First report of the diatom genus Playaensis (Bacillariophyceae, Bacillariophyta) in South America: valve Morphology, colony formation and biogeography of the genus | CU Experts

Background and aims: Described in 1994 in Northern Argentina, Navicula toba,exhibits all diagnostic features attributed to the genus Playaensis: linear, slightly panduriform due to undulate valves with a prominent longitudinal rib bordering the raphe and marginal spines. This species occurs in temporary wetlands in northern Argentina. A population of specimens forming short, ribbon-like colonies was found in the temporary Valerio Lake, on the Somuncurá Plateau, Patagonia, Argentina. Comparisons indicated that P. circumfimbria (the generitype), Navicula toba and Somuncurá specimens represent the same taxonomic entity.M&M: Specimens collected at the Somuncurá Plateau were analysed with LM and SEM.Results: Based on the priority principle, we propose the combination Playaensis toba, establishing P. circumfimbria as a heterotypic synonym. Since the holotype of N. toba is currently missing, we recognize the original drawing as lectotype and designate the Somuncurá material as epitype to ensure nomenclatural stability and provide an unambiguous morphological reference. Additionally, we consider that Craticula citrus and C. citroides transferred to Playaensis, lack several diagnostic features of the genus, so we recommend maintaining their previous names.Conclusions: The geographic distribution of Playaensis (sensu stricto) remains restricted to temporary to ephemeral wetlands throughout North and South America.

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