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Abstract:
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The general prevalence of sexual reproduction over asexual reproduction among metazoans testifies to the evolutionary , long -term benefits of genetic recombination . Despite the benefits of genetic recombination under sexual reproduction , asexual organisms sporadically occur throughout the tree of life , and a few asexual lineages persisted over significant evolutionary time without apparent recombination . The study of asexual organisms therefore may provide clues to answer why almost all eukaryotes reproduce via meiosis and syngamy and why asexual eukaryotes are almost always evolutionarily short -lived . Towards understanding the evolution of asexual lineages in the Hymenoptera , I first review the diversity of reproductive systems in the Hymenoptera , introduce the study organism , the fungus -gardening ant Mycocepurus smithii , and discuss my research objectives . Second , I integrate information from reproductive physiology , reproductive morphology , natural history and behavior , to document that that queens of M . smithii are capable of thelytokous parthenogenesis , workers are sterile , and males are absent from the surveyed population . These results suggest that M . smithii might be obligately asexual . To place the origin and maintenance of asexual reproduction in M . smithii in an evolutionary context , I use molecular phylogenetic and population -genetic methods to (i ) test if M . smithii reproduces asexually throughout its distribution range ; (ii ) infer if asexuality evolved once or multiple times ; (iii ) date the origin of asexual reproduction in M . smithii ; and (iv ) elucidate the cytogenetic mechanism of thelytokous parthenogenesis . During field collecting for these studies throughout the Neotropics , I discovered a new species of obligate social parasite in the genus Mycocepurus . Social parasites are of great interest to evolutionary biology in order to elucidate mechanisms demonstrating how parasites gained reproductive isolation from their host species in sympatry . I describe this new parasite species , characterize its morphological and behavioral adaptations to the parasitic lifestyle , and discuss the parasite’s life history evolution in the context of social parasitism in fungus -growing ants . The dissertation research integrates population -genetic , phylogenetic , physiological and morphological approaches to advance our understanding of the evolution of reproductive systems and diversity of life -history traits in animals . |