Experimental and Theoretical Studies of the Coevolution of Inbreeding Depression and Mating System

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9707684 Uyenoyama Mating between closely related individuals often results in inbreeding depression, or the production of offspring of lower quality. This project addresses the evolution of mating systems in response to inbreeding depression and its evolution in turn in response to the mating system. Theoretical analyses suggest that the penalty of inbreeding depression evolves to different magnitudes among familial lineages that practice different levels of inbreeding. Among the possible consequences of such interactions is the evolution of mixed mating systems, which entail both inbreeding and outbreeding. Natural populations of Datura stramonium, which practices a mixed mating system, provide a model system for the direct exploration of these issues. Previous work has demonstrated that a morphological character (stigma-anther distance) is both heritable and a determinant of the level of inbreeding in individuals. The magnitude of inbreeding depression will be estimated in individual families. This system permits a test of whether inbreeding depression at the family level is associated with mating system. In addition, numerical simulation studies will be conducted to explore various aspects of associations between inbreeding depression and familial lineage, including their genetic bases and consequences for the evolution of mating systems. All living organisms are subject to the deleterious effects of mutations. Processes that influence the generation, purging, and maintenance of mutational load directly affect the length and quality of life. Theoretical and empirical studies have established mating system as a major determinant as well as a consequence of inbreeding depression in natural populations.