Implications of High Molecular Divergence of Nuclear rRNA and Phylogenetic Structure for the Dinoflagellate Prorocentrum (Dinophyceae, Prorocentrales).

The small and large nuclear subunit molecular phylogeny of the genus Prorocentrum demonstrated that the species are dichotomized into two clades. These two clades were significantly different (one-factor ANOVA, p < 0.01) with patterns compatible for both small and large subunit Bayesian phylogenetic trees, and for a larger taxon sampled dinoflagellate phylogeny. Evaluation of the molecular divergence levels showed that intraspecies genetic variations were significantly low (t-test, p < 0.05), than those for interspecies variations (> 2.9% and > 26.8% dissimilarity in the small and large subunit [D1/D2], respectively). Based on the calculated molecular divergence, the genus comprises two genetically distinct groups that should be considered as two separate genera, thereby setting the pace for major systematic changes for the genus Prorocentrum sensu Dodge. Moreover, the information presented in this study would be useful for improving species identification, detection of novel clades from environmental samples.