Dawn of the dinophytes: A first attempt to date origin and diversification of harmful algae.

Unicellular dinophytes include a considerable number of harmful algae and potent producers of toxins. The dinophyte fossil record is one of the richest among protists and indicates a geologically old origin of the group dating back to the Triassic. Besides of these records, very few molecular dating studies of dinophytes have been published to date, precluding an understanding of the diversification history of these organisms. In the present study, we used first appearances in the fossil record for the best-represented dinophyte lineages, namely Gonyaulacales and Peridiniales, to calibrate a molecular phylogeny. It is inferred from ribosomal RNA sequence data covering a representative taxon sampling of all currently recognised lineages. Dinophytes may have started diversifying during main tectonic events of the supercontinent Pangaea, witnessing and surviving some of the biggest mass extinction events on Earth. Groups including harmful dinophytes originated at different points in time, but they all predate the Cretaceous-Paleogene boundary. Our chronogram provides a first time frame and may stimulate studies in future bringing molecular phylogenetics of dinophytes and their impressive fossil record together in more detail.