DISSERTATION RESEARCH: Evolutionary Genetics of Asexual Reproduction in a Wild Plant Species

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Despite the prevalence of sexual reproduction in nature, asexual reproduction is also found in many diverse organisms. Apomixis (asexual reproduction via clonal seed) occurs in approximately 400 genera across 40 different plant families, and is always associated with polyploidy (whole genome duplication) and hybridization. To date, these confounding factors have prevented investigation of the evolutionary and ecological processes maintaining apomixis in plant populations. The genus Boechera, a self-fertilizing wild relative of Arabidopsis thaliana, contains diploid apomicts. This offers a unique opportunity to disentangle the factors underlying apomixis and polyploidy. The proposed research examines the processes underlying a sexual/apomictic breeding system polymorphism in wild populations of Boechera, using population genetic models that historically are designed for diploid organisms. Understanding the link between apomixis and hybridization still remains problematic. Any putative fitness effects of apomixis may be due to hybridization, which introduces genetic variation to inbred Boechera. Through a combination of crossing experiments, field research, and genomic sequencing techniques, the PIs will investigate the fitness effects of hybridization and increased genetic diversity in Boechera. This research permits complete separation of these two confounding factors from the study of apomixis for the first time. Most crops are of hybrid origin, and the introduction of apomixis promises fixation of advantageous lineages through their clonal offspring; therefore, apomixis is of great agricultural interest. A developed understanding of the evolutionary maintenance of this breeding system in nature is critical to current and future efforts to battle hunger across the world. Training of students will occur.