DDR Experiments 2013

Diversity is often associated with the functional stability of ecological communities from microbes to macroorganisms. Understanding how diversity responds to environmental perturbations, and the consequences of this relationship for ecosystem function, are thus central challenges in microbial ecology. Unimodal diversity-disturbance relationships, in which maximum diversity occurs at intermediate levels of disturbance, have been predicted for ecosystems where life-history tradeoffs separate organisms along a disturbance gradient. However, empirical support for such peaked relationships in macrosystems is mixed, and few studies have explored these relationships in microbial systems. Here we use complex microbial microcosm communities to systematically determine diversity-disturbance relationships over a range of disturbance regimes. We observed a reproducible switch between community types, which gave rise to transient diversity maxima when community types were forced to mix. Communities showed reduced compositional stability when diversity was highest. To further explore these dynamics, we formulated a simple model that reveals specific regimes under which diversity maxima are stable. Together, our results show how both unimodal and non-unimodal diversity-disturbance relationships can be observed as a system switches between two distinct microbial community states; this process likely occurs across a wide range of spatially and temporally heterogeneous microbial ecosystems.

生物多样性通常与从微生物到大型生物的各类生态群落的功能稳定性密切相关。因此，阐明生物多样性如何响应环境扰动（environmental perturbation），以及该关联对生态系统功能的影响，是微生物生态学领域的核心研究挑战。已有理论预测，在那些通过生活史权衡沿扰动梯度对生物进行分选的生态系统中，会存在单峰型多样性-扰动关系（unimodal diversity-disturbance relationship），即生物多样性在中等扰动水平下达到峰值。然而，大型生态系统中这类单峰关系的实证研究结果并不一致，且鲜有研究在微生物系统中探究此类关联。本研究借助复杂的微生物微宇宙群落（microbial microcosm community），系统测定了不同扰动模式下的多样性-扰动关系。我们观测到群落类型间存在可重复的转换过程：当不同群落类型被迫混合时，会出现短暂的多样性峰值；当多样性处于最高水平时，群落的组成稳定性出现下降。为进一步探究这些动态机制，我们构建了一个简化模型，该模型揭示了多样性峰值能够保持稳定的特定扰动区间。综合来看，我们的研究结果阐明了：当系统在两种截然不同的微生物群落状态间转换时，既可观测到单峰型也可观测到非单峰型的多样性-扰动关系；这一过程大概率广泛存在于各类具有时空异质性的微生物生态系统中。