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Evolutionary and Ecological Consequences of Symbiosis in Paramecium bursaria
Mutualisms are fundamental elements of ecological systems and are affected by the abiotic and biotic environment. Overall, my dissertation has taken traditional approaches and applied them in creative and novel ways. I have used thermal performance curves, experimental evolution, movement analysis, and functional responses to investigate how symbioses move along the continuum of costs and benefits, shining light on the cost of mutualisms and the potential benefit of a pathogen for the host of its host fitness. Here I show that, despite discovering the cost of having algal endosymbionts at higher temperatures, prolonged thermal evolution does not result in a breakdown in the P. bursaria-zoochlorellae endosymbiosis. This result makes the question of who is controlling whom in this relationship more puzzling, as the paramecia appeared unable to remove their symbionts even when it would benefit them to do so. I also found that the presence of the algae significantly alters the movement patterns of the paramecium host, which has ecological implications for the physical encounters between paramecia and other organisms, including potential predators. Finally, I investigated how an often overlooked third party could affect the paramecium. Chloroviruses infect the zoochlorella and physically associate with the exterior of the paramecium. Paramecia with high viral loads had a higher standard deviation of turning angle and thus did not move as far away from their starting point as cells without viral symbionts. This could have consequences for predation risk, because movement behaviors play a large role in generating contacts between predator and prey. I then tested the impact of chlorovirus symbionts on P. bursaria predation risk. Using three different predators, I found no significant difference in functional response parameters for paramecia with or without virus. Thus, I found that having physically associated chlorovirus does not seem to benefit or cost the paramecia in terms of predation risk.
Ecology|Evolution and Development
Salsbery, Miranda E, "Evolutionary and Ecological Consequences of Symbiosis in Paramecium bursaria" (2022). ETD collection for University of Nebraska - Lincoln. AAI29166133.