Morphological and phylogenetic data do not support the split of Alexandrium into four genera

Area of Science:

• Marine biology
• Phycology
• Taxonomy

Background:

• The dinoflagellate genus Alexandrium is known to be paraphyletic.
• Recent studies have proposed splitting Alexandrium into multiple genera to resolve its polyphyly.

Purpose of the Study:

• To critically evaluate the proposed revision of the Alexandrium genus.
• To argue against the current proposal for splitting Alexandrium based on available data.

Main Methods:

• Review of molecular phylogenetic analyses.
• Assessment of morphological data for taxonomic delimitations.
• Discussion of cyst morphology and chemotaxonomy.

Main Results:

• The proposed new genera (Episemicolon, Gessnerium, Protogonyaulax) are not based on monophyletic groups.
• Morphological data do not convincingly support the proposed taxa delimitations.
• The proposed revision replaces one paraphyletic taxon with several non-monophyletic ones.

Conclusions:

• The proposal to split the genus Alexandrium is rejected based on current evidence.
• A robust revision requires more complete data and a stronger phylogenetic basis.
• Integrative taxonomy, combining molecular, morphological, and other data, is essential for future revisions.