Intraspecific diversity and distribution of the cosmopolitan species Pseudo‐nitzschia pungens (Bacillariophyceae): morphology, genetics, and ecophysiology of the three clades

Abstract

Three clades of Pseudo-nitzschia pungens, determined by the internal transcribed space (ITS) region, are distributed throughout the world. We studied 15 P. pungens clones from various geographical locations and confirmed the existence of the three clades within P. pungens, based on ITS sequencing and described the three subgroups (IIIaa, IIIab, and IIIb) of clade III. Clade III (clade IIIaa) populations were reported for the first time in Korean coastal waters and the East China Sea. In morphometric analysis, we found the ultrastructural differences in the number of fibulae, striae, and poroids that separate the three clades. We carried out physiological tests on nine clones belonging to the three clades growing under various culture conditions. In temperature tests, only clade III clones could not grow at lower temperatures (10°C and 15°C), although clade I and II clones grew well. The estimated optimal growth range of clade I clones was wider than that of clades II and III. Clade II clones were considered to be adapted to lower temperatures and clade III to higher temperatures. In salinity tests, clade II and III clones did not grow well at a salinity of 40. Clade I clones were regarded as euryhaline and clade II and III clones were stenohaline. This supports the hypothesis that P. pungens clades have different ecophysiological characteristics based on their habitats. Our data show that physiological and morphological features are correlated with genetic intraspecific differentiation in P. pungens.

Contrasting effects of copper limitation on the photosynthetic apparatus in two strains of the open ocean diatom Thalassiosira oceanica

“…In recent years, multiple intra-specific physiological variations have been demonstrated in various phytoplankton taxa, such as the harmful algal bloom (HAB) forming raphidophyte Heterosigma [102–104], and diatoms such as Skeletonema [105], Ditylum [106], Thalassiosira rotula [107] and the HAB forming Pseudo-nitzschia [108,109]. These intra-specific differences can manifest themselves in spatial and/or temporal distinct occurrences of one strain over the other.…”

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

“…In P. pungens , different physiological features are correlated with morphological and genetic intraspecific differentiation (Kim et al. ).…”

“…pungens has a significant geographic genetic structuring with very restricted gene flow between the different geographic populations (Casteleyn et al 2010). In P. pungens, different physiological features are correlated with morphological and genetic intraspecific differentiation (Kim et al 2015).…”

Temporal and spatial variability of the potentially toxic Pseudo-nitzschia spp. in a eutrophic estuary (Sea of Marmara)

“…Although Pseudo-nitzschia species were observed at a wide range of water temperatures from 9.38C (January) to 23.58C (August), peaks in abundance appeared between 9.38C (January) and 15.58C (early June) and abundances were very low, rarely exceeding 10 3 cells l 21 , in the summer months. But P. pungens comprises several varieties, and the temperature preference of these varieties have been found to differ (Kim et al, 2015), which may explain this disagreement. abundance and temperature indicates that low temperatures in nutrient-rich coastal areas and estuaries like the GHE may stimulate growth and bloom formation in different Pseudo-nitzschia species.…”