Pseudo‐nitzschia arctica sp. nov., a new cold‐water cryptic Pseudo‐nitzschia species within the P. pseudodelicatissima complex

Abstract

A new nontoxic Pseudo-nitzschia species belonging to the P. pseudodelicatissima complex, P. arctica, was isolated from different areas of the Arctic. The erection of P. arctica is mainly supported by molecular data, since the species shares identical ultrastructure with another species in the complex, P. fryxelliana, and represents a new case of crypticity within the genus. Despite their morphological similarity, the two species are not closely related in phylogenies based on LSU, ITS and rbcL. Interestingly, P. arctica is phylogenetically most closely related to P. granii and P. subcurvata, from which the species is, however, morphologically different. P. granii and P. subcurvata lack the central larger interspace which is one of the defining features of the P. pseudodelicatissima complex. The close genetic relationship between P. arctica and the two species P. granii and P. subcurvata is demonstrated by analysis of the secondary structure of ITS2 which revealed no compensatory base changes, two hemi-compensatory base changes, and two deletions in P. arctica with respect to the other two species. These findings emphasize that rates of morphological differentiation, molecular evolution and speciation are often incongruent for Pseudo-nitzschia species, resulting in a restricted phylogenetic value for taxonomic characters used to discriminate species. The description of a new cryptic species, widely distributed in the Arctic and potentially representing an endemic component of the Arctic diatom flora, reinforces the idea of the existence of noncosmopolitan Pseudo-nitzschia species and highlights the need for combined morphological and molecular analyses to assess the distributional patterns of phytoplankton species.

Phylogeny and species delineation in the marine diatomPseudo‐nitzschia(Bacillariophyta) usingcox1,LSU, andITS2rRNAgenes: A perspective in character evolution

“…Here, we studied the phylogenetic relationships among Pseudo‐nitzschia species based on cox1 , LSU, and ITS2 phylogenies, with the inclusion of recently identified new species of Pseudo‐nitzschia , i.e., P. arctica , P. bipertita , P. limii , and P. simulans (Percopo et al. , Teng et al. , Li et al.…”

Species occurrence of the potentially toxigenic diatom genus Pseudo-nitzschia and the associated neurotoxin domoic acid in the Argentine Sea

“…The number of described Pseudo-nitzschia species, as well as the number of confirmed DA producers in culture, has notably increased in the last few years (e.g., Lelong et al, 2012;Lim et al, 2013;Orive et al, 2013;Teng et al, 2016;Percopo et al, 2016). By contrast, the worldwide distribution of most of these species and their toxicity in natural populations is still poorly known.…”

“…The genus now comprises 48 recognized species (Teng et al, 2014(Teng et al, , 2015Percopo et al, 2016), most of them described within the last two decades. Among these species, at least 23 have been mentioned as potential producers of domoic acid (DA) (Teng et al, 2015, a secondary amine neurotoxin.…”

Microbial Eukaryotes in an Arctic Under-Ice Spring Bloom North of Svalbard

“…During the last decade, sequencing of 18S rDNA has been used to metabarcode communities of also the pico- (0.2–3 μm) and nano- (3–20 μm) sized eukaryotic fraction of Arctic marine systems (e.g., Lovejoy et al, 2006; Comeau et al, 2011; Kilias et al, 2014; Marquardt et al, 2016) as reviewed by Lovejoy (2014). The insights of arctic microbial eukaryotes gained by the use of molecular genetic tools include the identification of ecotypes endemic to the Arctic (Lovejoy et al, 2007; Terrado et al, 2013; Percopo et al, 2016), the existence of taxa-specific biogeographic patterns (Thaler et al, 2015), and a linking of distinct protist assemblages to water masses (Hamilton et al, 2008; Bachy et al, 2011; Monier et al, 2014; Metfies et al, 2016). It has been shown that the pronounced Arctic seasonality extends to the succession of microbial eukaryotes (Marquardt et al, 2016; Joli et al, 2017).…”