Marine bacteria exhibit a bipolar distribution.. marine metagenome

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. 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 employing the "Everything is everywhere" with no dispersal limitation scenario. Specifically, marine bacteria displayed bipolar distributions (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 "Rapoport's 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. Deposition to NCBI SRA via ISAcreator 1.6 tool (www.isatab.sf.net), compliant with MIMARKS requirements.

微生物广域扩散假说（microbial cosmopolitan dispersion hypothesis）常被用于阐释由海洋水团高连通性与广泛扩散能力所驱动的分布格局，但该假说至今尚未经过严格的实证检验。本研究依托全球海洋细菌数据集与迭代矩阵随机化模拟，结果表明海洋细菌的扩散限制程度显著高于基于“万物无处不在”且无扩散限制情景构建的零模型预测结果。具体而言，仅在南北两极出现且其余区域无分布的两极分布类群，其占比显著低于零模型的预期值。此外，本研究观测到同时分布于两个半球的类群数量少于零模型预期，而仅分布于单个半球的类群数量则多于预期。上述趋势均随比对生境的地理距离增大、环境相似度升高，与零假设的偏差进一步扩大。本研究的荟萃分析证实了细菌多样性的纬度梯度格局：低纬度区域物种丰富度更高，而向极地逐渐降低；热带区域的细菌类群在低纬度区域的纬度分布范围更窄，在高纬度区域则相对更宽，这符合颇具争议的“拉波波特法则（Rapoport's rule）”宏观生态格局。综合来看，本研究结果表明，细菌的生物地理格局更接近于大型生物的分布规律，而扩散限制而非仅环境选择，可能在其中发挥了关键作用。那些提供关键生态系统服务的微生物（尤其是极地区域的微生物），其分布可能同样面临着与动植物生物多样性所受胁迫一致的威胁，包括环境胁迫、气候变暖和生境质量退化。本数据集已通过ISAcreator 1.6工具上传至NCBI序列读取档案（NCBI SRA，www.isatab.sf.net），符合MIMARKS规范要求。