Genetic sub-populations (clades) of cosmopolitan marine diatom Pseudo-nitzschia pungens might have distinct habitats, and their hybrid zone is suspected in higher latitude area of the West Pacific area, however, it is still unrevealed because of technical difficulties and lack of evidences in natural environments. The aim of this study is to investigate the habitat characteristics of each clade of P. pungens on geographical distribution with the habitat temperature ranges of each clade and to reveal their hybrid zone in the West Pacific area. We employed the 137 number of nucleotide sequences of P. pungens and its sampling data (spatial and temporal scale) originated from the West Pacific area, and used field application of qPCR assay for intra-specific level of P. pungens. Only two genotypes, clade I and III, were identified in the West Pacific area. Clade I was distributed from 39 to 32.3°N, and clade III were from 1.4 to 34.4°N. The estimated habitat temperature for the clade I and clade III ranges were 8.1–26.9 °C and 24.2–31.2 °C, respectively. The latitudinal distributions and temperature ranges of each clade were significantly different. The qPCR assay employed, and results suggested that the hybrid zone for clade I and III has been observed in the southern Korean coasts, and clade III might be introduced from the Southern Pacific area. The cell abundances of clade III were strongly related with the higher seawater temperature and warm current force. This study has defined distinct habitat characteristics of genetically different sub-populations of P. pungens, and revealed its hybrid zone in natural environment for the first time. We also provided strong evidences about dispersion of the population of clade III to higher latitude in the West Pacific area.

大都会海洋硅藻假单胞菌的遗传亚群（进化枝）可能具有独特的栖息地，并且怀疑它们的杂种带位于西太平洋地区的较高纬度地区，但是由于技术上的困难和缺乏证据，它仍然没有被发现。在自然环境中。这项研究的目的是在地理分布上调查每个小枝ung的栖息地特征，以及每个枝丛的栖息地温度范围，并揭示它们在西太平洋地区的混合带。我们采用了137个P. pungens核苷酸序列及抽样数据（空间和时间尺度）来源于西太平洋地区，而对于特定帧内水平qPCR测定的使用的领域中的应用P. pungens。在西太平洋地区仅发现了两个基因型，进化枝I和III。第一类的分布范围为39至32.3°N，第三类的分布范围为1.4至34.4°N。I类和III类的估计栖息地温度分别为8.1–26.9°C和24.2–31.2°C。每个进化枝的纬度分布和温度范围明显不同。采用qPCR分析，结果表明，在韩国南部沿海地区已观察到I和III进化枝的杂种带，而III进化枝可能是从南太平洋地区引入的。进化枝III的细胞丰度与较高的海水温度和温暖的潮流强烈相关。这项研究已经定义了P. pungens基因不同亚群的独特生境特征，并首次揭示了其在自然环境中的混合带。我们还提供了有力的证据，表明第三类进化枝的种群在西太平洋地区向较高纬度的扩散。