Islands in the sand : are all hypolithic microbial communities the same?

• Published in: FEMS Microbiology Ecology
• Main Authors: Lebre, Pedro H., Bottos, Eric, Makhalanyane, Thulani P., Hogg, Ian D., Cowan, Don A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press 2021
• Subjects: Core community; Functional variability; Dispersal limitation; Phylogenetic turnover; Small-scale heterogeneity; Hypolithon; East Antarctica; McMurdo Dry Valleys; Taylor Valley; New Harbour; Antarc*; Antarctica
• Online Access: http://hdl.handle.net/2263/79414; https://doi.org/10.1093/femsec/fiaa216

Hypolithic microbial communities (hypolithons) are complex assemblages of phototrophic and heterotrophic organisms associated with the ventral surfaces of translucent minerals embedded in soil surfaces. Past studies on the assembly, structure and function of hypolithic communities have tended to use composite samples (i.e. bulked hypolithic biomass) with the underlying assumption that samples collected from within a ‘homogeneous’ locality are phylogenetically homogeneous. In this study, we question this assumption by analysing the prokaryote phylogenetic diversity of multiple individual hypolithons: i.e. asking the seemingly simple question of ‘Are all hypolithons the same’? Using 16S rRNA gene-based phylogenetic analysis of hypolithons recovered for a localized moraine region in the Taylor Valley, McMurdo Dry Valleys, Antarctica, we demonstrate that these communities are heterogeneous at very small spatial scales (<5 m). Using null models of phylogenetic turnover, we showed that this heterogeneity between hypolithons is probably due to stochastic effects such as dispersal limitations, which is entirely consistent with the physically isolated nature of the hypolithic communities (‘islands in the sand’) and the almost complete absence of a liquid continuum as a mode of microbial transport between communities. SUPPLEMENTARY FIGURES : FIGURE S1. Moraine pavement sampling location at New Harbour, Lower Taylor Valley, East Antarctica. FIGURE S2. Barplot of mean relative abundance of the 10 most abundant genera the hypolith communities. FIGURE S3. Distribution of genera as a function of number of samples in which they are present. Red dots represent taxa that are present in more than 90% of samples and are therefore considered “generalist” taxa. FIGURE S4. Significant differences in relative abundances of phyla across hypolith communities. Community clusters are colored according to the color-coding used throughout this study: Red- Group A; Green – Group B; Blue – Group C; Purple – Group D. FIGURE S5. Decay of ...