 operational taxonomic units (OTUs) of lichenised fungi per degree Celsius rise in air temperature. Soil Mn concentration, MASAT, C:N ratio, and pH value determined the taxonomic composition of the lichenised guild, and the relative abundance of the guild was best predicted by soil Mn concentration. There was a 3% decrease in the relative abundance of the saprotrophic fungal guild in the total community for each degree Celsius rise in air temperature, and the OTU richness of the guild, which accounted for 39% of the community, was negatively associated with Mn concentration. The taxonomic composition of the saprotrophic guild varied with MASAT, pH value, and Mn, NH4+-N, and SO42− concentrations. The richness of the yeast community, which comprised 3% of the total fungal community, was positively associated with soil K concentration, with its composition being determined by C:N ratio. In contrast with a similar study in the Arctic, the relative abundance and richness of lichenised fungi declined between 60°S and 69°S, with those of saprotrophic Agaricales also declining sharply in soils beyond 63°S. Basidiomycota, which accounted for 4% of reads, were much less frequent than in vegetated soils at lower latitudes, with the Ascomycota (70% of reads) being the dominant phylum. We conclude that the richness, relative abundance, and taxonomic composition of guilds and growth forms of maritime Antarctic soil fungi are influenced by air temperature and edaphic factors, with implications for the soils of the region as its climate changes during the 21st century.
Highlights
Recent studies have described the fungi present in continental Antarctic soils and identified the factors controlling their activities and frequencies (Chan et al, 2013; Dreesens et al, 2014; Archer et al, 2019; Canini et al, 2020; Sannino et al, 2020), our understanding of the fungi inhabiting maritime Antarctic soils is still in its infancy
The responses of soil fungal communities to the steep changes in environmental conditions across the maritime Antarctic – notably the significant reductions in surface air temperatures at higher latitudes in the region – have been foci for several studies (Lawley et al, 2004; Yergeau et al, 2007a; Dennis et al, 2012; Newsham et al, 2016). Edaphic factors such as soil pH, Mn concentration, and C:N ratio account for variation in community composition (Yergeau et al, 2007a; Dennis et al, 2012; Newsham et al, 2016), the species richness of all soil fungi in the region is primarily determined by mean annual surface air temperature (MASAT), with reductions in the total number of fungal species in colder soils at higher latitudes (Newsham et al, 2016)
Lichenised Fungi Multiple regression models using forward selection indicated that the relative abundance of lichenised fungi in the total fungal community was best predicted by soil Mn concentration, with a positive association between the abundance of the guild and this variable (t = 3.25, p = 0.003; Figure 5A)
Summary
Recent studies have described the fungi present in continental Antarctic soils and identified the factors controlling their activities and frequencies (Chan et al, 2013; Dreesens et al, 2014; Archer et al, 2019; Canini et al, 2020; Sannino et al, 2020), our understanding of the fungi inhabiting maritime Antarctic soils is still in its infancy This knowledge gap is significant, since fungi have pivotal roles in all terrestrial ecosystems as decomposers of organic matter and as partners in symbioses, and notably the lichen symbiosis, which is widespread in maritime Antarctica (Øvstedal and Smith, 2001). Increases in the abundances of yeasts might be anticipated in soils at higher latitudes in the region, since these are apparently the only fungi that can be isolated from soils in the McMurdo Dry Valleys in the continental Antarctic (Atlas et al, 1978), considered to be among some of the most hostile environments for life on Earth
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