Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan.
Department of Biology, Graduate School of Science, Chiba University, Chiba, Japan.
PLoS One. 2018 Jun 14;13(6):e0198451. doi: 10.1371/journal.pone.0198451. eCollection 2018.
The marine isopod genus Limnoria contains algae-eating species. Previous phylogeographic studies have suggested that Limnoria species feeding on buoyant kelp underwent low genetic differentiation on a large spatial scale because rafting on floating host kelps promotes high levels of gene flow. In this paper, we survey the genetic structure of Limnoria nagatai, which bores into the non-buoyant kelps Eisenia bicyclis and E. arborea. We analyze the mitochondrial DNA (cytochrome oxidase subunit I [COI] gene) and morphological traits of L. nagatai, and the host kelps E. bicyclis and E. arborea from 14 populations along the Japanese archipelago of the Pacific Ocean and the Sea of Japan. Four major lineages are recognized within L. nagatai: three lineages in the Pacific Ocean, and one lineage in the Sea of Japan which might be a cryptic species. For L. nagatai, we show high genetic differentiation between geographically separated habitats in the Pacific Ocean, while low differentiation is found among continuous host kelps habitats in the Pacific Ocean as well as the Sea of Japan. L. nagatai in E. bicyclis in the Pacific Ocean has experienced large population expansion after the Last Glacial Maximum (LGM), whereas the lineage in E. bicyclis in the Sea of Japan has not. We suggest that Limnoria feeding on non-buoyant kelps, may attain low genetic differentiation because they might be able to disperse long distance if the habitat of host kelps is continuous. The historical events affecting Limnoria after the LGM may differ between the coasts of the Pacific Ocean and the Sea of Japan.
海洋等足目属 Limnoria 包含以藻类为食的物种。先前的系统地理学研究表明，以漂浮海藻为食的 Limnoria 物种在大的空间尺度上遗传分化程度较低，因为漂浮在漂浮的宿主海藻上促进了高水平的基因流动。在本文中，我们调查了 Limnoria nagatai 的遗传结构，该物种钻入非漂浮海藻 Eisenia bicyclis 和 E. arborea 中。我们分析了 Limnoria nagatai 的线粒体 DNA（细胞色素氧化酶亚基 I [COI] 基因）和形态特征，以及来自太平洋和日本海的日本列岛的 14 个种群的宿主海藻 E. bicyclis 和 E. arborea。在 Limnoria nagatai 中，我们识别出四个主要谱系：太平洋中的三个谱系，以及日本海中的一个谱系，可能是一个隐种。对于 Limnoria nagatai，我们发现太平洋中地理上分隔的栖息地之间存在高度的遗传分化，而在太平洋和日本海的连续宿主海藻栖息地之间则发现了低分化。太平洋中的 E. bicyclis 中的 L. nagatai 在末次冰盛期（LGM）后经历了大规模的种群扩张，而日本海的 E. bicyclis 中的谱系则没有。我们认为，以非漂浮海藻为食的 Limnoria 可能达到低遗传分化，因为如果宿主海藻的栖息地是连续的，它们可能能够进行长距离的扩散。末次冰盛期后影响 Limnoria 的历史事件可能在太平洋和日本海的海岸之间有所不同。
