The Repository @ St. Cloud State

Open Access Knowledge and Scholarship

Date of Award


Culminating Project Type


Degree Name

Biological Sciences - Ecology and Natural Resources: M.S.




College of Science and Engineering

First Advisor

Matthew Julius

Second Advisor

Matthew Davis

Third Advisor

Omar Al-Azzam

Fourth Advisor

David Williams

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Keywords and Subject Headings

Eunotiophycidae; diatom; morphological phylogeny; raphe; evolution


The diatom subclass Eunotiophycidae is often considered to be the first raphe-bearing group of diatoms. However, the subclass has not been well-studied phylogenetically, making the evolutionary history of both Eunotioid diatoms and ancestral and early raphid diatoms largely unknown. This study conducts a formal phylogenetic analysis of 60 araphid, Eunotioid, and Naviculoid diatoms using a 124 character morphological analysis. Results indicate that the Naviculoid and Eunotioid diverged earlier than previously believed, so that Eunotioid diatoms do not form a transitional state between araphid and Naviculoid diatoms. Analyses conducted provide insight into the morphological characters in diatoms that are most informative when reconstructing a natural classification of diatoms based on shared evolutionary features (synapomorphies). The effects of including and excluding potentially homoplastic features in a large morphological analysis are also explored.


First, thanks to Dr. Matthew Julius for his unparalleled support and guidance throughout this research, and for his continuing collaboration beyond the culmination of this master’s project. Thanks to Prof. Mayama at Tokyo Gakugei University for hosting me for summer research and field sampling, guidance and insight on Eunotia morphology and physiology, and for access to his FE SEM. Thanks to my committee for their guidance, and particularly to Dr. David Williams for indulging me in lengthy discussions on the nature of morphological phylogenetic analysis, for hosting me at the Natural History Museum in London, and for making the long journey to St. Cloud to attend my defense. Thank you to Dr. Marina Potapova for her teaching and guidance during and after my tenure at the Academy of Natural Sciences, Philadelphia, and for access to material and specimens in the diatom herbarium. Thanks also to my family for their unwavering support for my decision to leave my job and home to pursue graduate research. This research was partially funded by NSF Award No. 1515305 and by the generous philanthropic gifts of the Uncle Bealey Foundation.



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