Genetic analysis of Noctiluca scintillans populations indicates low latitudinal differentiation in China but high China-America differences

Noctiluca scintillans is a globally distributed dinoflagellate that often forms a “Red Tide” bloom, but its geographically genetic differentiation is not well understood. In this study, three loci of the rRNA cistron were analyzed for populations from China and a population from Port Aransas, Texas, USA. Both phylogenetic and haplotypes network analyses based on ITS, SSU and LSU DNA markers revealed low genetic variation within and between populations along the Chinese coast, but substantial divergence based on ITS marker between the Chinese populations and the American population. Twelve single-cells were examined for intra-cell genetic variation and high levels of polymorphism were detected. The large genetic distance among the intra-cell ITS sequences (0-0.043) can exceed the species boundary (0.02 or 0.04) previously reported for dinoflagellates. High genetic diversity of intra-genomic, with the mean genetic distance being 5.1 folds greater than mean inter-genomic distance in the China Sea region, suggests high levels of gene flow and high frequency of recombination, while the divergence between the Chinese and the American populations indicates limited gene flow between the two continents. The present study suggests that the red N. scintillans is globally ubiquitous but genetically showing inter-region differentiation.