Epigenetic variation in a reptile with temperature-dependent sex determination and inspiring a diverse future for STEM

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Flores, Daniela
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Fredric J. Janzen
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Ecology, Evolution, and Organismal Biology

Vertebrates with temperature-dependent sex determination (TSD), a mechanism that relies on incubation temperature to irreversibly determine the sex of developing embryos, are threatened by ongoing changes in climate and local environmental conditions. Previous studies have suggested that behavioral and molecular plasticity in this system may provide opportunities for these species to adapt to these changes. Although decades of research have uncovered key aspects, a complete molecular mechanism of TSD remains elusive. Epigenetic studies have the potential to unlock crucial information previously cryptic in traditional genetic studies. Recent studies have shown that environmental factors and maternal effects can greatly influence an individual’s epigenome, resulting in altered phenotypes. DNA methylation in particular is well known for its dynamic ability to silence genes, and evidence is accumulating for its role in determining sex in TSD systems.

This thesis examines the presence and effects of epigenetic variation, specifically DNA methylation, in the context of TSD. Using the painted turtle, Chrysemys picta, as a model for TSD, I leveraged a population of painted turtles at a long-term study site to investigate the relationship between DNA methylation and sex in a TSD system. In Chapter 2, I quantified sex-specific genome-wide DNA methylation and its variation in adult turtles. Although I identified high within-sex variation in both sexes, adult female turtles had approximately 1/2 the amount of DNA methylation across their genome as the average adult male, despite otherwise identical genomic structures.

Dispersing knowledge is a critical aspect of scientific research. However, many public communities have less access to this information than others. Thus, many people from such communities pursue alternative career paths. Recruitment of diverse students is a national initiative across STEM fields. This thesis also addresses the issue of underrepresentation of minoritized groups in the sciences. In Chapter 3, I report on leveraging the long-term study site to create an immersive field research program for high school students, called TREE (Turtle Camp Research and Education in Ecology), to expose a diverse set of students to ecology research. I found that students not only improved their knowledge of biology-related topics by participating in this hands-on program, but a majority of the program’s alumni continued to pursue a college degree in a STEM-related field. This successful program demonstrates the importance of outreach, and near-peer mentoring in diversifying the STEM workforce.

Sun Dec 01 00:00:00 UTC 2019