Date of Award

Spring 4-16-2019

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Kalina M. Manoylov

Abstract

Pithophora and Cladophora are two representative genera of the order Cladophorales as filamentous Chlorophyta. These two genera are major contributors to the total algal biomass of littoral communities in freshwater and shallow marine water and have been reported as nuisance algae as they proliferate fast with the influx of nutrients. However, the wide geographical distribution and the overlap of plastic morphological characteristics between the two genera have complicated taxonomic identification at species level and phylogenetic studies. In the present study, a population of a monospecific, filamentous algal community was collected in Jewell, Georgia from the Ogeechee River. The monospecific, filamentous algal community was processed according to standard protocols and was identified by implementing a polyphasic approach of incorporating genotypic and phenotypic methods. The morphological analysis identified the monospecific, filamentous community as P. roettleri (Roth) Wittrock based on the average length and diameter of its heterosporous, intercalary akinetes (226 ± 3.50 µm, 125 ± 3.07 µm) and terminal akinetes (233 ± 1.03 µm, 117 ± 3.48 µm) along with the average diameter of the principal filaments (146 ± 5.92). To further support this identification, total DNA was sequenced from the monospecific, filamentous community resulting in 11 plastid, one mitochondrial, and five ribosomal DNA (rDNA) gene markers. Single-gene and concatenated-gene phylogenetic analyses of the LSU and SSU gene markers were analyzed to infer the evolutionary relationship of the monospecific, filamentous community for species-level identification. The molecular phylogenetic trees were inferred by three different methods and compared to the previously published data: maximum likelihood, maximum parsimony, and Bayesian inference. The overall phylogenetic analyses classified the monospecific, filamentous community as P. roettleri (Roth) Wittrock with strong bootstrap and posterior probability support values which are comparable to the morphological identification. Despite the overlapping morphology between Pithophora and Cladophora, the resulting molecular analyses revealed that the two genera evolutionary diverged from a distinct common ancestor. Instead, the molecular evidence showed that Pithophora is most similar to Aegagropila due to their sister relationship. Evidently, Pithophora has been reported in Georgia as a nuisance pond alga and this study represents the first population ecology research of the species in Georgia, USA. Further advancements in molecular data preceded by detailed morphological identifications will aid in differentiating between the species of Pithophora and their ecology based on individual genomes despite the overlapping phenotypic plasticity in morphological characters.

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