Phylogenetic position reevaluation of Kyrtuthrix and description of a new species K. huatulcensis from Mexico´s Pacific coast

Abstract

Benthic marine heterocytous cyanoprokaryotes of Mexico´s tropical coast are being recognized as an important and conspicuous component of the supralittoral and intertidal zones usually described as an extreme and low diversity biotope. Although Kyrtuthrix has been reported from different coasts worldwide, its complex morphology has led to differing taxonomic interpretations and positioning. Ten marine supra and intertidal populations of Kyrtuthrix were analyzed using a detailed morphological approach, complemented with ecological and geographical information as well as DNA sequence data of the 16S rRNA gene and associated 16S-23S ITS. Kyrtuthrix huatulcensis is described as a new species, different from K. dalmatica Ercegovic and K. maculans (Gomont) Umezaki based primarily on morphological data. Our material has smaller dimensions in thalli, filaments, trichomes and cells, and possesses differences in qualitative characters as well. Our material is epilithic as in K. maculans but not endolithic as in K. dalmatica. The analysis of molecular data, mainly 16S rRNA gene sequence, show that this genus is within the Rivulariaceae clade, and outside of the Scytonemataceae clade. ITS secondary structure comparison with some of the closer representatives of Rivulariaceae shows considerable differences with these related genera. Based on the evidence gathered in this study, inclusion of Kyrtuthrix within the Rivulariaceae, rather than the Scytonemataceae, is fully supported.

Nunduva, a new marine genus of Rivulariaceae (Nostocales, Cyanobacteria) from marine rocky shores

“…The genera within the Rivulariaceae have been morphologically defined by their heteropolar growth, basal heterocytes and tapered trichomes. More recently, with the inclusion of the marine genus Kyrtuthrix in the family based on molecular phylogeny, the morphological definition of the Rivulariaceae had to be expanded to include genera with isopolar trichomes disposed in a heteropolar growth form (León-Tejera et al 2016).…”

“…The 16S rRNA gene and 16S-23S ITS region, were amplified using primers 27F after Neilan et al (1997), and VRF1 after Wilmotte et al (1993). The PCR amplification was performed with an Eppendorf Mastercycler following the conditions described by León-Tejera et al (2016). PCR products were gel purified, quantified, and cloned with the CloneJET PCR Cloning Kit (ThermoFisher Scientific, Waltham, MA).…”

“…The family Rivulariaceae is comprised presently of 10 genera (Rivularia, Calothrix, Dichothrix, Gardnerula, Isactis, Sacconema, Microchaete, Phyllonema, Macrochaete and Kyrtuthrix -see Komárek et al 2014;Alvarenga et al 2016;Berrendero et al 2016;León-Tejera et al 2016). The family includes mainly heteropolar forms with tapered trichomes, which are widest at the base and sometimes end in a hyaline hair with thin, elongated cells, possess an obligately basal heterocyte in mature trichomes, and reproduce by hormogonia (Berrendero et al 2016).…”

“…Recently Kyrtuthrix was placed in the Rivulariaceae, even though it has isopolar trichomes and no basal heterocytes. However, it does possess an attenuated, heteropolar, differentiated growth form (León-Tejera et al 2016). The Scytonemataceae and Symphyonemataceae are similar to Kyrtuthrix in that they have tapering isopolar trichomes, but they are widest in the middle of the trichome and are phylogenetically distant (Komárek 2013).…”

Two new species of Phyllonema (Rivulariaceae, Cyanobacteria) with an emendation of the genus

“…Kyrtuthrix and Nunduva belong to a clade of marine Rivulariaceae that has a number of potentially new genera and species based on phylogenetic and morphological evidence (León‐Tejera et al. , González‐Resendiz et al. ).…”