Date of Award
1-1-2024
Document Type
Dissertation
Degree Name
Ph.D. in Biological Science
First Advisor
Colin R. Jackson
Second Advisor
Peter C. Zee
Third Advisor
Brice Noonan
School
University of Mississippi
Relational Format
dissertation/thesis
Abstract
Host-parasite interactions are ubiquitous and have negative risks and consequences on individual, population, and evolutionary scales. These risks and consequences include altered population densities, changes in interspecies interactions, and rapid changes in host phenotypes. In this thesis, I seek to understand the ecological and evolutionary ramifications of host-parasite interactions within ecosystems. To do this, I investigated the presence and environmental correlates of potential host-parasite interactions in a freshwater ecosystem and used a model ecosystem to explore how past host-parasite coevolution affects community assembly dynamics and future adaptation in the presence of new stressors. To examine the presence of potentially parasitic microorganisms in freshwater mussels and how they relate to mussel host species or environmental conditions, microbial community DNA was extracted from the gut tissue of over 300 freshwater mussels, representing 22 species collected from rivers in the southeastern USA. Microeukaryote DNA was detected using PCR amplification, followed by sequencing of positive amplicons. In these mussels, we found the presence of potentially parasitic taxa positively correlated with mussel species, pH, ammonia, and negatively correlated with, nitrite, dissolved oxygen, and conductivity. To test the extent to which host-pathogen coevolution impacts outcomes of community assembly, we experimentally coevolve Pseudomonas fluorescens and bacteriophage SBW25Φ2, followed by ecological assembly experiments with the evolved lineages. In these assembled model communities, we found that differences in evolutionary histories between the hosts and parasites can reduce the intensity of inhibitory priority effects.
To determine how selection history impacts response to selection in new environments, the Pseudomonas fluorescens and SBW25Φ2 model system was used to measure the adaptation of previously evolved lineages from different historical selection regimes (abiotic vs. biotic) to the novel stresses of acidification and antibiotic exposure. We found that at the initial introduction to these novel environments, the duration and selection regime of prior evolution history had variable effects on fitness. Over adaptation in the new environments, both the selection history and duration significantly impacted the fitness gained during adaptation to novel environments. These studies are important for the understanding of population and evolutionary scale dynamics and ecosystem structure.
Recommended Citation
Halliday-Isaac, Akacia, "Ecological and Evolutionary Ramifications of Host-Parasite Interaction in Aquatic and Model Ecosystems" (2024). Electronic Theses and Dissertations. 2936.
https://egrove.olemiss.edu/etd/2936