UCLA

Gene expression is an important mechanism that allows organisms to adapt to environmental stimuli. Recent advances in molecular techniques have enabled extensive research evaluating environmentally induced transcription rates across the genome in controlled laboratory conditions. However, relatively few studies have examined transcriptional responses to external changes in wild populations, where natural selection operates. For my dissertation, I aimed to evaluate how wild animals physiologically respond to various environmental stressors on the molecular level. In my first chapter, I provide an overview of my three empirical research chapters. In my second chapter, I evaluated gene expression changes in female yearling yellow-bellied marmots (Marmota flaviventer) as they prepared to disperse from the natal colony. Dispersers exhibited significant increases in the expression of genes involved in metabolism, muscle function, and pathogen defense, providing support for somatic preparation for the upcoming risks involved with dispersal. In my third chapter, I focused on both male and female marmots to evaluate the impact of social status on gene expression variation in blood. Previous studies in controlled systems have identified a conserved transcriptional response to adversity (CTRA) where socially stressed individuals often exhibit chronic inflammation and reduced antiviral responses. I found that affiliative and agonistic social interactions influenced the inflammatory transcriptional response, but not the antiviral response. This suggests that inflammation is an evolutionarily conserved trait when dealing with social stress, but that the viral response may depend on the social structure of the species. Finally, in my fourth chapter, I examined the transcriptional response to predator pressure in this species. I identified predator-induced differential expression in several genetic pathways including heat shock proteins, metabolism, brain function, and glucocorticoid signaling. My dissertation demonstrated the ability to observe the molecular response to external stimulis in a wild mammal, which could prove to be a powerful method for studying the cellular stress response in natural populations.