Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, USA.
ISME J. 2013 Nov;7(11):2069-79. doi: 10.1038/ismej.2013.93. Epub 2013 Jun 6.
Spatial turnover in the composition of biological communities is governed by (ecological) Drift, Selection and Dispersal. Commonly applied statistical tools cannot quantitatively estimate these processes, nor identify abiotic features that impose these processes. For interrogation of subsurface microbial communities distributed across two geologically distinct formations of the unconfined aquifer underlying the Hanford Site in southeastern Washington State, we developed an analytical framework that advances ecological understanding in two primary ways. First, we quantitatively estimate influences of Drift, Selection and Dispersal. Second, ecological patterns are used to characterize measured and unmeasured abiotic variables that impose Selection or that result in low levels of Dispersal. We find that (i) Drift alone consistently governs ∼25% of spatial turnover in community composition; (ii) in deeper, finer-grained sediments, Selection is strong (governing ∼60% of turnover), being imposed by an unmeasured but spatially structured environmental variable; (iii) in shallower, coarser-grained sediments, Selection is weaker (governing ∼30% of turnover), being imposed by vertically and horizontally structured hydrological factors;(iv) low levels of Dispersal can govern nearly 30% of turnover and be caused primarily by spatial isolation resulting from limited exchange between finer and coarser-grain sediments; and (v) highly permeable sediments are associated with high levels of Dispersal that homogenize community composition and govern over 20% of turnover. We further show that our framework provides inferences that cannot be achieved using preexisting approaches, and suggest that their broad application will facilitate a unified understanding of microbial communities.
生物群落组成的空间转换受（生态）漂变、选择和扩散的支配。常用的统计工具不能定量估计这些过程，也不能识别施加这些过程的非生物特征。为了研究分布在华盛顿州东南部汉福德场址无约束含水层两个地质截然不同的地层中的地下微生物群落，我们开发了一种分析框架，主要通过两种方式推进生态理解。首先，我们定量估计漂变、选择和扩散的影响。其次，生态模式用于描述施加选择或导致扩散水平低的测量和未测量的非生物变量。我们发现：(i) 漂变单独始终支配群落组成空间转换的约 25%；(ii) 在更深、更细粒的沉积物中，选择作用很强（支配约 60%的转换），由一个未测量但空间结构的环境变量施加；(iii) 在较浅、较粗粒的沉积物中，选择作用较弱（支配约 30%的转换），由垂直和水平结构的水文因素施加；(iv) 低水平的扩散可以支配近 30%的转换，主要是由细粒和粗粒沉积物之间有限交换导致的空间隔离造成的；(v) 高渗透性沉积物与高水平的扩散有关，扩散会使群落组成均匀化并支配超过 20%的转换。我们进一步表明，我们的框架提供了使用现有方法无法得出的推断，并表明其广泛应用将有助于对微生物群落的统一理解。
