Date of Graduation

5-2015

Document Type

Thesis

Degree Name

Master of Science in Biology (MS)

Degree Level

Graduate

Department

Biological Sciences

Advisor

Fredrick W. Spiegel

Committee Member

Andrew J. Aleverson

Second Committee Member

William J. Etges

Third Committee Member

Jeffrey D. Silberman

Keywords

Biological sciences; Amoebae; Cellular slime molds; Eukaryotic microbes; Molecular phylogenetics; Protists

Abstract

Cellular slime molds are amoeboid protists that have a unicellular trophic phase and multicellular dispersal stage formed through the aggregation of individuals in their life cycles. These organisms were once thought to form a monophyletic group in the Mycetozoa. After careful morphological, ultrastructural, and molecular studies, cellular slime molds are now thought to be distantly related organisms that have all converged on the cellular slime mold habit. The following thesis consists of two molecular phylogenetic studies on two named genera of cellular slime mold for which little or no molecular data were publically available. In the first study, gene sequence data were gathered for the first time from the dung inhabiting cellular slime mold Sorodiplophrys stercorea. Phylogenies constructed using the 18S SSU gene supported previous morphological and ultrastructural studies by placing S. stercorea in the labyrinthulid Stramenopiles, in a clade containing a marine amoeba (Amphifila marina) of similar morphology. This is the first report of an organism with the cellular slime mold habit in the entirety of the Stramenopiles. In the second study, sequence data from the SSU gene and the ITS region were acquired and used to assess the relationships of at least two species of the cellular slime mold genus Pocheina with respect to species of another cellular slime mold genus, Acrasis. In phylogenies based on the SSU gene, isolates identified as P. rosea formed a well-supported clade outside of Acrasis and sister to the allovahlkamfiid amoebae. However, the lone isolate identified as P. flagellata formed a sister relationship with A. takarsan. In contrast to the paraphyletic Pocheina recovered in SSU trees, the genus is recovered as a monophyloetic group in ITS analyses. The paraphyletic nature of the taxon seen with SSU analyses was not recovered using the 5.8s gene amplified with the ITS region. Phylogenies built using the 5.8s gene of all five isolates, of Pocheina formed a monophyletic group to the exclusion of Acrasis and Allovahlkampfia. Together, these two studies show that the cellular slime mold habit has evolved more times and is present in more lineages than previously thought.

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