Sun Exposure Shapes Functional Grouping of Fungi in Cryptoendolithic Antarctic Communities

Abstract

Antarctic cryptoendolithic microbial communities dominate ice-free areas of continental Antarctica, among the harshest environments on Earth. The endolithic lifestyle is a remarkable adaptation to the exceptional environmental extremes of this area, which is considered the closest terrestrial example to conditions on Mars. Recent efforts have attempted to elucidate composition of these extremely adapted communities, but the functionality of these microbes have remained unexplored. We have tested for interactions between measured environmental characteristics, fungal community membership, and inferred functional classification of the fungi present and found altitude and sun exposure were primary factors. Sandstone rocks were collected in Victoria Land, Antarctica along an altitudinal gradient from 834 to 3100 m a.s.l.; differently sun-exposed rocks were selected to test the influence of this parameter on endolithic settlement. Metabarcoding targeting the fungal internal transcribed spacer region 1 (ITS1) was used to catalogue the species found in these communities. Functional profile of guilds found in the samples was associated to species using FUNGuild and variation in functional groups compared across sunlight exposure and altitude. Results revealed clear dominance of lichenized and stress-tolerant fungi in endolithic communities. The main variations in composition and abundance of functional groups among sites correlated to sun exposure, but not to altitude.

Altitude and fungal diversity influence the structure of Antarctic cryptoendolithic Bacteria communities

“…water availability, average rock temperature and sun exposure) may be more important determinants of community diversity and structure. Indeed, sun exposure, which likely influences temperature and water availability as well as generating visible difference in texture and weathering properties (McKay and Friedmann, 1985), has been implicated in shaping composition and distribution of functional groups of fungi in Antarctic endolithic communities (Coleine et al, 2018b). Further analysis of functional roles and capabilities of endolithic bacteria can clarify relationships between physical-chemical parameters and the possible functional redundancy in bacterial assemblages associated to these communities.…”

Fungal evolution: major ecological adaptations and evolutionary transitions

“…Zoosporic fungi can propagate easily through semi‐melted ice surfaces, and even modern icy environments, such as periglaciar soils or arctic seas, contain an unsuspected abundance and diversity of zoosporic lineages (Freeman et al, ; Hassett & Gradinger, ; Rämä et al, ). Even cryptoendolithic communities in antarctic dry valleys, commonly regarded as one of the harshest environments on Earth (Scalzi et al, ), harbour a considerably diverse community spanning several hundreds of detectable OTUs that include mostly lichen‐forming Ascomycota, black fungi and yeast forms of both Ascomycota and Basidiomycota (Coleine et al, ).…”

“…Saitoella is another yeast genus within this subphylum that was isolated from soil in the Himalayas and from insect galleries in leaves (Goto et al, ; Kurtzman & Robnett, ). Environmental studies show that the genus Taphrina , typically a plant biotrophic pathogen, is also a member of antarctic soil communities (Coleine et al, ). Saitoella is phylogenetically related to the biotrophic plant pathogens Protomyces and Taphrina (Sugiyama, Hosaka & Suh, ; Kurtzman & Sugiyama, ), and the three genera share a low intron content, compact genome and similar gene numbers with Saccharomyces .…”

Sun exposure drives Antarctic cryptoendolithic community structure and composition

“…The observed shift in community composition correlated to sun exposure was also confirmed by Non-Metric Multidimensional scaling (NMDS) analysis, which organizes data into 2-D spatial graphs by reducing dimensionality. An apparent gradient in abundance and community composition in response to sun exposure was previously observed in Coleine et al (2018b), where authors investigated biodiversity and composition of functional groups of fungi in Antarctic endolithic communities and reported the absence of any correlation with altitude and sea distance, while a remarkable variability was observed considering the sun exposure parameter.…”

“…2.17) The effect of this abiotic parameter was tested displaying changes in communities’ composition with Non-Metric Multidimensional Scaling (NMDS) based both on abundance data (bands intensity), calculating Bray-Curtis distance index and presence–absence data, using Jaccard index (Clarke, 1993). Means of abundance data were square-root transformed and analyses were carried out with 999 permutations as described in Coleine et al (2018b). NMDS were plotted using the combined occurrence and abundance data of the three replicates from each site.…”