Sampling strategies to assess microbial diversity of Antarctic cryptoendolithic communities

Describing the total biodiversity of an environmental metacommunity is challenging due to the presence of cryptic and rare species and incompletely described taxonomy. How many samples to collect is a common issue that faces ecologists when designing fieldwork sampling. Nowadays, high-throughput sequencing allows examination of large numbers of samples enabling comprehensive biodiversity assessments. In this study, we sought to estimate how the scale of sampling affects accuracy of community diversity description in the McMurdo Dry Valleys (Southern Victoria Land) in Antarctica accounted as the closest Martian analogue on Earth, exhibiting extreme conditions such as low temperatures, wide thermal fluctuations, low nutrient availability and high UV radiation. We found that sampling effort, based on accumulation curves and statistical analysis, had a considerable impact on assessing species richness and composition in these ecosystems, confirming that a sampling as large as nine rock specimens was necessary to detect almost all fungal species present, but was not sufficient to capture whole bacterial assemblage. The sampling would require approximately four times more effort (40 samples) for a comprehensive description of bacterial diversity. Our findings will be helpful to develop strategies to exhaustively describe the microbial diversity of Antarctic cryptoendolithic communities.