PSEUDO-NITZSCHIA PUNGENS AND P-MULTISERIES (BACILLARIOPHYCEAE) - NUCLEAR RIBOSOMAL DNAS AND SPECIES-DIFFERENCES

The region of the nuclear ribosomal DNA (rDNA) operon containing the s mall subunit (SSU), internal transcribed spacer 1 (ITS1), and a portio n of the 5.8S rDNA gene was sequenced in one isolate each of Pseudo-ni tzschia multiseries (Hasle) Hasle and Pseudo-nitzschia pungens (Grunow in Cleve & Moller) Hasle. The SSUs of these two species were highly s imilar, differing only in 24 point mutations and one insertion/ deleti on in 2774 bp. The ITS1 sequences were more variable, with 57 point mu tations and three insertion/deletions in 257 bp. There were no differe nces in 44 bp of the 5.8S sequences. Restriction fragment patterns (RF Ps) for the restriction endonucleases HaeIII, HhaI, and RsaI for 13 is olates of P. multiseries from the Atlantic, Pacific, and Gulf coasts o f the United States and 16 isolates of P. pungens from the three coast s of the United States, in addition to Japan and China, were compared. There were differences between the RFPs of P. multiseries and P. pung ens that corresponded to sites mapped by the DNA sequences, but no int raspecific variation in RFPs was observed for either species. The diff erences in RFPs correlate with morphological, immunological, and other rDNA differences and support the recognition of these taxa as separat e species.