Background and Aims:

Pyrodinium is a monotypic genus with two varieties, var. bahamense in the Atlantic, non-toxic, and var. compressum in the Indo-Pacific and toxic. Recent findings of Paralytic Shellfish Poisoning (PSP) toxicity in populations of P. bahamense var. bahamense weakened the interest in accepting both varieties as independent, and even investigating the possibility of crypticism between them. In the few studies that have involved molecular evidence in the treatment of varieties, their taxonomic independence continues to be denied, despite the evident and consistent genetic separation shown in all analyses. Therefore, the aim of this study was to recognize, based on genetic evidence, the taxonomic independence of the two varieties of Pyrodinium: P. bahamense var. compressum and var. bahamense.

Methods:

Based on three molecular markers (Lcf, LSU, SSU) of sequences available in Genbank, statistical parsimony networks and a concatenated phylogenetic analysis were constructed.

Key results:

In all analyses, a genetic structure was consistently obtained for P. bahamense var. bahamense and another one for P. bahamense var. compressum. Furthermore, the correspondence of the resulting haplotypes and ribotypes was always the same in both networks and phylogeny, i.e., the samples from the Pacific Ocean were always placed in a different group than those from the Atlantic Ocean.

Conclusions:

The evidence provided in this study demonstrated the reproductive isolation between both varieties, and even the possible presence of a not yet described third variety, as a consequence of which we propose the validity and taxonomic independence of P. bahamense var. compressum and P. bahamense var. bahamense.

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