Antarctic Cryptoendolithic Fungal Communities Are Highly Adapted and Dominated by Lecanoromycetes and Dothideomycetes

Abstract

Endolithic growth is one of the most spectacular microbial adaptations to extreme environmental constraints and the predominant life-form in the ice-free areas of Continental Antarctica. Although Antarctic endolithic microbial communities are known to host among the most resistant and extreme-adapted organisms, our knowledge on microbial diversity and composition in this peculiar niche is still limited. In this study, we investigated the diversity and structure of the fungal assemblage in the cryptoendolithic communities inhabiting sandstone using a meta-barcoding approach targeting the fungal Internal Transcribed Sequence region 1 (ITS1). Samples were collected from 14 sites in the Victoria Land, along an altitudinal gradient ranging from 1,000 to 3,300 m a.s.l. and from 29 to 96 km distance to coast. Our study revealed a clear dominance of a ‘core’ group of fungal taxa consistently present across all the samples, mainly composed of lichen-forming and Dothideomycetous fungi. Pareto-Lorenz curves indicated a very high degree of specialization (F0 approximately 95%), suggesting these communities are highly adapted but have limited ability to recover after perturbations. Overall, both fungal community biodiversity and composition did not show any correlation with the considered abiotic parameters, potentially due to strong fluctuations of environmental conditions at local scales.

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

“…Biodiversity analysis of species richness (from 50 to 287) and Shannon's index (ranging from 1.1 to 4.24) (Table 1) confirmed that Antarctic microbial endolithic communities harbour relatively low diversity (see also Archer et al, 2017;Selbmann et al, 2017;Coleine et al, 2018a), compared with temperate microbial biotopes, which typically have values of Shannon's index between 6 and 7 (Dunbar et al, 2000). The β diversity across the 14 sampled sites was measured with a Jaccard index and the contribution of altitude and sea distance in shaping the bacterial communities was estimated using an multiplelinear regression on distance matrices analysis.…”

“…In this study, 16S rDNA gene amplicon sequencing was used to profile bacterial composition and to test the effects on bacterial assemblages of environmental parameters (altitude and sea distance) and fungal diversity, already investigated in Coleine et al (2018a), on bacterial assemblage. 16S rDNA gene metabarcoding produced a total of 864 425 quality-filtered reads, ranging from 32 481 up to 75 174 reads per sample (Table 1).…”

“…It has been reported that lichen species and individual thallus traits may influence associated bacterial diversity (Bates et al, 2011;Cardinale et al, 2012); therefore, we also tested the effects of fungal community composition (reported in Coleine et al, 2018a) in our samples, where lichen species represent 91% of fungal community, on bacterial counterpart. The results clearly indicate a significant correlation between fungal and bacterial biodiversity (Fig.…”

“…Sequencing, bioinformatics, and molecular ecological analysis of this study was performed in same manner as previous study (Coleine et al, 2018a) and description of the materials and methods is available in Appendix S1. The amplicon sequence data and metadata have been deposited in the NCBI Sequence Read Archive database under BioProject Accession Number PRJNA379160.…”

“…In this study, we investigated diversity and community composition of bacterial assemblages associated to cryptoendolithic lichendominated communities in 42 samples collected over a wide area along Victoria Land (Continental Antarctica), exposed to different degrees of environmental pressures due to variation in altitude and sea distance. The fungal community makeup of these same samples was recently described by Coleine et al (2018a). The present work supplies a high-resolution inventory of microbial diversity and test if environmental constraints shape and structure diversity in these communities.…”