Matching Items (2)
Filtering by
- All Subjects: Natural selection
- Genre: Academic theses
- Creators: Armendt, Brad
Description
Gene-centric theories of evolution by natural selection have been popularized and remain generally accepted in both scientific and public paradigms. While gene-centrism is certainly parsimonious, its explanations fall short of describing two patterns of evolutionary and social phenomena: the evolution of sex and the evolution of social altruism. I review and analyze current theories on the evolution of sex. I then introduce the conflict presented to gene-centric evolution by social phenomena such as altruism and caste sterility in eusocial insects. I review gene-centric models of inclusive fitness and kin selection proposed by Hamilton and Maynard Smith. Based their assumptions, that relatedness should be equal between sterile workers and reproductives, I present several empirical examples that conflict with their models. Following that, I introduce a unique system of genetic caste determination (GCD) observed in hybrid populations of two sister-species of seed harvester ants, Pogonomyrmex rugosus and Pogonomyrmex barbatus. I review the evidence for GCD in those species, followed by a critique of the current gene-centric models used to explain it. In chapter two I present my own theoretical model that is both simple and extricable in nature to explain the origin, evolution, and maintenance of GCD in Pogonomyrmex. Furthermore, I use that model to fill in the gaps left behind by the contributing authors of the other GCD models. As both populations in my study system formed from inter-specific hybridization, I review modern discussions of heterosis (also called hybrid vigor) and use those to help explain the ecological competitiveness of GCD. I empirically address the inbreeding depression the lineages of GCD must overcome in order to remain ecologically stable, demonstrating that as a result of their unique system of caste determination, GCD lineages have elevated recombination frequencies. I summarize and conclude with an argument for why GCD evolved under selective mechanisms which cannot be considered gene-centric, providing evidence that natural selection can effectively operate on non-heritable genotypes appearing in groups and other social contexts.
ContributorsJacobson, Neal (Author) / Gadau, Juergen (Thesis advisor) / Laubichler, Manfred (Committee member) / Pratt, Stephen (Committee member) / Arizona State University (Publisher)
Created2012
Description
The Modern Synthesis embodies a theory of natural selection where selection is to be fundamentally understood in terms of measures of fitness and the covariance of reproductive success and trait or character variables. Whether made explicit or left implicit, the notion that selection requires that some trait variable cause reproductive success has been deemphasized in our modern understanding of exactly what selection amounts to. The dissertation seeks to advance a theory of natural selection that is fundamentally causal. By focusing on the causal nature of natural selection (rather than on fitness or statistical formulae), certain conceptual and methodological problems are seen in a new, clarifying light and avenues toward new, interesting solutions to those problems are illustrated. First, the dissertation offers an update to explicitly causal theories of when exactly a trait counts as an adaptation upon fixation in a population and draws out theoretical and practical implications for evolutionary biology. Second, I examine a case of a novel character that evolves by niche construction and argue that it evolves by selection for it and consider implications for understanding adaptations and drift. The third contribution of the dissertation is an argument for the importance of defining group selection causally and an argument against model pluralism in the levels of selection debate. Fourth, the dissertation makes a methodological contribution. I offer the first steps toward an explicitly causal methodology for inferring the causes of selection—something often required in addition to inferring the causes of reproductive success. The concluding chapter summarizes the work and discusses potential paths for future work.
ContributorsAnderson, Wesley (Author) / Armendt, Brad (Thesis advisor) / Creath, Richard (Committee member) / Glymour, Bruce (Committee member) / Kinzig, Ann (Committee member) / Perrings, Charles (Committee member) / Arizona State University (Publisher)
Created2016