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

最近在测量自然选择的理论和统计学方面的发展使得选择对表型的作用可以与表型的遗传分开来测量，这些对表型性状的自然选择的估计已经被用来解决当代植物生物学中的许多理论问题。用盐沼植物补血草进行的拟议实验将提供生殖性状的选择措施，并解决对更全面地理解选择估计和野生种群对自然选择的基因反应至关重要的三个问题：1)了解为选择估计而测量的数量性状的遗传基础和遗传力，2)邻域参数，它决定了选择可以通过自然选择或随机遗传漂移引起适应性变化的空间尺度，并控制了这种变化之间的平衡；3)对环境的实验操纵，可以识别偶然的选择因素或部分解释为什么选择以观察到的方式进行。局部可变的自然选择、随机的遗传漂移和有限的基因流动都被认为在植物种群的局部适应中发挥了重要作用。然而，在野生植物物种中，对选择的空间尺度、可用于响应选择的数量遗传变异量以及邻域大小和面积的同时估计从未得到过。这项研究将有助于更好地了解敏感和不断缩小的盐沼生态系统中的植物种群变化。

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.