Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA 02543, USA.
Proc Natl Acad Sci U S A. 2013 Feb 5;110(6):2342-7. doi: 10.1073/pnas.1212424110. Epub 2013 Jan 16.
The microbial cosmopolitan dispersion hypothesis often invoked to explain distribution patterns driven by high connectivity of oceanographic water masses and widespread dispersal ability has never been rigorously tested. By using a global marine bacterial dataset and iterative matrix randomization simulation, we show that marine bacteria exhibit a significantly greater dispersal limitation than predicted by our null model using the "everything is everywhere" tenet with no dispersal limitation scenario. Specifically, marine bacteria displayed bipolar distributions (i.e., species occurring exclusively at both poles and nowhere else) significantly less often than in the null model. Furthermore, we observed fewer taxa present in both hemispheres but more taxa present only in a single hemisphere than expected under the null model. Each of these trends diverged further from the null expectation as the compared habitats became more geographically distant but more environmentally similar. Our meta-analysis supported a latitudinal gradient in bacterial diversity with higher richness at lower latitudes, but decreased richness toward the poles. Bacteria in the tropics also demonstrated narrower latitudinal ranges at lower latitudes and relatively larger ranges in higher latitudes, conforming to the controversial macroecological pattern of the "Rapoport rule." Collectively, our findings suggest that bacteria follow biogeographic patterns more typical of macroscopic organisms, and that dispersal limitation, not just environmental selection, likely plays an important role. Distributions of microbes that deliver critical ecosystem services, particularly those in polar regions, may be vulnerable to the same impacts that environmental stressors, climate warming, and degradation in habitat quality are having on biodiversity in animal and plant species.
微生物世界主义分散假说经常被用来解释由海洋水团的高连通性和广泛的扩散能力驱动的分布模式，但从未经过严格的检验。通过使用全球海洋细菌数据集和迭代矩阵随机化模拟，我们表明，海洋细菌的扩散限制比我们使用无扩散限制情景的“万物无处不在”原则的零模型预测的要大得多。具体来说，海洋细菌的两极分布（即，仅在两极出现而不在其他地方出现的物种）明显比零模型中少。此外，我们观察到在两个半球都存在的分类群比零模型中少，而仅在一个半球存在的分类群比零模型中多。随着比较的栖息地变得更远离地理距离但更相似的环境，这些趋势与零模型的差异进一步扩大。我们的荟萃分析支持细菌多样性的纬度梯度，即低纬度的丰富度较高，但随着向两极的增加而减少。热带地区的细菌在较低的纬度也表现出较窄的纬度范围，而在较高的纬度则相对较大，这符合有争议的宏观生态学模式“拉波波特法则”。总的来说，我们的发现表明，细菌遵循的生物地理模式更类似于宏观生物，而扩散限制，而不仅仅是环境选择，可能起着重要作用。提供关键生态系统服务的微生物的分布，特别是在极地地区的微生物分布，可能容易受到环境胁迫、气候变暖以及生境质量退化对动物和植物物种生物多样性的相同影响。
