Molecular Phylogeny of the Benthic Dinoflagellate Genus Amphidiniopsis and its Relationships with the Family Protoperidiniaceae.

The genus Amphidiniopsis is a benthic (sand-dwelling) lineage of thecate dinoflagellates, containing 19 morphologically diverse species. Past work has shown that some Amphidiniopsis species form a clade with the sand-dwelling Herdmania litoralis as well as some planktonic species in the family Protoperidiniaceae (i.e. the Monovela group). Still, our contemporary knowledge regarding Amphidiniopsis is limited, compared to the Protoperidiniaceae. To this end, we obtained 18S rDNA data from seven Amphidiniopsis species and a part of the 28S rDNA from four Amphidiniopsis species, with the goal of improving our understanding of phylogenetic relationships among Amphidiniopsis and the Monovela group. Results from the molecular phylogenetic analyses showed that Amphidiniopsis spp., with the exception of A. cf. arenaria, H. litoralis, and members within the Monovela group formed a single clade. Within the clade, relationships among Amphidiniopsis spp. and the Monovela group were more complicated - some subclades contained both representatives of Amphidiniopsis and the Monovela group. Our study suggests that habitat (benthic or planktonic), as well as traditionally used, general morphological characteristics, do not reflect molecular phylogenetic relationships, and that the taxonomy of the sand-dwelling genus Amphidiniopsis, and the planktonic family Protoperidiniaceae, should be reconsidered simultaneously.