Phylogenetic relationships, morphological variation, and toxin patterns in theAlexandrium ostenfeldii(Dinophyceae) complex: implications for species boundaries and identities

Abstract

Alexandrium ostenfeldii (Paulsen) Balech and Tangen and A. peruvianum (Balech and B.R. Mendiola) Balech and Tangen are morphologically closely related dinoflagellates known to produce potent neurotoxins. Together with Gonyaulax dimorpha Biecheler, they constitute the A. ostenfeldii species complex. Due to the subtle differences in the morphological characters used to differentiate these species, unambiguous species identification has proven problematic. To better understand the species boundaries within the A. ostenfeldii complex we compared rDNA data, morphometric characters and toxin profiles of multiple cultured isolates from different geographic regions. Phylogenetic analysis of rDNA sequences from cultures characterized as A. ostenfeldii or A. peruvianum formed a monophyletic clade consisting of six distinct groups. Each group examined contained strains morphologically identified as either A. ostenfeldii or A. peruvianum. Though key morphological characters were generally found to be highly variable and not consistently distributed, selected plate features and toxin profiles differed significantly among phylogenetic clusters. Additional sequence analyses revealed a lack of compensatory base changes in ITS2 rRNA structure, low to intermediate ITS/5.8S uncorrected genetic distances, and evidence of reticulation. Together these data (criteria currently used for species delineation in dinoflagellates) imply that the A. ostenfeldii complex should be regarded a single genetically structured species until more material and alternative criteria for species delimitation are available. Consequently, we propose that A. peruvianum is a heterotypic synonym of A. ostenfeldii and this taxon name should be discontinued.

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

“…The species of Alexandrium that are established to produce STXs are: Alexandrium minutum, A. ostenfeldii, A. australiense (these three species also include some non-STX producing strains (Yang et al, 2010;Touzet et al, 2007;Murray et al, 2012a,b;Kremp et al, 2014), A. pacificum, A. fundyense, and A. tamiyavanichi. We searched for sxtA domains in the following strains which were known to produce STXs: fifteen strains of species of Alexandrium, one strain of Gymnodinium catenatum and one strain of Pyrodinium bahamense, using PCR (14 strains) and by searching transcriptome libraries (3 strains) ( Table 1).…”

Distinctly different behavioral responses of a copepod, Temora longicornis , to different strains of toxic dinoflagellates, Alexandrium spp.

“…in addition to the PSTs, making interpretations of past reports difficult: spiroimines (spirolides, gymnodimines), goniodomin A and lytic compounds. The spiroimines are potent fast-acting neurotoxins that have so far only been found in the European and North Atlantic A. ostenfeldii but not Baltic A. ostenfeldii (Kremp et al, 2014;Sopanen et al, 2011). Goniodomin A is also a neurotoxin that has been reported to affect vertebrates (Klein et al, 2010) as well as invertebrates (Murakami et al, 1988).…”

Characterization of multiple isolates from an Alexandrium ostenfeldii bloom in The Netherlands

“…Besides PSP toxins, some Alexandrium species are known to produce other toxins including different spirolides (SPX) or gymnodimines (Cembella, 2003;Van Wagoner et al, 2011;Borkman et al, 2012;Kremp et al, 2014). These species belong to different phylogenetic groups of Alexandrium ostenfeldii as recently defined by Kremp et al (2014), including Alexandrium peruvianum. Most A. ostenfeldii strains have been shown to produce SPX, some strains also produce detectable amounts of PSP toxins, while only a few strains were reported to combine PSP toxin, SPX and 12-methylgymnodimine production (Cembella, 2003;Borkman et al, 2012;Kremp et al, 2014).…”

“…Alexandrium is among the most common bloom forming toxic dinoflagellate genera and is generally held responsible for the outbreak of paralytic shellfish poisoning (PSP; Anderson et al, 2012). Besides PSP toxins, some Alexandrium species are known to produce other toxins including different spirolides (SPX) or gymnodimines (Cembella, 2003;Van Wagoner et al, 2011;Borkman et al, 2012;Kremp et al, 2014). These species belong to different phylogenetic groups of Alexandrium ostenfeldii as recently defined by Kremp et al (2014), including Alexandrium peruvianum.…”

“…These species belong to different phylogenetic groups of Alexandrium ostenfeldii as recently defined by Kremp et al (2014), including Alexandrium peruvianum. Most A. ostenfeldii strains have been shown to produce SPX, some strains also produce detectable amounts of PSP toxins, while only a few strains were reported to combine PSP toxin, SPX and 12-methylgymnodimine production (Cembella, 2003;Borkman et al, 2012;Kremp et al, 2014).…”