Adaptation and Plasticity in Damselfishes (genus Abudefduf) separated by the Central American Isthmus

Abstract

Marine ecosystems are characterized by having substantial differences in abiotic conditions at small spatial scales. The organisms that are exposed to these variable environments must have the capacity to respond to the environmental conditions and their fluctuations, either through evolved adaptations, or phenotypic plasticity. This dissertation was focused on understanding how two sister species, Abudefduf saxatilis and A. troschelii, respond to their respective environments, the former which experiences constant temperatures year-round, and the latter seasonal variability from cold-water upwellings. We used a genomic approach to better understand how each species is adapted to its respective environment, and an experimental approach to test for plasticity in response to environmental changes. The genomic analyses showed differences between the two species, that can be related to their respective environments and show that both have the capacity for phenotypic plasticity in response to temperature changes. When examining plasticity to temperature changes, we see that both species have similar responses to heatwaves, however A. saxatilis, which does not experience cold-water upwellings, shows a cellular stress response when exposed to colder temperatures. In addition to studying how species can respond to environmental changes, and how their native environment can influence this response, we also looked at the broader role of scientists as teachers for the next generation. The last section of this dissertation examines student experiences in introductory biology courses, often considered weed-out courses, to see what sources of struggle students experienced, and which of these students were more often able to overcome. When teaching students, both science majors and non-science majors, instructors directly influence the ability for critical thinking. Recommendations that can be applied in the classroom to improve student success in introductory biology courses are provided as part of this study.