Effect of environmental parameters on biodiversity of the fungal component in lithic Antarctic communities

Abstract

A wide sampling of rocks, colonized by microbial epi-endolithic communities, was performed along an altitudinal gradient from sea level to 3600 m asl and sea distance from the coast to 100 km inland along the Victoria Land Coast, Antarctica. Seventy-two rock samples of different typology, representative of the entire survey, were selected and studied using denaturing gradient gel electrophoresis to compare variation in fungal diversity according to environmental conditions along this altitudinal and sea distance transect. Lichenized fungi were largely predominant in all the samples studied and the biodiversity was heavily influenced even by minimal local variations. The n-MDS analysis showed that altitude and sea distance affect fungal biodiversity, while sandstone allows the communities to maintain high biodiversity indices. The Pareto-Lorenz curves indicate that all the communities analyzed are highly adapted to extreme conditions but scarcely resilient, so any external perturbation may have irreversible effects on these fragile ecosystems.

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.…”

“…The present work supplies a high-resolution inventory of microbial diversity and test if environmental constraints shape and structure diversity in these communities. These observations are important for development of tools to evaluate how communities respond to changes in global temperature especial in polar regions where the change is expected to be most pronounced (Selbmann et al, 2017). A metabarcoding approach was used to measure and describe microbial diversity in a relatively unbiased manner (Ji et al, 2013).…”

Sun exposure drives Antarctic cryptoendolithic community structure and composition

“…Airspaces within rocks offer to microbiota a protected and buffered microenvironment, allowing life to expand into different extreme conditions, i.e., hot and cold deserts or geothermal environments (Friedmann and Ocampo, 1976; Friedmann, 1982; Bell, 1993; Walker et al, 2005). Rocks are the prevailing substratum for life in the ice-free areas of Antarctica, supporting the highest standing biomass in the Antarctic ice-free desert and mountain tops emerging from the Polar Plateau (Cowan and Tow, 2004; Cary et al, 2010; Cowan et al, 2014; Selbmann et al, 2017). Endolithic microbial life represents the predominant recorded life-form in these areas (Nienow and Friedmann, 1993).…”

“…These self-supporting microbial ecosystems are composed of algae, mainly lichenized fungi, bacteria and cyanobacteria, many of which are endemic species to the regions (Nienow and Friedmann, 1993; Selbmann et al, 2005, 2008; Egidi et al, 2014). The high degree of adaptation and specialization in exploiting such ultimate niches makes these communities very susceptible to physical and climatic alteration (Selbmann et al, 2017) and any shift in microbial communities composition may serve as early-alarm system of environmental perturbation. Based on a substantial sampling of different typologies (volcanic and sedimentary) of colonised rocks in the Victoria Land, Antarctica, sandstone was determined to be the most suitable substratum for microbial endoliths, allowing them to spread and persist under stronger environmental pressure (Zucconi et al, 2016; Selbmann et al, 2017).…”

Metabolic responses in opposite sun-exposed Antarctic cryptoendolithic communities

“…Antarctic cryptoendolithic microorganisms have to face several stresses simultaneously and they need to concurrently develop survival strategies to address external conditions. A conspicuous number of studies have been performed on the adaptation strategies on black fungi from these communities, resulted highly resistant in terms of extremes of temperatures, acidity, osmotic stress and salinity, dehydration and irradiation (Sterflinger, 2006;Sterflinger et al, 2012;Gorbushina et al, 2003;Dadachova et al, 2007;Onofri et al, 2007;2008;Selbmann et al, 2017); besides, the stress-response mechanisms of whole metacommunity has not yet been investigated, either on metagenomic or metabolomic level. In this investigation, for the first time to our knowledge, metabolomics was successfully applied to Antarctic cryptoendolithic communities to start defining adaptation strategies adopted by these communities to survive in these harsh conditions.…”