High diversity of fungal ecological groups from ice-free pristine and disturbed areas in the Fildes Peninsula, King George Island, Antarctica

Abstract

Ice-free areas are habitats for most of Antarctica's terrestrial biodiversity. Although fungal communities are an important element of these habitats, knowledge of their assemblages and ecological functions is still limited. Herein, we investigated the diversity, composition, and ecological functionality of fungal communities inhabiting sediments from ice-free areas across pristine and anthropogenically impacted sites in the Fildes Peninsula on King George Island, Antarctica. Samples were collected from both pristine and disturbed areas. We used the internal transcribed spacer (ITS1) region via Illumina sequencing of 34 sediment samples for fungal identification. The Ascomycota (14.6%) and Chytridiomycota (11.8%) were the most dominant phyla, followed by Basidiomycota (8.1%), Rozellomycota (7.0%), Mucoromycota (4.0%), while 34.9% of the fungal diversity remained unidentified. From a total of 1073 OTUs, 532 OTUs corresponded to 114 fungal taxa at the genus level, and 541 OTUs remained unassigned taxonomically. The highest diversity, with 18 genera, was detected at site A-3. At the genus level, there was no preference for either pristine or disturbed sites. The most widely distributed genera were Betamyces (Chytridiomycota), occurring in 29 of the 34 sites, and Thelebolus (Ascomycota), detected in 8 pristine sites and 7 disturbed sites. The Glomeraceae gen. incertae sedis was more common in disturbed sites. A total of 23 different ecological guilds were recorded, with the most abundant guilds being undefined saprotrophs, plant pathogens, plant saprotrophs, pollen saprotrophs, and endophytes. The fungal communities did not show significant differences between pristine and disturbed sites, suggesting that the anthropogenic impact is either not too intense or prolonged, that the spatial distance between the sampled sites is small, and/or that the environmental factors are similar. Although our study revealed a high fungal diversity with various ecological specializations within these communities, nearly one-third of the diversity could not be assigned to any specific taxonomic category. These findings highlight the need for further taxonomic research on fungal species inhabiting ice-free areas. Without identifying the species present, it is difficult to assess potential biodiversity loss due to environmental changes and/or human activities.

Fig 1. Sites sampled during the Antarctic Scientific Expedition (ECA59), Fildes Peninsula, King George Island, Antarctica.

(A) Map showing collecting sites; (B) and (C) Pictures of sampling S1 (pristine), (D) Picture of sampling S2 (disturbed), (E) Picture of sampling S3 (disturbed), (F) Picture of sampling S4 (disturbed), (G) Picture of sampling S5 (pristine), near Bellinghausen Glacier, and (H) Picture of sampling S6 near to Bellinghausen Glacier (pristine). ©OpenStreetMap contributors (2015); maps retrieved in September 2024 from https://planet.openstreetmap.org.

Fig 2. Relative abundance of fungal communities at the phylum level from coastal sediment from ice-free areas on the Fildes Peninsula, King Jorge Island, Antarctica.

For the site locations, see Fig 1. Relative abundance values < 0.1% were discarded.

Fig 3. Heatmap of the fungal communities at order level inhabiting coastal sediments from ice-free areas spanning pristine and disturbed sites in the Fildes Peninsula, King George Island, Antarctica.

Sites 1, 5, and 6 are pristine. Sites 2, 3, and 4 are disturbed. Relative abundance values < 0.1% were discarded.

Fig 4. Upset plot showing different number of genera across collecting sites in the Fildes Peninsula, King George Island, Antarctica.

Horizontal lines correspond to the total number of elements per sampling point and the various vertical lines represent the number of elements intercepted by the matrix. The black circles in the matrix indicate elements in common between the sampling points.

Fig 5. Relative abundance of fungal communities at the genus level across coastal sediments from pristine and disturbed sites on the Fildes Peninsula, King George Island, Antarctica.

Fungal genera are ordered according to their mean relative abundances. All genera with less than 10% of relative frequency are grouped into ‘Other’. Non taxonomically classified reads are named as ‘Unassigned’.

Fig 6. NMDS plot of fungal OTUs inhabiting coastal sediments from ice-free areas across pristine and disturbed sites in the Fildes Peninsula, King George Island, Antarctica based on the ITS1 sequences.

For the site locations, see Fig 1. Dots represent locations: Sites 1, 5, and 6 are pristine and Sites 2, 3, and 4 are disturbed. Samples are grouped according to the collecting sites.

Fig 7. Estimates of diversity indices of fungal communities in coastal sediments for each of the sites sampled on the Fildes Peninsula, King George Island, Antarctica.

(A) Shannon Index. (B) Simpson Index. Both diversity indices (97% sequence similarity) are delineated at the genus level.

Fig 8. Ecological associations of fungal communities inhabiting coastal sediments from ice-free areas in pristine and disturbed sites on the Fildes Peninsula, King George Island, Antarctica.

Samples from pristine and perturbed sites are depicted. The fungal taxa (OTUs) were submitted ecological guilds with the FUNGuild tool and the corresponding database. Guild output was distributed into individual guilds.