Taxonomic Clarification of the Unusual Dinophyte Gymnodinium limneticum Wołosz. (Gymnodiniaceae) from the Tatra Mountains

The Gymnodiniaceae –even in a strict sense– comprise a vast diversity of dinophytes regarding morphology and ecology. Taxonomy and nomenclature of their constituent species remain problematic, although crucial to fully explore the biology of the group. Here, we present the rarely documented dinophyte Gymnodinium limneticum from its type locality at Lake Morskie Oko in Poland, for which we established strains and made extensive morphological studies. The species was unusual in exhibiting capsoid cells as predominant life-history stage, which were embedded and dividing in extensive mucilage leading to an enkaptic pseudocolonial system. We also generated ribosomal RNA sequences that were included in a comprehensive molecular phylogeny. Our species was clearly identified as a member of the Gymnodiniaceae s.str. but within the lineage, it was only distantly related to the type species of Gymnodinium, G. fuscum. Rather, it constituted a monophyletic group together with species assigned to Spiniferodinium and as a nomenclatural result, we propose two new combinations (i.e., Sp. limneticum comb. nov., Sp. palustre comb. nov.). As Spiniferodinium now includes dinophyte species inhabiting marine or freshwater environments as well, our investigations may provide evidence for an evolutionary scenario with corresponding transitions being more frequent than considered before.