Three novel species in the P seudo‐nitzschia pseudodelicatissima complex: P . batesiana sp. nov., P . lundholmiae sp. nov., and P . fukuyoi sp. nov. ( B acillariophyceae) from the S trait of M alacca, M alaysia

A study on the morphology and phylogeny of 18 strains of P seudo‐nitzschia established from the S trait of M alacca, P eninsular M alaysia, was undertaken. Morphological data combined with molecular evidence show that they constitute three new species, for which the names, P . batesiana sp. nov., P . lundholmiae sp. nov., and P . fukuyoi sp. nov., are proposed. The three new species closely resemble species in the P . pseudodelicatissima complex sensu lato . Morphologically, P . batesiana differs from other species in the complex by having a smaller part of cell overlapping in the chain, whereas P . lundholmiae differs by having fewer poroid sectors and P . fukuyoi by having a distinct type of poroid sectors. Nucleotide sequences of the LSU rDNA (D1–D3) of the three new species reveal significant nucleotide sequence divergence (0.1%–9.3%) from each other and from other species in the P . pseudodelicatissima complex s.l . The three species are phylogenetically closely related to species in the P . pseudodelicatissima complex, with P . batesiana appearing as a sister taxon to P . circumpora , P . caciantha , and P . subpacifica ; whereas P . lundholmiae and P . fukuyoi are more closely related to P . pseudodelicatissima and P . cuspidata . The three species show 2–3 compensatory base changes ( CBCs ) in their ITS 2 transcripts when compared to the closely related species. The ITS 2 with its structural information has proven its robustness in constructing a better resolved phylogenetic framework for P seudo‐nitzschia .