Biological crusts of serpentine and non-serpentine soils from the Barberton Greenstone Belt of South Africa

Climate and geography can influence biological soil crust (BSC) community composition, but local heterogeneity in variables such as soil characteristics or microclimate gradients can also impact cryptogamic diversity. Heavy metals and nutrient imbalances in serpentine soils are known to influence the distributions of higher plants, but cryptogamic species appear to be more tolerant of substrate. The aim of this study was to compare the cryptogamic composition of serpentine and non-serpentine soils by using integrative taxonomy, which combines morphological and DNA barcoding data, to determine how soil characteristics in combination with rainfall can influence BSC community composition. Samples from serpentine and non-serpentine soils were enumerated and total genomic DNA was isolated from the soil samples. Analyses of the 16S rRNA gene and ITS sequences were done using the quantitative insights into microbial ecology (QIIME) workflow to determine which eukaryotic microorganisms were present in the samples. Sixty genera from the Cyanophyceae (38), Chlorophyceae (10), Bacillariophyceae (6), Eustigmatophyceae (4), Trebouxiophyceae (1) and Xanthophyceae (1) classes were detected with this approach. Results confirm that algae and cyanobacteria are tolerant of most substrates and can even colonize environments with high levels of heavy metal and nutrient imbalances, if moisture is present. Genera such as Acaryochloris, Annamia, Brasilonema, Chrocosphaera, Halomicronema, Planktothricoides, Rubidibacter, and Toxopsis are reported for the first time for South African soil.