When will taxonomic saturation be achieved? A case study in Nunduva and Kyrtuthrix (Rivulariaceae, Cyanobacteria)

Abstract

A number of heterocytous, mat-forming, tapering cyanobacteria in Rivulariaceae have recently been observed in both the Atlantic and Pacific coasts in the rocky intertidal and supratidal zones. These belong to the genera Nunduva, Kyrtuthrix, and Phyllonema and have been the subject of several recent studies. Herein, two new species of Nunduva (N. komarkovae and N. sanagustinensis) and two new species of Kyrtuthrix (K. munecosensis and K. totonaca) are characterized and described from the coasts of Mexico. Genetic separation based on the 16S-23S ITS region was pronounced (>10% in all comparisons). Morphological differences between all existing species in these two genera were also observed, but the group is morphologically complex, and these taxa are considered pseudocryptic. Nunduva and Kyrtuthrix remain morphologically and phylogenetically separate even with the addition of new species. However, how long will this remain the case? Many new genera and species of cyanobacteria have recently been described. Will the taxonomy of cyanobacteria eventually become saturated? Will we start to see multiple populations for the same cryptic species, or will future taxonomists collapse multiple species into fewer species, or multiple genera into single genera. The description of even more Nunduva and Kyrtuthrix species causes us to pause and evaluate the future of cyanobacterial taxonomy. These same questions are faced by algal taxonomists studying other phyla, and the resolution may ultimately be similar.

An updated classification of cyanobacterial orders and families based on phylogenomic and polyphasic analysis

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Phylogeny and fatty acid profiles of Aliinostoc vietnamicum sp. nov. (cyanobacteria) from the soils of Vietnam

“…The 16S rRNA gene is highly divergent within Nostocales, and the number of operons varies between one and five (Johansen et al 2017(Johansen et al , 2021. However, such additional operons have not been noted for Aliinostoc strains (Bagchi et al 2017, Kabirnataj et al 2020.…”

Unsuspected findings about phylogeny and ultrastructure of the enigmatic cyanobacterium Microcrocis geminata resulted in its epitypification and novel placement in Geminocystaceae

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