9707223 Rausher The goal of this project is to attempt to understand the degree to which a model organism, the morning glory Ipomorea purpurea, is optimally adapted to various environments it encounters. Specifically, this project seeks to characterize empirically the optimal value for several traits in different environments and then determine whether natural populations have evolved to exhibit those values in the respective environments. The project also seeks to characterize any constraints that may prevent populations from evolving to those optimal values. Characteristics of the range of natural environments normally encountered by I. purpurea will initially be surveyed. Using this information, two field experiments will be conducted in which I. purpurea is grown either a gradient of soil nutrient levels or a gradient of competitive intensity. The pattern of natural selection acting on traits related to plant growth and size will be measured to determine how far the means of these traits are from their optima in each environment. A set of breeding and selection experiments will provide a characterization of any genetic constraints acting to prevent evolution toward these optima, and the importance of these constraints will be evaluated by computer simulation. Evolution by natural selection is a compromise between what is favored (how selection acts) and what is possible (determined by the genetics of organisms). While biologists have made great strides understanding evolution in model organisms (e.g. fruit flies) living in simple, controlled environments, much less is known about the evolutionary responses of plant and animal populations to complex natural environments. The broad aim of this project is to begin to provide an understanding of such a response in an organism that typically encounters a complex environment.
