Becraft Eric D, Wood Jason M, Cohan Frederick M, Ward David M
Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, United States.
Department of Biology, University of North Alabama, Florence, AL, United States.
Front Microbiol. 2020 Feb 24;11:77. doi: 10.3389/fmicb.2020.00077. eCollection 2020.
Previous analyses have shown how diversity among unicellular cyanobacteria inhabiting island-like hot springs is structured relative to physical separation and physiochemical differences among springs, especially at local to regional scales. However, these studies have been limited by the low resolution provided by the molecular markers surveyed. We analyzed large datasets obtained by high-throughput sequencing of a segment of the photosynthesis gene from samples collected in hot springs from geothermal basins in Yellowstone National Park, Montana, and Oregon, all known from previous studies to contain populations of A/B'-lineage . The fraction of identical sequences was greater among springs separated by <50 km than among springs separated by >50 km, and springs separated by >800 km shared sequence variants only rarely. Phylogenetic analyses provided evidence for endemic lineages that could be related to geographic isolation and/or geochemical differences on regional scales. Ecotype Simulation 2 was used to predict putative ecotypes (ecologically distinct populations), and their membership, and canonical correspondence analysis was used to examine the geographical and geochemical bases for variation in their distribution. Across the range of Oregon and Yellowstone, geographical separation explained the largest percentage of the differences in distribution of ecotypes (9.5% correlated to longitude; 9.4% to latitude), with geochemical differences explaining the largest percentage of the remaining differences in distribution (7.4-9.3% correlated to magnesium, sulfate, and sulfide). Among samples within the Greater Yellowstone Ecosystem, geochemical differences significantly explained the distribution of ecotypes (6.5-9.3% correlated to magnesium, boron, sulfate, silicon dioxide, chloride, and pH). Nevertheless, differences in the abundance and membership of ecotypes in Yellowstone springs with similar chemistry suggested that allopatry may be involved even at local scales. populations have diverged both by physical isolation and physiochemical differences, and populations on surprisingly local scales have been evolving independently.
以往的分析表明，栖息在岛屿状温泉中的单细胞蓝藻多样性是如何相对于温泉之间的物理隔离和物理化学差异而构建的，特别是在局部到区域尺度上。然而，这些研究受到所调查分子标记提供的低分辨率的限制。我们分析了通过对黄石国家公园、蒙大拿州和俄勒冈州地热盆地温泉中采集的样本的光合作用基因片段进行高通量测序获得的大型数据集，所有这些温泉在以往的研究中都已知含有A/B'谱系的种群。在距离小于50公里的温泉之间，相同序列的比例高于距离大于50公里的温泉之间，而距离大于800公里的温泉仅很少共享序列变体。系统发育分析为可能与区域尺度上的地理隔离和/或地球化学差异相关的特有谱系提供了证据。生态型模拟2被用于预测假定的生态型（生态上不同的种群）及其成员，典范对应分析被用于研究其分布变化的地理和地球化学基础。在俄勒冈州和黄石公园的范围内，地理隔离解释了生态型分布差异的最大百分比（9.5%与经度相关；9.4%与纬度相关），地球化学差异解释了其余分布差异的最大百分比（7.4 - 9.3%与镁、硫酸盐和硫化物相关）。在大黄石生态系统内的样本中，地球化学差异显著解释了生态型的分布（6.5 - 9.3%与镁、硼、硫酸盐、二氧化硅、氯化物和pH相关）。然而，化学性质相似的黄石温泉中生态型的丰度和成员差异表明，即使在局部尺度上也可能涉及异域分布。种群通过物理隔离和物理化学差异而分化，并且令人惊讶的是，在局部尺度上的种群一直在独立进化。
