Antarctic eukaryotic soil diversity of the Prince Charles Mountains revealed by high-throughput sequencing

Studies of Antarctic eukaryotes have been hampered by their morphological conservatism, small size and the logistical constraints of remote field work, resulting in a deficiency of baseline biodiversity information about Antarctic terrestrial environments. The application of high throughput sequencing (HTS) in metataxonomic approaches is a promising alternative. Here, we apply such HTS approaches to the hitherto largely unsurveyed micro-eukaryote fauna of the Prince Charles Mountains, East Antarctica. We sequenced 18S rDNA amplicons of twelve Antarctic bulk-soil DNA extracts, retrieved from three sampling regions (four bulk-soil extracts per sampling region). After isolating eukaryotic phylotypes with a stringent filtering approach and initial network visualization, we firstly used rarefied data to compare four α diversity metrics between the three regions. Weighted and unweighted inter-sample UniFrac distances were then used for β diversity comparisons among rarefied data. Furthermore, we analysed the distribution of the most abundant phylotypes and phylotype groups. Lastly, we checked the validity of species-level taxonomic assignments using different sets of reference data in conjunction with two different taxonomy assignment approaches. Phylotype numbers in un-rarefied data compared across regions were lowest for Mount Menzies (73°S; 3330 m), intermediate at Mawson Escarpment (73°S; 807 m) and highest at Lake Terrasovoje (70°S; 173 m), likely due to low biological load at the higher latitude and elevation inland sites. Analysis of rarefied data was difficult due to low sequence coverage particularly from Mount Menzies, but indicated differences in Shannon diversity between Mawson Escarpment and Lake Terrasovoje. PCoA of weighted UniFrac distances between samples from Mawson Escarpment and Lake Terrasovoje indicated changes in community composition in relation to elevation of the sampling locations. The most widespread phylotypes were fungal, followed by non-algal protists. Species-level assignments included known Antarctic taxa in all sampling regions. We show that HTS can provide a rapid survey of the micro-eukaryote fauna to provide baseline biodiversity information for remote, harsh, and hitherto largely unsurveyed environments in the Prince Charles Mountains.