Date of Award


Degree Type


Degree Name

Master of Science (MS)



First Advisor

Dr. Jeffrey R. Johansen


Historically, the Rivulariaceae family has grouped all heteropolar, tapered and heterocitous Cyanobacteria, however recent description of multiple cyanobacterial populations with this morphotype using 16S rRNA phylogenies have reported that the populations with this morphotype are polyphyletic, and many new and old tapered and heteropolar genera (Cyanomargarita, Gloeothrichia, Rohoaltiella, etc.) have been classified and reclassified to different families than the Rivulariaceae. This is also the case of the main genera of the family (Rivularia and Calothrix), which have been repeatedly reported as polyphyletic, and whose separation to different families has been called for. In this project I carried out the evaluation of the internal relations of the clade that contains Rivularia sensu stricto and its placement among the Nostocales, by sequencing multiple protein coding genes (nifD, rbcL, rbcX, rpoCl) of Mexican marine populations of the clade and constructing phylogenies with these genes and the 16S rRNA gene. I additionally compared how the phylogenies based on these genes and the secondary structure of the 16S rRNA gene compare to the more commonly used phylogenies based on unfolded 16S rRNA gene datasets.