Cyst–theca relationship and phylogenetic positions of the diplopsalioideans (Peridiniales, Dinophyceae), with description of Niea and Qia gen. nov.

Abstract

:Nine genera have been assigned to the subfamily Diplopsalioideae, but since most have not been characterized molecularly and their cyst–theca relationships are largely unknown, the phylogenetic relationships among these genera are not well understood. Here we established the cyst–theca relationships of 11 species (Boreadinium breve, Diplopelta globula, Diplopsalis lenticula, Diplopsalopsis ovata, Lebouraia pusilla, Niea acanthocysta, Niea chinensis, Niea torta, Oblea rotunda, Preperidinium cf. meunieri and Qia lebouriae) belonging to nine genera by incubating cysts collected along the coast of China. In addition, we obtained 22 large-subunit ribosomal DNA sequences from the germinated motile cells of these 11 species by single-cell polymerase chain reaction. A new genus, Niea, was erected to encompass species with a plate formula identical to that of Oblea, that is, Po, X, 3′, 1a, 6′′, 3C+t, 5′′′, 2′′′′, but with an ortho 1′. Niea chinensis was described based on both theca and cyst morphology. The genus Oblea was emended to incorporate only species with a meta 1′. As a consequence, Oblea acanthocysta and O. torta were transferred to the newly erected genus Niea. A second new genus, Qia, was established to encompass Diplopsalis lebouriae, and the genus Diplopsalis was emended, differing from Qia in the shape of the anterior intercalary (1a) plate. Phylogenetic analyses were carried out using maximum likelihood and Bayesian inference. Molecular phylogeny revealed that the diplopsalioideans were not monophyletic and were subdivided into three clades. From our results, the shape of the first apical and anterior intercalary plates and the number of apical, anterior intercalary and antapical plates were useful characteristics to distinguish the diplopsalioideans at the genus level.