Department of Ecology, Evolution and Behavior, University of Minnesota, Twin Cities, Saint Paul, MN 55108, USA.
Department of Biological Sciences, University of Denver, Denver, CO 80208, USA.
FEMS Microbiol Ecol. 2020 Sep 1;96(9). doi: 10.1093/femsec/fiaa122.
Mountains have a long history in the study of diversity. Like macroscopic taxa, soil microbes are hypothesized to be strongly structured by montane gradients, and recently there has been important progress in understanding how microbes are shaped by these conditions. Here, we summarize this literature and synthesize patterns of microbial diversity on mountains. Unlike flora and fauna that often display a mid-elevation peak in diversity, we found a decline (34% of the time) or no trend (33%) in total microbial diversity with increasing elevation. Diversity of functional groups also varied with elevation (e.g. saprotrophic fungi declined 83% of the time). Most studies (82%) found that climate and soils (especially pH) were the primary mechanisms driving shifts in composition, and drivers differed across taxa-fungi were mostly determined by climate, while bacteria (48%) and archaea (71%) were structured primarily by soils. We hypothesize that the central role of soils-which can vary independently of other abiotic and geographic gradients-in structuring microbial communities weakens diversity patterns expected on montane gradients. Moving forward, we need improved cross-study comparability of microbial diversity indices (i.e. standardizing sequencing) and more geographic replication using experiments to broaden our knowledge of microbial biogeography on global gradients.
山脉在多样性研究中有着悠久的历史。与宏观分类群一样，土壤微生物被假设受到山地梯度的强烈影响，最近在理解微生物如何受到这些条件的影响方面取得了重要进展。在这里，我们总结了这方面的文献，并综合了山地微生物多样性的模式。与通常在海拔中间出现多样性峰值的植物区系和动物区系不同，我们发现随着海拔的升高，总微生物多样性呈下降趋势（34%的时间）或没有趋势（33%）。功能群的多样性也随海拔而变化（例如，腐生真菌的多样性下降了 83%）。大多数研究（82%）发现气候和土壤（特别是 pH 值）是导致组成变化的主要机制，驱动因素因分类群而异——真菌主要受气候决定，而细菌（48%）和古菌（71%）主要受土壤决定。我们假设土壤在结构微生物群落方面的核心作用——它可以独立于其他非生物和地理梯度而变化——削弱了在山地梯度上预期的多样性模式。展望未来，我们需要改进微生物多样性指数的跨研究可比性（即标准化测序），并通过实验在更多的地理区域进行复制，以扩大我们对全球梯度上微生物生物地理学的认识。
