ABSTRACT

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.

中文翻译：

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沙中的岛屿：所有的次石质微生物群落都一样吗？

摘要

寡聚微生物群落（hypolithons）是光养和异养生物的复杂组合，与埋在土壤表面的半透明矿物的腹面有关。过去关于下石器社区的组装，结构和功能的研究倾向于使用复合样本（即大量的下石器生物质），其基本假设是从“均质”局部收集的样本在系统发育上是同质的。在这项研究中，我们通过分析多个个体hypolithons的原核生物系统发育多样性来质疑这一假设：即，提出一个看似简单的问题：“所有hypolithons是否都相同？”？使用基于16S rRNA基因的系统发育分析对南极州麦克默多干旱谷泰勒河谷局部冰ora地区所发现的亚伏兰进行了系统发育分析，我们证明了这些社区在非常小的空间尺度（<5 m）上是异质的。使用系统发生转换的无效模型，我们表明，次石器之间的这种异质性可能是由于诸如散布限制等随机效应造成的，这完全与次石器群落的物理隔离性质（“沙中岛”）一致，并且几乎完全没有液体连续体作为社区之间微生物运输的一种方式。