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. 2018 Jun 29:9:1392.
doi: 10.3389/fmicb.2018.01392. eCollection 2018.

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

Claudia Coleine  1   2 , Jason E Stajich  2 , Laura Zucconi  1 , Silvano Onofri  1 , Nuttapon Pombubpa  2 , Eleonora Egidi  3 , Ashley Franks  4   5 , Pietro Buzzini  6 , Laura Selbmann  1   7
Affiliations

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

Claudia Coleine et al. Front Microbiol. .

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.

Keywords: Antarctica; ITS meta-barcoding; endolithic communities; extremophiles; fungi.

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Figures

FIGURE 1
FIGURE 1
Map of the study area showing the location of the sampling sites. All locations visited were in Northern Victoria Land, except for Battleship Promontory, the only one visited in Southern Victoria Land. Victoria Land is pointed in the Antarctic continent.
FIGURE 2
FIGURE 2
(A) Cryptoendolithic lichen dominated community colonizing a sandstone sample at Battleship Promontory, Southern Victoria Land. (B) A diffuse endolithic colonization on and within rock at Mt Billing. (C) Sandstone outcrops at Battleship Promontory. (D) Laura Selbmann sampling at Mt New Zealand, Northern Victoria Land, during the XXVI Italian Campaign (2010–2011).
FIGURE 3
FIGURE 3
Relative abundances of the dominant fungal OTUs in the cryptoendolithic communities in Victoria Land, Antarctica. All relative abundances are based upon the sequences identified at the Phylum level.
FIGURE 4
FIGURE 4
Relative abundances of the dominant fungal OTUs in the cryptoendolithic communities in Victoria Land, Antarctica. All relative abundances are based upon sequences identified at the class level. Others include classes Agaricomycetes, Microbotryomycetes, Saccharomycetes, Taphrinomycetes, and Cystobasidiomycetes, with relative abundances ≤ 5%.
FIGURE 5
FIGURE 5
Heat map of the ‘core’ taxa relative frequency and UPGMA hierarchical clustering of samples. Values are scaled (log transformed) by taxon relative frequency across all samples. Frequencies are indicated by the color intensity: dark gray indicates a taxon with high relative frequency; white indicates absence and light gray represents low relative frequency. Both the ‘core’ OTUs and sites were clustered using a Bray–Curtis index.
FIGURE 6
FIGURE 6
Spearman’s correlation coefficients between the biodiversity indices calculated on 14 endolithic communities and altitudinal gradient. A significant correlation between fungal diversity and altitude was not found when R, H′, D, and J′ indices were considered (Spearman’s correlation coefficient, P-value > 0.1).
FIGURE 7
FIGURE 7
Pareto-Lorenz curves. The analysis was based on number of OTUs and their frequencies in the meta-barcoding profiles. Theoretical perfect evenness (perfect evenness line) is characterized by a curve close to the 45°C diagonal.
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