All ETDs from UAB

Advisory Committee Chair

James B McClintock

Advisory Committee Members

Charles D Amsler

Thomas Klinger

Stacy A Krueger-Hadfield

John M Lawrence

Stephen A Watts

Document Type


Date of Award


Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences


Luidia spp. (Family Luidiidae) are important predators in the benthic food web and are abundant in near-shore, shallow soft-bottom habitats throughout the northern Gulf of Mexico. Climate change-related environmental changes, such as ocean warming and acidification, are rapidly intensifying in this region and can have consequences for species diversity as well as individual sea star health through modification of host-associated bacterial communities. Our knowledge of sea star-associated bacterial community structure and dynamics is limited and conflicting genetic evidence has called into question the accuracy of species delimitation of five-armed Luidia in the northern GOM. The primary purpose of this dissertation was to investigate species delimitation between Luidia clathrata and L. lawrencei and to characterize the bacterial communities associated with these sea stars in the natural environment and under exposure to near-future warming under experimental conditions. Sequence divergence at the cytochrome oxidase subunit I (CO1) gene was sufficient to support the maintenance of L. lawrencei as a separate species from L. clathrata. Furthermore, the presence of some individuals that appeared to be L. lawrencei morphologically but were L. clathrata based on CO1 suggests the potential for hybridization. A significant shift in bacterial community composition with experimental exposure to projected end-of-century (32°C) warming was observed in stomach tissue of L. clathrata. Luidia lawrencei from the natural environment had tissue-specific bacterial communities which were also distinct from iv bacterial communities in the surrounding sand and seawater. Together, these results underlie the importance of obtaining and maintaining accurate records of species delimitation and of bacterial community composition associated with healthy hosts under non-stressful environmental conditions. This will provide a baseline from which to measure modification in diversity and community structure in a changing world.



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