All ETDs from UAB

Advisory Committee Chair

Robert W Thacker

Advisory Committee Members

Asim K Bej

Julie B Olson

Document Type

Thesis

Date of Award

2014

Degree Name by School

Master of Science (MS) College of Arts and Sciences

Abstract

Sponges (phylum Porifera) can comprise a large portion of benthic communities in freshwater and marine environments. Because sponges possess simple body plans and can have substantial phenotypic plasticity within species, reconstructing phylogenies of Porifera based upon morphologies alone has proven difficult. With the advent of nucleic acid sequencing technologies, interest in sponge phylogenetics has significantly increased among researchers. Additionally, sponges host a wide range of microbial symbionts, including the cyanobacterium Synechococcus spongiarum. This study examined the evolution of both sets of organisms in the symbiotic relationship between Aplysina sponges and Synechococcus cyanobacteria. In Chapter 3, gene sequences coding for the large subunit (28S) of nuclear ribosomal RNA (rRNA), as well as the internal transcribed spacer region, were used to reconstruct a phylogeny of Aplysina to determine the evolutionary relationships of sponges among three geographic locations. Aplysina species from the Eastern Pacific Ocean and the Caribbean Sea were more closely related to each other than they were to species from the Mediterranean Sea. In Chapter 4, cyanobacterial 16S rRNA gene sequences were used to reconstruct a phylogeny of Synechococcus to test the hypothesis that each sponge species hosts a unique clade of Synechococcus. By reconstructing the cyanobacterial phylogeny, new hosts were found for existing clades. iv Multiple statistical analyses indicated that symbiont phylogeny was significantly associated with geographic location and host species identity. Additionally, a ParaFit analysis was used to test the hypothesis of coevolution among hosts and symbionts. This analysis showed that several, but not all, host-symbiont parings displayed significant evidence of coevolution. This study implemented new statistical tests to improve previously established methods. These updated methods demonstrate the recent rapid progression of new statistical tools and methods, and with further development of new analytical approaches, these results can be further refined.

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