Morphological and molecular variability of Peridinium volzii Lemmerm. (Peridiniaceae, Dinophyceae) and its relevance for infraspecific taxonomy

Abstract

Contemporary delimitation of species and populations in the microbial domain relies on an integrative approach combining molecular and morphological techniques. In case of the dinophyte Peridinium volzii, a considerable number of infraspecific taxonomic entities have been reported, but it is unclear at present whether the corresponding traits are stable within reproductively isolated units or refer to intraspecific variability. We established 26 monoclonal strains from Central Europe with a morphology that is consistent for P. volzii and characterised them by sequences gained from the rRNA operon. Ten of such strains, representative for the entire diversity observed, were investigated in detail morphologically using light and electron microscopy. In the molecular tree, P. volzii was monophyletic, sister group of Peridinium willei, and three ITS ribotypes could be distinguished. Some traits corresponding to previously described varieties and forms were found in individual cells across the strains under investigation, but not as stable characters correlating to certain ribotypes. We also observed new morphological variability (e.g., unusual shape of plate 4″). Cell size and displacement of the cingulum were significantly different between certain ribotypes but in turn, such diagnostic traits are impossible to assign to already described taxa due to their ambiguity. Based on the small first apical plate as diagnostic trait and putative apomorphy, P. volzii is a characteristic species but the present data given, we are reserved to accept more than a single reproductive unit. Thus, more research is necessary, including a focus on species delimitation to putative close relatives such as Peridinium maeandricum.

Spatial fragmentation in the distribution of diatom endosymbionts from the taxonomically clarified dinophyte Kryptoperidinium triquetrum (= Kryptoperidinium foliaceum, Peridiniales)

“…Benthic dinophytes do not show a clear signal, with ITS ribotypes of Coolia (Ostreopsidaceae) found worldwide 83 , whereas epiphytic Ostreopsis (also Ostreopsidaceae) in fact show a correlation between molecular sequence data and distribution, with genetically distinct Atlantic/Mediterranean versus Indo-Pacific populations 84 . In the freshwater environment, there may be some morphological differentiation within species, such as in Peridinium volzii between specimens from Europe and Eastern Asia 85 . In the present study, K. triquetrum does show a spatial distinction based on multiple gatherings, as the Baltic strains have different endosymbionts in this species than strains from other localities.…”