Gene Expression Response to Naturally Fluctuating Temperature in Turtles with Alternative Sex Determining Mechanisms

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Sex is determined by genetic constitution (GSD) in most animals (as by sex chromosomes in humans), and by environmental temperature (TSD) in others, including reptiles. The proportion of males to females (sex ratio) greatly influences populations. Male-biased populations reproduce slowly because females are limited, while female-biased populations may have lower genetic variability because few males father all offspring. Yet we know little about how naturally-fluctuating temperatures of nests affect sex ratios of TSD reptiles. This gap obscures the effect of TSD on sex ratio evolution, the growth potential of populations, the rate of change of genetic variability, and how species adapt to the environment. This project will help elucidate the effect that naturally-fluctuating temperature has on the expression of genes involved in gonadal formation in TSD turtles, and how males and females are produced in nature. Explicit hypotheses derived from previous gene expression and ecological research will be tested to help reveal how TSD species may respond to short- and long-term climate change. Intellectual Merit: This project will advance our understanding of the effects of environmental change on the regulation of sexual development and sex ratio production at the gene-expression level in TSD species. The application of molecular techniques under ecologically-relevant conditions will shed light on how and why sex is determined by nest temperature in so many reptiles, thus facilitating the study of sex ratio evolution under TSD and its implications for the conservation of endangered TSD species facing global warming. Broader Impacts: This project will (a) integrate undergraduate discovery-based learning through a novel service-learning activity to recruit biology undergraduates into the field and lab modules of this project; and (b) broaden the participation of underrepresented groups in biology by providing direct training opportunities for students and their mentors; and by engaging women and minorities through outreach activities.