Abstract
Proliferations of the genus Pseudo-nitzschia recur along the Catalan coast (NW Mediterranean) throughout the year. The establishment of 58 clonal cultures facilitated morphological studies with scanning electron microscopy (SEM) and ITS 5.8S rDNA sequence characterization. Moreover, strains of each species were examined with respect to sexual compatibility and toxicity. The results of the morphological and phylogenetic studies confirmed nine species of the genus Pseudo-nitzschia: P. brasiliana, P. calliantha, P. delicatissima clade A/del 2, P. arenysensis, P. fraudulenta, P. galaxiae, P. linea, P. multistriata and P. pungens clade I. Moreover, two Pseudo-nitzschia species, P. caciantha and P. cf mannii , could only be identified following SEM analysis of their morphology. None of the cultured strains of Pseudo-nitzschia analyzed produced domoic acid in amounts above the limit of detection. The current distributions of the Pseudo-nitzschia species in the Mediterranean Sea were plotted on maps, which led to the following observations: i) diversity within this genus is much greater than previously considered, ii) some species have a broad distribution (e.g. P. calliantha ), iii) whereas the distribution of others is narrowly restricted (e.g. P. pungens clade I). Moreover, this study reports the first detection of P. linea in the Mediterranean Sea and is the first description of P. galaxiae and P. cf mannii along the Catalan coast. Morphological studies coupled with molecular biological characterization, mating tests and biogeographic distribution analyses provide a critical theoretical basis for testing and/or implementing the current phylogenetic framework in the genus Pseudo-nitzschia .
Highlights
Identifying and characterizing species, in terms of distribution and biogeography, are critical components of ecological investigations
The use of morphology to identify species is problematic because taxon delimitation is arbitrary if it relies only on morphological characters and does not precisely fix the variation allowed within species (Mann et al, 1999; Lundholm and Moestrup, 2006; Amato et al, 2007)
All the established cultures of Pseudo-nitzschia were isolated from planktonic cells except in the case of P. linea, which was found growing on a Chaetoceros species
Summary
Identifying and characterizing species, in terms of distribution and biogeography, are critical components of ecological investigations. Recent evidence suggests that semi-cryptic diversity (genetically distinct but morphologically almost undistinguishable, see Quijano-Scheggia et al, 2009b) is more widespread among diatoms than previously considered (Amato et al, 2007; Amato and Montresor, 2008; Kaczmarska et al, 2008). If this is the case, the concept of morphospecies is in some cases inadequate for assessing the ecology, distribution and biogeography of diatom populations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
