Sex Chromosome Evolution in Lizards and Snakes

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Sex chromosomes play an important role in the embryonic development of many animal species by controlling an individual's sex. However, the sex chromosomes of most animals remain unidentified limiting our understanding of broad patterns of sex chromosome evolution. This project will advance the study of sex chromosome evolution by investigating lizards and snakes. These reptiles have a variety of sex-determining systems with numerous evolutionary transitions among them. Each of these independently derived systems can act as a replicate evolutionary “experiment” to test the general principles and processes that govern sex chromosome evolution. This research will fill gaps in our knowledge by identifying sex chromosomes in these under-studied reptiles and then use these data to characterize some general properties of sex chromosome evolution. The research will train a postdoctoral researcher and students, including PhD students and undergraduates, in genomics and bioinformatics, skills that are in high demand for careers in agriculture, biotechnology, and health care. Researchers will develop genetic sex tests for several reptile species. Such tests are important for the management and breeding of endangered species and sexing embryonic material in developmental research. Researchers will engage in outreach to pet reptile hobbyists and the general public about genetics, evolution, and sex chromosomes via a museum exhibit and a booth at pet reptile trade shows.Comparative studies of sex chromosomes in animal groups with repeated transitions among sex-determining mechanisms, like the lizards and snakes, can help answer longstanding questions about sex chromosome evolution. This research will integrate comparative genomics, transcriptomics, and phylogenetics to enhance the utility of lizards and snakes as a model clade to investigate sex chromosome evolution and address the following questions: 1) Are sex chromosomes an evolutionary trap? 2) Are some chromosomes particularly good at being sex chromosomes? 3) Is sex chromosome dosage compensation more likely to evolve in XX/XY vs. ZZ/ZW taxa? 4) What is the relative role of rearrangements vs. sex-biased recombination in suppressing recombination between the sex chromosomes? Upon completion, this project will enable subsequent investigations into the mechanisms that drive sex chromosome evolution in lizards and snakes and establish a framework for comparative analyses of sex chromosome evolution across the tree of life. Data collected for this project will have broad utility to other scientists, including new, high quality genome assemblies for multiple lizard and snake species.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.