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


Mertens, KN and Adachi, M and Anderson, DM and Band-Schmidt, CJ and Bravo, I and Brosnahan, ML and Bolch, CJS and Calado, AJ and Carbonell-Moore, MC and Chomerat, N and Elbrachter, M and Figueroa, RI and Fraga, S and Garate-Lizarraga, I and Garces, E and Gu, H and Hallegraeff, G and Hess, P and Hoppenrath, M and Horiguchi, T and Iwataki, M and John, U and Kremp, A and Larsen, J and Leaw, CP and Li, Z and Lim, PT and Litaker, W and MacKenzie, L and Masseret, E and Matsuoka, K and Moestrup, O and Montresor, M and Nagai, S and Nezan, E and Nishimura, T and Okolodkov, YB and Orlova, TY and Rene, A and Sampedro, N and Satta, CT and Shin, HH and Siano, R and Smith, KF and Steidinger, K and Takano, Y and Tillmann, U and Wolny, J and Yamaguchi, A and Murray, S, Morphological and phylogenetic data do not support the split of Alexandrium into four genera, Harmful Algae, 98 Article 101902. ISSN 1568-9883 (2020) [Refereed Article]

Copyright Statement

Crown copyright 2020

DOI: doi:10.1016/j.hal.2020.101902


A recently published study analyzed the phylogenetic relationship between the genera Centrodinium and Alexandrium, confirming an earlier publication showing the genus Alexandrium as paraphyletic. This most recent manuscript retained the genus Alexandrium, introduced a new genus Episemicolon, resurrected two genera, Gessnerium and Protogonyaulax, and stated that: "The polyphyly [sic] of Alexandrium is solved with the split into four genera". However, these reintroduced taxa were not based on monophyletic groups. Therefore this work, if accepted, would result in replacing a single paraphyletic taxon with several non-monophyletic ones. The morphological data presented for genus characterization also do not convincingly support taxa delimitations. The combination of weak molecular phylogenetics and the lack of diagnostic traits (i.e., autapomorphies) render the applicability of the concept of limited use. The proposal to split the genus Alexandrium on the basis of our current knowledge is rejected herein. The aim here is not to present an alternative analysis and revision, but to maintain Alexandrium. A better constructed and more phylogenetically accurate revision can and should wait until more complete evidence becomes available and there is a strong reason to revise the genus Alexandrium. The reasons are explained in detail by a review of the available molecular and morphological data for species of the genera Alexandrium and Centrodinium. In addition, cyst morphology and chemotaxonomy are discussed, and the need for integrative taxonomy is highlighted.

Item Details

Item Type:Refereed Article
Keywords:Alexandrium taxonomy, phylogenetics, paraphyletic, saxitoxin, spirolides, harmful algal blooms
Research Division:Biological Sciences
Research Group:Plant biology
Research Field:Phycology (incl. marine grasses)
Objective Division:Environmental Management
Objective Group:Marine systems and management
Objective Field:Marine biodiversity
UTAS Author:Bolch, CJS (Associate Professor Christopher Bolch)
UTAS Author:Hallegraeff, G (Professor Gustaaf Hallegraeff)
ID Code:141030
Year Published:2020
Web of Science® Times Cited:4
Deposited By:Ecology and Biodiversity
Deposited On:2020-09-19
Last Modified:2021-02-15

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