Dissertation Research: The Evolutionary Impact of Natural Selection, Quantitative Genetic Variation, and Gene Flow in a Salt Marsh Perennial, Limonium carolinianum

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Recent developments in the theory and statistics for measuring natural selection have allowed the action of selection on the phenotype to be measured separately from the inheritance of that phenotype and these estimates of natural selection on phenotypic traits have been used to address many contemporary theoretical issues in plant biology. The proposed experiments with the salt marsh plant Limonium carolinianum would provide measures of selection on reproductive traits and address three issues crucial to a more complete understanding of selection estimates and genotypic responses to natural selection in wild populations: 1) understanding the genetic basis and heritability of the quantitative traits being measured for selection estimates, 2) neighborhood parameters that determine the spatial scale over which selection could cause adaptive change by and control the balance between such change by natural selection or by random genetic drift, 3) experimental manipulation of environment that can identify the casual selective agents or partially explain why selection operates in an observed way. Locally variable natural selection, random genetic drift, and limited gene flow are all believed to play major roles in the local adaptation of plant populations. However, simultaneous estimates of the spatial scale of selection, amount of quantitative genetic variation available to respond to selection, and neighborhood size and area have never been obtained in a wild plant species. The study will contribute to better knowledge of plant population change in sensitive and shrinking salt-marsh ecosystems.