The study of population genetics has shaped the field of phylogeography and provided insights into the biotic and abiotic mechanisms that influence gene flow and adaptation. Changes at the DNA sequence level are thought to occur when populations are isolated by physical barriers or strong environmental gradients that limit gene flow, allowing divergence over several generations unless strong selection accelerates the process. As environmental fluctuations are becoming more common, organisms need to rapidly adapt to anthropogenic, climatic, and ecological changes. Epigenetic modifications, such as DNA methylation, are thought to be a mechanism for phenotypic responses to occur at a pace faster than adaptation by natural selection on standing genetic variation. For my dissertation, I am focusing on pipefish species in the genus Syngnathus, combining both population genetic and DNA methylation analyses to investigate the molecular mechanisms underlying local adaptation to heterogeneous environments in Florida’s estuarine habitats. In Chapter 1, I assess the fine-scale population structure of three closely related species (Syngnathus scovelli, S. floridae, and S. louisianae), sampled across multiple locations in Florida to infer drivers of phylogeographic patterns and barriers to gene flow across the region. In Chapters 2 and 3 I focus on the euryhaline species S. scovelli, examining both genetic and epigenetic variation across salinity gradients to investigate the role of DNA methylation in local adaptation. This approach will provide novel insights into the mechanisms driving rapid adaptation in marine organisms, highlighting the potential for epigenetic changes to mediate resilience in response to environmental variability and ongoing climate change.
Kathryn Greiner-Ferris
Michelle Gaither, Advisor
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