DISSERTATION RESEARCH: Quantifying the tempo of genome theft in polyploid, female-only Ambystoma salamanders

Ohio State University, The, Columbus OH

Investigators

Abstract

This project will test a hypothesis to explain how a lineage of female-only salamanders has been able to persist for millions of years. Most animals reproduce sexually even though there is a high evolutionary cost of making males. Males compete with females for resources and decrease the genetic resemblance between a female and her offspring. Few animal species reproduce without mating and most only live for a short evolutionary time. However, an all-female lineage of salamanders (the oldest known all-female vertebrate in North American) has been able to persist for approximately 6 million years. Because the persistence of asexual animals is rare, they can provide valuable clues about the costs and benefits of sexual reproduction. Sometimes these female-only salamanders are able to obtain new genetic material from males of closely related species. Thus, they may gain the benefits of both sexual and asexual reproduction. To test this idea, the researchers will measure the importance of genetic contributions from sexual species into the all-female asexual species over evolutionary time. In addition, the project will include the training of undergraduate and graduate students and outreach activities such as museum displays and social blogs. This research will quantify the rate and evolutionary history of genome leakage from sexual species in to the unisexual Ambystoma lineage, which will allow us to test the hypothesis that recurrent genome contribution accounts for the greater lineage age of unisexual Ambystoma as compared to other gynogenetic taxa. The researchers will use genome-scale data and evolutionary demographic modeling to evaluate multiple evolutionary scenarios ranging from no genetic contributions from sexual species, to recent (but limited) genome contributions only, or ongoing genome contributions. This will be accomplished by using custom bioinformatics tools to sort genetic variation among the multiple genomes of unisexual salamanders, comparing this variation to that of the genomes of sexual species thought to be the source of novel genetic variation in unisexuals and then using statistical genetic models to estimate the magnitude and timing of genetic exchange between unisexual and sexual salamanders.