Phylogenetic analysis ofAlexandriumspecies andPyrodinium bahamense(Dinophyceae) based on theca morphology and nuclear ribosomal gene sequence

A reinvestigation of saxitoxin production and sxtA in the ‘non-toxic’ Alexandrium tamarense Group V clade

“…In contrast to the information based on morphology, the many phylogenetic studies of Alexandrium species, based on regions of the rRNA operon, including the SSU, ITS/5.8s, and LSU genes, have clearly distinguished clades (Groups I-V) from one another (John et al, 2003;Scholin et al, 1994;Kim and Sako, 2005;Leaw et al, 2005;Lilly et al, 2007;Montresor et al, 2004;Rogers et al, 2006;Orr et al, 2011). Based on a survey of dinoflagellate diversity and its relationship to rDNA sequences, Litaker et al (2007) suggested that a conservative ''species level'' marker in dinoflagellates could be considered a difference of 4% (=uncorrected genetic distance of 0.04) in aligned regions of ITS1/5.8S/ITS2 rDNA.…”

“…The identification of A. tamarense/catenella/fundyense strains to a particular genetic clade (Groups I-V) has been considered more predictive of their propensity for STX production than species identifications based on morphology (Scholin et al, 1994;John et al, 2003;Kim and Sako, 2005;Leaw et al, 2005;Montresor et al, 2004;Lilly et al, 2007;Rogers et al, 2006). All strains of Groups I and IV analysed to date produce varying quantities of STX, with diverse toxin profiles (Table 2, Anderson et al, 1994), while no strains of Group II have been reported to produce STX (John et al, 2003).…”

Gene duplication, loss and selection in the evolution of saxitoxin biosynthesis in alveolates

“…Alexandrium has often appeared to form a monophyletic clade in phylogenetic analyses based on regions of the ribosomal DNA array, with a selected outgroup (John et al, 2003;Leaw et al, 2005;Orr et al, 2011;Anderson et al, 2012). Questions remain about the evolution of Alexandrium, as different studies have shown that the most basal clade is either: A. taylori (John et al, 2003;Rogers et al, 2006), A. leei (Leaw et al, 2005), a clade composed of the species A. satoanum, A. monilatum, A. taylori, A. hiranoi, A. pseudogonyaulax , and a clade including most of those species and A. leei (Anderson et al, 2012), or a clade including A. minutum, A. tamutum and A. ostenfeldii . A recent phylogeny of the group with a comprehensive species coverage, based on a concatenated alignment of the three rRNA regions, found that clades within Alexandrium were generally not well supported .…”

Description of the new phototrophic dinoflagellate Alexandrium pohangense sp. nov. from Korean coastal waters

“…However, because of ambiguity in some morphological features, molecular and phylogenetic methods have been used for the identification of Alexandrium species (Scholin et al, 1994;John et al, 2014;Kremp et al, 2014). In phylogenetic trees based on ribosomal DNA (rDNA) regions, some morphological features have supported monophyletic clades (John et al, 2003;Leaw et al, 2005;Lilly et al, 2007;Orr et al, 2011). Saxitoxin (STX) is the principal toxin responsible for PSP (Bates and Rapoport, 1975).…”