title: The genus Pseudo-nitzschia (Bacillariophyceae) in a temperate estuary with description of two new species: Pseudo-nitzschia plurisecta sp. nov. and Pseudo-nitzschia abrensis sp. nov.
abstract: The genus Pseudo-nitzschia contains potentially toxic species of problematic taxonomy, making it one of the most intensively studied diatom genera. The study of 35 clonal strains isolated from the Bilbao estuary, an area that experiences recurrent blooms of Pseudo-nitzschia, revealed the presence of two new species, P. abrensis and P. plurisecta, differing from their congeners in both morphology and gene sequence. The morphological features were analyzed by LM and EM, whereas molecular analyses were based on the internal transcribed spacer (ITS) and large subunit (LSU) regions of the rDNA. P. plurisecta appears closely related to P. cuspidata/P. pseudodelicatissima in the phylogenetic tree, whereas P. abrensis forms a moderately supported clade with P. heimii/P. subpacifica and P. caciantha/P. circumpora. Comparison of the secondary structure of ITS2 regions reveals marked differences in the most highly conserved regions among related taxa. Morphologically, the new species differ from their closest congeners in the arrangement of the poroid sectors and the density of valve striae and fibulae. The two species share similar pigment composition, and belong to the group of Pseudo-nitzschia species containing only chlorophyll c2 and c3 .
authors.affiliation: Department of Plant Biology and Ecology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Leioa, 48940, Spain.
authors.forename: Emma
authors.initials: E
authors.lastname: Orive
authors.affiliation: Department of Plant Biology and Ecology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Leioa, 48940, Spain.
authors.forename: Lara
authors.initials: L
authors.lastname: Pérez-Aicua
authors.affiliation: Department of Plant Biology and Ecology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Leioa, 48940, Spain.
authors.forename: Helena
authors.initials: H
authors.lastname: David
authors.affiliation: Department of Genetic, Physical Anthropology and Animal Physiology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Leioa, 48940, Spain.
authors.forename: Koldo
authors.initials: K
authors.lastname: García-Etxebarria
authors.affiliation: Department of Plant Biology and Ecology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Leioa, 48940, Spain.
authors.forename: Aitor
authors.initials: A
authors.lastname: Laza-Martínez
authors.affiliation: Department of Plant Biology and Ecology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Leioa, 48940, Spain.
authors.forename: Sergio
authors.initials: S
authors.lastname: Seoane
authors.affiliation: Genomic Service, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Leioa, 48940, Spain.
authors.forename: Irati
authors.initials: I
authors.lastname: Miguel
keywords: Bilbao estuary; ITS; LSU; Pseudo-nitzschia abrensis; Pseudo-nitzschia plurisecta; TEM