Sequence comparisons of toxic and non-toxic Alexandrium tamarense (Dinophyceae) isolates from UK waters

Polymerase chain reaction was used to amplify and sequence the LSU rDNA gene of 21 isolates of Alexandrium tamarense collected from the United Kingdom. Analysis of a 621 bp sequence covering the D1/D2 region of LSU rDNA revealed two distinct genetic lineages. In all cases, the strains shown to be nontoxic by ELISA or high-performance liquid chromatography were assigned to a 'Western European' lineage, whereas those producing the paralytic shellfish poisoning (PSP) toxin were assigned to the 'North American' lineage, which also included toxic isolates from the Orkneys. Our data are consistent with previous findings that an isolate's ability to produce PSP toxin, or lack thereof, correlates with its phylogenetic position and supports the hypothesis that at least two distinct populations of Alexandrium exist in UK waters.