Tuesday June 3, 2025, 10 am GMT+2 (CEST)

Nansheng Chen¹

Quantitative molecular diversity and evolution of ribosomal genes in dinoflagellates

¹Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China

Metabarcoding technology has been widely applied to probe the diversity and dynamics of dinoflagellates, some protists can develop harmful algal blooms (HABs) with negative impact on marine ecosystems worldwide. Although metabarcoding analysis is effective in characterizing protist biodiversity and spatiotemporal dynamics with high resolution, being able to identify dinoflagellates that could not be properly identified using morphology-based approaches because some are too small in cell sizes, too similar in cell morphologies, and too fragile in sample fixation, accurate identification of individual species from mountains of sequences remains challenging. Inaccurate interpretation of sequences obtained in metabarcoding analysis can lead to the overestimation and even erroneous identification of biodiversity of marine ecosystems. To address this problem, the molecular marker 18S rDNA V4 that has been a common molecular marker used in metabarcoding analyses of single cells or single strains of a few representative dinoflagellate HAB species (including the dinoflagellate Noctiluca scintillans and Tripos species) were sequenced and analyzed to examine the nature of molecular diversity revealed in metabarcoding analyses. Each single cell was found to harbor a large number of variants with different relative abundances, with usually a few dominant variants and many non-dominant variants, indicating high intra-genomic variations (IGVs). Different cells of a particular species usually share the dominant variant, but not always. Some variants were found to be the dominant variants of one species, but non-dominant variants in other species of the same genus. Thus, proper understanding of the nature of molecular diversity of molecular marker is critical for extracting species and genetic diversity information.