DISSERTATION RESEARCH: Persistence of Monoecy in Deep Time: An Integrated Biological and Paleontological Approach

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This project integrates paleontology and evolutionary biology to investigate the evolution of sexual systems. The existence of so many methods of reproduction in the natural world remains difficult to explain. Contemporary theories assume that sexual reproduction should allow long term survival as the dispersal and recombination of genetic material provides a population of organisms with the ability to adapt to environmental change. Small freshwater crustaceans, or ?clam shrimp,? are ideal for the study of sexual system evolution as the group contains species that comprise males and females, species where females no longer exist and have been completely replaced by self-fertilizing hermaphrodites (with the ability to fertilize their own eggs) coexisting with males, and species with only self-fertilizing hermaphrodites. Using the otherwise inconspicuous ?clam shrimp? as a study group, it is possible to identify sex via carapace (shell) shape analysis techniques in both living and fossil populations. Once sexes are identified, we can deduce sexual system via sex ratio of the population. This study aims to collect fossil data from worldwide repositories in order to provide, for the first time, empirical evidence to test established theories about the origination, duration and extinction of sexual systems over geologic timescales. We can then address the commonly held belief that unisexual systems represent an evolutionary ?dead end.? The results of this study will also provide a foundation for future research utilizing the fossil record to perform transformative studies into the evolution of mating systems.